'VirtualRESTService' => __DIR__ . '/includes/libs/virtualrest/VirtualRESTService.php',
'VirtualRESTServiceClient' => __DIR__ . '/includes/libs/virtualrest/VirtualRESTServiceClient.php',
'WANCacheReapUpdate' => __DIR__ . '/includes/deferred/WANCacheReapUpdate.php',
- 'WANObjectCache' => __DIR__ . '/includes/libs/objectcache/WANObjectCache.php',
+ 'WANObjectCache' => __DIR__ . '/includes/libs/objectcache/wancache/WANObjectCache.php',
'WANObjectCacheReaper' => __DIR__ . '/includes/libs/objectcache/wancache/WANObjectCacheReaper.php',
'WantedCategoriesPage' => __DIR__ . '/includes/specials/SpecialWantedcategories.php',
'WantedFilesPage' => __DIR__ . '/includes/specials/SpecialWantedfiles.php',
'WikitextContent' => __DIR__ . '/includes/content/WikitextContent.php',
'WikitextContentHandler' => __DIR__ . '/includes/content/WikitextContentHandler.php',
'WikitextLogFormatter' => __DIR__ . '/includes/logging/WikitextLogFormatter.php',
- 'WinCacheBagOStuff' => __DIR__ . '/includes/libs/objectcache/wancache/WinCacheBagOStuff.php',
+ 'WinCacheBagOStuff' => __DIR__ . '/includes/libs/objectcache/WinCacheBagOStuff.php',
'WithoutInterwikiPage' => __DIR__ . '/includes/specials/SpecialWithoutinterwiki.php',
'WordLevelDiff' => __DIR__ . '/includes/diff/WordLevelDiff.php',
'WrapOldPasswords' => __DIR__ . '/maintenance/wrapOldPasswords.php',
+++ /dev/null
-<?php
-/**
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
- * http://www.gnu.org/copyleft/gpl.html
- *
- * @file
- * @ingroup Cache
- */
-
-use Liuggio\StatsdClient\Factory\StatsdDataFactoryInterface;
-use Psr\Log\LoggerAwareInterface;
-use Psr\Log\LoggerInterface;
-use Psr\Log\NullLogger;
-
-/**
- * Multi-datacenter aware caching interface
- *
- * ### Using WANObjectCache
- *
- * All operations go to the local datacenter cache, except for delete(),
- * touchCheckKey(), and resetCheckKey(), which broadcast to all datacenters.
- *
- * This class is intended for caching data from primary stores.
- * If the get() method does not return a value, then the caller
- * should query the new value and backfill the cache using set().
- * The preferred way to do this logic is through getWithSetCallback().
- * When querying the store on cache miss, the closest DB replica
- * should be used. Try to avoid heavyweight DB master or quorum reads.
- *
- * To ensure consumers of the cache see new values in a timely manner,
- * you either need to follow either the validation strategy, or the
- * purge strategy.
- *
- * The validation strategy refers to the natural avoidance of stale data
- * by one of the following means:
- *
- * - A) The cached value is immutable.
- * If the consumer has access to an identifier that uniquely describes a value,
- * cached value need not change. Instead, the key can change. This also allows
- * all servers to access their perceived current version. This is important
- * in context of multiple deployed versions of your application and/or cross-dc
- * database replication, to ensure deterministic values without oscillation.
- * - B) Validity is checked against the source after get().
- * This is the inverse of A. The unique identifier is embedded inside the value
- * and validated after on retreival. If outdated, the value is recomputed.
- * - C) The value is cached with a modest TTL (without validation).
- * If value recomputation is reasonably performant, and the value is allowed to
- * be stale, one should consider using TTL only – using the value's age as
- * method of validation.
- *
- * The purge strategy refers to the the approach whereby your application knows that
- * source data has changed and can react by purging the relevant cache keys.
- * As purges are expensive, this strategy should be avoided if possible.
- * The simplest purge method is delete().
- *
- * No matter which strategy you choose, callers must not rely on updates or purges
- * being immediately visible to other servers. It should be treated similarly as
- * one would a database replica.
- *
- * The need for immediate updates should be avoided. If needed, solutions must be
- * sought outside WANObjectCache.
- *
- * ### Deploying WANObjectCache
- *
- * There are two supported ways to set up broadcasted operations:
- *
- * - A) Set up mcrouter as the underlying cache backend, using a memcached BagOStuff class
- * for the 'cache' parameter. The 'region' and 'cluster' parameters must be provided
- * and 'mcrouterAware' must be set to `true`.
- * Configure mcrouter as follows:
- * - 1) Use Route Prefixing based on region (datacenter) and cache cluster.
- * See https://github.com/facebook/mcrouter/wiki/Routing-Prefix and
- * https://github.com/facebook/mcrouter/wiki/Multi-cluster-broadcast-setup.
- * - 2) To increase the consistency of delete() and touchCheckKey() during cache
- * server membership changes, you can use the OperationSelectorRoute to
- * configure 'set' and 'delete' operations to go to all servers in the cache
- * cluster, instead of just one server determined by hashing.
- * See https://github.com/facebook/mcrouter/wiki/List-of-Route-Handles.
- * - B) Set up dynomite as a cache middleware between the web servers and either memcached
- * or redis and use it as the underlying cache backend, using a memcached BagOStuff
- * class for the 'cache' parameter. This will broadcast all key setting operations,
- * not just purges, which can be useful for cache warming. Writes are eventually
- * consistent via the Dynamo replication model. See https://github.com/Netflix/dynomite.
- *
- * Broadcasted operations like delete() and touchCheckKey() are intended to run
- * immediately in the local datacenter and asynchronously in remote datacenters.
- *
- * This means that callers in all datacenters may see older values for however many
- * milliseconds that the purge took to reach that datacenter. As with any cache, this
- * should not be relied on for cases where reads are used to determine writes to source
- * (e.g. non-cache) data stores, except when reading immutable data.
- *
- * All values are wrapped in metadata arrays. Keys use a "WANCache:" prefix
- * to avoid collisions with keys that are not wrapped as metadata arrays. The
- * prefixes are as follows:
- * - a) "WANCache:v" : used for regular value keys
- * - b) "WANCache:i" : used for temporarily storing values of tombstoned keys
- * - c) "WANCache:t" : used for storing timestamp "check" keys
- * - d) "WANCache:m" : used for temporary mutex keys to avoid cache stampedes
- *
- * @ingroup Cache
- * @since 1.26
- */
-class WANObjectCache implements IExpiringStore, IStoreKeyEncoder, LoggerAwareInterface {
- /** @var BagOStuff The local datacenter cache */
- protected $cache;
- /** @var MapCacheLRU[] Map of group PHP instance caches */
- protected $processCaches = [];
- /** @var LoggerInterface */
- protected $logger;
- /** @var StatsdDataFactoryInterface */
- protected $stats;
- /** @var callable|null Function that takes a WAN cache callback and runs it later */
- protected $asyncHandler;
-
- /** @bar bool Whether to use mcrouter key prefixing for routing */
- protected $mcrouterAware;
- /** @var string Physical region for mcrouter use */
- protected $region;
- /** @var string Cache cluster name for mcrouter use */
- protected $cluster;
- /** @var bool Whether to use "interim" caching while keys are tombstoned */
- protected $useInterimHoldOffCaching = true;
- /** @var float Unix timestamp of the oldest possible valid values */
- protected $epoch;
- /** @var string Stable secret used for hasing long strings into key components */
- protected $secret;
-
- /** @var int Callback stack depth for getWithSetCallback() */
- private $callbackDepth = 0;
- /** @var mixed[] Temporary warm-up cache */
- private $warmupCache = [];
- /** @var int Key fetched */
- private $warmupKeyMisses = 0;
-
- /** @var float|null */
- private $wallClockOverride;
-
- /** @var int Max expected seconds to pass between delete() and DB commit finishing */
- const MAX_COMMIT_DELAY = 3;
- /** @var int Max expected seconds of combined lag from replication and view snapshots */
- const MAX_READ_LAG = 7;
- /** @var int Seconds to tombstone keys on delete() and treat as volatile after invalidation */
- const HOLDOFF_TTL = self::MAX_COMMIT_DELAY + self::MAX_READ_LAG + 1;
-
- /** @var int Idiom for getWithSetCallback() meaning "do not store the callback result" */
- const TTL_UNCACHEABLE = -1;
-
- /** @var int Consider regeneration if the key will expire within this many seconds */
- const LOW_TTL = 30;
- /** @var int Max TTL, in seconds, to store keys when a data sourced is lagged */
- const TTL_LAGGED = 30;
-
- /** @var int Expected time-till-refresh, in seconds, if the key is accessed once per second */
- const HOT_TTR = 900;
- /** @var int Minimum key age, in seconds, for expected time-till-refresh to be considered */
- const AGE_NEW = 60;
-
- /** @var int Idiom for getWithSetCallback() meaning "no cache stampede mutex required" */
- const TSE_NONE = -1;
-
- /** @var int Idiom for set()/getWithSetCallback() meaning "no post-expiration persistence" */
- const STALE_TTL_NONE = 0;
- /** @var int Idiom for set()/getWithSetCallback() meaning "no post-expiration grace period" */
- const GRACE_TTL_NONE = 0;
- /** @var int Idiom for delete()/touchCheckKey() meaning "no hold-off period" */
- const HOLDOFF_TTL_NONE = 0;
- /** @var int Alias for HOLDOFF_TTL_NONE (b/c) (deprecated since 1.34) */
- const HOLDOFF_NONE = self::HOLDOFF_TTL_NONE;
-
- /** @var float Idiom for getWithSetCallback() meaning "no minimum required as-of timestamp" */
- const MIN_TIMESTAMP_NONE = 0.0;
-
- /** @var string Default process cache name and max key count */
- const PC_PRIMARY = 'primary:1000';
-
- /** @var int Idion for get()/getMulti() to return extra information by reference */
- const PASS_BY_REF = -1;
-
- /** @var int Seconds to keep dependency purge keys around */
- private static $CHECK_KEY_TTL = self::TTL_YEAR;
- /** @var int Seconds to keep interim value keys for tombstoned keys around */
- private static $INTERIM_KEY_TTL = 1;
-
- /** @var int Seconds to keep lock keys around */
- private static $LOCK_TTL = 10;
- /** @var int Seconds to no-op key set() calls to avoid large blob I/O stampedes */
- private static $COOLOFF_TTL = 1;
- /** @var int Seconds to ramp up the chance of regeneration due to expected time-till-refresh */
- private static $RAMPUP_TTL = 30;
-
- /** @var float Tiny negative float to use when CTL comes up >= 0 due to clock skew */
- private static $TINY_NEGATIVE = -0.000001;
- /** @var float Tiny positive float to use when using "minTime" to assert an inequality */
- private static $TINY_POSTIVE = 0.000001;
-
- /** @var int Milliseconds of key fetch/validate/regenerate delay prone to set() stampedes */
- private static $SET_DELAY_HIGH_MS = 50;
- /** @var int Min millisecond set() backoff during hold-off (far less than INTERIM_KEY_TTL) */
- private static $RECENT_SET_LOW_MS = 50;
- /** @var int Max millisecond set() backoff during hold-off (far less than INTERIM_KEY_TTL) */
- private static $RECENT_SET_HIGH_MS = 100;
-
- /** @var int Consider value generation slow if it takes more than this many seconds */
- private static $GENERATION_SLOW_SEC = 3;
-
- /** @var int Key to the tombstone entry timestamp */
- private static $PURGE_TIME = 0;
- /** @var int Key to the tombstone entry hold-off TTL */
- private static $PURGE_HOLDOFF = 1;
-
- /** @var int Cache format version number */
- private static $VERSION = 1;
-
- /** @var int Key to WAN cache version number */
- private static $FLD_FORMAT_VERSION = 0;
- /** @var int Key to the cached value */
- private static $FLD_VALUE = 1;
- /** @var int Key to the original TTL */
- private static $FLD_TTL = 2;
- /** @var int Key to the cache timestamp */
- private static $FLD_TIME = 3;
- /** @var int Key to the flags bit field (reserved number) */
- private static /** @noinspection PhpUnusedPrivateFieldInspection */ $FLD_FLAGS = 4;
- /** @var int Key to collection cache version number */
- private static $FLD_VALUE_VERSION = 5;
- /** @var int Key to how long it took to generate the value */
- private static $FLD_GENERATION_TIME = 6;
-
- private static $VALUE_KEY_PREFIX = 'WANCache:v:';
- private static $INTERIM_KEY_PREFIX = 'WANCache:i:';
- private static $TIME_KEY_PREFIX = 'WANCache:t:';
- private static $MUTEX_KEY_PREFIX = 'WANCache:m:';
- private static $COOLOFF_KEY_PREFIX = 'WANCache:c:';
-
- private static $PURGE_VAL_PREFIX = 'PURGED:';
-
- /**
- * @param array $params
- * - cache : BagOStuff object for a persistent cache
- * - logger : LoggerInterface object
- * - stats : StatsdDataFactoryInterface object
- * - asyncHandler : A function that takes a callback and runs it later. If supplied,
- * whenever a preemptive refresh would be triggered in getWithSetCallback(), the
- * current cache value is still used instead. However, the async-handler function
- * receives a WAN cache callback that, when run, will execute the value generation
- * callback supplied by the getWithSetCallback() caller. The result will be saved
- * as normal. The handler is expected to call the WAN cache callback at an opportune
- * time (e.g. HTTP post-send), though generally within a few 100ms. [optional]
- * - region: the current physical region. This is required when using mcrouter as the
- * backing store proxy. [optional]
- * - cluster: name of the cache cluster used by this WAN cache. The name must be the
- * same in all datacenters; the ("region","cluster") tuple is what distinguishes
- * the counterpart cache clusters among all the datacenter. The contents of
- * https://github.com/facebook/mcrouter/wiki/Config-Files give background on this.
- * This is required when using mcrouter as the backing store proxy. [optional]
- * - mcrouterAware: set as true if mcrouter is the backing store proxy and mcrouter
- * is configured to interpret /<region>/<cluster>/ key prefixes as routes. This
- * requires that "region" and "cluster" are both set above. [optional]
- * - epoch: lowest UNIX timestamp a value/tombstone must have to be valid. [optional]
- * - secret: stable secret used for hashing long strings into key components. [optional]
- */
- public function __construct( array $params ) {
- $this->cache = $params['cache'];
- $this->region = $params['region'] ?? 'main';
- $this->cluster = $params['cluster'] ?? 'wan-main';
- $this->mcrouterAware = !empty( $params['mcrouterAware'] );
- $this->epoch = $params['epoch'] ?? 0;
- $this->secret = $params['secret'] ?? (string)$this->epoch;
-
- $this->setLogger( $params['logger'] ?? new NullLogger() );
- $this->stats = $params['stats'] ?? new NullStatsdDataFactory();
- $this->asyncHandler = $params['asyncHandler'] ?? null;
- }
-
- /**
- * @param LoggerInterface $logger
- */
- public function setLogger( LoggerInterface $logger ) {
- $this->logger = $logger;
- }
-
- /**
- * Get an instance that wraps EmptyBagOStuff
- *
- * @return WANObjectCache
- */
- public static function newEmpty() {
- return new static( [ 'cache' => new EmptyBagOStuff() ] );
- }
-
- /**
- * Fetch the value of a key from cache
- *
- * If supplied, $curTTL is set to the remaining TTL (current time left):
- * - a) INF; if $key exists, has no TTL, and is not invalidated by $checkKeys
- * - b) float (>=0); if $key exists, has a TTL, and is not invalidated by $checkKeys
- * - c) float (<0); if $key is tombstoned, stale, or existing but invalidated by $checkKeys
- * - d) null; if $key does not exist and is not tombstoned
- *
- * If a key is tombstoned, $curTTL will reflect the time since delete().
- *
- * The timestamp of $key will be checked against the last-purge timestamp
- * of each of $checkKeys. Those $checkKeys not in cache will have the last-purge
- * initialized to the current timestamp. If any of $checkKeys have a timestamp
- * greater than that of $key, then $curTTL will reflect how long ago $key
- * became invalid. Callers can use $curTTL to know when the value is stale.
- * The $checkKeys parameter allow mass invalidations by updating a single key:
- * - a) Each "check" key represents "last purged" of some source data
- * - b) Callers pass in relevant "check" keys as $checkKeys in get()
- * - c) When the source data that "check" keys represent changes,
- * the touchCheckKey() method is called on them
- *
- * Source data entities might exists in a DB that uses snapshot isolation
- * (e.g. the default REPEATABLE-READ in innoDB). Even for mutable data, that
- * isolation can largely be maintained by doing the following:
- * - a) Calling delete() on entity change *and* creation, before DB commit
- * - b) Keeping transaction duration shorter than the delete() hold-off TTL
- * - c) Disabling interim key caching via useInterimHoldOffCaching() before get() calls
- *
- * However, pre-snapshot values might still be seen if an update was made
- * in a remote datacenter but the purge from delete() didn't relay yet.
- *
- * Consider using getWithSetCallback() instead of get() and set() cycles.
- * That method has cache slam avoiding features for hot/expensive keys.
- *
- * Pass $info as WANObjectCache::PASS_BY_REF to transform it into a cache key metadata map.
- * This map includes the following metadata:
- * - asOf: UNIX timestamp of the value or null if the key is nonexistant
- * - tombAsOf: UNIX timestamp of the tombstone or null if the key is not tombstoned
- * - lastCKPurge: UNIX timestamp of the highest check key or null if none provided
- * - version: cached value version number or null if the key is nonexistant
- *
- * Otherwise, $info will transform into the cached value timestamp.
- *
- * @param string $key Cache key made from makeKey() or makeGlobalKey()
- * @param mixed|null &$curTTL Approximate TTL left on the key if present/tombstoned [returned]
- * @param string[] $checkKeys The "check" keys used to validate the value
- * @param mixed|null &$info Key info if WANObjectCache::PASS_BY_REF [returned]
- * @return mixed Value of cache key or false on failure
- */
- final public function get(
- $key, &$curTTL = null, array $checkKeys = [], &$info = null
- ) {
- $curTTLs = self::PASS_BY_REF;
- $infoByKey = self::PASS_BY_REF;
- $values = $this->getMulti( [ $key ], $curTTLs, $checkKeys, $infoByKey );
- $curTTL = $curTTLs[$key] ?? null;
- if ( $info === self::PASS_BY_REF ) {
- $info = [
- 'asOf' => $infoByKey[$key]['asOf'] ?? null,
- 'tombAsOf' => $infoByKey[$key]['tombAsOf'] ?? null,
- 'lastCKPurge' => $infoByKey[$key]['lastCKPurge'] ?? null,
- 'version' => $infoByKey[$key]['version'] ?? null
- ];
- } else {
- $info = $infoByKey[$key]['asOf'] ?? null; // b/c
- }
-
- return $values[$key] ?? false;
- }
-
- /**
- * Fetch the value of several keys from cache
- *
- * Pass $info as WANObjectCache::PASS_BY_REF to transform it into a map of cache keys
- * to cache key metadata maps, each having the same style as those of WANObjectCache::get().
- * All the cache keys listed in $keys will have an entry.
- *
- * Othwerwise, $info will transform into a map of (cache key => cached value timestamp).
- * Only the cache keys listed in $keys that exists or are tombstoned will have an entry.
- *
- * $checkKeys holds the "check" keys used to validate values of applicable keys. The integer
- * indexes hold "check" keys that apply to all of $keys while the string indexes hold "check"
- * keys that only apply to the cache key with that name.
- *
- * @see WANObjectCache::get()
- *
- * @param string[] $keys List of cache keys made from makeKey() or makeGlobalKey()
- * @param mixed|null &$curTTLs Map of (key => TTL left) for existing/tombstoned keys [returned]
- * @param string[]|string[][] $checkKeys Map of (integer or cache key => "check" key(s))
- * @param mixed|null &$info Map of (key => info) if WANObjectCache::PASS_BY_REF [returned]
- * @return mixed[] Map of (key => value) for existing values; order of $keys is preserved
- */
- final public function getMulti(
- array $keys,
- &$curTTLs = [],
- array $checkKeys = [],
- &$info = null
- ) {
- $result = [];
- $curTTLs = [];
- $infoByKey = [];
-
- $vPrefixLen = strlen( self::$VALUE_KEY_PREFIX );
- $valueKeys = self::prefixCacheKeys( $keys, self::$VALUE_KEY_PREFIX );
-
- $checkKeysForAll = [];
- $checkKeysByKey = [];
- $checkKeysFlat = [];
- foreach ( $checkKeys as $i => $checkKeyGroup ) {
- $prefixed = self::prefixCacheKeys( (array)$checkKeyGroup, self::$TIME_KEY_PREFIX );
- $checkKeysFlat = array_merge( $checkKeysFlat, $prefixed );
- // Are these check keys for a specific cache key, or for all keys being fetched?
- if ( is_int( $i ) ) {
- $checkKeysForAll = array_merge( $checkKeysForAll, $prefixed );
- } else {
- $checkKeysByKey[$i] = $prefixed;
- }
- }
-
- // Fetch all of the raw values
- $keysGet = array_merge( $valueKeys, $checkKeysFlat );
- if ( $this->warmupCache ) {
- $wrappedValues = array_intersect_key( $this->warmupCache, array_flip( $keysGet ) );
- $keysGet = array_diff( $keysGet, array_keys( $wrappedValues ) ); // keys left to fetch
- $this->warmupKeyMisses += count( $keysGet );
- } else {
- $wrappedValues = [];
- }
- if ( $keysGet ) {
- $wrappedValues += $this->cache->getMulti( $keysGet );
- }
- // Time used to compare/init "check" keys (derived after getMulti() to be pessimistic)
- $now = $this->getCurrentTime();
-
- // Collect timestamps from all "check" keys
- $purgeValuesForAll = $this->processCheckKeys( $checkKeysForAll, $wrappedValues, $now );
- $purgeValuesByKey = [];
- foreach ( $checkKeysByKey as $cacheKey => $checks ) {
- $purgeValuesByKey[$cacheKey] =
- $this->processCheckKeys( $checks, $wrappedValues, $now );
- }
-
- // Get the main cache value for each key and validate them
- foreach ( $valueKeys as $vKey ) {
- $key = substr( $vKey, $vPrefixLen ); // unprefix
- list( $value, $keyInfo ) = $this->unwrap( $wrappedValues[$vKey] ?? false, $now );
- // Force dependent keys to be seen as stale for a while after purging
- // to reduce race conditions involving stale data getting cached
- $purgeValues = $purgeValuesForAll;
- if ( isset( $purgeValuesByKey[$key] ) ) {
- $purgeValues = array_merge( $purgeValues, $purgeValuesByKey[$key] );
- }
-
- $lastCKPurge = null; // timestamp of the highest check key
- foreach ( $purgeValues as $purge ) {
- $lastCKPurge = max( $purge[self::$PURGE_TIME], $lastCKPurge );
- $safeTimestamp = $purge[self::$PURGE_TIME] + $purge[self::$PURGE_HOLDOFF];
- if ( $value !== false && $safeTimestamp >= $keyInfo['asOf'] ) {
- // How long ago this value was invalidated by *this* check key
- $ago = min( $purge[self::$PURGE_TIME] - $now, self::$TINY_NEGATIVE );
- // How long ago this value was invalidated by *any* known check key
- $keyInfo['curTTL'] = min( $keyInfo['curTTL'], $ago );
- }
- }
- $keyInfo[ 'lastCKPurge'] = $lastCKPurge;
-
- if ( $value !== false ) {
- $result[$key] = $value;
- }
- if ( $keyInfo['curTTL'] !== null ) {
- $curTTLs[$key] = $keyInfo['curTTL'];
- }
-
- $infoByKey[$key] = ( $info === self::PASS_BY_REF )
- ? $keyInfo
- : $keyInfo['asOf']; // b/c
- }
-
- $info = $infoByKey;
-
- return $result;
- }
-
- /**
- * @since 1.27
- * @param string[] $timeKeys List of prefixed time check keys
- * @param mixed[] $wrappedValues
- * @param float $now
- * @return array[] List of purge value arrays
- */
- private function processCheckKeys( array $timeKeys, array $wrappedValues, $now ) {
- $purgeValues = [];
- foreach ( $timeKeys as $timeKey ) {
- $purge = isset( $wrappedValues[$timeKey] )
- ? $this->parsePurgeValue( $wrappedValues[$timeKey] )
- : false;
- if ( $purge === false ) {
- // Key is not set or malformed; regenerate
- $newVal = $this->makePurgeValue( $now, self::HOLDOFF_TTL );
- $this->cache->add( $timeKey, $newVal, self::$CHECK_KEY_TTL );
- $purge = $this->parsePurgeValue( $newVal );
- }
- $purgeValues[] = $purge;
- }
- return $purgeValues;
- }
-
- /**
- * Set the value of a key in cache
- *
- * Simply calling this method when source data changes is not valid because
- * the changes do not replicate to the other WAN sites. In that case, delete()
- * should be used instead. This method is intended for use on cache misses.
- *
- * If the data was read from a snapshot-isolated transactions (e.g. the default
- * REPEATABLE-READ in innoDB), use 'since' to avoid the following race condition:
- * - a) T1 starts
- * - b) T2 updates a row, calls delete(), and commits
- * - c) The HOLDOFF_TTL passes, expiring the delete() tombstone
- * - d) T1 reads the row and calls set() due to a cache miss
- * - e) Stale value is stuck in cache
- *
- * Setting 'lag' and 'since' help avoids keys getting stuck in stale states.
- *
- * Be aware that this does not update the process cache for getWithSetCallback()
- * callers. Keys accessed via that method are not generally meant to also be set
- * using this primitive method.
- *
- * Do not use this method on versioned keys accessed via getWithSetCallback().
- *
- * Example usage:
- * @code
- * $dbr = wfGetDB( DB_REPLICA );
- * $setOpts = Database::getCacheSetOptions( $dbr );
- * // Fetch the row from the DB
- * $row = $dbr->selectRow( ... );
- * $key = $cache->makeKey( 'building', $buildingId );
- * $cache->set( $key, $row, $cache::TTL_DAY, $setOpts );
- * @endcode
- *
- * @param string $key Cache key
- * @param mixed $value
- * @param int $ttl Seconds to live. Special values are:
- * - WANObjectCache::TTL_INDEFINITE: Cache forever (default)
- * - WANObjectCache::TTL_UNCACHEABLE: Do not cache (if the key exists, it is not deleted)
- * @param array $opts Options map:
- * - lag: Seconds of replica DB lag. Typically, this is either the replica DB lag
- * before the data was read or, if applicable, the replica DB lag before
- * the snapshot-isolated transaction the data was read from started.
- * Use false to indicate that replication is not running.
- * Default: 0 seconds
- * - since: UNIX timestamp of the data in $value. Typically, this is either
- * the current time the data was read or (if applicable) the time when
- * the snapshot-isolated transaction the data was read from started.
- * Default: 0 seconds
- * - pending: Whether this data is possibly from an uncommitted write transaction.
- * Generally, other threads should not see values from the future and
- * they certainly should not see ones that ended up getting rolled back.
- * Default: false
- * - lockTSE: If excessive replication/snapshot lag is detected, then store the value
- * with this TTL and flag it as stale. This is only useful if the reads for this key
- * use getWithSetCallback() with "lockTSE" set. Note that if "staleTTL" is set
- * then it will still add on to this TTL in the excessive lag scenario.
- * Default: WANObjectCache::TSE_NONE
- * - staleTTL: Seconds to keep the key around if it is stale. The get()/getMulti()
- * methods return such stale values with a $curTTL of 0, and getWithSetCallback()
- * will call the regeneration callback in such cases, passing in the old value
- * and its as-of time to the callback. This is useful if adaptiveTTL() is used
- * on the old value's as-of time when it is verified as still being correct.
- * Default: WANObjectCache::STALE_TTL_NONE
- * - creating: Optimize for the case where the key does not already exist.
- * Default: false
- * - version: Integer version number signifiying the format of the value.
- * Default: null
- * - walltime: How long the value took to generate in seconds. Default: 0.0
- * @note Options added in 1.28: staleTTL
- * @note Options added in 1.33: creating
- * @note Options added in 1.34: version, walltime
- * @return bool Success
- */
- final public function set( $key, $value, $ttl = self::TTL_INDEFINITE, array $opts = [] ) {
- $now = $this->getCurrentTime();
- $lag = $opts['lag'] ?? 0;
- $age = isset( $opts['since'] ) ? max( 0, $now - $opts['since'] ) : 0;
- $pending = $opts['pending'] ?? false;
- $lockTSE = $opts['lockTSE'] ?? self::TSE_NONE;
- $staleTTL = $opts['staleTTL'] ?? self::STALE_TTL_NONE;
- $creating = $opts['creating'] ?? false;
- $version = $opts['version'] ?? null;
- $walltime = $opts['walltime'] ?? 0.0;
-
- if ( $ttl < 0 ) {
- return true;
- }
-
- // Do not cache potentially uncommitted data as it might get rolled back
- if ( $pending ) {
- $this->logger->info(
- 'Rejected set() for {cachekey} due to pending writes.',
- [ 'cachekey' => $key ]
- );
-
- return true; // no-op the write for being unsafe
- }
-
- $logicalTTL = null; // logical TTL override
- // Check if there's a risk of writing stale data after the purge tombstone expired
- if ( $lag === false || ( $lag + $age ) > self::MAX_READ_LAG ) {
- // Case A: any long-running transaction
- if ( $age > self::MAX_READ_LAG ) {
- if ( $lockTSE >= 0 ) {
- // Store value as *almost* stale to avoid cache and mutex stampedes
- $logicalTTL = self::TTL_SECOND;
- $this->logger->info(
- 'Lowered set() TTL for {cachekey} due to snapshot lag.',
- [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
- );
- } else {
- $this->logger->info(
- 'Rejected set() for {cachekey} due to snapshot lag.',
- [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
- );
-
- return true; // no-op the write for being unsafe
- }
- // Case B: high replication lag; lower TTL instead of ignoring all set()s
- } elseif ( $lag === false || $lag > self::MAX_READ_LAG ) {
- if ( $lockTSE >= 0 ) {
- $logicalTTL = min( $ttl ?: INF, self::TTL_LAGGED );
- } else {
- $ttl = min( $ttl ?: INF, self::TTL_LAGGED );
- }
- $this->logger->warning(
- 'Lowered set() TTL for {cachekey} due to replication lag.',
- [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
- );
- // Case C: medium length request with medium replication lag
- } elseif ( $lockTSE >= 0 ) {
- // Store value as *almost* stale to avoid cache and mutex stampedes
- $logicalTTL = self::TTL_SECOND;
- $this->logger->info(
- 'Lowered set() TTL for {cachekey} due to high read lag.',
- [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
- );
- } else {
- $this->logger->info(
- 'Rejected set() for {cachekey} due to high read lag.',
- [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
- );
-
- return true; // no-op the write for being unsafe
- }
- }
-
- // Wrap that value with time/TTL/version metadata
- $wrapped = $this->wrap( $value, $logicalTTL ?: $ttl, $version, $now, $walltime );
- $storeTTL = $ttl + $staleTTL;
-
- if ( $creating ) {
- $ok = $this->cache->add( self::$VALUE_KEY_PREFIX . $key, $wrapped, $storeTTL );
- } else {
- $ok = $this->cache->merge(
- self::$VALUE_KEY_PREFIX . $key,
- function ( $cache, $key, $cWrapped ) use ( $wrapped ) {
- // A string value means that it is a tombstone; do nothing in that case
- return ( is_string( $cWrapped ) ) ? false : $wrapped;
- },
- $storeTTL,
- 1 // 1 attempt
- );
- }
-
- return $ok;
- }
-
- /**
- * Purge a key from all datacenters
- *
- * This should only be called when the underlying data (being cached)
- * changes in a significant way. This deletes the key and starts a hold-off
- * period where the key cannot be written to for a few seconds (HOLDOFF_TTL).
- * This is done to avoid the following race condition:
- * - a) Some DB data changes and delete() is called on a corresponding key
- * - b) A request refills the key with a stale value from a lagged DB
- * - c) The stale value is stuck there until the key is expired/evicted
- *
- * This is implemented by storing a special "tombstone" value at the cache
- * key that this class recognizes; get() calls will return false for the key
- * and any set() calls will refuse to replace tombstone values at the key.
- * For this to always avoid stale value writes, the following must hold:
- * - a) Replication lag is bounded to being less than HOLDOFF_TTL; or
- * - b) If lag is higher, the DB will have gone into read-only mode already
- *
- * Note that set() can also be lag-aware and lower the TTL if it's high.
- *
- * Be aware that this does not clear the process cache. Even if it did, callbacks
- * used by getWithSetCallback() might still return stale data in the case of either
- * uncommitted or not-yet-replicated changes (callback generally use replica DBs).
- *
- * When using potentially long-running ACID transactions, a good pattern is
- * to use a pre-commit hook to issue the delete. This means that immediately
- * after commit, callers will see the tombstone in cache upon purge relay.
- * It also avoids the following race condition:
- * - a) T1 begins, changes a row, and calls delete()
- * - b) The HOLDOFF_TTL passes, expiring the delete() tombstone
- * - c) T2 starts, reads the row and calls set() due to a cache miss
- * - d) T1 finally commits
- * - e) Stale value is stuck in cache
- *
- * Example usage:
- * @code
- * $dbw->startAtomic( __METHOD__ ); // start of request
- * ... <execute some stuff> ...
- * // Update the row in the DB
- * $dbw->update( ... );
- * $key = $cache->makeKey( 'homes', $homeId );
- * // Purge the corresponding cache entry just before committing
- * $dbw->onTransactionPreCommitOrIdle( function() use ( $cache, $key ) {
- * $cache->delete( $key );
- * } );
- * ... <execute some stuff> ...
- * $dbw->endAtomic( __METHOD__ ); // end of request
- * @endcode
- *
- * The $ttl parameter can be used when purging values that have not actually changed
- * recently. For example, a cleanup script to purge cache entries does not really need
- * a hold-off period, so it can use HOLDOFF_TTL_NONE. Likewise for user-requested purge.
- * Note that $ttl limits the effective range of 'lockTSE' for getWithSetCallback().
- *
- * If called twice on the same key, then the last hold-off TTL takes precedence. For
- * idempotence, the $ttl should not vary for different delete() calls on the same key.
- *
- * @param string $key Cache key
- * @param int $ttl Tombstone TTL; Default: WANObjectCache::HOLDOFF_TTL
- * @return bool True if the item was purged or not found, false on failure
- */
- final public function delete( $key, $ttl = self::HOLDOFF_TTL ) {
- if ( $ttl <= 0 ) {
- // Publish the purge to all datacenters
- $ok = $this->relayDelete( self::$VALUE_KEY_PREFIX . $key );
- } else {
- // Publish the purge to all datacenters
- $ok = $this->relayPurge( self::$VALUE_KEY_PREFIX . $key, $ttl, self::HOLDOFF_TTL_NONE );
- }
-
- $kClass = $this->determineKeyClassForStats( $key );
- $this->stats->increment( "wanobjectcache.$kClass.delete." . ( $ok ? 'ok' : 'error' ) );
-
- return $ok;
- }
-
- /**
- * Fetch the value of a timestamp "check" key
- *
- * The key will be *initialized* to the current time if not set,
- * so only call this method if this behavior is actually desired
- *
- * The timestamp can be used to check whether a cached value is valid.
- * Callers should not assume that this returns the same timestamp in
- * all datacenters due to relay delays.
- *
- * The level of staleness can roughly be estimated from this key, but
- * if the key was evicted from cache, such calculations may show the
- * time since expiry as ~0 seconds.
- *
- * Note that "check" keys won't collide with other regular keys.
- *
- * @param string $key
- * @return float UNIX timestamp
- */
- final public function getCheckKeyTime( $key ) {
- return $this->getMultiCheckKeyTime( [ $key ] )[$key];
- }
-
- /**
- * Fetch the values of each timestamp "check" key
- *
- * This works like getCheckKeyTime() except it takes a list of keys
- * and returns a map of timestamps instead of just that of one key
- *
- * This might be useful if both:
- * - a) a class of entities each depend on hundreds of other entities
- * - b) these other entities are depended upon by millions of entities
- *
- * The later entities can each use a "check" key to invalidate their dependee entities.
- * However, it is expensive for the former entities to verify against all of the relevant
- * "check" keys during each getWithSetCallback() call. A less expensive approach is to do
- * these verifications only after a "time-till-verify" (TTV) has passed. This is a middle
- * ground between using blind TTLs and using constant verification. The adaptiveTTL() method
- * can be used to dynamically adjust the TTV. Also, the initial TTV can make use of the
- * last-modified times of the dependant entities (either from the DB or the "check" keys).
- *
- * Example usage:
- * @code
- * $value = $cache->getWithSetCallback(
- * $cache->makeGlobalKey( 'wikibase-item', $id ),
- * self::INITIAL_TTV, // initial time-till-verify
- * function ( $oldValue, &$ttv, &$setOpts, $oldAsOf ) use ( $checkKeys, $cache ) {
- * $now = microtime( true );
- * // Use $oldValue if it passes max ultimate age and "check" key comparisons
- * if ( $oldValue &&
- * $oldAsOf > max( $cache->getMultiCheckKeyTime( $checkKeys ) ) &&
- * ( $now - $oldValue['ctime'] ) <= self::MAX_CACHE_AGE
- * ) {
- * // Increase time-till-verify by 50% of last time to reduce overhead
- * $ttv = $cache->adaptiveTTL( $oldAsOf, self::MAX_TTV, self::MIN_TTV, 1.5 );
- * // Unlike $oldAsOf, "ctime" is the ultimate age of the cached data
- * return $oldValue;
- * }
- *
- * $mtimes = []; // dependency last-modified times; passed by reference
- * $value = [ 'data' => $this->fetchEntityData( $mtimes ), 'ctime' => $now ];
- * // Guess time-till-change among the dependencies, e.g. 1/(total change rate)
- * $ttc = 1 / array_sum( array_map(
- * function ( $mtime ) use ( $now ) {
- * return 1 / ( $mtime ? ( $now - $mtime ) : 900 );
- * },
- * $mtimes
- * ) );
- * // The time-to-verify should not be overly pessimistic nor optimistic
- * $ttv = min( max( $ttc, self::MIN_TTV ), self::MAX_TTV );
- *
- * return $value;
- * },
- * [ 'staleTTL' => $cache::TTL_DAY ] // keep around to verify and re-save
- * );
- * @endcode
- *
- * @see WANObjectCache::getCheckKeyTime()
- * @see WANObjectCache::getWithSetCallback()
- *
- * @param string[] $keys
- * @return float[] Map of (key => UNIX timestamp)
- * @since 1.31
- */
- final public function getMultiCheckKeyTime( array $keys ) {
- $rawKeys = [];
- foreach ( $keys as $key ) {
- $rawKeys[$key] = self::$TIME_KEY_PREFIX . $key;
- }
-
- $rawValues = $this->cache->getMulti( $rawKeys );
- $rawValues += array_fill_keys( $rawKeys, false );
-
- $times = [];
- foreach ( $rawKeys as $key => $rawKey ) {
- $purge = $this->parsePurgeValue( $rawValues[$rawKey] );
- if ( $purge !== false ) {
- $time = $purge[self::$PURGE_TIME];
- } else {
- // Casting assures identical floats for the next getCheckKeyTime() calls
- $now = (string)$this->getCurrentTime();
- $this->cache->add(
- $rawKey,
- $this->makePurgeValue( $now, self::HOLDOFF_TTL ),
- self::$CHECK_KEY_TTL
- );
- $time = (float)$now;
- }
-
- $times[$key] = $time;
- }
-
- return $times;
- }
-
- /**
- * Purge a "check" key from all datacenters, invalidating keys that use it
- *
- * This should only be called when the underlying data (being cached)
- * changes in a significant way, and it is impractical to call delete()
- * on all keys that should be changed. When get() is called on those
- * keys, the relevant "check" keys must be supplied for this to work.
- *
- * The "check" key essentially represents a last-modified time of an entity.
- * When the key is touched, the timestamp will be updated to the current time.
- * Keys using the "check" key via get(), getMulti(), or getWithSetCallback() will
- * be invalidated. This approach is useful if many keys depend on a single entity.
- *
- * The timestamp of the "check" key is treated as being HOLDOFF_TTL seconds in the
- * future by get*() methods in order to avoid race conditions where keys are updated
- * with stale values (e.g. from a lagged replica DB). A high TTL is set on the "check"
- * key, making it possible to know the timestamp of the last change to the corresponding
- * entities in most cases. This might use more cache space than resetCheckKey().
- *
- * When a few important keys get a large number of hits, a high cache time is usually
- * desired as well as "lockTSE" logic. The resetCheckKey() method is less appropriate
- * in such cases since the "time since expiry" cannot be inferred, causing any get()
- * after the reset to treat the key as being "hot", resulting in more stale value usage.
- *
- * Note that "check" keys won't collide with other regular keys.
- *
- * @see WANObjectCache::get()
- * @see WANObjectCache::getWithSetCallback()
- * @see WANObjectCache::resetCheckKey()
- *
- * @param string $key Cache key
- * @param int $holdoff HOLDOFF_TTL or HOLDOFF_TTL_NONE constant
- * @return bool True if the item was purged or not found, false on failure
- */
- final public function touchCheckKey( $key, $holdoff = self::HOLDOFF_TTL ) {
- // Publish the purge to all datacenters
- $ok = $this->relayPurge( self::$TIME_KEY_PREFIX . $key, self::$CHECK_KEY_TTL, $holdoff );
-
- $kClass = $this->determineKeyClassForStats( $key );
- $this->stats->increment( "wanobjectcache.$kClass.ck_touch." . ( $ok ? 'ok' : 'error' ) );
-
- return $ok;
- }
-
- /**
- * Delete a "check" key from all datacenters, invalidating keys that use it
- *
- * This is similar to touchCheckKey() in that keys using it via get(), getMulti(),
- * or getWithSetCallback() will be invalidated. The differences are:
- * - a) The "check" key will be deleted from all caches and lazily
- * re-initialized when accessed (rather than set everywhere)
- * - b) Thus, dependent keys will be known to be stale, but not
- * for how long (they are treated as "just" purged), which
- * effects any lockTSE logic in getWithSetCallback()
- * - c) Since "check" keys are initialized only on the server the key hashes
- * to, any temporary ejection of that server will cause the value to be
- * seen as purged as a new server will initialize the "check" key.
- *
- * The advantage here is that the "check" keys, which have high TTLs, will only
- * be created when a get*() method actually uses that key. This is better when
- * a large number of "check" keys are invalided in a short period of time.
- *
- * Note that "check" keys won't collide with other regular keys.
- *
- * @see WANObjectCache::get()
- * @see WANObjectCache::getWithSetCallback()
- * @see WANObjectCache::touchCheckKey()
- *
- * @param string $key Cache key
- * @return bool True if the item was purged or not found, false on failure
- */
- final public function resetCheckKey( $key ) {
- // Publish the purge to all datacenters
- $ok = $this->relayDelete( self::$TIME_KEY_PREFIX . $key );
-
- $kClass = $this->determineKeyClassForStats( $key );
- $this->stats->increment( "wanobjectcache.$kClass.ck_reset." . ( $ok ? 'ok' : 'error' ) );
-
- return $ok;
- }
-
- /**
- * Method to fetch/regenerate cache keys
- *
- * On cache miss, the key will be set to the callback result via set()
- * (unless the callback returns false) and that result will be returned.
- * The arguments supplied to the callback are:
- * - $oldValue : current cache value or false if not present
- * - &$ttl : a reference to the TTL which can be altered
- * - &$setOpts : a reference to options for set() which can be altered
- * - $oldAsOf : generation UNIX timestamp of $oldValue or null if not present (since 1.28)
- *
- * It is strongly recommended to set the 'lag' and 'since' fields to avoid race conditions
- * that can cause stale values to get stuck at keys. Usually, callbacks ignore the current
- * value, but it can be used to maintain "most recent X" values that come from time or
- * sequence based source data, provided that the "as of" id/time is tracked. Note that
- * preemptive regeneration and $checkKeys can result in a non-false current value.
- *
- * Usage of $checkKeys is similar to get() and getMulti(). However, rather than the caller
- * having to inspect a "current time left" variable (e.g. $curTTL, $curTTLs), a cache
- * regeneration will automatically be triggered using the callback.
- *
- * The $ttl argument and "hotTTR" option (in $opts) use time-dependant randomization
- * to avoid stampedes. Keys that are slow to regenerate and either heavily used
- * or subject to explicit (unpredictable) purges, may need additional mechanisms.
- * The simplest way to avoid stampedes for such keys is to use 'lockTSE' (in $opts).
- * If explicit purges are needed, also:
- * - a) Pass $key into $checkKeys
- * - b) Use touchCheckKey( $key ) instead of delete( $key )
- *
- * Example usage (typical key):
- * @code
- * $catInfo = $cache->getWithSetCallback(
- * // Key to store the cached value under
- * $cache->makeKey( 'cat-attributes', $catId ),
- * // Time-to-live (in seconds)
- * $cache::TTL_MINUTE,
- * // Function that derives the new key value
- * function ( $oldValue, &$ttl, array &$setOpts ) {
- * $dbr = wfGetDB( DB_REPLICA );
- * // Account for any snapshot/replica DB lag
- * $setOpts += Database::getCacheSetOptions( $dbr );
- *
- * return $dbr->selectRow( ... );
- * }
- * );
- * @endcode
- *
- * Example usage (key that is expensive and hot):
- * @code
- * $catConfig = $cache->getWithSetCallback(
- * // Key to store the cached value under
- * $cache->makeKey( 'site-cat-config' ),
- * // Time-to-live (in seconds)
- * $cache::TTL_DAY,
- * // Function that derives the new key value
- * function ( $oldValue, &$ttl, array &$setOpts ) {
- * $dbr = wfGetDB( DB_REPLICA );
- * // Account for any snapshot/replica DB lag
- * $setOpts += Database::getCacheSetOptions( $dbr );
- *
- * return CatConfig::newFromRow( $dbr->selectRow( ... ) );
- * },
- * [
- * // Calling touchCheckKey() on this key invalidates the cache
- * 'checkKeys' => [ $cache->makeKey( 'site-cat-config' ) ],
- * // Try to only let one datacenter thread manage cache updates at a time
- * 'lockTSE' => 30,
- * // Avoid querying cache servers multiple times in a web request
- * 'pcTTL' => $cache::TTL_PROC_LONG
- * ]
- * );
- * @endcode
- *
- * Example usage (key with dynamic dependencies):
- * @code
- * $catState = $cache->getWithSetCallback(
- * // Key to store the cached value under
- * $cache->makeKey( 'cat-state', $cat->getId() ),
- * // Time-to-live (seconds)
- * $cache::TTL_HOUR,
- * // Function that derives the new key value
- * function ( $oldValue, &$ttl, array &$setOpts ) {
- * // Determine new value from the DB
- * $dbr = wfGetDB( DB_REPLICA );
- * // Account for any snapshot/replica DB lag
- * $setOpts += Database::getCacheSetOptions( $dbr );
- *
- * return CatState::newFromResults( $dbr->select( ... ) );
- * },
- * [
- * // The "check" keys that represent things the value depends on;
- * // Calling touchCheckKey() on any of them invalidates the cache
- * 'checkKeys' => [
- * $cache->makeKey( 'sustenance-bowls', $cat->getRoomId() ),
- * $cache->makeKey( 'people-present', $cat->getHouseId() ),
- * $cache->makeKey( 'cat-laws', $cat->getCityId() ),
- * ]
- * ]
- * );
- * @endcode
- *
- * Example usage (key that is expensive with too many DB dependencies for "check keys"):
- * @code
- * $catToys = $cache->getWithSetCallback(
- * // Key to store the cached value under
- * $cache->makeKey( 'cat-toys', $catId ),
- * // Time-to-live (seconds)
- * $cache::TTL_HOUR,
- * // Function that derives the new key value
- * function ( $oldValue, &$ttl, array &$setOpts ) {
- * // Determine new value from the DB
- * $dbr = wfGetDB( DB_REPLICA );
- * // Account for any snapshot/replica DB lag
- * $setOpts += Database::getCacheSetOptions( $dbr );
- *
- * return CatToys::newFromResults( $dbr->select( ... ) );
- * },
- * [
- * // Get the highest timestamp of any of the cat's toys
- * 'touchedCallback' => function ( $value ) use ( $catId ) {
- * $dbr = wfGetDB( DB_REPLICA );
- * $ts = $dbr->selectField( 'cat_toys', 'MAX(ct_touched)', ... );
- *
- * return wfTimestampOrNull( TS_UNIX, $ts );
- * },
- * // Avoid DB queries for repeated access
- * 'pcTTL' => $cache::TTL_PROC_SHORT
- * ]
- * );
- * @endcode
- *
- * Example usage (hot key holding most recent 100 events):
- * @code
- * $lastCatActions = $cache->getWithSetCallback(
- * // Key to store the cached value under
- * $cache->makeKey( 'cat-last-actions', 100 ),
- * // Time-to-live (in seconds)
- * 10,
- * // Function that derives the new key value
- * function ( $oldValue, &$ttl, array &$setOpts ) {
- * $dbr = wfGetDB( DB_REPLICA );
- * // Account for any snapshot/replica DB lag
- * $setOpts += Database::getCacheSetOptions( $dbr );
- *
- * // Start off with the last cached list
- * $list = $oldValue ?: [];
- * // Fetch the last 100 relevant rows in descending order;
- * // only fetch rows newer than $list[0] to reduce scanning
- * $rows = iterator_to_array( $dbr->select( ... ) );
- * // Merge them and get the new "last 100" rows
- * return array_slice( array_merge( $new, $list ), 0, 100 );
- * },
- * [
- * // Try to only let one datacenter thread manage cache updates at a time
- * 'lockTSE' => 30,
- * // Use a magic value when no cache value is ready rather than stampeding
- * 'busyValue' => 'computing'
- * ]
- * );
- * @endcode
- *
- * Example usage (key holding an LRU subkey:value map; this can avoid flooding cache with
- * keys for an unlimited set of (constraint,situation) pairs, thereby avoiding elevated
- * cache evictions and wasted memory):
- * @code
- * $catSituationTolerabilityCache = $this->cache->getWithSetCallback(
- * // Group by constraint ID/hash, cat family ID/hash, or something else useful
- * $this->cache->makeKey( 'cat-situation-tolerability-checks', $groupKey ),
- * WANObjectCache::TTL_DAY, // rarely used groups should fade away
- * // The $scenarioKey format is $constraintId:<ID/hash of $situation>
- * function ( $cacheMap ) use ( $scenarioKey, $constraintId, $situation ) {
- * $lruCache = MapCacheLRU::newFromArray( $cacheMap ?: [], self::CACHE_SIZE );
- * $result = $lruCache->get( $scenarioKey ); // triggers LRU bump if present
- * if ( $result === null || $this->isScenarioResultExpired( $result ) ) {
- * $result = $this->checkScenarioTolerability( $constraintId, $situation );
- * $lruCache->set( $scenarioKey, $result, 3 / 8 );
- * }
- * // Save the new LRU cache map and reset the map's TTL
- * return $lruCache->toArray();
- * },
- * [
- * // Once map is > 1 sec old, consider refreshing
- * 'ageNew' => 1,
- * // Update within 5 seconds after "ageNew" given a 1hz cache check rate
- * 'hotTTR' => 5,
- * // Avoid querying cache servers multiple times in a request; this also means
- * // that a request can only alter the value of any given constraint key once
- * 'pcTTL' => WANObjectCache::TTL_PROC_LONG
- * ]
- * );
- * $tolerability = isset( $catSituationTolerabilityCache[$scenarioKey] )
- * ? $catSituationTolerabilityCache[$scenarioKey]
- * : $this->checkScenarioTolerability( $constraintId, $situation );
- * @endcode
- *
- * @see WANObjectCache::get()
- * @see WANObjectCache::set()
- *
- * @param string $key Cache key made from makeKey() or makeGlobalKey()
- * @param int $ttl Seconds to live for key updates. Special values are:
- * - WANObjectCache::TTL_INDEFINITE: Cache forever (subject to LRU-style evictions)
- * - WANObjectCache::TTL_UNCACHEABLE: Do not cache (if the key exists, it is not deleted)
- * @param callable $callback Value generation function
- * @param array $opts Options map:
- * - checkKeys: List of "check" keys. The key at $key will be seen as stale when either
- * touchCheckKey() or resetCheckKey() is called on any of the keys in this list. This
- * is useful if thousands or millions of keys depend on the same entity. The entity can
- * simply have its "check" key updated whenever the entity is modified.
- * Default: [].
- * - graceTTL: If the key is invalidated (by "checkKeys"/"touchedCallback") less than this
- * many seconds ago, consider reusing the stale value. The odds of a refresh becomes
- * more likely over time, becoming certain once the grace period is reached. This can
- * reduce traffic spikes when millions of keys are compared to the same "check" key and
- * touchCheckKey() or resetCheckKey() is called on that "check" key. This option is not
- * useful for avoiding traffic spikes in the case of the key simply expiring on account
- * of its TTL (use "lowTTL" instead).
- * Default: WANObjectCache::GRACE_TTL_NONE.
- * - lockTSE: If the key is tombstoned or invalidated (by "checkKeys"/"touchedCallback")
- * less than this many seconds ago, try to have a single thread handle cache regeneration
- * at any given time. Other threads will use stale values if possible. If, on miss,
- * the time since expiration is low, the assumption is that the key is hot and that a
- * stampede is worth avoiding. Note that if the key falls out of cache then concurrent
- * threads will all run the callback on cache miss until the value is saved in cache.
- * The only stampede protection in that case is from duplicate cache sets when the
- * callback takes longer than WANObjectCache::SET_DELAY_HIGH_MS milliseconds; consider
- * using "busyValue" if such stampedes are a problem. Note that the higher "lockTSE" is
- * set, the higher the worst-case staleness of returned values can be. Also note that
- * this option does not by itself handle the case of the key simply expiring on account
- * of its TTL, so make sure that "lowTTL" is not disabled when using this option. Avoid
- * combining this option with delete() as it can always cause a stampede due to their
- * being no stale value available until after a thread completes the callback.
- * Use WANObjectCache::TSE_NONE to disable this logic.
- * Default: WANObjectCache::TSE_NONE.
- * - busyValue: Specify a placeholder value to use when no value exists and another thread
- * is currently regenerating it. This assures that cache stampedes cannot happen if the
- * value falls out of cache. This also mitigates stampedes when value regeneration
- * becomes very slow (greater than $ttl/"lowTTL"). If this is a closure, then it will
- * be invoked to get the placeholder when needed.
- * Default: null.
- * - pcTTL: Process cache the value in this PHP instance for this many seconds. This avoids
- * network I/O when a key is read several times. This will not cache when the callback
- * returns false, however. Note that any purges will not be seen while process cached;
- * since the callback should use replica DBs and they may be lagged or have snapshot
- * isolation anyway, this should not typically matter.
- * Default: WANObjectCache::TTL_UNCACHEABLE.
- * - pcGroup: Process cache group to use instead of the primary one. If set, this must be
- * of the format ALPHANUMERIC_NAME:MAX_KEY_SIZE, e.g. "mydata:10". Use this for storing
- * large values, small yet numerous values, or some values with a high cost of eviction.
- * It is generally preferable to use a class constant when setting this value.
- * This has no effect unless pcTTL is used.
- * Default: WANObjectCache::PC_PRIMARY.
- * - version: Integer version number. This lets callers make breaking changes to the format
- * of cached values without causing problems for sites that use non-instantaneous code
- * deployments. Old and new code will recognize incompatible versions and purges from
- * both old and new code will been seen by each other. When this method encounters an
- * incompatibly versioned value at the provided key, a "variant key" will be used for
- * reading from and saving to cache. The variant key is specific to the key and version
- * number provided to this method. If the variant key value is older than that of the
- * provided key, or the provided key is non-existant, then the variant key will be seen
- * as non-existant. Therefore, delete() calls invalidate the provided key's variant keys.
- * The "checkKeys" and "touchedCallback" options still apply to variant keys as usual.
- * Avoid storing class objects, as this reduces compatibility (due to serialization).
- * Default: null.
- * - minAsOf: Reject values if they were generated before this UNIX timestamp.
- * This is useful if the source of a key is suspected of having possibly changed
- * recently, and the caller wants any such changes to be reflected.
- * Default: WANObjectCache::MIN_TIMESTAMP_NONE.
- * - hotTTR: Expected time-till-refresh (TTR) in seconds for keys that average ~1 hit per
- * second (e.g. 1Hz). Keys with a hit rate higher than 1Hz will refresh sooner than this
- * TTR and vise versa. Such refreshes won't happen until keys are "ageNew" seconds old.
- * This uses randomization to avoid triggering cache stampedes. The TTR is useful at
- * reducing the impact of missed cache purges, since the effect of a heavily referenced
- * key being stale is worse than that of a rarely referenced key. Unlike simply lowering
- * $ttl, seldomly used keys are largely unaffected by this option, which makes it
- * possible to have a high hit rate for the "long-tail" of less-used keys.
- * Default: WANObjectCache::HOT_TTR.
- * - lowTTL: Consider pre-emptive updates when the current TTL (seconds) of the key is less
- * than this. It becomes more likely over time, becoming certain once the key is expired.
- * This helps avoid cache stampedes that might be triggered due to the key expiring.
- * Default: WANObjectCache::LOW_TTL.
- * - ageNew: Consider popularity refreshes only once a key reaches this age in seconds.
- * Default: WANObjectCache::AGE_NEW.
- * - staleTTL: Seconds to keep the key around if it is stale. This means that on cache
- * miss the callback may get $oldValue/$oldAsOf values for keys that have already been
- * expired for this specified time. This is useful if adaptiveTTL() is used on the old
- * value's as-of time when it is verified as still being correct.
- * Default: WANObjectCache::STALE_TTL_NONE
- * - touchedCallback: A callback that takes the current value and returns a UNIX timestamp
- * indicating the last time a dynamic dependency changed. Null can be returned if there
- * are no relevant dependency changes to check. This can be used to check against things
- * like last-modified times of files or DB timestamp fields. This should generally not be
- * used for small and easily queried values in a DB if the callback itself ends up doing
- * a similarly expensive DB query to check a timestamp. Usages of this option makes the
- * most sense for values that are moderately to highly expensive to regenerate and easy
- * to query for dependency timestamps. The use of "pcTTL" reduces timestamp queries.
- * Default: null.
- * @return mixed Value found or written to the key
- * @note Options added in 1.28: version, busyValue, hotTTR, ageNew, pcGroup, minAsOf
- * @note Options added in 1.31: staleTTL, graceTTL
- * @note Options added in 1.33: touchedCallback
- * @note Callable type hints are not used to avoid class-autoloading
- */
- final public function getWithSetCallback( $key, $ttl, $callback, array $opts = [] ) {
- $version = $opts['version'] ?? null;
- $pcTTL = $opts['pcTTL'] ?? self::TTL_UNCACHEABLE;
- $pCache = ( $pcTTL >= 0 )
- ? $this->getProcessCache( $opts['pcGroup'] ?? self::PC_PRIMARY )
- : null;
-
- // Use the process cache if requested as long as no outer cache callback is running.
- // Nested callback process cache use is not lag-safe with regard to HOLDOFF_TTL since
- // process cached values are more lagged than persistent ones as they are not purged.
- if ( $pCache && $this->callbackDepth == 0 ) {
- $cached = $pCache->get( $this->getProcessCacheKey( $key, $version ), INF, false );
- if ( $cached !== false ) {
- return $cached;
- }
- }
-
- $res = $this->fetchOrRegenerate( $key, $ttl, $callback, $opts );
- list( $value, $valueVersion, $curAsOf ) = $res;
- if ( $valueVersion !== $version ) {
- // Current value has a different version; use the variant key for this version.
- // Regenerate the variant value if it is not newer than the main value at $key
- // so that purges to the main key propagate to the variant value.
- list( $value ) = $this->fetchOrRegenerate(
- $this->makeGlobalKey( 'WANCache-key-variant', md5( $key ), $version ),
- $ttl,
- $callback,
- [ 'version' => null, 'minAsOf' => $curAsOf ] + $opts
- );
- }
-
- // Update the process cache if enabled
- if ( $pCache && $value !== false ) {
- $pCache->set( $this->getProcessCacheKey( $key, $version ), $value );
- }
-
- return $value;
- }
-
- /**
- * Do the actual I/O for getWithSetCallback() when needed
- *
- * @see WANObjectCache::getWithSetCallback()
- *
- * @param string $key
- * @param int $ttl
- * @param callable $callback
- * @param array $opts Options map for getWithSetCallback()
- * @return array Ordered list of the following:
- * - Cached or regenerated value
- * - Cached or regenerated value version number or null if not versioned
- * - Timestamp of the current cached value at the key or null if there is no value
- * @note Callable type hints are not used to avoid class-autoloading
- */
- private function fetchOrRegenerate( $key, $ttl, $callback, array $opts ) {
- $checkKeys = $opts['checkKeys'] ?? [];
- $graceTTL = $opts['graceTTL'] ?? self::GRACE_TTL_NONE;
- $minAsOf = $opts['minAsOf'] ?? self::MIN_TIMESTAMP_NONE;
- $hotTTR = $opts['hotTTR'] ?? self::HOT_TTR;
- $lowTTL = $opts['lowTTL'] ?? min( self::LOW_TTL, $ttl );
- $ageNew = $opts['ageNew'] ?? self::AGE_NEW;
- $touchedCb = $opts['touchedCallback'] ?? null;
- $initialTime = $this->getCurrentTime();
-
- $kClass = $this->determineKeyClassForStats( $key );
-
- // Get the current key value and its metadata
- $curTTL = self::PASS_BY_REF;
- $curInfo = self::PASS_BY_REF; /** @var array $curInfo */
- $curValue = $this->get( $key, $curTTL, $checkKeys, $curInfo );
- // Apply any $touchedCb invalidation timestamp to get the "last purge timestamp"
- list( $curTTL, $LPT ) = $this->resolveCTL( $curValue, $curTTL, $curInfo, $touchedCb );
- // Use the cached value if it exists and is not due for synchronous regeneration
- if (
- $this->isValid( $curValue, $curInfo['asOf'], $minAsOf ) &&
- $this->isAliveOrInGracePeriod( $curTTL, $graceTTL )
- ) {
- $preemptiveRefresh = (
- $this->worthRefreshExpiring( $curTTL, $lowTTL ) ||
- $this->worthRefreshPopular( $curInfo['asOf'], $ageNew, $hotTTR, $initialTime )
- );
- if ( !$preemptiveRefresh ) {
- $this->stats->increment( "wanobjectcache.$kClass.hit.good" );
-
- return [ $curValue, $curInfo['version'], $curInfo['asOf'] ];
- } elseif ( $this->scheduleAsyncRefresh( $key, $ttl, $callback, $opts ) ) {
- $this->stats->increment( "wanobjectcache.$kClass.hit.refresh" );
-
- return [ $curValue, $curInfo['version'], $curInfo['asOf'] ];
- }
- }
-
- // Determine if there is stale or volatile cached value that is still usable
- $isKeyTombstoned = ( $curInfo['tombAsOf'] !== null );
- if ( $isKeyTombstoned ) {
- // Key is write-holed; use the (volatile) interim key as an alternative
- list( $possValue, $possInfo ) = $this->getInterimValue( $key, $minAsOf );
- // Update the "last purge time" since the $touchedCb timestamp depends on $value
- $LPT = $this->resolveTouched( $possValue, $LPT, $touchedCb );
- } else {
- $possValue = $curValue;
- $possInfo = $curInfo;
- }
-
- // Avoid overhead from callback runs, regeneration locks, and cache sets during
- // hold-off periods for the key by reusing very recently generated cached values
- if (
- $this->isValid( $possValue, $possInfo['asOf'], $minAsOf, $LPT ) &&
- $this->isVolatileValueAgeNegligible( $initialTime - $possInfo['asOf'] )
- ) {
- $this->stats->increment( "wanobjectcache.$kClass.hit.volatile" );
-
- return [ $possValue, $possInfo['version'], $curInfo['asOf'] ];
- }
-
- $lockTSE = $opts['lockTSE'] ?? self::TSE_NONE;
- $busyValue = $opts['busyValue'] ?? null;
- $staleTTL = $opts['staleTTL'] ?? self::STALE_TTL_NONE;
- $version = $opts['version'] ?? null;
-
- // Determine whether one thread per datacenter should handle regeneration at a time
- $useRegenerationLock =
- // Note that since tombstones no-op set(), $lockTSE and $curTTL cannot be used to
- // deduce the key hotness because |$curTTL| will always keep increasing until the
- // tombstone expires or is overwritten by a new tombstone. Also, even if $lockTSE
- // is not set, constant regeneration of a key for the tombstone lifetime might be
- // very expensive. Assume tombstoned keys are possibly hot in order to reduce
- // the risk of high regeneration load after the delete() method is called.
- $isKeyTombstoned ||
- // Assume a key is hot if requested soon ($lockTSE seconds) after invalidation.
- // This avoids stampedes when timestamps from $checkKeys/$touchedCb bump.
- ( $curTTL !== null && $curTTL <= 0 && abs( $curTTL ) <= $lockTSE ) ||
- // Assume a key is hot if there is no value and a busy fallback is given.
- // This avoids stampedes on eviction or preemptive regeneration taking too long.
- ( $busyValue !== null && $possValue === false );
-
- // If a regeneration lock is required, threads that do not get the lock will try to use
- // the stale value, the interim value, or the $busyValue placeholder, in that order. If
- // none of those are set then all threads will bypass the lock and regenerate the value.
- $hasLock = $useRegenerationLock && $this->claimStampedeLock( $key );
- if ( $useRegenerationLock && !$hasLock ) {
- if ( $this->isValid( $possValue, $possInfo['asOf'], $minAsOf ) ) {
- $this->stats->increment( "wanobjectcache.$kClass.hit.stale" );
-
- return [ $possValue, $possInfo['version'], $curInfo['asOf'] ];
- } elseif ( $busyValue !== null ) {
- $miss = is_infinite( $minAsOf ) ? 'renew' : 'miss';
- $this->stats->increment( "wanobjectcache.$kClass.$miss.busy" );
-
- return [ $this->resolveBusyValue( $busyValue ), $version, $curInfo['asOf'] ];
- }
- }
-
- // Generate the new value given any prior value with a matching version
- $setOpts = [];
- $preCallbackTime = $this->getCurrentTime();
- ++$this->callbackDepth;
- try {
- $value = $callback(
- ( $curInfo['version'] === $version ) ? $curValue : false,
- $ttl,
- $setOpts,
- ( $curInfo['version'] === $version ) ? $curInfo['asOf'] : null
- );
- } finally {
- --$this->callbackDepth;
- }
- $postCallbackTime = $this->getCurrentTime();
-
- // How long it took to fetch, validate, and generate the value
- $elapsed = max( $postCallbackTime - $initialTime, 0.0 );
-
- // Attempt to save the newly generated value if applicable
- if (
- // Callback yielded a cacheable value
- ( $value !== false && $ttl >= 0 ) &&
- // Current thread was not raced out of a regeneration lock or key is tombstoned
- ( !$useRegenerationLock || $hasLock || $isKeyTombstoned ) &&
- // Key does not appear to be undergoing a set() stampede
- $this->checkAndSetCooloff( $key, $kClass, $elapsed, $lockTSE, $hasLock )
- ) {
- // How long it took to generate the value
- $walltime = max( $postCallbackTime - $preCallbackTime, 0.0 );
- $this->stats->timing( "wanobjectcache.$kClass.regen_walltime", 1e3 * $walltime );
- // If the key is write-holed then use the (volatile) interim key as an alternative
- if ( $isKeyTombstoned ) {
- $this->setInterimValue( $key, $value, $lockTSE, $version, $walltime );
- } else {
- $finalSetOpts = [
- 'since' => $setOpts['since'] ?? $preCallbackTime,
- 'version' => $version,
- 'staleTTL' => $staleTTL,
- 'lockTSE' => $lockTSE, // informs lag vs performance trade-offs
- 'creating' => ( $curValue === false ), // optimization
- 'walltime' => $walltime
- ] + $setOpts;
- $this->set( $key, $value, $ttl, $finalSetOpts );
- }
- }
-
- $this->yieldStampedeLock( $key, $hasLock );
-
- $miss = is_infinite( $minAsOf ) ? 'renew' : 'miss';
- $this->stats->increment( "wanobjectcache.$kClass.$miss.compute" );
-
- return [ $value, $version, $curInfo['asOf'] ];
- }
-
- /**
- * @param string $key
- * @return bool Success
- */
- private function claimStampedeLock( $key ) {
- // Note that locking is not bypassed due to I/O errors; this avoids stampedes
- return $this->cache->add( self::$MUTEX_KEY_PREFIX . $key, 1, self::$LOCK_TTL );
- }
-
- /**
- * @param string $key
- * @param bool $hasLock
- */
- private function yieldStampedeLock( $key, $hasLock ) {
- if ( $hasLock ) {
- // The backend might be a mcrouter proxy set to broadcast DELETE to *all* the local
- // datacenter cache servers via OperationSelectorRoute (for increased consistency).
- // Since that would be excessive for these locks, use TOUCH to expire the key.
- $this->cache->changeTTL( self::$MUTEX_KEY_PREFIX . $key, $this->getCurrentTime() - 60 );
- }
- }
-
- /**
- * @param float $age Age of volatile/interim key in seconds
- * @return bool Whether the age of a volatile value is negligible
- */
- private function isVolatileValueAgeNegligible( $age ) {
- return ( $age < mt_rand( self::$RECENT_SET_LOW_MS, self::$RECENT_SET_HIGH_MS ) / 1e3 );
- }
-
- /**
- * @param string $key
- * @param string $kClass
- * @param float $elapsed Seconds spent regenerating the value
- * @param float $lockTSE
- * @param bool $hasLock
- * @return bool Whether it is OK to proceed with a key set operation
- */
- private function checkAndSetCooloff( $key, $kClass, $elapsed, $lockTSE, $hasLock ) {
- $this->stats->timing( "wanobjectcache.$kClass.regen_set_delay", 1e3 * $elapsed );
-
- // If $lockTSE is set, the lock was bypassed because there was no stale/interim value,
- // and $elapsed indicates that regeration is slow, then there is a risk of set()
- // stampedes with large blobs. With a typical scale-out infrastructure, CPU and query
- // load from $callback invocations is distributed among appservers and replica DBs,
- // but cache operations for a given key route to a single cache server (e.g. striped
- // consistent hashing).
- if ( $lockTSE < 0 || $hasLock ) {
- return true; // either not a priori hot or thread has the lock
- } elseif ( $elapsed <= self::$SET_DELAY_HIGH_MS * 1e3 ) {
- return true; // not enough time for threads to pile up
- }
-
- $this->cache->clearLastError();
- if (
- !$this->cache->add( self::$COOLOFF_KEY_PREFIX . $key, 1, self::$COOLOFF_TTL ) &&
- // Don't treat failures due to I/O errors as the key being in cooloff
- $this->cache->getLastError() === BagOStuff::ERR_NONE
- ) {
- $this->stats->increment( "wanobjectcache.$kClass.cooloff_bounce" );
-
- return false;
- }
-
- return true;
- }
-
- /**
- * @param mixed $value
- * @param float|null $curTTL
- * @param array $curInfo
- * @param callable|null $touchedCallback
- * @return array (current time left or null, UNIX timestamp of last purge or null)
- * @note Callable type hints are not used to avoid class-autoloading
- */
- private function resolveCTL( $value, $curTTL, $curInfo, $touchedCallback ) {
- if ( $touchedCallback === null || $value === false ) {
- return [ $curTTL, max( $curInfo['tombAsOf'], $curInfo['lastCKPurge'] ) ];
- }
-
- $touched = $touchedCallback( $value );
- if ( $touched !== null && $touched >= $curInfo['asOf'] ) {
- $curTTL = min( $curTTL, self::$TINY_NEGATIVE, $curInfo['asOf'] - $touched );
- }
-
- return [ $curTTL, max( $curInfo['tombAsOf'], $curInfo['lastCKPurge'], $touched ) ];
- }
-
- /**
- * @param mixed $value
- * @param float|null $lastPurge
- * @param callable|null $touchedCallback
- * @return float|null UNIX timestamp of last purge or null
- * @note Callable type hints are not used to avoid class-autoloading
- */
- private function resolveTouched( $value, $lastPurge, $touchedCallback ) {
- return ( $touchedCallback === null || $value === false )
- ? $lastPurge // nothing to derive the "touched timestamp" from
- : max( $touchedCallback( $value ), $lastPurge );
- }
-
- /**
- * @param string $key
- * @param float $minAsOf Minimum acceptable "as of" timestamp
- * @return array (cached value or false, cache key metadata map)
- */
- private function getInterimValue( $key, $minAsOf ) {
- $now = $this->getCurrentTime();
-
- if ( $this->useInterimHoldOffCaching ) {
- $wrapped = $this->cache->get( self::$INTERIM_KEY_PREFIX . $key );
-
- list( $value, $keyInfo ) = $this->unwrap( $wrapped, $now );
- if ( $this->isValid( $value, $keyInfo['asOf'], $minAsOf ) ) {
- return [ $value, $keyInfo ];
- }
- }
-
- return $this->unwrap( false, $now );
- }
-
- /**
- * @param string $key
- * @param mixed $value
- * @param int $ttl
- * @param int|null $version Value version number
- * @param float $walltime How long it took to generate the value in seconds
- */
- private function setInterimValue( $key, $value, $ttl, $version, $walltime ) {
- $ttl = max( self::$INTERIM_KEY_TTL, (int)$ttl );
-
- $wrapped = $this->wrap( $value, $ttl, $version, $this->getCurrentTime(), $walltime );
- $this->cache->merge(
- self::$INTERIM_KEY_PREFIX . $key,
- function () use ( $wrapped ) {
- return $wrapped;
- },
- $ttl,
- 1
- );
- }
-
- /**
- * @param mixed $busyValue
- * @return mixed
- */
- private function resolveBusyValue( $busyValue ) {
- return ( $busyValue instanceof Closure ) ? $busyValue() : $busyValue;
- }
-
- /**
- * Method to fetch multiple cache keys at once with regeneration
- *
- * This works the same as getWithSetCallback() except:
- * - a) The $keys argument expects the result of WANObjectCache::makeMultiKeys()
- * - b) The $callback argument expects a callback taking the following arguments:
- * - $id: ID of an entity to query
- * - $oldValue : the prior cache value or false if none was present
- * - &$ttl : a reference to the new value TTL in seconds
- * - &$setOpts : a reference to options for set() which can be altered
- * - $oldAsOf : generation UNIX timestamp of $oldValue or null if not present
- * Aside from the additional $id argument, the other arguments function the same
- * way they do in getWithSetCallback().
- * - c) The return value is a map of (cache key => value) in the order of $keyedIds
- *
- * @see WANObjectCache::getWithSetCallback()
- * @see WANObjectCache::getMultiWithUnionSetCallback()
- *
- * Example usage:
- * @code
- * $rows = $cache->getMultiWithSetCallback(
- * // Map of cache keys to entity IDs
- * $cache->makeMultiKeys(
- * $this->fileVersionIds(),
- * function ( $id ) use ( $cache ) {
- * return $cache->makeKey( 'file-version', $id );
- * }
- * ),
- * // Time-to-live (in seconds)
- * $cache::TTL_DAY,
- * // Function that derives the new key value
- * function ( $id, $oldValue, &$ttl, array &$setOpts ) {
- * $dbr = wfGetDB( DB_REPLICA );
- * // Account for any snapshot/replica DB lag
- * $setOpts += Database::getCacheSetOptions( $dbr );
- *
- * // Load the row for this file
- * $queryInfo = File::getQueryInfo();
- * $row = $dbr->selectRow(
- * $queryInfo['tables'],
- * $queryInfo['fields'],
- * [ 'id' => $id ],
- * __METHOD__,
- * [],
- * $queryInfo['joins']
- * );
- *
- * return $row ? (array)$row : false;
- * },
- * [
- * // Process cache for 30 seconds
- * 'pcTTL' => 30,
- * // Use a dedicated 500 item cache (initialized on-the-fly)
- * 'pcGroup' => 'file-versions:500'
- * ]
- * );
- * $files = array_map( [ __CLASS__, 'newFromRow' ], $rows );
- * @endcode
- *
- * @param ArrayIterator $keyedIds Result of WANObjectCache::makeMultiKeys()
- * @param int $ttl Seconds to live for key updates
- * @param callable $callback Callback the yields entity regeneration callbacks
- * @param array $opts Options map
- * @return mixed[] Map of (cache key => value) in the same order as $keyedIds
- * @since 1.28
- */
- final public function getMultiWithSetCallback(
- ArrayIterator $keyedIds, $ttl, callable $callback, array $opts = []
- ) {
- // Load required keys into process cache in one go
- $this->warmupCache = $this->getRawKeysForWarmup(
- $this->getNonProcessCachedMultiKeys( $keyedIds, $opts ),
- $opts['checkKeys'] ?? []
- );
- $this->warmupKeyMisses = 0;
-
- // Wrap $callback to match the getWithSetCallback() format while passing $id to $callback
- $id = null; // current entity ID
- $func = function ( $oldValue, &$ttl, &$setOpts, $oldAsOf ) use ( $callback, &$id ) {
- return $callback( $id, $oldValue, $ttl, $setOpts, $oldAsOf );
- };
-
- $values = [];
- foreach ( $keyedIds as $key => $id ) { // preserve order
- $values[$key] = $this->getWithSetCallback( $key, $ttl, $func, $opts );
- }
-
- $this->warmupCache = [];
-
- return $values;
- }
-
- /**
- * Method to fetch/regenerate multiple cache keys at once
- *
- * This works the same as getWithSetCallback() except:
- * - a) The $keys argument expects the result of WANObjectCache::makeMultiKeys()
- * - b) The $callback argument expects a callback returning a map of (ID => new value)
- * for all entity IDs in $ids and it takes the following arguments:
- * - $ids: a list of entity IDs that require cache regeneration
- * - &$ttls: a reference to the (entity ID => new TTL) map
- * - &$setOpts: a reference to options for set() which can be altered
- * - c) The return value is a map of (cache key => value) in the order of $keyedIds
- * - d) The "lockTSE" and "busyValue" options are ignored
- *
- * @see WANObjectCache::getWithSetCallback()
- * @see WANObjectCache::getMultiWithSetCallback()
- *
- * Example usage:
- * @code
- * $rows = $cache->getMultiWithUnionSetCallback(
- * // Map of cache keys to entity IDs
- * $cache->makeMultiKeys(
- * $this->fileVersionIds(),
- * function ( $id ) use ( $cache ) {
- * return $cache->makeKey( 'file-version', $id );
- * }
- * ),
- * // Time-to-live (in seconds)
- * $cache::TTL_DAY,
- * // Function that derives the new key value
- * function ( array $ids, array &$ttls, array &$setOpts ) {
- * $dbr = wfGetDB( DB_REPLICA );
- * // Account for any snapshot/replica DB lag
- * $setOpts += Database::getCacheSetOptions( $dbr );
- *
- * // Load the rows for these files
- * $rows = [];
- * $queryInfo = File::getQueryInfo();
- * $res = $dbr->select(
- * $queryInfo['tables'],
- * $queryInfo['fields'],
- * [ 'id' => $ids ],
- * __METHOD__,
- * [],
- * $queryInfo['joins']
- * );
- * foreach ( $res as $row ) {
- * $rows[$row->id] = $row;
- * $mtime = wfTimestamp( TS_UNIX, $row->timestamp );
- * $ttls[$row->id] = $this->adaptiveTTL( $mtime, $ttls[$row->id] );
- * }
- *
- * return $rows;
- * },
- * ]
- * );
- * $files = array_map( [ __CLASS__, 'newFromRow' ], $rows );
- * @endcode
- *
- * @param ArrayIterator $keyedIds Result of WANObjectCache::makeMultiKeys()
- * @param int $ttl Seconds to live for key updates
- * @param callable $callback Callback the yields entity regeneration callbacks
- * @param array $opts Options map
- * @return mixed[] Map of (cache key => value) in the same order as $keyedIds
- * @since 1.30
- */
- final public function getMultiWithUnionSetCallback(
- ArrayIterator $keyedIds, $ttl, callable $callback, array $opts = []
- ) {
- $checkKeys = $opts['checkKeys'] ?? [];
- unset( $opts['lockTSE'] ); // incompatible
- unset( $opts['busyValue'] ); // incompatible
-
- // Load required keys into process cache in one go
- $keysByIdGet = $this->getNonProcessCachedMultiKeys( $keyedIds, $opts );
- $this->warmupCache = $this->getRawKeysForWarmup( $keysByIdGet, $checkKeys );
- $this->warmupKeyMisses = 0;
-
- // IDs of entities known to be in need of regeneration
- $idsRegen = [];
-
- // Find out which keys are missing/deleted/stale
- $curTTLs = [];
- $asOfs = [];
- $curByKey = $this->getMulti( $keysByIdGet, $curTTLs, $checkKeys, $asOfs );
- foreach ( $keysByIdGet as $id => $key ) {
- if ( !array_key_exists( $key, $curByKey ) || $curTTLs[$key] < 0 ) {
- $idsRegen[] = $id;
- }
- }
-
- // Run the callback to populate the regeneration value map for all required IDs
- $newSetOpts = [];
- $newTTLsById = array_fill_keys( $idsRegen, $ttl );
- $newValsById = $idsRegen ? $callback( $idsRegen, $newTTLsById, $newSetOpts ) : [];
-
- // Wrap $callback to match the getWithSetCallback() format while passing $id to $callback
- $id = null; // current entity ID
- $func = function ( $oldValue, &$ttl, &$setOpts, $oldAsOf )
- use ( $callback, &$id, $newValsById, $newTTLsById, $newSetOpts )
- {
- if ( array_key_exists( $id, $newValsById ) ) {
- // Value was already regerated as expected, so use the value in $newValsById
- $newValue = $newValsById[$id];
- $ttl = $newTTLsById[$id];
- $setOpts = $newSetOpts;
- } else {
- // Pre-emptive/popularity refresh and version mismatch cases are not detected
- // above and thus $newValsById has no entry. Run $callback on this single entity.
- $ttls = [ $id => $ttl ];
- $newValue = $callback( [ $id ], $ttls, $setOpts )[$id];
- $ttl = $ttls[$id];
- }
-
- return $newValue;
- };
-
- // Run the cache-aside logic using warmupCache instead of persistent cache queries
- $values = [];
- foreach ( $keyedIds as $key => $id ) { // preserve order
- $values[$key] = $this->getWithSetCallback( $key, $ttl, $func, $opts );
- }
-
- $this->warmupCache = [];
-
- return $values;
- }
-
- /**
- * Set a key to soon expire in the local cluster if it pre-dates $purgeTimestamp
- *
- * This sets stale keys' time-to-live at HOLDOFF_TTL seconds, which both avoids
- * broadcasting in mcrouter setups and also avoids races with new tombstones.
- *
- * @param string $key Cache key
- * @param int $purgeTimestamp UNIX timestamp of purge
- * @param bool &$isStale Whether the key is stale
- * @return bool Success
- * @since 1.28
- */
- final public function reap( $key, $purgeTimestamp, &$isStale = false ) {
- $minAsOf = $purgeTimestamp + self::HOLDOFF_TTL;
- $wrapped = $this->cache->get( self::$VALUE_KEY_PREFIX . $key );
- if ( is_array( $wrapped ) && $wrapped[self::$FLD_TIME] < $minAsOf ) {
- $isStale = true;
- $this->logger->warning( "Reaping stale value key '$key'." );
- $ttlReap = self::HOLDOFF_TTL; // avoids races with tombstone creation
- $ok = $this->cache->changeTTL( self::$VALUE_KEY_PREFIX . $key, $ttlReap );
- if ( !$ok ) {
- $this->logger->error( "Could not complete reap of key '$key'." );
- }
-
- return $ok;
- }
-
- $isStale = false;
-
- return true;
- }
-
- /**
- * Set a "check" key to soon expire in the local cluster if it pre-dates $purgeTimestamp
- *
- * @param string $key Cache key
- * @param int $purgeTimestamp UNIX timestamp of purge
- * @param bool &$isStale Whether the key is stale
- * @return bool Success
- * @since 1.28
- */
- final public function reapCheckKey( $key, $purgeTimestamp, &$isStale = false ) {
- $purge = $this->parsePurgeValue( $this->cache->get( self::$TIME_KEY_PREFIX . $key ) );
- if ( $purge && $purge[self::$PURGE_TIME] < $purgeTimestamp ) {
- $isStale = true;
- $this->logger->warning( "Reaping stale check key '$key'." );
- $ok = $this->cache->changeTTL( self::$TIME_KEY_PREFIX . $key, self::TTL_SECOND );
- if ( !$ok ) {
- $this->logger->error( "Could not complete reap of check key '$key'." );
- }
-
- return $ok;
- }
-
- $isStale = false;
-
- return false;
- }
-
- /**
- * @see BagOStuff::makeKey()
- * @param string $class Key class
- * @param string ...$components Key components (starting with a key collection name)
- * @return string Colon-delimited list of $keyspace followed by escaped components
- * @since 1.27
- */
- public function makeKey( $class, ...$components ) {
- return $this->cache->makeKey( ...func_get_args() );
- }
-
- /**
- * @see BagOStuff::makeGlobalKey()
- * @param string $class Key class
- * @param string ...$components Key components (starting with a key collection name)
- * @return string Colon-delimited list of $keyspace followed by escaped components
- * @since 1.27
- */
- public function makeGlobalKey( $class, ...$components ) {
- return $this->cache->makeGlobalKey( ...func_get_args() );
- }
-
- /**
- * Hash a possibly long string into a suitable component for makeKey()/makeGlobalKey()
- *
- * @param string $component A raw component used in building a cache key
- * @return string 64 character HMAC using a stable secret for public collision resistance
- * @since 1.34
- */
- public function hash256( $component ) {
- return hash_hmac( 'sha256', $component, $this->secret );
- }
-
- /**
- * Get an iterator of (cache key => entity ID) for a list of entity IDs
- *
- * The callback takes an ID string and returns a key via makeKey()/makeGlobalKey().
- * There should be no network nor filesystem I/O used in the callback. The entity
- * ID/key mapping must be 1:1 or an exception will be thrown. If hashing is needed,
- * then use the hash256() method.
- *
- * Example usage for the default keyspace:
- * @code
- * $keyedIds = $cache->makeMultiKeys(
- * $modules,
- * function ( $module ) use ( $cache ) {
- * return $cache->makeKey( 'module-info', $module );
- * }
- * );
- * @endcode
- *
- * Example usage for mixed default and global keyspace:
- * @code
- * $keyedIds = $cache->makeMultiKeys(
- * $filters,
- * function ( $filter ) use ( $cache ) {
- * return ( strpos( $filter, 'central:' ) === 0 )
- * ? $cache->makeGlobalKey( 'regex-filter', $filter )
- * : $cache->makeKey( 'regex-filter', $filter )
- * }
- * );
- * @endcode
- *
- * Example usage with hashing:
- * @code
- * $keyedIds = $cache->makeMultiKeys(
- * $urls,
- * function ( $url ) use ( $cache ) {
- * return $cache->makeKey( 'url-info', $cache->hash256( $url ) );
- * }
- * );
- * @endcode
- *
- * @see WANObjectCache::makeKey()
- * @see WANObjectCache::makeGlobalKey()
- * @see WANObjectCache::hash256()
- *
- * @param string[]|int[] $ids List of entity IDs
- * @param callable $keyCallback Function returning makeKey()/makeGlobalKey() on the input ID
- * @return ArrayIterator Iterator of (cache key => ID); order of $ids is preserved
- * @throws UnexpectedValueException
- * @since 1.28
- */
- final public function makeMultiKeys( array $ids, $keyCallback ) {
- $idByKey = [];
- foreach ( $ids as $id ) {
- // Discourage triggering of automatic makeKey() hashing in some backends
- if ( strlen( $id ) > 64 ) {
- $this->logger->warning( __METHOD__ . ": long ID '$id'; use hash256()" );
- }
- $key = $keyCallback( $id, $this );
- // Edge case: ignore key collisions due to duplicate $ids like "42" and 42
- if ( !isset( $idByKey[$key] ) ) {
- $idByKey[$key] = $id;
- } elseif ( (string)$id !== (string)$idByKey[$key] ) {
- throw new UnexpectedValueException(
- "Cache key collision; IDs ('$id','{$idByKey[$key]}') map to '$key'"
- );
- }
- }
-
- return new ArrayIterator( $idByKey );
- }
-
- /**
- * Get an (ID => value) map from (i) a non-unique list of entity IDs, and (ii) the list
- * of corresponding entity values by first appearance of each ID in the entity ID list
- *
- * For use with getMultiWithSetCallback() and getMultiWithUnionSetCallback().
- *
- * *Only* use this method if the entity ID/key mapping is trivially 1:1 without exception.
- * Key generation method must utitilize the *full* entity ID in the key (not a hash of it).
- *
- * Example usage:
- * @code
- * $poems = $cache->getMultiWithSetCallback(
- * $cache->makeMultiKeys(
- * $uuids,
- * function ( $uuid ) use ( $cache ) {
- * return $cache->makeKey( 'poem', $uuid );
- * }
- * ),
- * $cache::TTL_DAY,
- * function ( $uuid ) use ( $url ) {
- * return $this->http->run( [ 'method' => 'GET', 'url' => "$url/$uuid" ] );
- * }
- * );
- * $poemsByUUID = $cache->multiRemap( $uuids, $poems );
- * @endcode
- *
- * @see WANObjectCache::makeMultiKeys()
- * @see WANObjectCache::getMultiWithSetCallback()
- * @see WANObjectCache::getMultiWithUnionSetCallback()
- *
- * @param string[]|int[] $ids Entity ID list makeMultiKeys()
- * @param mixed[] $res Result of getMultiWithSetCallback()/getMultiWithUnionSetCallback()
- * @return mixed[] Map of (ID => value); order of $ids is preserved
- * @since 1.34
- */
- final public function multiRemap( array $ids, array $res ) {
- if ( count( $ids ) !== count( $res ) ) {
- // If makeMultiKeys() is called on a list of non-unique IDs, then the resulting
- // ArrayIterator will have less entries due to "first appearance" de-duplication
- $ids = array_keys( array_flip( $ids ) );
- if ( count( $ids ) !== count( $res ) ) {
- throw new UnexpectedValueException( "Multi-key result does not match ID list" );
- }
- }
-
- return array_combine( $ids, $res );
- }
-
- /**
- * Get the "last error" registered; clearLastError() should be called manually
- * @return int ERR_* class constant for the "last error" registry
- */
- final public function getLastError() {
- $code = $this->cache->getLastError();
- switch ( $code ) {
- case BagOStuff::ERR_NONE:
- return self::ERR_NONE;
- case BagOStuff::ERR_NO_RESPONSE:
- return self::ERR_NO_RESPONSE;
- case BagOStuff::ERR_UNREACHABLE:
- return self::ERR_UNREACHABLE;
- default:
- return self::ERR_UNEXPECTED;
- }
- }
-
- /**
- * Clear the "last error" registry
- */
- final public function clearLastError() {
- $this->cache->clearLastError();
- }
-
- /**
- * Clear the in-process caches; useful for testing
- *
- * @since 1.27
- */
- public function clearProcessCache() {
- $this->processCaches = [];
- }
-
- /**
- * Enable or disable the use of brief caching for tombstoned keys
- *
- * When a key is purged via delete(), there normally is a period where caching
- * is hold-off limited to an extremely short time. This method will disable that
- * caching, forcing the callback to run for any of:
- * - WANObjectCache::getWithSetCallback()
- * - WANObjectCache::getMultiWithSetCallback()
- * - WANObjectCache::getMultiWithUnionSetCallback()
- *
- * This is useful when both:
- * - a) the database used by the callback is known to be up-to-date enough
- * for some particular purpose (e.g. replica DB has applied transaction X)
- * - b) the caller needs to exploit that fact, and therefore needs to avoid the
- * use of inherently volatile and possibly stale interim keys
- *
- * @see WANObjectCache::delete()
- * @param bool $enabled Whether to enable interim caching
- * @since 1.31
- */
- final public function useInterimHoldOffCaching( $enabled ) {
- $this->useInterimHoldOffCaching = $enabled;
- }
-
- /**
- * @param int $flag ATTR_* class constant
- * @return int QOS_* class constant
- * @since 1.28
- */
- public function getQoS( $flag ) {
- return $this->cache->getQoS( $flag );
- }
-
- /**
- * Get a TTL that is higher for objects that have not changed recently
- *
- * This is useful for keys that get explicit purges and DB or purge relay
- * lag is a potential concern (especially how it interacts with CDN cache)
- *
- * Example usage:
- * @code
- * // Last-modified time of page
- * $mtime = wfTimestamp( TS_UNIX, $page->getTimestamp() );
- * // Get adjusted TTL. If $mtime is 3600 seconds ago and $minTTL/$factor left at
- * // defaults, then $ttl is 3600 * .2 = 720. If $minTTL was greater than 720, then
- * // $ttl would be $minTTL. If $maxTTL was smaller than 720, $ttl would be $maxTTL.
- * $ttl = $cache->adaptiveTTL( $mtime, $cache::TTL_DAY );
- * @endcode
- *
- * Another use case is when there are no applicable "last modified" fields in the DB,
- * and there are too many dependencies for explicit purges to be viable, and the rate of
- * change to relevant content is unstable, and it is highly valued to have the cached value
- * be as up-to-date as possible.
- *
- * Example usage:
- * @code
- * $query = "<some complex query>";
- * $idListFromComplexQuery = $cache->getWithSetCallback(
- * $cache->makeKey( 'complex-graph-query', $hashOfQuery ),
- * GraphQueryClass::STARTING_TTL,
- * function ( $oldValue, &$ttl, array &$setOpts, $oldAsOf ) use ( $query, $cache ) {
- * $gdb = $this->getReplicaGraphDbConnection();
- * // Account for any snapshot/replica DB lag
- * $setOpts += GraphDatabase::getCacheSetOptions( $gdb );
- *
- * $newList = iterator_to_array( $gdb->query( $query ) );
- * sort( $newList, SORT_NUMERIC ); // normalize
- *
- * $minTTL = GraphQueryClass::MIN_TTL;
- * $maxTTL = GraphQueryClass::MAX_TTL;
- * if ( $oldValue !== false ) {
- * // Note that $oldAsOf is the last time this callback ran
- * $ttl = ( $newList === $oldValue )
- * // No change: cache for 150% of the age of $oldValue
- * ? $cache->adaptiveTTL( $oldAsOf, $maxTTL, $minTTL, 1.5 )
- * // Changed: cache for 50% of the age of $oldValue
- * : $cache->adaptiveTTL( $oldAsOf, $maxTTL, $minTTL, .5 );
- * }
- *
- * return $newList;
- * },
- * [
- * // Keep stale values around for doing comparisons for TTL calculations.
- * // High values improve long-tail keys hit-rates, though might waste space.
- * 'staleTTL' => GraphQueryClass::GRACE_TTL
- * ]
- * );
- * @endcode
- *
- * @param int|float $mtime UNIX timestamp
- * @param int $maxTTL Maximum TTL (seconds)
- * @param int $minTTL Minimum TTL (seconds); Default: 30
- * @param float $factor Value in the range (0,1); Default: .2
- * @return int Adaptive TTL
- * @since 1.28
- */
- public function adaptiveTTL( $mtime, $maxTTL, $minTTL = 30, $factor = 0.2 ) {
- if ( is_float( $mtime ) || ctype_digit( $mtime ) ) {
- $mtime = (int)$mtime; // handle fractional seconds and string integers
- }
-
- if ( !is_int( $mtime ) || $mtime <= 0 ) {
- return $minTTL; // no last-modified time provided
- }
-
- $age = $this->getCurrentTime() - $mtime;
-
- return (int)min( $maxTTL, max( $minTTL, $factor * $age ) );
- }
-
- /**
- * @return int Number of warmup key cache misses last round
- * @since 1.30
- */
- final public function getWarmupKeyMisses() {
- return $this->warmupKeyMisses;
- }
-
- /**
- * Do the actual async bus purge of a key
- *
- * This must set the key to "PURGED:<UNIX timestamp>:<holdoff>"
- *
- * @param string $key Cache key
- * @param int $ttl Seconds to keep the tombstone around
- * @param int $holdoff HOLDOFF_* constant controlling how long to ignore sets for this key
- * @return bool Success
- */
- protected function relayPurge( $key, $ttl, $holdoff ) {
- if ( $this->mcrouterAware ) {
- // See https://github.com/facebook/mcrouter/wiki/Multi-cluster-broadcast-setup
- // Wildcards select all matching routes, e.g. the WAN cluster on all DCs
- $ok = $this->cache->set(
- "/*/{$this->cluster}/{$key}",
- $this->makePurgeValue( $this->getCurrentTime(), self::HOLDOFF_TTL_NONE ),
- $ttl
- );
- } else {
- // This handles the mcrouter and the single-DC case
- $ok = $this->cache->set(
- $key,
- $this->makePurgeValue( $this->getCurrentTime(), self::HOLDOFF_TTL_NONE ),
- $ttl
- );
- }
-
- return $ok;
- }
-
- /**
- * Do the actual async bus delete of a key
- *
- * @param string $key Cache key
- * @return bool Success
- */
- protected function relayDelete( $key ) {
- if ( $this->mcrouterAware ) {
- // See https://github.com/facebook/mcrouter/wiki/Multi-cluster-broadcast-setup
- // Wildcards select all matching routes, e.g. the WAN cluster on all DCs
- $ok = $this->cache->delete( "/*/{$this->cluster}/{$key}" );
- } else {
- // Some other proxy handles broadcasting or there is only one datacenter
- $ok = $this->cache->delete( $key );
- }
-
- return $ok;
- }
-
- /**
- * @param string $key
- * @param int $ttl Seconds to live
- * @param callable $callback
- * @param array $opts
- * @return bool Success
- * @note Callable type hints are not used to avoid class-autoloading
- */
- private function scheduleAsyncRefresh( $key, $ttl, $callback, $opts ) {
- if ( !$this->asyncHandler ) {
- return false;
- }
- // Update the cache value later, such during post-send of an HTTP request
- $func = $this->asyncHandler;
- $func( function () use ( $key, $ttl, $callback, $opts ) {
- $opts['minAsOf'] = INF; // force a refresh
- $this->fetchOrRegenerate( $key, $ttl, $callback, $opts );
- } );
-
- return true;
- }
-
- /**
- * Check if a key is fresh or in the grace window and thus due for randomized reuse
- *
- * If $curTTL > 0 (e.g. not expired) this returns true. Otherwise, the chance of returning
- * true decrease steadily from 100% to 0% as the |$curTTL| moves from 0 to $graceTTL seconds.
- * This handles widely varying levels of cache access traffic.
- *
- * If $curTTL <= -$graceTTL (e.g. already expired), then this returns false.
- *
- * @param float $curTTL Approximate TTL left on the key if present
- * @param int $graceTTL Consider using stale values if $curTTL is greater than this
- * @return bool
- */
- private function isAliveOrInGracePeriod( $curTTL, $graceTTL ) {
- if ( $curTTL > 0 ) {
- return true;
- } elseif ( $graceTTL <= 0 ) {
- return false;
- }
-
- $ageStale = abs( $curTTL ); // seconds of staleness
- $curGTTL = ( $graceTTL - $ageStale ); // current grace-time-to-live
- if ( $curGTTL <= 0 ) {
- return false; // already out of grace period
- }
-
- // Chance of using a stale value is the complement of the chance of refreshing it
- return !$this->worthRefreshExpiring( $curGTTL, $graceTTL );
- }
-
- /**
- * Check if a key is nearing expiration and thus due for randomized regeneration
- *
- * This returns false if $curTTL >= $lowTTL. Otherwise, the chance of returning true
- * increases steadily from 0% to 100% as the $curTTL moves from $lowTTL to 0 seconds.
- * This handles widely varying levels of cache access traffic.
- *
- * If $curTTL <= 0 (e.g. already expired), then this returns false.
- *
- * @param float $curTTL Approximate TTL left on the key if present
- * @param float $lowTTL Consider a refresh when $curTTL is less than this
- * @return bool
- */
- protected function worthRefreshExpiring( $curTTL, $lowTTL ) {
- if ( $lowTTL <= 0 ) {
- return false;
- } elseif ( $curTTL >= $lowTTL ) {
- return false;
- } elseif ( $curTTL <= 0 ) {
- return false;
- }
-
- $chance = ( 1 - $curTTL / $lowTTL );
-
- return mt_rand( 1, 1e9 ) <= 1e9 * $chance;
- }
-
- /**
- * Check if a key is due for randomized regeneration due to its popularity
- *
- * This is used so that popular keys can preemptively refresh themselves for higher
- * consistency (especially in the case of purge loss/delay). Unpopular keys can remain
- * in cache with their high nominal TTL. This means popular keys keep good consistency,
- * whether the data changes frequently or not, and long-tail keys get to stay in cache
- * and get hits too. Similar to worthRefreshExpiring(), randomization is used.
- *
- * @param float $asOf UNIX timestamp of the value
- * @param int $ageNew Age of key when this might recommend refreshing (seconds)
- * @param int $timeTillRefresh Age of key when it should be refreshed if popular (seconds)
- * @param float $now The current UNIX timestamp
- * @return bool
- */
- protected function worthRefreshPopular( $asOf, $ageNew, $timeTillRefresh, $now ) {
- if ( $ageNew < 0 || $timeTillRefresh <= 0 ) {
- return false;
- }
-
- $age = $now - $asOf;
- $timeOld = $age - $ageNew;
- if ( $timeOld <= 0 ) {
- return false;
- }
-
- $popularHitsPerSec = 1;
- // Lifecycle is: new, ramp-up refresh chance, full refresh chance.
- // Note that the "expected # of refreshes" for the ramp-up time range is half
- // of what it would be if P(refresh) was at its full value during that time range.
- $refreshWindowSec = max( $timeTillRefresh - $ageNew - self::$RAMPUP_TTL / 2, 1 );
- // P(refresh) * (# hits in $refreshWindowSec) = (expected # of refreshes)
- // P(refresh) * ($refreshWindowSec * $popularHitsPerSec) = 1 (by definition)
- // P(refresh) = 1/($refreshWindowSec * $popularHitsPerSec)
- $chance = 1 / ( $popularHitsPerSec * $refreshWindowSec );
-
- // Ramp up $chance from 0 to its nominal value over RAMPUP_TTL seconds to avoid stampedes
- $chance *= ( $timeOld <= self::$RAMPUP_TTL ) ? $timeOld / self::$RAMPUP_TTL : 1;
-
- return mt_rand( 1, 1e9 ) <= 1e9 * $chance;
- }
-
- /**
- * Check if $value is not false, versioned (if needed), and not older than $minTime (if set)
- *
- * @param array|bool $value
- * @param float $asOf The time $value was generated
- * @param float $minAsOf Minimum acceptable "as of" timestamp
- * @param float|null $purgeTime The last time the value was invalidated
- * @return bool
- */
- protected function isValid( $value, $asOf, $minAsOf, $purgeTime = null ) {
- // Avoid reading any key not generated after the latest delete() or touch
- $safeMinAsOf = max( $minAsOf, $purgeTime + self::$TINY_POSTIVE );
-
- if ( $value === false ) {
- return false;
- } elseif ( $safeMinAsOf > 0 && $asOf < $minAsOf ) {
- return false;
- }
-
- return true;
- }
-
- /**
- * @param mixed $value
- * @param int $ttl Seconds to live or zero for "indefinite"
- * @param int|null $version Value version number or null if not versioned
- * @param float $now Unix Current timestamp just before calling set()
- * @param float $walltime How long it took to generate the value in seconds
- * @return array
- */
- private function wrap( $value, $ttl, $version, $now, $walltime ) {
- // Returns keys in ascending integer order for PHP7 array packing:
- // https://nikic.github.io/2014/12/22/PHPs-new-hashtable-implementation.html
- $wrapped = [
- self::$FLD_FORMAT_VERSION => self::$VERSION,
- self::$FLD_VALUE => $value,
- self::$FLD_TTL => $ttl,
- self::$FLD_TIME => $now
- ];
- if ( $version !== null ) {
- $wrapped[self::$FLD_VALUE_VERSION] = $version;
- }
- if ( $walltime >= self::$GENERATION_SLOW_SEC ) {
- $wrapped[self::$FLD_GENERATION_TIME] = $walltime;
- }
-
- return $wrapped;
- }
-
- /**
- * @param array|string|bool $wrapped The entry at a cache key
- * @param float $now Unix Current timestamp (preferrably pre-query)
- * @return array (value or false if absent/tombstoned/malformed, value metadata map).
- * The cache key metadata includes the following metadata:
- * - asOf: UNIX timestamp of the value or null if there is no value
- * - curTTL: remaining time-to-live (negative if tombstoned) or null if there is no value
- * - version: value version number or null if the if there is no value
- * - tombAsOf: UNIX timestamp of the tombstone or null if there is no tombstone
- */
- private function unwrap( $wrapped, $now ) {
- $value = false;
- $info = [ 'asOf' => null, 'curTTL' => null, 'version' => null, 'tombAsOf' => null ];
-
- if ( is_array( $wrapped ) ) {
- // Entry expected to be a cached value; validate it
- if (
- ( $wrapped[self::$FLD_FORMAT_VERSION] ?? null ) === self::$VERSION &&
- $wrapped[self::$FLD_TIME] >= $this->epoch
- ) {
- if ( $wrapped[self::$FLD_TTL] > 0 ) {
- // Get the approximate time left on the key
- $age = $now - $wrapped[self::$FLD_TIME];
- $curTTL = max( $wrapped[self::$FLD_TTL] - $age, 0.0 );
- } else {
- // Key had no TTL, so the time left is unbounded
- $curTTL = INF;
- }
- $value = $wrapped[self::$FLD_VALUE];
- $info['version'] = $wrapped[self::$FLD_VALUE_VERSION] ?? null;
- $info['asOf'] = $wrapped[self::$FLD_TIME];
- $info['curTTL'] = $curTTL;
- }
- } else {
- // Entry expected to be a tombstone; parse it
- $purge = $this->parsePurgeValue( $wrapped );
- if ( $purge !== false ) {
- // Tombstoned keys should always have a negative current $ttl
- $info['curTTL'] = min( $purge[self::$PURGE_TIME] - $now, self::$TINY_NEGATIVE );
- $info['tombAsOf'] = $purge[self::$PURGE_TIME];
- }
- }
-
- return [ $value, $info ];
- }
-
- /**
- * @param string[] $keys
- * @param string $prefix
- * @return string[] Prefix keys; the order of $keys is preserved
- */
- protected static function prefixCacheKeys( array $keys, $prefix ) {
- $res = [];
- foreach ( $keys as $key ) {
- $res[] = $prefix . $key;
- }
-
- return $res;
- }
-
- /**
- * @param string $key String of the format <scope>:<class>[:<class or variable>]...
- * @return string A collection name to describe this class of key
- */
- private function determineKeyClassForStats( $key ) {
- $parts = explode( ':', $key, 3 );
-
- return $parts[1] ?? $parts[0]; // sanity
- }
-
- /**
- * @param string|array|bool $value Possible string of the form "PURGED:<timestamp>:<holdoff>"
- * @return array|bool Array containing a UNIX timestamp (float) and holdoff period (integer),
- * or false if value isn't a valid purge value
- */
- private function parsePurgeValue( $value ) {
- if ( !is_string( $value ) ) {
- return false;
- }
-
- $segments = explode( ':', $value, 3 );
- if (
- !isset( $segments[0] ) ||
- !isset( $segments[1] ) ||
- "{$segments[0]}:" !== self::$PURGE_VAL_PREFIX
- ) {
- return false;
- }
-
- if ( !isset( $segments[2] ) ) {
- // Back-compat with old purge values without holdoff
- $segments[2] = self::HOLDOFF_TTL;
- }
-
- if ( $segments[1] < $this->epoch ) {
- // Values this old are ignored
- return false;
- }
-
- return [
- self::$PURGE_TIME => (float)$segments[1],
- self::$PURGE_HOLDOFF => (int)$segments[2],
- ];
- }
-
- /**
- * @param float $timestamp
- * @param int $holdoff In seconds
- * @return string Wrapped purge value
- */
- private function makePurgeValue( $timestamp, $holdoff ) {
- return self::$PURGE_VAL_PREFIX . (float)$timestamp . ':' . (int)$holdoff;
- }
-
- /**
- * @param string $group
- * @return MapCacheLRU
- */
- private function getProcessCache( $group ) {
- if ( !isset( $this->processCaches[$group] ) ) {
- list( , $size ) = explode( ':', $group );
- $this->processCaches[$group] = new MapCacheLRU( (int)$size );
- }
-
- return $this->processCaches[$group];
- }
-
- /**
- * @param string $key
- * @param int $version
- * @return string
- */
- private function getProcessCacheKey( $key, $version ) {
- return $key . ' ' . (int)$version;
- }
-
- /**
- * @param ArrayIterator $keys
- * @param array $opts
- * @return string[] Map of (ID => cache key)
- */
- private function getNonProcessCachedMultiKeys( ArrayIterator $keys, array $opts ) {
- $pcTTL = $opts['pcTTL'] ?? self::TTL_UNCACHEABLE;
-
- $keysMissing = [];
- if ( $pcTTL > 0 && $this->callbackDepth == 0 ) {
- $version = $opts['version'] ?? null;
- $pCache = $this->getProcessCache( $opts['pcGroup'] ?? self::PC_PRIMARY );
- foreach ( $keys as $key => $id ) {
- if ( !$pCache->has( $this->getProcessCacheKey( $key, $version ), $pcTTL ) ) {
- $keysMissing[$id] = $key;
- }
- }
- }
-
- return $keysMissing;
- }
-
- /**
- * @param string[] $keys
- * @param string[]|string[][] $checkKeys
- * @return string[] List of cache keys
- */
- private function getRawKeysForWarmup( array $keys, array $checkKeys ) {
- if ( !$keys ) {
- return [];
- }
-
- $keysWarmUp = [];
- // Get all the value keys to fetch...
- foreach ( $keys as $key ) {
- $keysWarmUp[] = self::$VALUE_KEY_PREFIX . $key;
- }
- // Get all the check keys to fetch...
- foreach ( $checkKeys as $i => $checkKeyOrKeys ) {
- if ( is_int( $i ) ) {
- // Single check key that applies to all value keys
- $keysWarmUp[] = self::$TIME_KEY_PREFIX . $checkKeyOrKeys;
- } else {
- // List of check keys that apply to value key $i
- $keysWarmUp = array_merge(
- $keysWarmUp,
- self::prefixCacheKeys( $checkKeyOrKeys, self::$TIME_KEY_PREFIX )
- );
- }
- }
-
- $warmupCache = $this->cache->getMulti( $keysWarmUp );
- $warmupCache += array_fill_keys( $keysWarmUp, false );
-
- return $warmupCache;
- }
-
- /**
- * @return float UNIX timestamp
- * @codeCoverageIgnore
- */
- protected function getCurrentTime() {
- if ( $this->wallClockOverride ) {
- return $this->wallClockOverride;
- }
-
- $clockTime = (float)time(); // call this first
- // microtime() uses an initial gettimeofday() call added to usage clocks.
- // This can severely drift from time() and the microtime() value of other threads
- // due to undercounting of the amount of time elapsed. Instead of seeing the current
- // time as being in the past, use the value of time(). This avoids setting cache values
- // that will immediately be seen as expired and possibly cause stampedes.
- return max( microtime( true ), $clockTime );
- }
-
- /**
- * @param float|null &$time Mock UNIX timestamp for testing
- * @codeCoverageIgnore
- */
- public function setMockTime( &$time ) {
- $this->wallClockOverride =& $time;
- $this->cache->setMockTime( $time );
- }
-}
--- /dev/null
+<?php
+/**
+ * Object caching using WinCache.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup Cache
+ */
+
+/**
+ * Wrapper for WinCache object caching functions; identical interface
+ * to the APC wrapper
+ *
+ * @ingroup Cache
+ */
+class WinCacheBagOStuff extends MediumSpecificBagOStuff {
+ protected function doGet( $key, $flags = 0, &$casToken = null ) {
+ $casToken = null;
+
+ $blob = wincache_ucache_get( $key );
+ if ( !is_string( $blob ) && !is_int( $blob ) ) {
+ return false;
+ }
+
+ $value = $this->unserialize( $blob );
+ if ( $value !== false ) {
+ $casToken = (string)$blob; // don't bother hashing this
+ }
+
+ return $value;
+ }
+
+ protected function cas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
+ if ( !wincache_lock( $key ) ) { // optimize with FIFO lock
+ return false;
+ }
+
+ $curCasToken = null; // passed by reference
+ $this->doGet( $key, self::READ_LATEST, $curCasToken );
+ if ( $casToken === $curCasToken ) {
+ $success = $this->set( $key, $value, $exptime, $flags );
+ } else {
+ $this->logger->info(
+ __METHOD__ . ' failed due to race condition for {key}.',
+ [ 'key' => $key ]
+ );
+
+ $success = false; // mismatched or failed
+ }
+
+ wincache_unlock( $key );
+
+ return $success;
+ }
+
+ protected function doSet( $key, $value, $exptime = 0, $flags = 0 ) {
+ $result = wincache_ucache_set( $key, $this->serialize( $value ), $exptime );
+
+ // false positive, wincache_ucache_set returns an empty array
+ // in some circumstances.
+ // @phan-suppress-next-line PhanTypeComparisonToArray
+ return ( $result === [] || $result === true );
+ }
+
+ public function add( $key, $value, $exptime = 0, $flags = 0 ) {
+ if ( wincache_ucache_exists( $key ) ) {
+ return false; // avoid warnings
+ }
+
+ $result = wincache_ucache_add( $key, $this->serialize( $value ), $exptime );
+
+ // false positive, wincache_ucache_add returns an empty array
+ // in some circumstances.
+ // @phan-suppress-next-line PhanTypeComparisonToArray
+ return ( $result === [] || $result === true );
+ }
+
+ protected function doDelete( $key, $flags = 0 ) {
+ wincache_ucache_delete( $key );
+
+ return true;
+ }
+
+ /**
+ * Construct a cache key.
+ *
+ * @since 1.27
+ * @param string $keyspace
+ * @param array $args
+ * @return string
+ */
+ public function makeKeyInternal( $keyspace, $args ) {
+ // WinCache keys have a maximum length of 150 characters. From that,
+ // subtract the number of characters we need for the keyspace and for
+ // the separator character needed for each argument. To handle some
+ // custom prefixes used by thing like WANObjectCache, limit to 125.
+ // NOTE: Same as in memcached, except the max key length there is 255.
+ $charsLeft = 125 - strlen( $keyspace ) - count( $args );
+
+ $args = array_map(
+ function ( $arg ) use ( &$charsLeft ) {
+ // 33 = 32 characters for the MD5 + 1 for the '#' prefix.
+ if ( $charsLeft > 33 && strlen( $arg ) > $charsLeft ) {
+ $arg = '#' . md5( $arg );
+ }
+
+ $charsLeft -= strlen( $arg );
+ return $arg;
+ },
+ $args
+ );
+
+ if ( $charsLeft < 0 ) {
+ return $keyspace . ':BagOStuff-long-key:##' . md5( implode( ':', $args ) );
+ }
+
+ return $keyspace . ':' . implode( ':', $args );
+ }
+
+ /**
+ * Increase stored value of $key by $value while preserving its original TTL
+ * @param string $key Key to increase
+ * @param int $value Value to add to $key (Default 1)
+ * @return int|bool New value or false on failure
+ */
+ public function incr( $key, $value = 1 ) {
+ if ( !wincache_lock( $key ) ) { // optimize with FIFO lock
+ return false;
+ }
+
+ $n = $this->doGet( $key );
+ if ( $this->isInteger( $n ) ) {
+ $n = max( $n + (int)$value, 0 );
+ $oldTTL = wincache_ucache_info( false, $key )["ucache_entries"][1]["ttl_seconds"];
+ $this->set( $key, $n, $oldTTL );
+ } else {
+ $n = false;
+ }
+
+ wincache_unlock( $key );
+
+ return $n;
+ }
+}
--- /dev/null
+<?php
+/**
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup Cache
+ */
+
+use Liuggio\StatsdClient\Factory\StatsdDataFactoryInterface;
+use Psr\Log\LoggerAwareInterface;
+use Psr\Log\LoggerInterface;
+use Psr\Log\NullLogger;
+
+/**
+ * Multi-datacenter aware caching interface
+ *
+ * ### Using WANObjectCache
+ *
+ * All operations go to the local datacenter cache, except for delete(),
+ * touchCheckKey(), and resetCheckKey(), which broadcast to all datacenters.
+ *
+ * This class is intended for caching data from primary stores.
+ * If the get() method does not return a value, then the caller
+ * should query the new value and backfill the cache using set().
+ * The preferred way to do this logic is through getWithSetCallback().
+ * When querying the store on cache miss, the closest DB replica
+ * should be used. Try to avoid heavyweight DB master or quorum reads.
+ *
+ * To ensure consumers of the cache see new values in a timely manner,
+ * you either need to follow either the validation strategy, or the
+ * purge strategy.
+ *
+ * The validation strategy refers to the natural avoidance of stale data
+ * by one of the following means:
+ *
+ * - A) The cached value is immutable.
+ * If the consumer has access to an identifier that uniquely describes a value,
+ * cached value need not change. Instead, the key can change. This also allows
+ * all servers to access their perceived current version. This is important
+ * in context of multiple deployed versions of your application and/or cross-dc
+ * database replication, to ensure deterministic values without oscillation.
+ * - B) Validity is checked against the source after get().
+ * This is the inverse of A. The unique identifier is embedded inside the value
+ * and validated after on retreival. If outdated, the value is recomputed.
+ * - C) The value is cached with a modest TTL (without validation).
+ * If value recomputation is reasonably performant, and the value is allowed to
+ * be stale, one should consider using TTL only – using the value's age as
+ * method of validation.
+ *
+ * The purge strategy refers to the the approach whereby your application knows that
+ * source data has changed and can react by purging the relevant cache keys.
+ * As purges are expensive, this strategy should be avoided if possible.
+ * The simplest purge method is delete().
+ *
+ * No matter which strategy you choose, callers must not rely on updates or purges
+ * being immediately visible to other servers. It should be treated similarly as
+ * one would a database replica.
+ *
+ * The need for immediate updates should be avoided. If needed, solutions must be
+ * sought outside WANObjectCache.
+ *
+ * ### Deploying WANObjectCache
+ *
+ * There are two supported ways to set up broadcasted operations:
+ *
+ * - A) Set up mcrouter as the underlying cache backend, using a memcached BagOStuff class
+ * for the 'cache' parameter. The 'region' and 'cluster' parameters must be provided
+ * and 'mcrouterAware' must be set to `true`.
+ * Configure mcrouter as follows:
+ * - 1) Use Route Prefixing based on region (datacenter) and cache cluster.
+ * See https://github.com/facebook/mcrouter/wiki/Routing-Prefix and
+ * https://github.com/facebook/mcrouter/wiki/Multi-cluster-broadcast-setup.
+ * - 2) To increase the consistency of delete() and touchCheckKey() during cache
+ * server membership changes, you can use the OperationSelectorRoute to
+ * configure 'set' and 'delete' operations to go to all servers in the cache
+ * cluster, instead of just one server determined by hashing.
+ * See https://github.com/facebook/mcrouter/wiki/List-of-Route-Handles.
+ * - B) Set up dynomite as a cache middleware between the web servers and either memcached
+ * or redis and use it as the underlying cache backend, using a memcached BagOStuff
+ * class for the 'cache' parameter. This will broadcast all key setting operations,
+ * not just purges, which can be useful for cache warming. Writes are eventually
+ * consistent via the Dynamo replication model. See https://github.com/Netflix/dynomite.
+ *
+ * Broadcasted operations like delete() and touchCheckKey() are intended to run
+ * immediately in the local datacenter and asynchronously in remote datacenters.
+ *
+ * This means that callers in all datacenters may see older values for however many
+ * milliseconds that the purge took to reach that datacenter. As with any cache, this
+ * should not be relied on for cases where reads are used to determine writes to source
+ * (e.g. non-cache) data stores, except when reading immutable data.
+ *
+ * All values are wrapped in metadata arrays. Keys use a "WANCache:" prefix
+ * to avoid collisions with keys that are not wrapped as metadata arrays. The
+ * prefixes are as follows:
+ * - a) "WANCache:v" : used for regular value keys
+ * - b) "WANCache:i" : used for temporarily storing values of tombstoned keys
+ * - c) "WANCache:t" : used for storing timestamp "check" keys
+ * - d) "WANCache:m" : used for temporary mutex keys to avoid cache stampedes
+ *
+ * @ingroup Cache
+ * @since 1.26
+ */
+class WANObjectCache implements IExpiringStore, IStoreKeyEncoder, LoggerAwareInterface {
+ /** @var BagOStuff The local datacenter cache */
+ protected $cache;
+ /** @var MapCacheLRU[] Map of group PHP instance caches */
+ protected $processCaches = [];
+ /** @var LoggerInterface */
+ protected $logger;
+ /** @var StatsdDataFactoryInterface */
+ protected $stats;
+ /** @var callable|null Function that takes a WAN cache callback and runs it later */
+ protected $asyncHandler;
+
+ /** @bar bool Whether to use mcrouter key prefixing for routing */
+ protected $mcrouterAware;
+ /** @var string Physical region for mcrouter use */
+ protected $region;
+ /** @var string Cache cluster name for mcrouter use */
+ protected $cluster;
+ /** @var bool Whether to use "interim" caching while keys are tombstoned */
+ protected $useInterimHoldOffCaching = true;
+ /** @var float Unix timestamp of the oldest possible valid values */
+ protected $epoch;
+ /** @var string Stable secret used for hasing long strings into key components */
+ protected $secret;
+
+ /** @var int Callback stack depth for getWithSetCallback() */
+ private $callbackDepth = 0;
+ /** @var mixed[] Temporary warm-up cache */
+ private $warmupCache = [];
+ /** @var int Key fetched */
+ private $warmupKeyMisses = 0;
+
+ /** @var float|null */
+ private $wallClockOverride;
+
+ /** @var int Max expected seconds to pass between delete() and DB commit finishing */
+ const MAX_COMMIT_DELAY = 3;
+ /** @var int Max expected seconds of combined lag from replication and view snapshots */
+ const MAX_READ_LAG = 7;
+ /** @var int Seconds to tombstone keys on delete() and treat as volatile after invalidation */
+ const HOLDOFF_TTL = self::MAX_COMMIT_DELAY + self::MAX_READ_LAG + 1;
+
+ /** @var int Idiom for getWithSetCallback() meaning "do not store the callback result" */
+ const TTL_UNCACHEABLE = -1;
+
+ /** @var int Consider regeneration if the key will expire within this many seconds */
+ const LOW_TTL = 30;
+ /** @var int Max TTL, in seconds, to store keys when a data sourced is lagged */
+ const TTL_LAGGED = 30;
+
+ /** @var int Expected time-till-refresh, in seconds, if the key is accessed once per second */
+ const HOT_TTR = 900;
+ /** @var int Minimum key age, in seconds, for expected time-till-refresh to be considered */
+ const AGE_NEW = 60;
+
+ /** @var int Idiom for getWithSetCallback() meaning "no cache stampede mutex required" */
+ const TSE_NONE = -1;
+
+ /** @var int Idiom for set()/getWithSetCallback() meaning "no post-expiration persistence" */
+ const STALE_TTL_NONE = 0;
+ /** @var int Idiom for set()/getWithSetCallback() meaning "no post-expiration grace period" */
+ const GRACE_TTL_NONE = 0;
+ /** @var int Idiom for delete()/touchCheckKey() meaning "no hold-off period" */
+ const HOLDOFF_TTL_NONE = 0;
+ /** @var int Alias for HOLDOFF_TTL_NONE (b/c) (deprecated since 1.34) */
+ const HOLDOFF_NONE = self::HOLDOFF_TTL_NONE;
+
+ /** @var float Idiom for getWithSetCallback() meaning "no minimum required as-of timestamp" */
+ const MIN_TIMESTAMP_NONE = 0.0;
+
+ /** @var string Default process cache name and max key count */
+ const PC_PRIMARY = 'primary:1000';
+
+ /** @var int Idion for get()/getMulti() to return extra information by reference */
+ const PASS_BY_REF = -1;
+
+ /** @var int Seconds to keep dependency purge keys around */
+ private static $CHECK_KEY_TTL = self::TTL_YEAR;
+ /** @var int Seconds to keep interim value keys for tombstoned keys around */
+ private static $INTERIM_KEY_TTL = 1;
+
+ /** @var int Seconds to keep lock keys around */
+ private static $LOCK_TTL = 10;
+ /** @var int Seconds to no-op key set() calls to avoid large blob I/O stampedes */
+ private static $COOLOFF_TTL = 1;
+ /** @var int Seconds to ramp up the chance of regeneration due to expected time-till-refresh */
+ private static $RAMPUP_TTL = 30;
+
+ /** @var float Tiny negative float to use when CTL comes up >= 0 due to clock skew */
+ private static $TINY_NEGATIVE = -0.000001;
+ /** @var float Tiny positive float to use when using "minTime" to assert an inequality */
+ private static $TINY_POSTIVE = 0.000001;
+
+ /** @var int Milliseconds of key fetch/validate/regenerate delay prone to set() stampedes */
+ private static $SET_DELAY_HIGH_MS = 50;
+ /** @var int Min millisecond set() backoff during hold-off (far less than INTERIM_KEY_TTL) */
+ private static $RECENT_SET_LOW_MS = 50;
+ /** @var int Max millisecond set() backoff during hold-off (far less than INTERIM_KEY_TTL) */
+ private static $RECENT_SET_HIGH_MS = 100;
+
+ /** @var int Consider value generation slow if it takes more than this many seconds */
+ private static $GENERATION_SLOW_SEC = 3;
+
+ /** @var int Key to the tombstone entry timestamp */
+ private static $PURGE_TIME = 0;
+ /** @var int Key to the tombstone entry hold-off TTL */
+ private static $PURGE_HOLDOFF = 1;
+
+ /** @var int Cache format version number */
+ private static $VERSION = 1;
+
+ /** @var int Key to WAN cache version number */
+ private static $FLD_FORMAT_VERSION = 0;
+ /** @var int Key to the cached value */
+ private static $FLD_VALUE = 1;
+ /** @var int Key to the original TTL */
+ private static $FLD_TTL = 2;
+ /** @var int Key to the cache timestamp */
+ private static $FLD_TIME = 3;
+ /** @var int Key to the flags bit field (reserved number) */
+ private static /** @noinspection PhpUnusedPrivateFieldInspection */ $FLD_FLAGS = 4;
+ /** @var int Key to collection cache version number */
+ private static $FLD_VALUE_VERSION = 5;
+ /** @var int Key to how long it took to generate the value */
+ private static $FLD_GENERATION_TIME = 6;
+
+ private static $VALUE_KEY_PREFIX = 'WANCache:v:';
+ private static $INTERIM_KEY_PREFIX = 'WANCache:i:';
+ private static $TIME_KEY_PREFIX = 'WANCache:t:';
+ private static $MUTEX_KEY_PREFIX = 'WANCache:m:';
+ private static $COOLOFF_KEY_PREFIX = 'WANCache:c:';
+
+ private static $PURGE_VAL_PREFIX = 'PURGED:';
+
+ /**
+ * @param array $params
+ * - cache : BagOStuff object for a persistent cache
+ * - logger : LoggerInterface object
+ * - stats : StatsdDataFactoryInterface object
+ * - asyncHandler : A function that takes a callback and runs it later. If supplied,
+ * whenever a preemptive refresh would be triggered in getWithSetCallback(), the
+ * current cache value is still used instead. However, the async-handler function
+ * receives a WAN cache callback that, when run, will execute the value generation
+ * callback supplied by the getWithSetCallback() caller. The result will be saved
+ * as normal. The handler is expected to call the WAN cache callback at an opportune
+ * time (e.g. HTTP post-send), though generally within a few 100ms. [optional]
+ * - region: the current physical region. This is required when using mcrouter as the
+ * backing store proxy. [optional]
+ * - cluster: name of the cache cluster used by this WAN cache. The name must be the
+ * same in all datacenters; the ("region","cluster") tuple is what distinguishes
+ * the counterpart cache clusters among all the datacenter. The contents of
+ * https://github.com/facebook/mcrouter/wiki/Config-Files give background on this.
+ * This is required when using mcrouter as the backing store proxy. [optional]
+ * - mcrouterAware: set as true if mcrouter is the backing store proxy and mcrouter
+ * is configured to interpret /<region>/<cluster>/ key prefixes as routes. This
+ * requires that "region" and "cluster" are both set above. [optional]
+ * - epoch: lowest UNIX timestamp a value/tombstone must have to be valid. [optional]
+ * - secret: stable secret used for hashing long strings into key components. [optional]
+ */
+ public function __construct( array $params ) {
+ $this->cache = $params['cache'];
+ $this->region = $params['region'] ?? 'main';
+ $this->cluster = $params['cluster'] ?? 'wan-main';
+ $this->mcrouterAware = !empty( $params['mcrouterAware'] );
+ $this->epoch = $params['epoch'] ?? 0;
+ $this->secret = $params['secret'] ?? (string)$this->epoch;
+
+ $this->setLogger( $params['logger'] ?? new NullLogger() );
+ $this->stats = $params['stats'] ?? new NullStatsdDataFactory();
+ $this->asyncHandler = $params['asyncHandler'] ?? null;
+ }
+
+ /**
+ * @param LoggerInterface $logger
+ */
+ public function setLogger( LoggerInterface $logger ) {
+ $this->logger = $logger;
+ }
+
+ /**
+ * Get an instance that wraps EmptyBagOStuff
+ *
+ * @return WANObjectCache
+ */
+ public static function newEmpty() {
+ return new static( [ 'cache' => new EmptyBagOStuff() ] );
+ }
+
+ /**
+ * Fetch the value of a key from cache
+ *
+ * If supplied, $curTTL is set to the remaining TTL (current time left):
+ * - a) INF; if $key exists, has no TTL, and is not invalidated by $checkKeys
+ * - b) float (>=0); if $key exists, has a TTL, and is not invalidated by $checkKeys
+ * - c) float (<0); if $key is tombstoned, stale, or existing but invalidated by $checkKeys
+ * - d) null; if $key does not exist and is not tombstoned
+ *
+ * If a key is tombstoned, $curTTL will reflect the time since delete().
+ *
+ * The timestamp of $key will be checked against the last-purge timestamp
+ * of each of $checkKeys. Those $checkKeys not in cache will have the last-purge
+ * initialized to the current timestamp. If any of $checkKeys have a timestamp
+ * greater than that of $key, then $curTTL will reflect how long ago $key
+ * became invalid. Callers can use $curTTL to know when the value is stale.
+ * The $checkKeys parameter allow mass invalidations by updating a single key:
+ * - a) Each "check" key represents "last purged" of some source data
+ * - b) Callers pass in relevant "check" keys as $checkKeys in get()
+ * - c) When the source data that "check" keys represent changes,
+ * the touchCheckKey() method is called on them
+ *
+ * Source data entities might exists in a DB that uses snapshot isolation
+ * (e.g. the default REPEATABLE-READ in innoDB). Even for mutable data, that
+ * isolation can largely be maintained by doing the following:
+ * - a) Calling delete() on entity change *and* creation, before DB commit
+ * - b) Keeping transaction duration shorter than the delete() hold-off TTL
+ * - c) Disabling interim key caching via useInterimHoldOffCaching() before get() calls
+ *
+ * However, pre-snapshot values might still be seen if an update was made
+ * in a remote datacenter but the purge from delete() didn't relay yet.
+ *
+ * Consider using getWithSetCallback() instead of get() and set() cycles.
+ * That method has cache slam avoiding features for hot/expensive keys.
+ *
+ * Pass $info as WANObjectCache::PASS_BY_REF to transform it into a cache key metadata map.
+ * This map includes the following metadata:
+ * - asOf: UNIX timestamp of the value or null if the key is nonexistant
+ * - tombAsOf: UNIX timestamp of the tombstone or null if the key is not tombstoned
+ * - lastCKPurge: UNIX timestamp of the highest check key or null if none provided
+ * - version: cached value version number or null if the key is nonexistant
+ *
+ * Otherwise, $info will transform into the cached value timestamp.
+ *
+ * @param string $key Cache key made from makeKey() or makeGlobalKey()
+ * @param mixed|null &$curTTL Approximate TTL left on the key if present/tombstoned [returned]
+ * @param string[] $checkKeys The "check" keys used to validate the value
+ * @param mixed|null &$info Key info if WANObjectCache::PASS_BY_REF [returned]
+ * @return mixed Value of cache key or false on failure
+ */
+ final public function get(
+ $key, &$curTTL = null, array $checkKeys = [], &$info = null
+ ) {
+ $curTTLs = self::PASS_BY_REF;
+ $infoByKey = self::PASS_BY_REF;
+ $values = $this->getMulti( [ $key ], $curTTLs, $checkKeys, $infoByKey );
+ $curTTL = $curTTLs[$key] ?? null;
+ if ( $info === self::PASS_BY_REF ) {
+ $info = [
+ 'asOf' => $infoByKey[$key]['asOf'] ?? null,
+ 'tombAsOf' => $infoByKey[$key]['tombAsOf'] ?? null,
+ 'lastCKPurge' => $infoByKey[$key]['lastCKPurge'] ?? null,
+ 'version' => $infoByKey[$key]['version'] ?? null
+ ];
+ } else {
+ $info = $infoByKey[$key]['asOf'] ?? null; // b/c
+ }
+
+ return $values[$key] ?? false;
+ }
+
+ /**
+ * Fetch the value of several keys from cache
+ *
+ * Pass $info as WANObjectCache::PASS_BY_REF to transform it into a map of cache keys
+ * to cache key metadata maps, each having the same style as those of WANObjectCache::get().
+ * All the cache keys listed in $keys will have an entry.
+ *
+ * Othwerwise, $info will transform into a map of (cache key => cached value timestamp).
+ * Only the cache keys listed in $keys that exists or are tombstoned will have an entry.
+ *
+ * $checkKeys holds the "check" keys used to validate values of applicable keys. The integer
+ * indexes hold "check" keys that apply to all of $keys while the string indexes hold "check"
+ * keys that only apply to the cache key with that name.
+ *
+ * @see WANObjectCache::get()
+ *
+ * @param string[] $keys List of cache keys made from makeKey() or makeGlobalKey()
+ * @param mixed|null &$curTTLs Map of (key => TTL left) for existing/tombstoned keys [returned]
+ * @param string[]|string[][] $checkKeys Map of (integer or cache key => "check" key(s))
+ * @param mixed|null &$info Map of (key => info) if WANObjectCache::PASS_BY_REF [returned]
+ * @return mixed[] Map of (key => value) for existing values; order of $keys is preserved
+ */
+ final public function getMulti(
+ array $keys,
+ &$curTTLs = [],
+ array $checkKeys = [],
+ &$info = null
+ ) {
+ $result = [];
+ $curTTLs = [];
+ $infoByKey = [];
+
+ $vPrefixLen = strlen( self::$VALUE_KEY_PREFIX );
+ $valueKeys = self::prefixCacheKeys( $keys, self::$VALUE_KEY_PREFIX );
+
+ $checkKeysForAll = [];
+ $checkKeysByKey = [];
+ $checkKeysFlat = [];
+ foreach ( $checkKeys as $i => $checkKeyGroup ) {
+ $prefixed = self::prefixCacheKeys( (array)$checkKeyGroup, self::$TIME_KEY_PREFIX );
+ $checkKeysFlat = array_merge( $checkKeysFlat, $prefixed );
+ // Are these check keys for a specific cache key, or for all keys being fetched?
+ if ( is_int( $i ) ) {
+ $checkKeysForAll = array_merge( $checkKeysForAll, $prefixed );
+ } else {
+ $checkKeysByKey[$i] = $prefixed;
+ }
+ }
+
+ // Fetch all of the raw values
+ $keysGet = array_merge( $valueKeys, $checkKeysFlat );
+ if ( $this->warmupCache ) {
+ $wrappedValues = array_intersect_key( $this->warmupCache, array_flip( $keysGet ) );
+ $keysGet = array_diff( $keysGet, array_keys( $wrappedValues ) ); // keys left to fetch
+ $this->warmupKeyMisses += count( $keysGet );
+ } else {
+ $wrappedValues = [];
+ }
+ if ( $keysGet ) {
+ $wrappedValues += $this->cache->getMulti( $keysGet );
+ }
+ // Time used to compare/init "check" keys (derived after getMulti() to be pessimistic)
+ $now = $this->getCurrentTime();
+
+ // Collect timestamps from all "check" keys
+ $purgeValuesForAll = $this->processCheckKeys( $checkKeysForAll, $wrappedValues, $now );
+ $purgeValuesByKey = [];
+ foreach ( $checkKeysByKey as $cacheKey => $checks ) {
+ $purgeValuesByKey[$cacheKey] =
+ $this->processCheckKeys( $checks, $wrappedValues, $now );
+ }
+
+ // Get the main cache value for each key and validate them
+ foreach ( $valueKeys as $vKey ) {
+ $key = substr( $vKey, $vPrefixLen ); // unprefix
+ list( $value, $keyInfo ) = $this->unwrap( $wrappedValues[$vKey] ?? false, $now );
+ // Force dependent keys to be seen as stale for a while after purging
+ // to reduce race conditions involving stale data getting cached
+ $purgeValues = $purgeValuesForAll;
+ if ( isset( $purgeValuesByKey[$key] ) ) {
+ $purgeValues = array_merge( $purgeValues, $purgeValuesByKey[$key] );
+ }
+
+ $lastCKPurge = null; // timestamp of the highest check key
+ foreach ( $purgeValues as $purge ) {
+ $lastCKPurge = max( $purge[self::$PURGE_TIME], $lastCKPurge );
+ $safeTimestamp = $purge[self::$PURGE_TIME] + $purge[self::$PURGE_HOLDOFF];
+ if ( $value !== false && $safeTimestamp >= $keyInfo['asOf'] ) {
+ // How long ago this value was invalidated by *this* check key
+ $ago = min( $purge[self::$PURGE_TIME] - $now, self::$TINY_NEGATIVE );
+ // How long ago this value was invalidated by *any* known check key
+ $keyInfo['curTTL'] = min( $keyInfo['curTTL'], $ago );
+ }
+ }
+ $keyInfo[ 'lastCKPurge'] = $lastCKPurge;
+
+ if ( $value !== false ) {
+ $result[$key] = $value;
+ }
+ if ( $keyInfo['curTTL'] !== null ) {
+ $curTTLs[$key] = $keyInfo['curTTL'];
+ }
+
+ $infoByKey[$key] = ( $info === self::PASS_BY_REF )
+ ? $keyInfo
+ : $keyInfo['asOf']; // b/c
+ }
+
+ $info = $infoByKey;
+
+ return $result;
+ }
+
+ /**
+ * @since 1.27
+ * @param string[] $timeKeys List of prefixed time check keys
+ * @param mixed[] $wrappedValues
+ * @param float $now
+ * @return array[] List of purge value arrays
+ */
+ private function processCheckKeys( array $timeKeys, array $wrappedValues, $now ) {
+ $purgeValues = [];
+ foreach ( $timeKeys as $timeKey ) {
+ $purge = isset( $wrappedValues[$timeKey] )
+ ? $this->parsePurgeValue( $wrappedValues[$timeKey] )
+ : false;
+ if ( $purge === false ) {
+ // Key is not set or malformed; regenerate
+ $newVal = $this->makePurgeValue( $now, self::HOLDOFF_TTL );
+ $this->cache->add( $timeKey, $newVal, self::$CHECK_KEY_TTL );
+ $purge = $this->parsePurgeValue( $newVal );
+ }
+ $purgeValues[] = $purge;
+ }
+ return $purgeValues;
+ }
+
+ /**
+ * Set the value of a key in cache
+ *
+ * Simply calling this method when source data changes is not valid because
+ * the changes do not replicate to the other WAN sites. In that case, delete()
+ * should be used instead. This method is intended for use on cache misses.
+ *
+ * If the data was read from a snapshot-isolated transactions (e.g. the default
+ * REPEATABLE-READ in innoDB), use 'since' to avoid the following race condition:
+ * - a) T1 starts
+ * - b) T2 updates a row, calls delete(), and commits
+ * - c) The HOLDOFF_TTL passes, expiring the delete() tombstone
+ * - d) T1 reads the row and calls set() due to a cache miss
+ * - e) Stale value is stuck in cache
+ *
+ * Setting 'lag' and 'since' help avoids keys getting stuck in stale states.
+ *
+ * Be aware that this does not update the process cache for getWithSetCallback()
+ * callers. Keys accessed via that method are not generally meant to also be set
+ * using this primitive method.
+ *
+ * Do not use this method on versioned keys accessed via getWithSetCallback().
+ *
+ * Example usage:
+ * @code
+ * $dbr = wfGetDB( DB_REPLICA );
+ * $setOpts = Database::getCacheSetOptions( $dbr );
+ * // Fetch the row from the DB
+ * $row = $dbr->selectRow( ... );
+ * $key = $cache->makeKey( 'building', $buildingId );
+ * $cache->set( $key, $row, $cache::TTL_DAY, $setOpts );
+ * @endcode
+ *
+ * @param string $key Cache key
+ * @param mixed $value
+ * @param int $ttl Seconds to live. Special values are:
+ * - WANObjectCache::TTL_INDEFINITE: Cache forever (default)
+ * - WANObjectCache::TTL_UNCACHEABLE: Do not cache (if the key exists, it is not deleted)
+ * @param array $opts Options map:
+ * - lag: Seconds of replica DB lag. Typically, this is either the replica DB lag
+ * before the data was read or, if applicable, the replica DB lag before
+ * the snapshot-isolated transaction the data was read from started.
+ * Use false to indicate that replication is not running.
+ * Default: 0 seconds
+ * - since: UNIX timestamp of the data in $value. Typically, this is either
+ * the current time the data was read or (if applicable) the time when
+ * the snapshot-isolated transaction the data was read from started.
+ * Default: 0 seconds
+ * - pending: Whether this data is possibly from an uncommitted write transaction.
+ * Generally, other threads should not see values from the future and
+ * they certainly should not see ones that ended up getting rolled back.
+ * Default: false
+ * - lockTSE: If excessive replication/snapshot lag is detected, then store the value
+ * with this TTL and flag it as stale. This is only useful if the reads for this key
+ * use getWithSetCallback() with "lockTSE" set. Note that if "staleTTL" is set
+ * then it will still add on to this TTL in the excessive lag scenario.
+ * Default: WANObjectCache::TSE_NONE
+ * - staleTTL: Seconds to keep the key around if it is stale. The get()/getMulti()
+ * methods return such stale values with a $curTTL of 0, and getWithSetCallback()
+ * will call the regeneration callback in such cases, passing in the old value
+ * and its as-of time to the callback. This is useful if adaptiveTTL() is used
+ * on the old value's as-of time when it is verified as still being correct.
+ * Default: WANObjectCache::STALE_TTL_NONE
+ * - creating: Optimize for the case where the key does not already exist.
+ * Default: false
+ * - version: Integer version number signifiying the format of the value.
+ * Default: null
+ * - walltime: How long the value took to generate in seconds. Default: 0.0
+ * @note Options added in 1.28: staleTTL
+ * @note Options added in 1.33: creating
+ * @note Options added in 1.34: version, walltime
+ * @return bool Success
+ */
+ final public function set( $key, $value, $ttl = self::TTL_INDEFINITE, array $opts = [] ) {
+ $now = $this->getCurrentTime();
+ $lag = $opts['lag'] ?? 0;
+ $age = isset( $opts['since'] ) ? max( 0, $now - $opts['since'] ) : 0;
+ $pending = $opts['pending'] ?? false;
+ $lockTSE = $opts['lockTSE'] ?? self::TSE_NONE;
+ $staleTTL = $opts['staleTTL'] ?? self::STALE_TTL_NONE;
+ $creating = $opts['creating'] ?? false;
+ $version = $opts['version'] ?? null;
+ $walltime = $opts['walltime'] ?? 0.0;
+
+ if ( $ttl < 0 ) {
+ return true;
+ }
+
+ // Do not cache potentially uncommitted data as it might get rolled back
+ if ( $pending ) {
+ $this->logger->info(
+ 'Rejected set() for {cachekey} due to pending writes.',
+ [ 'cachekey' => $key ]
+ );
+
+ return true; // no-op the write for being unsafe
+ }
+
+ $logicalTTL = null; // logical TTL override
+ // Check if there's a risk of writing stale data after the purge tombstone expired
+ if ( $lag === false || ( $lag + $age ) > self::MAX_READ_LAG ) {
+ // Case A: any long-running transaction
+ if ( $age > self::MAX_READ_LAG ) {
+ if ( $lockTSE >= 0 ) {
+ // Store value as *almost* stale to avoid cache and mutex stampedes
+ $logicalTTL = self::TTL_SECOND;
+ $this->logger->info(
+ 'Lowered set() TTL for {cachekey} due to snapshot lag.',
+ [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
+ );
+ } else {
+ $this->logger->info(
+ 'Rejected set() for {cachekey} due to snapshot lag.',
+ [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
+ );
+
+ return true; // no-op the write for being unsafe
+ }
+ // Case B: high replication lag; lower TTL instead of ignoring all set()s
+ } elseif ( $lag === false || $lag > self::MAX_READ_LAG ) {
+ if ( $lockTSE >= 0 ) {
+ $logicalTTL = min( $ttl ?: INF, self::TTL_LAGGED );
+ } else {
+ $ttl = min( $ttl ?: INF, self::TTL_LAGGED );
+ }
+ $this->logger->warning(
+ 'Lowered set() TTL for {cachekey} due to replication lag.',
+ [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
+ );
+ // Case C: medium length request with medium replication lag
+ } elseif ( $lockTSE >= 0 ) {
+ // Store value as *almost* stale to avoid cache and mutex stampedes
+ $logicalTTL = self::TTL_SECOND;
+ $this->logger->info(
+ 'Lowered set() TTL for {cachekey} due to high read lag.',
+ [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
+ );
+ } else {
+ $this->logger->info(
+ 'Rejected set() for {cachekey} due to high read lag.',
+ [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
+ );
+
+ return true; // no-op the write for being unsafe
+ }
+ }
+
+ // Wrap that value with time/TTL/version metadata
+ $wrapped = $this->wrap( $value, $logicalTTL ?: $ttl, $version, $now, $walltime );
+ $storeTTL = $ttl + $staleTTL;
+
+ if ( $creating ) {
+ $ok = $this->cache->add( self::$VALUE_KEY_PREFIX . $key, $wrapped, $storeTTL );
+ } else {
+ $ok = $this->cache->merge(
+ self::$VALUE_KEY_PREFIX . $key,
+ function ( $cache, $key, $cWrapped ) use ( $wrapped ) {
+ // A string value means that it is a tombstone; do nothing in that case
+ return ( is_string( $cWrapped ) ) ? false : $wrapped;
+ },
+ $storeTTL,
+ 1 // 1 attempt
+ );
+ }
+
+ return $ok;
+ }
+
+ /**
+ * Purge a key from all datacenters
+ *
+ * This should only be called when the underlying data (being cached)
+ * changes in a significant way. This deletes the key and starts a hold-off
+ * period where the key cannot be written to for a few seconds (HOLDOFF_TTL).
+ * This is done to avoid the following race condition:
+ * - a) Some DB data changes and delete() is called on a corresponding key
+ * - b) A request refills the key with a stale value from a lagged DB
+ * - c) The stale value is stuck there until the key is expired/evicted
+ *
+ * This is implemented by storing a special "tombstone" value at the cache
+ * key that this class recognizes; get() calls will return false for the key
+ * and any set() calls will refuse to replace tombstone values at the key.
+ * For this to always avoid stale value writes, the following must hold:
+ * - a) Replication lag is bounded to being less than HOLDOFF_TTL; or
+ * - b) If lag is higher, the DB will have gone into read-only mode already
+ *
+ * Note that set() can also be lag-aware and lower the TTL if it's high.
+ *
+ * Be aware that this does not clear the process cache. Even if it did, callbacks
+ * used by getWithSetCallback() might still return stale data in the case of either
+ * uncommitted or not-yet-replicated changes (callback generally use replica DBs).
+ *
+ * When using potentially long-running ACID transactions, a good pattern is
+ * to use a pre-commit hook to issue the delete. This means that immediately
+ * after commit, callers will see the tombstone in cache upon purge relay.
+ * It also avoids the following race condition:
+ * - a) T1 begins, changes a row, and calls delete()
+ * - b) The HOLDOFF_TTL passes, expiring the delete() tombstone
+ * - c) T2 starts, reads the row and calls set() due to a cache miss
+ * - d) T1 finally commits
+ * - e) Stale value is stuck in cache
+ *
+ * Example usage:
+ * @code
+ * $dbw->startAtomic( __METHOD__ ); // start of request
+ * ... <execute some stuff> ...
+ * // Update the row in the DB
+ * $dbw->update( ... );
+ * $key = $cache->makeKey( 'homes', $homeId );
+ * // Purge the corresponding cache entry just before committing
+ * $dbw->onTransactionPreCommitOrIdle( function() use ( $cache, $key ) {
+ * $cache->delete( $key );
+ * } );
+ * ... <execute some stuff> ...
+ * $dbw->endAtomic( __METHOD__ ); // end of request
+ * @endcode
+ *
+ * The $ttl parameter can be used when purging values that have not actually changed
+ * recently. For example, a cleanup script to purge cache entries does not really need
+ * a hold-off period, so it can use HOLDOFF_TTL_NONE. Likewise for user-requested purge.
+ * Note that $ttl limits the effective range of 'lockTSE' for getWithSetCallback().
+ *
+ * If called twice on the same key, then the last hold-off TTL takes precedence. For
+ * idempotence, the $ttl should not vary for different delete() calls on the same key.
+ *
+ * @param string $key Cache key
+ * @param int $ttl Tombstone TTL; Default: WANObjectCache::HOLDOFF_TTL
+ * @return bool True if the item was purged or not found, false on failure
+ */
+ final public function delete( $key, $ttl = self::HOLDOFF_TTL ) {
+ if ( $ttl <= 0 ) {
+ // Publish the purge to all datacenters
+ $ok = $this->relayDelete( self::$VALUE_KEY_PREFIX . $key );
+ } else {
+ // Publish the purge to all datacenters
+ $ok = $this->relayPurge( self::$VALUE_KEY_PREFIX . $key, $ttl, self::HOLDOFF_TTL_NONE );
+ }
+
+ $kClass = $this->determineKeyClassForStats( $key );
+ $this->stats->increment( "wanobjectcache.$kClass.delete." . ( $ok ? 'ok' : 'error' ) );
+
+ return $ok;
+ }
+
+ /**
+ * Fetch the value of a timestamp "check" key
+ *
+ * The key will be *initialized* to the current time if not set,
+ * so only call this method if this behavior is actually desired
+ *
+ * The timestamp can be used to check whether a cached value is valid.
+ * Callers should not assume that this returns the same timestamp in
+ * all datacenters due to relay delays.
+ *
+ * The level of staleness can roughly be estimated from this key, but
+ * if the key was evicted from cache, such calculations may show the
+ * time since expiry as ~0 seconds.
+ *
+ * Note that "check" keys won't collide with other regular keys.
+ *
+ * @param string $key
+ * @return float UNIX timestamp
+ */
+ final public function getCheckKeyTime( $key ) {
+ return $this->getMultiCheckKeyTime( [ $key ] )[$key];
+ }
+
+ /**
+ * Fetch the values of each timestamp "check" key
+ *
+ * This works like getCheckKeyTime() except it takes a list of keys
+ * and returns a map of timestamps instead of just that of one key
+ *
+ * This might be useful if both:
+ * - a) a class of entities each depend on hundreds of other entities
+ * - b) these other entities are depended upon by millions of entities
+ *
+ * The later entities can each use a "check" key to invalidate their dependee entities.
+ * However, it is expensive for the former entities to verify against all of the relevant
+ * "check" keys during each getWithSetCallback() call. A less expensive approach is to do
+ * these verifications only after a "time-till-verify" (TTV) has passed. This is a middle
+ * ground between using blind TTLs and using constant verification. The adaptiveTTL() method
+ * can be used to dynamically adjust the TTV. Also, the initial TTV can make use of the
+ * last-modified times of the dependant entities (either from the DB or the "check" keys).
+ *
+ * Example usage:
+ * @code
+ * $value = $cache->getWithSetCallback(
+ * $cache->makeGlobalKey( 'wikibase-item', $id ),
+ * self::INITIAL_TTV, // initial time-till-verify
+ * function ( $oldValue, &$ttv, &$setOpts, $oldAsOf ) use ( $checkKeys, $cache ) {
+ * $now = microtime( true );
+ * // Use $oldValue if it passes max ultimate age and "check" key comparisons
+ * if ( $oldValue &&
+ * $oldAsOf > max( $cache->getMultiCheckKeyTime( $checkKeys ) ) &&
+ * ( $now - $oldValue['ctime'] ) <= self::MAX_CACHE_AGE
+ * ) {
+ * // Increase time-till-verify by 50% of last time to reduce overhead
+ * $ttv = $cache->adaptiveTTL( $oldAsOf, self::MAX_TTV, self::MIN_TTV, 1.5 );
+ * // Unlike $oldAsOf, "ctime" is the ultimate age of the cached data
+ * return $oldValue;
+ * }
+ *
+ * $mtimes = []; // dependency last-modified times; passed by reference
+ * $value = [ 'data' => $this->fetchEntityData( $mtimes ), 'ctime' => $now ];
+ * // Guess time-till-change among the dependencies, e.g. 1/(total change rate)
+ * $ttc = 1 / array_sum( array_map(
+ * function ( $mtime ) use ( $now ) {
+ * return 1 / ( $mtime ? ( $now - $mtime ) : 900 );
+ * },
+ * $mtimes
+ * ) );
+ * // The time-to-verify should not be overly pessimistic nor optimistic
+ * $ttv = min( max( $ttc, self::MIN_TTV ), self::MAX_TTV );
+ *
+ * return $value;
+ * },
+ * [ 'staleTTL' => $cache::TTL_DAY ] // keep around to verify and re-save
+ * );
+ * @endcode
+ *
+ * @see WANObjectCache::getCheckKeyTime()
+ * @see WANObjectCache::getWithSetCallback()
+ *
+ * @param string[] $keys
+ * @return float[] Map of (key => UNIX timestamp)
+ * @since 1.31
+ */
+ final public function getMultiCheckKeyTime( array $keys ) {
+ $rawKeys = [];
+ foreach ( $keys as $key ) {
+ $rawKeys[$key] = self::$TIME_KEY_PREFIX . $key;
+ }
+
+ $rawValues = $this->cache->getMulti( $rawKeys );
+ $rawValues += array_fill_keys( $rawKeys, false );
+
+ $times = [];
+ foreach ( $rawKeys as $key => $rawKey ) {
+ $purge = $this->parsePurgeValue( $rawValues[$rawKey] );
+ if ( $purge !== false ) {
+ $time = $purge[self::$PURGE_TIME];
+ } else {
+ // Casting assures identical floats for the next getCheckKeyTime() calls
+ $now = (string)$this->getCurrentTime();
+ $this->cache->add(
+ $rawKey,
+ $this->makePurgeValue( $now, self::HOLDOFF_TTL ),
+ self::$CHECK_KEY_TTL
+ );
+ $time = (float)$now;
+ }
+
+ $times[$key] = $time;
+ }
+
+ return $times;
+ }
+
+ /**
+ * Purge a "check" key from all datacenters, invalidating keys that use it
+ *
+ * This should only be called when the underlying data (being cached)
+ * changes in a significant way, and it is impractical to call delete()
+ * on all keys that should be changed. When get() is called on those
+ * keys, the relevant "check" keys must be supplied for this to work.
+ *
+ * The "check" key essentially represents a last-modified time of an entity.
+ * When the key is touched, the timestamp will be updated to the current time.
+ * Keys using the "check" key via get(), getMulti(), or getWithSetCallback() will
+ * be invalidated. This approach is useful if many keys depend on a single entity.
+ *
+ * The timestamp of the "check" key is treated as being HOLDOFF_TTL seconds in the
+ * future by get*() methods in order to avoid race conditions where keys are updated
+ * with stale values (e.g. from a lagged replica DB). A high TTL is set on the "check"
+ * key, making it possible to know the timestamp of the last change to the corresponding
+ * entities in most cases. This might use more cache space than resetCheckKey().
+ *
+ * When a few important keys get a large number of hits, a high cache time is usually
+ * desired as well as "lockTSE" logic. The resetCheckKey() method is less appropriate
+ * in such cases since the "time since expiry" cannot be inferred, causing any get()
+ * after the reset to treat the key as being "hot", resulting in more stale value usage.
+ *
+ * Note that "check" keys won't collide with other regular keys.
+ *
+ * @see WANObjectCache::get()
+ * @see WANObjectCache::getWithSetCallback()
+ * @see WANObjectCache::resetCheckKey()
+ *
+ * @param string $key Cache key
+ * @param int $holdoff HOLDOFF_TTL or HOLDOFF_TTL_NONE constant
+ * @return bool True if the item was purged or not found, false on failure
+ */
+ final public function touchCheckKey( $key, $holdoff = self::HOLDOFF_TTL ) {
+ // Publish the purge to all datacenters
+ $ok = $this->relayPurge( self::$TIME_KEY_PREFIX . $key, self::$CHECK_KEY_TTL, $holdoff );
+
+ $kClass = $this->determineKeyClassForStats( $key );
+ $this->stats->increment( "wanobjectcache.$kClass.ck_touch." . ( $ok ? 'ok' : 'error' ) );
+
+ return $ok;
+ }
+
+ /**
+ * Delete a "check" key from all datacenters, invalidating keys that use it
+ *
+ * This is similar to touchCheckKey() in that keys using it via get(), getMulti(),
+ * or getWithSetCallback() will be invalidated. The differences are:
+ * - a) The "check" key will be deleted from all caches and lazily
+ * re-initialized when accessed (rather than set everywhere)
+ * - b) Thus, dependent keys will be known to be stale, but not
+ * for how long (they are treated as "just" purged), which
+ * effects any lockTSE logic in getWithSetCallback()
+ * - c) Since "check" keys are initialized only on the server the key hashes
+ * to, any temporary ejection of that server will cause the value to be
+ * seen as purged as a new server will initialize the "check" key.
+ *
+ * The advantage here is that the "check" keys, which have high TTLs, will only
+ * be created when a get*() method actually uses that key. This is better when
+ * a large number of "check" keys are invalided in a short period of time.
+ *
+ * Note that "check" keys won't collide with other regular keys.
+ *
+ * @see WANObjectCache::get()
+ * @see WANObjectCache::getWithSetCallback()
+ * @see WANObjectCache::touchCheckKey()
+ *
+ * @param string $key Cache key
+ * @return bool True if the item was purged or not found, false on failure
+ */
+ final public function resetCheckKey( $key ) {
+ // Publish the purge to all datacenters
+ $ok = $this->relayDelete( self::$TIME_KEY_PREFIX . $key );
+
+ $kClass = $this->determineKeyClassForStats( $key );
+ $this->stats->increment( "wanobjectcache.$kClass.ck_reset." . ( $ok ? 'ok' : 'error' ) );
+
+ return $ok;
+ }
+
+ /**
+ * Method to fetch/regenerate cache keys
+ *
+ * On cache miss, the key will be set to the callback result via set()
+ * (unless the callback returns false) and that result will be returned.
+ * The arguments supplied to the callback are:
+ * - $oldValue : current cache value or false if not present
+ * - &$ttl : a reference to the TTL which can be altered
+ * - &$setOpts : a reference to options for set() which can be altered
+ * - $oldAsOf : generation UNIX timestamp of $oldValue or null if not present (since 1.28)
+ *
+ * It is strongly recommended to set the 'lag' and 'since' fields to avoid race conditions
+ * that can cause stale values to get stuck at keys. Usually, callbacks ignore the current
+ * value, but it can be used to maintain "most recent X" values that come from time or
+ * sequence based source data, provided that the "as of" id/time is tracked. Note that
+ * preemptive regeneration and $checkKeys can result in a non-false current value.
+ *
+ * Usage of $checkKeys is similar to get() and getMulti(). However, rather than the caller
+ * having to inspect a "current time left" variable (e.g. $curTTL, $curTTLs), a cache
+ * regeneration will automatically be triggered using the callback.
+ *
+ * The $ttl argument and "hotTTR" option (in $opts) use time-dependant randomization
+ * to avoid stampedes. Keys that are slow to regenerate and either heavily used
+ * or subject to explicit (unpredictable) purges, may need additional mechanisms.
+ * The simplest way to avoid stampedes for such keys is to use 'lockTSE' (in $opts).
+ * If explicit purges are needed, also:
+ * - a) Pass $key into $checkKeys
+ * - b) Use touchCheckKey( $key ) instead of delete( $key )
+ *
+ * Example usage (typical key):
+ * @code
+ * $catInfo = $cache->getWithSetCallback(
+ * // Key to store the cached value under
+ * $cache->makeKey( 'cat-attributes', $catId ),
+ * // Time-to-live (in seconds)
+ * $cache::TTL_MINUTE,
+ * // Function that derives the new key value
+ * function ( $oldValue, &$ttl, array &$setOpts ) {
+ * $dbr = wfGetDB( DB_REPLICA );
+ * // Account for any snapshot/replica DB lag
+ * $setOpts += Database::getCacheSetOptions( $dbr );
+ *
+ * return $dbr->selectRow( ... );
+ * }
+ * );
+ * @endcode
+ *
+ * Example usage (key that is expensive and hot):
+ * @code
+ * $catConfig = $cache->getWithSetCallback(
+ * // Key to store the cached value under
+ * $cache->makeKey( 'site-cat-config' ),
+ * // Time-to-live (in seconds)
+ * $cache::TTL_DAY,
+ * // Function that derives the new key value
+ * function ( $oldValue, &$ttl, array &$setOpts ) {
+ * $dbr = wfGetDB( DB_REPLICA );
+ * // Account for any snapshot/replica DB lag
+ * $setOpts += Database::getCacheSetOptions( $dbr );
+ *
+ * return CatConfig::newFromRow( $dbr->selectRow( ... ) );
+ * },
+ * [
+ * // Calling touchCheckKey() on this key invalidates the cache
+ * 'checkKeys' => [ $cache->makeKey( 'site-cat-config' ) ],
+ * // Try to only let one datacenter thread manage cache updates at a time
+ * 'lockTSE' => 30,
+ * // Avoid querying cache servers multiple times in a web request
+ * 'pcTTL' => $cache::TTL_PROC_LONG
+ * ]
+ * );
+ * @endcode
+ *
+ * Example usage (key with dynamic dependencies):
+ * @code
+ * $catState = $cache->getWithSetCallback(
+ * // Key to store the cached value under
+ * $cache->makeKey( 'cat-state', $cat->getId() ),
+ * // Time-to-live (seconds)
+ * $cache::TTL_HOUR,
+ * // Function that derives the new key value
+ * function ( $oldValue, &$ttl, array &$setOpts ) {
+ * // Determine new value from the DB
+ * $dbr = wfGetDB( DB_REPLICA );
+ * // Account for any snapshot/replica DB lag
+ * $setOpts += Database::getCacheSetOptions( $dbr );
+ *
+ * return CatState::newFromResults( $dbr->select( ... ) );
+ * },
+ * [
+ * // The "check" keys that represent things the value depends on;
+ * // Calling touchCheckKey() on any of them invalidates the cache
+ * 'checkKeys' => [
+ * $cache->makeKey( 'sustenance-bowls', $cat->getRoomId() ),
+ * $cache->makeKey( 'people-present', $cat->getHouseId() ),
+ * $cache->makeKey( 'cat-laws', $cat->getCityId() ),
+ * ]
+ * ]
+ * );
+ * @endcode
+ *
+ * Example usage (key that is expensive with too many DB dependencies for "check keys"):
+ * @code
+ * $catToys = $cache->getWithSetCallback(
+ * // Key to store the cached value under
+ * $cache->makeKey( 'cat-toys', $catId ),
+ * // Time-to-live (seconds)
+ * $cache::TTL_HOUR,
+ * // Function that derives the new key value
+ * function ( $oldValue, &$ttl, array &$setOpts ) {
+ * // Determine new value from the DB
+ * $dbr = wfGetDB( DB_REPLICA );
+ * // Account for any snapshot/replica DB lag
+ * $setOpts += Database::getCacheSetOptions( $dbr );
+ *
+ * return CatToys::newFromResults( $dbr->select( ... ) );
+ * },
+ * [
+ * // Get the highest timestamp of any of the cat's toys
+ * 'touchedCallback' => function ( $value ) use ( $catId ) {
+ * $dbr = wfGetDB( DB_REPLICA );
+ * $ts = $dbr->selectField( 'cat_toys', 'MAX(ct_touched)', ... );
+ *
+ * return wfTimestampOrNull( TS_UNIX, $ts );
+ * },
+ * // Avoid DB queries for repeated access
+ * 'pcTTL' => $cache::TTL_PROC_SHORT
+ * ]
+ * );
+ * @endcode
+ *
+ * Example usage (hot key holding most recent 100 events):
+ * @code
+ * $lastCatActions = $cache->getWithSetCallback(
+ * // Key to store the cached value under
+ * $cache->makeKey( 'cat-last-actions', 100 ),
+ * // Time-to-live (in seconds)
+ * 10,
+ * // Function that derives the new key value
+ * function ( $oldValue, &$ttl, array &$setOpts ) {
+ * $dbr = wfGetDB( DB_REPLICA );
+ * // Account for any snapshot/replica DB lag
+ * $setOpts += Database::getCacheSetOptions( $dbr );
+ *
+ * // Start off with the last cached list
+ * $list = $oldValue ?: [];
+ * // Fetch the last 100 relevant rows in descending order;
+ * // only fetch rows newer than $list[0] to reduce scanning
+ * $rows = iterator_to_array( $dbr->select( ... ) );
+ * // Merge them and get the new "last 100" rows
+ * return array_slice( array_merge( $new, $list ), 0, 100 );
+ * },
+ * [
+ * // Try to only let one datacenter thread manage cache updates at a time
+ * 'lockTSE' => 30,
+ * // Use a magic value when no cache value is ready rather than stampeding
+ * 'busyValue' => 'computing'
+ * ]
+ * );
+ * @endcode
+ *
+ * Example usage (key holding an LRU subkey:value map; this can avoid flooding cache with
+ * keys for an unlimited set of (constraint,situation) pairs, thereby avoiding elevated
+ * cache evictions and wasted memory):
+ * @code
+ * $catSituationTolerabilityCache = $this->cache->getWithSetCallback(
+ * // Group by constraint ID/hash, cat family ID/hash, or something else useful
+ * $this->cache->makeKey( 'cat-situation-tolerability-checks', $groupKey ),
+ * WANObjectCache::TTL_DAY, // rarely used groups should fade away
+ * // The $scenarioKey format is $constraintId:<ID/hash of $situation>
+ * function ( $cacheMap ) use ( $scenarioKey, $constraintId, $situation ) {
+ * $lruCache = MapCacheLRU::newFromArray( $cacheMap ?: [], self::CACHE_SIZE );
+ * $result = $lruCache->get( $scenarioKey ); // triggers LRU bump if present
+ * if ( $result === null || $this->isScenarioResultExpired( $result ) ) {
+ * $result = $this->checkScenarioTolerability( $constraintId, $situation );
+ * $lruCache->set( $scenarioKey, $result, 3 / 8 );
+ * }
+ * // Save the new LRU cache map and reset the map's TTL
+ * return $lruCache->toArray();
+ * },
+ * [
+ * // Once map is > 1 sec old, consider refreshing
+ * 'ageNew' => 1,
+ * // Update within 5 seconds after "ageNew" given a 1hz cache check rate
+ * 'hotTTR' => 5,
+ * // Avoid querying cache servers multiple times in a request; this also means
+ * // that a request can only alter the value of any given constraint key once
+ * 'pcTTL' => WANObjectCache::TTL_PROC_LONG
+ * ]
+ * );
+ * $tolerability = isset( $catSituationTolerabilityCache[$scenarioKey] )
+ * ? $catSituationTolerabilityCache[$scenarioKey]
+ * : $this->checkScenarioTolerability( $constraintId, $situation );
+ * @endcode
+ *
+ * @see WANObjectCache::get()
+ * @see WANObjectCache::set()
+ *
+ * @param string $key Cache key made from makeKey() or makeGlobalKey()
+ * @param int $ttl Seconds to live for key updates. Special values are:
+ * - WANObjectCache::TTL_INDEFINITE: Cache forever (subject to LRU-style evictions)
+ * - WANObjectCache::TTL_UNCACHEABLE: Do not cache (if the key exists, it is not deleted)
+ * @param callable $callback Value generation function
+ * @param array $opts Options map:
+ * - checkKeys: List of "check" keys. The key at $key will be seen as stale when either
+ * touchCheckKey() or resetCheckKey() is called on any of the keys in this list. This
+ * is useful if thousands or millions of keys depend on the same entity. The entity can
+ * simply have its "check" key updated whenever the entity is modified.
+ * Default: [].
+ * - graceTTL: If the key is invalidated (by "checkKeys"/"touchedCallback") less than this
+ * many seconds ago, consider reusing the stale value. The odds of a refresh becomes
+ * more likely over time, becoming certain once the grace period is reached. This can
+ * reduce traffic spikes when millions of keys are compared to the same "check" key and
+ * touchCheckKey() or resetCheckKey() is called on that "check" key. This option is not
+ * useful for avoiding traffic spikes in the case of the key simply expiring on account
+ * of its TTL (use "lowTTL" instead).
+ * Default: WANObjectCache::GRACE_TTL_NONE.
+ * - lockTSE: If the key is tombstoned or invalidated (by "checkKeys"/"touchedCallback")
+ * less than this many seconds ago, try to have a single thread handle cache regeneration
+ * at any given time. Other threads will use stale values if possible. If, on miss,
+ * the time since expiration is low, the assumption is that the key is hot and that a
+ * stampede is worth avoiding. Note that if the key falls out of cache then concurrent
+ * threads will all run the callback on cache miss until the value is saved in cache.
+ * The only stampede protection in that case is from duplicate cache sets when the
+ * callback takes longer than WANObjectCache::SET_DELAY_HIGH_MS milliseconds; consider
+ * using "busyValue" if such stampedes are a problem. Note that the higher "lockTSE" is
+ * set, the higher the worst-case staleness of returned values can be. Also note that
+ * this option does not by itself handle the case of the key simply expiring on account
+ * of its TTL, so make sure that "lowTTL" is not disabled when using this option. Avoid
+ * combining this option with delete() as it can always cause a stampede due to their
+ * being no stale value available until after a thread completes the callback.
+ * Use WANObjectCache::TSE_NONE to disable this logic.
+ * Default: WANObjectCache::TSE_NONE.
+ * - busyValue: Specify a placeholder value to use when no value exists and another thread
+ * is currently regenerating it. This assures that cache stampedes cannot happen if the
+ * value falls out of cache. This also mitigates stampedes when value regeneration
+ * becomes very slow (greater than $ttl/"lowTTL"). If this is a closure, then it will
+ * be invoked to get the placeholder when needed.
+ * Default: null.
+ * - pcTTL: Process cache the value in this PHP instance for this many seconds. This avoids
+ * network I/O when a key is read several times. This will not cache when the callback
+ * returns false, however. Note that any purges will not be seen while process cached;
+ * since the callback should use replica DBs and they may be lagged or have snapshot
+ * isolation anyway, this should not typically matter.
+ * Default: WANObjectCache::TTL_UNCACHEABLE.
+ * - pcGroup: Process cache group to use instead of the primary one. If set, this must be
+ * of the format ALPHANUMERIC_NAME:MAX_KEY_SIZE, e.g. "mydata:10". Use this for storing
+ * large values, small yet numerous values, or some values with a high cost of eviction.
+ * It is generally preferable to use a class constant when setting this value.
+ * This has no effect unless pcTTL is used.
+ * Default: WANObjectCache::PC_PRIMARY.
+ * - version: Integer version number. This lets callers make breaking changes to the format
+ * of cached values without causing problems for sites that use non-instantaneous code
+ * deployments. Old and new code will recognize incompatible versions and purges from
+ * both old and new code will been seen by each other. When this method encounters an
+ * incompatibly versioned value at the provided key, a "variant key" will be used for
+ * reading from and saving to cache. The variant key is specific to the key and version
+ * number provided to this method. If the variant key value is older than that of the
+ * provided key, or the provided key is non-existant, then the variant key will be seen
+ * as non-existant. Therefore, delete() calls invalidate the provided key's variant keys.
+ * The "checkKeys" and "touchedCallback" options still apply to variant keys as usual.
+ * Avoid storing class objects, as this reduces compatibility (due to serialization).
+ * Default: null.
+ * - minAsOf: Reject values if they were generated before this UNIX timestamp.
+ * This is useful if the source of a key is suspected of having possibly changed
+ * recently, and the caller wants any such changes to be reflected.
+ * Default: WANObjectCache::MIN_TIMESTAMP_NONE.
+ * - hotTTR: Expected time-till-refresh (TTR) in seconds for keys that average ~1 hit per
+ * second (e.g. 1Hz). Keys with a hit rate higher than 1Hz will refresh sooner than this
+ * TTR and vise versa. Such refreshes won't happen until keys are "ageNew" seconds old.
+ * This uses randomization to avoid triggering cache stampedes. The TTR is useful at
+ * reducing the impact of missed cache purges, since the effect of a heavily referenced
+ * key being stale is worse than that of a rarely referenced key. Unlike simply lowering
+ * $ttl, seldomly used keys are largely unaffected by this option, which makes it
+ * possible to have a high hit rate for the "long-tail" of less-used keys.
+ * Default: WANObjectCache::HOT_TTR.
+ * - lowTTL: Consider pre-emptive updates when the current TTL (seconds) of the key is less
+ * than this. It becomes more likely over time, becoming certain once the key is expired.
+ * This helps avoid cache stampedes that might be triggered due to the key expiring.
+ * Default: WANObjectCache::LOW_TTL.
+ * - ageNew: Consider popularity refreshes only once a key reaches this age in seconds.
+ * Default: WANObjectCache::AGE_NEW.
+ * - staleTTL: Seconds to keep the key around if it is stale. This means that on cache
+ * miss the callback may get $oldValue/$oldAsOf values for keys that have already been
+ * expired for this specified time. This is useful if adaptiveTTL() is used on the old
+ * value's as-of time when it is verified as still being correct.
+ * Default: WANObjectCache::STALE_TTL_NONE
+ * - touchedCallback: A callback that takes the current value and returns a UNIX timestamp
+ * indicating the last time a dynamic dependency changed. Null can be returned if there
+ * are no relevant dependency changes to check. This can be used to check against things
+ * like last-modified times of files or DB timestamp fields. This should generally not be
+ * used for small and easily queried values in a DB if the callback itself ends up doing
+ * a similarly expensive DB query to check a timestamp. Usages of this option makes the
+ * most sense for values that are moderately to highly expensive to regenerate and easy
+ * to query for dependency timestamps. The use of "pcTTL" reduces timestamp queries.
+ * Default: null.
+ * @return mixed Value found or written to the key
+ * @note Options added in 1.28: version, busyValue, hotTTR, ageNew, pcGroup, minAsOf
+ * @note Options added in 1.31: staleTTL, graceTTL
+ * @note Options added in 1.33: touchedCallback
+ * @note Callable type hints are not used to avoid class-autoloading
+ */
+ final public function getWithSetCallback( $key, $ttl, $callback, array $opts = [] ) {
+ $version = $opts['version'] ?? null;
+ $pcTTL = $opts['pcTTL'] ?? self::TTL_UNCACHEABLE;
+ $pCache = ( $pcTTL >= 0 )
+ ? $this->getProcessCache( $opts['pcGroup'] ?? self::PC_PRIMARY )
+ : null;
+
+ // Use the process cache if requested as long as no outer cache callback is running.
+ // Nested callback process cache use is not lag-safe with regard to HOLDOFF_TTL since
+ // process cached values are more lagged than persistent ones as they are not purged.
+ if ( $pCache && $this->callbackDepth == 0 ) {
+ $cached = $pCache->get( $this->getProcessCacheKey( $key, $version ), INF, false );
+ if ( $cached !== false ) {
+ return $cached;
+ }
+ }
+
+ $res = $this->fetchOrRegenerate( $key, $ttl, $callback, $opts );
+ list( $value, $valueVersion, $curAsOf ) = $res;
+ if ( $valueVersion !== $version ) {
+ // Current value has a different version; use the variant key for this version.
+ // Regenerate the variant value if it is not newer than the main value at $key
+ // so that purges to the main key propagate to the variant value.
+ list( $value ) = $this->fetchOrRegenerate(
+ $this->makeGlobalKey( 'WANCache-key-variant', md5( $key ), $version ),
+ $ttl,
+ $callback,
+ [ 'version' => null, 'minAsOf' => $curAsOf ] + $opts
+ );
+ }
+
+ // Update the process cache if enabled
+ if ( $pCache && $value !== false ) {
+ $pCache->set( $this->getProcessCacheKey( $key, $version ), $value );
+ }
+
+ return $value;
+ }
+
+ /**
+ * Do the actual I/O for getWithSetCallback() when needed
+ *
+ * @see WANObjectCache::getWithSetCallback()
+ *
+ * @param string $key
+ * @param int $ttl
+ * @param callable $callback
+ * @param array $opts Options map for getWithSetCallback()
+ * @return array Ordered list of the following:
+ * - Cached or regenerated value
+ * - Cached or regenerated value version number or null if not versioned
+ * - Timestamp of the current cached value at the key or null if there is no value
+ * @note Callable type hints are not used to avoid class-autoloading
+ */
+ private function fetchOrRegenerate( $key, $ttl, $callback, array $opts ) {
+ $checkKeys = $opts['checkKeys'] ?? [];
+ $graceTTL = $opts['graceTTL'] ?? self::GRACE_TTL_NONE;
+ $minAsOf = $opts['minAsOf'] ?? self::MIN_TIMESTAMP_NONE;
+ $hotTTR = $opts['hotTTR'] ?? self::HOT_TTR;
+ $lowTTL = $opts['lowTTL'] ?? min( self::LOW_TTL, $ttl );
+ $ageNew = $opts['ageNew'] ?? self::AGE_NEW;
+ $touchedCb = $opts['touchedCallback'] ?? null;
+ $initialTime = $this->getCurrentTime();
+
+ $kClass = $this->determineKeyClassForStats( $key );
+
+ // Get the current key value and its metadata
+ $curTTL = self::PASS_BY_REF;
+ $curInfo = self::PASS_BY_REF; /** @var array $curInfo */
+ $curValue = $this->get( $key, $curTTL, $checkKeys, $curInfo );
+ // Apply any $touchedCb invalidation timestamp to get the "last purge timestamp"
+ list( $curTTL, $LPT ) = $this->resolveCTL( $curValue, $curTTL, $curInfo, $touchedCb );
+ // Use the cached value if it exists and is not due for synchronous regeneration
+ if (
+ $this->isValid( $curValue, $curInfo['asOf'], $minAsOf ) &&
+ $this->isAliveOrInGracePeriod( $curTTL, $graceTTL )
+ ) {
+ $preemptiveRefresh = (
+ $this->worthRefreshExpiring( $curTTL, $lowTTL ) ||
+ $this->worthRefreshPopular( $curInfo['asOf'], $ageNew, $hotTTR, $initialTime )
+ );
+ if ( !$preemptiveRefresh ) {
+ $this->stats->increment( "wanobjectcache.$kClass.hit.good" );
+
+ return [ $curValue, $curInfo['version'], $curInfo['asOf'] ];
+ } elseif ( $this->scheduleAsyncRefresh( $key, $ttl, $callback, $opts ) ) {
+ $this->stats->increment( "wanobjectcache.$kClass.hit.refresh" );
+
+ return [ $curValue, $curInfo['version'], $curInfo['asOf'] ];
+ }
+ }
+
+ // Determine if there is stale or volatile cached value that is still usable
+ $isKeyTombstoned = ( $curInfo['tombAsOf'] !== null );
+ if ( $isKeyTombstoned ) {
+ // Key is write-holed; use the (volatile) interim key as an alternative
+ list( $possValue, $possInfo ) = $this->getInterimValue( $key, $minAsOf );
+ // Update the "last purge time" since the $touchedCb timestamp depends on $value
+ $LPT = $this->resolveTouched( $possValue, $LPT, $touchedCb );
+ } else {
+ $possValue = $curValue;
+ $possInfo = $curInfo;
+ }
+
+ // Avoid overhead from callback runs, regeneration locks, and cache sets during
+ // hold-off periods for the key by reusing very recently generated cached values
+ if (
+ $this->isValid( $possValue, $possInfo['asOf'], $minAsOf, $LPT ) &&
+ $this->isVolatileValueAgeNegligible( $initialTime - $possInfo['asOf'] )
+ ) {
+ $this->stats->increment( "wanobjectcache.$kClass.hit.volatile" );
+
+ return [ $possValue, $possInfo['version'], $curInfo['asOf'] ];
+ }
+
+ $lockTSE = $opts['lockTSE'] ?? self::TSE_NONE;
+ $busyValue = $opts['busyValue'] ?? null;
+ $staleTTL = $opts['staleTTL'] ?? self::STALE_TTL_NONE;
+ $version = $opts['version'] ?? null;
+
+ // Determine whether one thread per datacenter should handle regeneration at a time
+ $useRegenerationLock =
+ // Note that since tombstones no-op set(), $lockTSE and $curTTL cannot be used to
+ // deduce the key hotness because |$curTTL| will always keep increasing until the
+ // tombstone expires or is overwritten by a new tombstone. Also, even if $lockTSE
+ // is not set, constant regeneration of a key for the tombstone lifetime might be
+ // very expensive. Assume tombstoned keys are possibly hot in order to reduce
+ // the risk of high regeneration load after the delete() method is called.
+ $isKeyTombstoned ||
+ // Assume a key is hot if requested soon ($lockTSE seconds) after invalidation.
+ // This avoids stampedes when timestamps from $checkKeys/$touchedCb bump.
+ ( $curTTL !== null && $curTTL <= 0 && abs( $curTTL ) <= $lockTSE ) ||
+ // Assume a key is hot if there is no value and a busy fallback is given.
+ // This avoids stampedes on eviction or preemptive regeneration taking too long.
+ ( $busyValue !== null && $possValue === false );
+
+ // If a regeneration lock is required, threads that do not get the lock will try to use
+ // the stale value, the interim value, or the $busyValue placeholder, in that order. If
+ // none of those are set then all threads will bypass the lock and regenerate the value.
+ $hasLock = $useRegenerationLock && $this->claimStampedeLock( $key );
+ if ( $useRegenerationLock && !$hasLock ) {
+ if ( $this->isValid( $possValue, $possInfo['asOf'], $minAsOf ) ) {
+ $this->stats->increment( "wanobjectcache.$kClass.hit.stale" );
+
+ return [ $possValue, $possInfo['version'], $curInfo['asOf'] ];
+ } elseif ( $busyValue !== null ) {
+ $miss = is_infinite( $minAsOf ) ? 'renew' : 'miss';
+ $this->stats->increment( "wanobjectcache.$kClass.$miss.busy" );
+
+ return [ $this->resolveBusyValue( $busyValue ), $version, $curInfo['asOf'] ];
+ }
+ }
+
+ // Generate the new value given any prior value with a matching version
+ $setOpts = [];
+ $preCallbackTime = $this->getCurrentTime();
+ ++$this->callbackDepth;
+ try {
+ $value = $callback(
+ ( $curInfo['version'] === $version ) ? $curValue : false,
+ $ttl,
+ $setOpts,
+ ( $curInfo['version'] === $version ) ? $curInfo['asOf'] : null
+ );
+ } finally {
+ --$this->callbackDepth;
+ }
+ $postCallbackTime = $this->getCurrentTime();
+
+ // How long it took to fetch, validate, and generate the value
+ $elapsed = max( $postCallbackTime - $initialTime, 0.0 );
+
+ // Attempt to save the newly generated value if applicable
+ if (
+ // Callback yielded a cacheable value
+ ( $value !== false && $ttl >= 0 ) &&
+ // Current thread was not raced out of a regeneration lock or key is tombstoned
+ ( !$useRegenerationLock || $hasLock || $isKeyTombstoned ) &&
+ // Key does not appear to be undergoing a set() stampede
+ $this->checkAndSetCooloff( $key, $kClass, $elapsed, $lockTSE, $hasLock )
+ ) {
+ // How long it took to generate the value
+ $walltime = max( $postCallbackTime - $preCallbackTime, 0.0 );
+ $this->stats->timing( "wanobjectcache.$kClass.regen_walltime", 1e3 * $walltime );
+ // If the key is write-holed then use the (volatile) interim key as an alternative
+ if ( $isKeyTombstoned ) {
+ $this->setInterimValue( $key, $value, $lockTSE, $version, $walltime );
+ } else {
+ $finalSetOpts = [
+ 'since' => $setOpts['since'] ?? $preCallbackTime,
+ 'version' => $version,
+ 'staleTTL' => $staleTTL,
+ 'lockTSE' => $lockTSE, // informs lag vs performance trade-offs
+ 'creating' => ( $curValue === false ), // optimization
+ 'walltime' => $walltime
+ ] + $setOpts;
+ $this->set( $key, $value, $ttl, $finalSetOpts );
+ }
+ }
+
+ $this->yieldStampedeLock( $key, $hasLock );
+
+ $miss = is_infinite( $minAsOf ) ? 'renew' : 'miss';
+ $this->stats->increment( "wanobjectcache.$kClass.$miss.compute" );
+
+ return [ $value, $version, $curInfo['asOf'] ];
+ }
+
+ /**
+ * @param string $key
+ * @return bool Success
+ */
+ private function claimStampedeLock( $key ) {
+ // Note that locking is not bypassed due to I/O errors; this avoids stampedes
+ return $this->cache->add( self::$MUTEX_KEY_PREFIX . $key, 1, self::$LOCK_TTL );
+ }
+
+ /**
+ * @param string $key
+ * @param bool $hasLock
+ */
+ private function yieldStampedeLock( $key, $hasLock ) {
+ if ( $hasLock ) {
+ // The backend might be a mcrouter proxy set to broadcast DELETE to *all* the local
+ // datacenter cache servers via OperationSelectorRoute (for increased consistency).
+ // Since that would be excessive for these locks, use TOUCH to expire the key.
+ $this->cache->changeTTL( self::$MUTEX_KEY_PREFIX . $key, $this->getCurrentTime() - 60 );
+ }
+ }
+
+ /**
+ * @param float $age Age of volatile/interim key in seconds
+ * @return bool Whether the age of a volatile value is negligible
+ */
+ private function isVolatileValueAgeNegligible( $age ) {
+ return ( $age < mt_rand( self::$RECENT_SET_LOW_MS, self::$RECENT_SET_HIGH_MS ) / 1e3 );
+ }
+
+ /**
+ * @param string $key
+ * @param string $kClass
+ * @param float $elapsed Seconds spent regenerating the value
+ * @param float $lockTSE
+ * @param bool $hasLock
+ * @return bool Whether it is OK to proceed with a key set operation
+ */
+ private function checkAndSetCooloff( $key, $kClass, $elapsed, $lockTSE, $hasLock ) {
+ $this->stats->timing( "wanobjectcache.$kClass.regen_set_delay", 1e3 * $elapsed );
+
+ // If $lockTSE is set, the lock was bypassed because there was no stale/interim value,
+ // and $elapsed indicates that regeration is slow, then there is a risk of set()
+ // stampedes with large blobs. With a typical scale-out infrastructure, CPU and query
+ // load from $callback invocations is distributed among appservers and replica DBs,
+ // but cache operations for a given key route to a single cache server (e.g. striped
+ // consistent hashing).
+ if ( $lockTSE < 0 || $hasLock ) {
+ return true; // either not a priori hot or thread has the lock
+ } elseif ( $elapsed <= self::$SET_DELAY_HIGH_MS * 1e3 ) {
+ return true; // not enough time for threads to pile up
+ }
+
+ $this->cache->clearLastError();
+ if (
+ !$this->cache->add( self::$COOLOFF_KEY_PREFIX . $key, 1, self::$COOLOFF_TTL ) &&
+ // Don't treat failures due to I/O errors as the key being in cooloff
+ $this->cache->getLastError() === BagOStuff::ERR_NONE
+ ) {
+ $this->stats->increment( "wanobjectcache.$kClass.cooloff_bounce" );
+
+ return false;
+ }
+
+ return true;
+ }
+
+ /**
+ * @param mixed $value
+ * @param float|null $curTTL
+ * @param array $curInfo
+ * @param callable|null $touchedCallback
+ * @return array (current time left or null, UNIX timestamp of last purge or null)
+ * @note Callable type hints are not used to avoid class-autoloading
+ */
+ private function resolveCTL( $value, $curTTL, $curInfo, $touchedCallback ) {
+ if ( $touchedCallback === null || $value === false ) {
+ return [ $curTTL, max( $curInfo['tombAsOf'], $curInfo['lastCKPurge'] ) ];
+ }
+
+ $touched = $touchedCallback( $value );
+ if ( $touched !== null && $touched >= $curInfo['asOf'] ) {
+ $curTTL = min( $curTTL, self::$TINY_NEGATIVE, $curInfo['asOf'] - $touched );
+ }
+
+ return [ $curTTL, max( $curInfo['tombAsOf'], $curInfo['lastCKPurge'], $touched ) ];
+ }
+
+ /**
+ * @param mixed $value
+ * @param float|null $lastPurge
+ * @param callable|null $touchedCallback
+ * @return float|null UNIX timestamp of last purge or null
+ * @note Callable type hints are not used to avoid class-autoloading
+ */
+ private function resolveTouched( $value, $lastPurge, $touchedCallback ) {
+ return ( $touchedCallback === null || $value === false )
+ ? $lastPurge // nothing to derive the "touched timestamp" from
+ : max( $touchedCallback( $value ), $lastPurge );
+ }
+
+ /**
+ * @param string $key
+ * @param float $minAsOf Minimum acceptable "as of" timestamp
+ * @return array (cached value or false, cache key metadata map)
+ */
+ private function getInterimValue( $key, $minAsOf ) {
+ $now = $this->getCurrentTime();
+
+ if ( $this->useInterimHoldOffCaching ) {
+ $wrapped = $this->cache->get( self::$INTERIM_KEY_PREFIX . $key );
+
+ list( $value, $keyInfo ) = $this->unwrap( $wrapped, $now );
+ if ( $this->isValid( $value, $keyInfo['asOf'], $minAsOf ) ) {
+ return [ $value, $keyInfo ];
+ }
+ }
+
+ return $this->unwrap( false, $now );
+ }
+
+ /**
+ * @param string $key
+ * @param mixed $value
+ * @param int $ttl
+ * @param int|null $version Value version number
+ * @param float $walltime How long it took to generate the value in seconds
+ */
+ private function setInterimValue( $key, $value, $ttl, $version, $walltime ) {
+ $ttl = max( self::$INTERIM_KEY_TTL, (int)$ttl );
+
+ $wrapped = $this->wrap( $value, $ttl, $version, $this->getCurrentTime(), $walltime );
+ $this->cache->merge(
+ self::$INTERIM_KEY_PREFIX . $key,
+ function () use ( $wrapped ) {
+ return $wrapped;
+ },
+ $ttl,
+ 1
+ );
+ }
+
+ /**
+ * @param mixed $busyValue
+ * @return mixed
+ */
+ private function resolveBusyValue( $busyValue ) {
+ return ( $busyValue instanceof Closure ) ? $busyValue() : $busyValue;
+ }
+
+ /**
+ * Method to fetch multiple cache keys at once with regeneration
+ *
+ * This works the same as getWithSetCallback() except:
+ * - a) The $keys argument expects the result of WANObjectCache::makeMultiKeys()
+ * - b) The $callback argument expects a callback taking the following arguments:
+ * - $id: ID of an entity to query
+ * - $oldValue : the prior cache value or false if none was present
+ * - &$ttl : a reference to the new value TTL in seconds
+ * - &$setOpts : a reference to options for set() which can be altered
+ * - $oldAsOf : generation UNIX timestamp of $oldValue or null if not present
+ * Aside from the additional $id argument, the other arguments function the same
+ * way they do in getWithSetCallback().
+ * - c) The return value is a map of (cache key => value) in the order of $keyedIds
+ *
+ * @see WANObjectCache::getWithSetCallback()
+ * @see WANObjectCache::getMultiWithUnionSetCallback()
+ *
+ * Example usage:
+ * @code
+ * $rows = $cache->getMultiWithSetCallback(
+ * // Map of cache keys to entity IDs
+ * $cache->makeMultiKeys(
+ * $this->fileVersionIds(),
+ * function ( $id ) use ( $cache ) {
+ * return $cache->makeKey( 'file-version', $id );
+ * }
+ * ),
+ * // Time-to-live (in seconds)
+ * $cache::TTL_DAY,
+ * // Function that derives the new key value
+ * function ( $id, $oldValue, &$ttl, array &$setOpts ) {
+ * $dbr = wfGetDB( DB_REPLICA );
+ * // Account for any snapshot/replica DB lag
+ * $setOpts += Database::getCacheSetOptions( $dbr );
+ *
+ * // Load the row for this file
+ * $queryInfo = File::getQueryInfo();
+ * $row = $dbr->selectRow(
+ * $queryInfo['tables'],
+ * $queryInfo['fields'],
+ * [ 'id' => $id ],
+ * __METHOD__,
+ * [],
+ * $queryInfo['joins']
+ * );
+ *
+ * return $row ? (array)$row : false;
+ * },
+ * [
+ * // Process cache for 30 seconds
+ * 'pcTTL' => 30,
+ * // Use a dedicated 500 item cache (initialized on-the-fly)
+ * 'pcGroup' => 'file-versions:500'
+ * ]
+ * );
+ * $files = array_map( [ __CLASS__, 'newFromRow' ], $rows );
+ * @endcode
+ *
+ * @param ArrayIterator $keyedIds Result of WANObjectCache::makeMultiKeys()
+ * @param int $ttl Seconds to live for key updates
+ * @param callable $callback Callback the yields entity regeneration callbacks
+ * @param array $opts Options map
+ * @return mixed[] Map of (cache key => value) in the same order as $keyedIds
+ * @since 1.28
+ */
+ final public function getMultiWithSetCallback(
+ ArrayIterator $keyedIds, $ttl, callable $callback, array $opts = []
+ ) {
+ // Load required keys into process cache in one go
+ $this->warmupCache = $this->getRawKeysForWarmup(
+ $this->getNonProcessCachedMultiKeys( $keyedIds, $opts ),
+ $opts['checkKeys'] ?? []
+ );
+ $this->warmupKeyMisses = 0;
+
+ // Wrap $callback to match the getWithSetCallback() format while passing $id to $callback
+ $id = null; // current entity ID
+ $func = function ( $oldValue, &$ttl, &$setOpts, $oldAsOf ) use ( $callback, &$id ) {
+ return $callback( $id, $oldValue, $ttl, $setOpts, $oldAsOf );
+ };
+
+ $values = [];
+ foreach ( $keyedIds as $key => $id ) { // preserve order
+ $values[$key] = $this->getWithSetCallback( $key, $ttl, $func, $opts );
+ }
+
+ $this->warmupCache = [];
+
+ return $values;
+ }
+
+ /**
+ * Method to fetch/regenerate multiple cache keys at once
+ *
+ * This works the same as getWithSetCallback() except:
+ * - a) The $keys argument expects the result of WANObjectCache::makeMultiKeys()
+ * - b) The $callback argument expects a callback returning a map of (ID => new value)
+ * for all entity IDs in $ids and it takes the following arguments:
+ * - $ids: a list of entity IDs that require cache regeneration
+ * - &$ttls: a reference to the (entity ID => new TTL) map
+ * - &$setOpts: a reference to options for set() which can be altered
+ * - c) The return value is a map of (cache key => value) in the order of $keyedIds
+ * - d) The "lockTSE" and "busyValue" options are ignored
+ *
+ * @see WANObjectCache::getWithSetCallback()
+ * @see WANObjectCache::getMultiWithSetCallback()
+ *
+ * Example usage:
+ * @code
+ * $rows = $cache->getMultiWithUnionSetCallback(
+ * // Map of cache keys to entity IDs
+ * $cache->makeMultiKeys(
+ * $this->fileVersionIds(),
+ * function ( $id ) use ( $cache ) {
+ * return $cache->makeKey( 'file-version', $id );
+ * }
+ * ),
+ * // Time-to-live (in seconds)
+ * $cache::TTL_DAY,
+ * // Function that derives the new key value
+ * function ( array $ids, array &$ttls, array &$setOpts ) {
+ * $dbr = wfGetDB( DB_REPLICA );
+ * // Account for any snapshot/replica DB lag
+ * $setOpts += Database::getCacheSetOptions( $dbr );
+ *
+ * // Load the rows for these files
+ * $rows = [];
+ * $queryInfo = File::getQueryInfo();
+ * $res = $dbr->select(
+ * $queryInfo['tables'],
+ * $queryInfo['fields'],
+ * [ 'id' => $ids ],
+ * __METHOD__,
+ * [],
+ * $queryInfo['joins']
+ * );
+ * foreach ( $res as $row ) {
+ * $rows[$row->id] = $row;
+ * $mtime = wfTimestamp( TS_UNIX, $row->timestamp );
+ * $ttls[$row->id] = $this->adaptiveTTL( $mtime, $ttls[$row->id] );
+ * }
+ *
+ * return $rows;
+ * },
+ * ]
+ * );
+ * $files = array_map( [ __CLASS__, 'newFromRow' ], $rows );
+ * @endcode
+ *
+ * @param ArrayIterator $keyedIds Result of WANObjectCache::makeMultiKeys()
+ * @param int $ttl Seconds to live for key updates
+ * @param callable $callback Callback the yields entity regeneration callbacks
+ * @param array $opts Options map
+ * @return mixed[] Map of (cache key => value) in the same order as $keyedIds
+ * @since 1.30
+ */
+ final public function getMultiWithUnionSetCallback(
+ ArrayIterator $keyedIds, $ttl, callable $callback, array $opts = []
+ ) {
+ $checkKeys = $opts['checkKeys'] ?? [];
+ unset( $opts['lockTSE'] ); // incompatible
+ unset( $opts['busyValue'] ); // incompatible
+
+ // Load required keys into process cache in one go
+ $keysByIdGet = $this->getNonProcessCachedMultiKeys( $keyedIds, $opts );
+ $this->warmupCache = $this->getRawKeysForWarmup( $keysByIdGet, $checkKeys );
+ $this->warmupKeyMisses = 0;
+
+ // IDs of entities known to be in need of regeneration
+ $idsRegen = [];
+
+ // Find out which keys are missing/deleted/stale
+ $curTTLs = [];
+ $asOfs = [];
+ $curByKey = $this->getMulti( $keysByIdGet, $curTTLs, $checkKeys, $asOfs );
+ foreach ( $keysByIdGet as $id => $key ) {
+ if ( !array_key_exists( $key, $curByKey ) || $curTTLs[$key] < 0 ) {
+ $idsRegen[] = $id;
+ }
+ }
+
+ // Run the callback to populate the regeneration value map for all required IDs
+ $newSetOpts = [];
+ $newTTLsById = array_fill_keys( $idsRegen, $ttl );
+ $newValsById = $idsRegen ? $callback( $idsRegen, $newTTLsById, $newSetOpts ) : [];
+
+ // Wrap $callback to match the getWithSetCallback() format while passing $id to $callback
+ $id = null; // current entity ID
+ $func = function ( $oldValue, &$ttl, &$setOpts, $oldAsOf )
+ use ( $callback, &$id, $newValsById, $newTTLsById, $newSetOpts )
+ {
+ if ( array_key_exists( $id, $newValsById ) ) {
+ // Value was already regerated as expected, so use the value in $newValsById
+ $newValue = $newValsById[$id];
+ $ttl = $newTTLsById[$id];
+ $setOpts = $newSetOpts;
+ } else {
+ // Pre-emptive/popularity refresh and version mismatch cases are not detected
+ // above and thus $newValsById has no entry. Run $callback on this single entity.
+ $ttls = [ $id => $ttl ];
+ $newValue = $callback( [ $id ], $ttls, $setOpts )[$id];
+ $ttl = $ttls[$id];
+ }
+
+ return $newValue;
+ };
+
+ // Run the cache-aside logic using warmupCache instead of persistent cache queries
+ $values = [];
+ foreach ( $keyedIds as $key => $id ) { // preserve order
+ $values[$key] = $this->getWithSetCallback( $key, $ttl, $func, $opts );
+ }
+
+ $this->warmupCache = [];
+
+ return $values;
+ }
+
+ /**
+ * Set a key to soon expire in the local cluster if it pre-dates $purgeTimestamp
+ *
+ * This sets stale keys' time-to-live at HOLDOFF_TTL seconds, which both avoids
+ * broadcasting in mcrouter setups and also avoids races with new tombstones.
+ *
+ * @param string $key Cache key
+ * @param int $purgeTimestamp UNIX timestamp of purge
+ * @param bool &$isStale Whether the key is stale
+ * @return bool Success
+ * @since 1.28
+ */
+ final public function reap( $key, $purgeTimestamp, &$isStale = false ) {
+ $minAsOf = $purgeTimestamp + self::HOLDOFF_TTL;
+ $wrapped = $this->cache->get( self::$VALUE_KEY_PREFIX . $key );
+ if ( is_array( $wrapped ) && $wrapped[self::$FLD_TIME] < $minAsOf ) {
+ $isStale = true;
+ $this->logger->warning( "Reaping stale value key '$key'." );
+ $ttlReap = self::HOLDOFF_TTL; // avoids races with tombstone creation
+ $ok = $this->cache->changeTTL( self::$VALUE_KEY_PREFIX . $key, $ttlReap );
+ if ( !$ok ) {
+ $this->logger->error( "Could not complete reap of key '$key'." );
+ }
+
+ return $ok;
+ }
+
+ $isStale = false;
+
+ return true;
+ }
+
+ /**
+ * Set a "check" key to soon expire in the local cluster if it pre-dates $purgeTimestamp
+ *
+ * @param string $key Cache key
+ * @param int $purgeTimestamp UNIX timestamp of purge
+ * @param bool &$isStale Whether the key is stale
+ * @return bool Success
+ * @since 1.28
+ */
+ final public function reapCheckKey( $key, $purgeTimestamp, &$isStale = false ) {
+ $purge = $this->parsePurgeValue( $this->cache->get( self::$TIME_KEY_PREFIX . $key ) );
+ if ( $purge && $purge[self::$PURGE_TIME] < $purgeTimestamp ) {
+ $isStale = true;
+ $this->logger->warning( "Reaping stale check key '$key'." );
+ $ok = $this->cache->changeTTL( self::$TIME_KEY_PREFIX . $key, self::TTL_SECOND );
+ if ( !$ok ) {
+ $this->logger->error( "Could not complete reap of check key '$key'." );
+ }
+
+ return $ok;
+ }
+
+ $isStale = false;
+
+ return false;
+ }
+
+ /**
+ * @see BagOStuff::makeKey()
+ * @param string $class Key class
+ * @param string ...$components Key components (starting with a key collection name)
+ * @return string Colon-delimited list of $keyspace followed by escaped components
+ * @since 1.27
+ */
+ public function makeKey( $class, ...$components ) {
+ return $this->cache->makeKey( ...func_get_args() );
+ }
+
+ /**
+ * @see BagOStuff::makeGlobalKey()
+ * @param string $class Key class
+ * @param string ...$components Key components (starting with a key collection name)
+ * @return string Colon-delimited list of $keyspace followed by escaped components
+ * @since 1.27
+ */
+ public function makeGlobalKey( $class, ...$components ) {
+ return $this->cache->makeGlobalKey( ...func_get_args() );
+ }
+
+ /**
+ * Hash a possibly long string into a suitable component for makeKey()/makeGlobalKey()
+ *
+ * @param string $component A raw component used in building a cache key
+ * @return string 64 character HMAC using a stable secret for public collision resistance
+ * @since 1.34
+ */
+ public function hash256( $component ) {
+ return hash_hmac( 'sha256', $component, $this->secret );
+ }
+
+ /**
+ * Get an iterator of (cache key => entity ID) for a list of entity IDs
+ *
+ * The callback takes an ID string and returns a key via makeKey()/makeGlobalKey().
+ * There should be no network nor filesystem I/O used in the callback. The entity
+ * ID/key mapping must be 1:1 or an exception will be thrown. If hashing is needed,
+ * then use the hash256() method.
+ *
+ * Example usage for the default keyspace:
+ * @code
+ * $keyedIds = $cache->makeMultiKeys(
+ * $modules,
+ * function ( $module ) use ( $cache ) {
+ * return $cache->makeKey( 'module-info', $module );
+ * }
+ * );
+ * @endcode
+ *
+ * Example usage for mixed default and global keyspace:
+ * @code
+ * $keyedIds = $cache->makeMultiKeys(
+ * $filters,
+ * function ( $filter ) use ( $cache ) {
+ * return ( strpos( $filter, 'central:' ) === 0 )
+ * ? $cache->makeGlobalKey( 'regex-filter', $filter )
+ * : $cache->makeKey( 'regex-filter', $filter )
+ * }
+ * );
+ * @endcode
+ *
+ * Example usage with hashing:
+ * @code
+ * $keyedIds = $cache->makeMultiKeys(
+ * $urls,
+ * function ( $url ) use ( $cache ) {
+ * return $cache->makeKey( 'url-info', $cache->hash256( $url ) );
+ * }
+ * );
+ * @endcode
+ *
+ * @see WANObjectCache::makeKey()
+ * @see WANObjectCache::makeGlobalKey()
+ * @see WANObjectCache::hash256()
+ *
+ * @param string[]|int[] $ids List of entity IDs
+ * @param callable $keyCallback Function returning makeKey()/makeGlobalKey() on the input ID
+ * @return ArrayIterator Iterator of (cache key => ID); order of $ids is preserved
+ * @throws UnexpectedValueException
+ * @since 1.28
+ */
+ final public function makeMultiKeys( array $ids, $keyCallback ) {
+ $idByKey = [];
+ foreach ( $ids as $id ) {
+ // Discourage triggering of automatic makeKey() hashing in some backends
+ if ( strlen( $id ) > 64 ) {
+ $this->logger->warning( __METHOD__ . ": long ID '$id'; use hash256()" );
+ }
+ $key = $keyCallback( $id, $this );
+ // Edge case: ignore key collisions due to duplicate $ids like "42" and 42
+ if ( !isset( $idByKey[$key] ) ) {
+ $idByKey[$key] = $id;
+ } elseif ( (string)$id !== (string)$idByKey[$key] ) {
+ throw new UnexpectedValueException(
+ "Cache key collision; IDs ('$id','{$idByKey[$key]}') map to '$key'"
+ );
+ }
+ }
+
+ return new ArrayIterator( $idByKey );
+ }
+
+ /**
+ * Get an (ID => value) map from (i) a non-unique list of entity IDs, and (ii) the list
+ * of corresponding entity values by first appearance of each ID in the entity ID list
+ *
+ * For use with getMultiWithSetCallback() and getMultiWithUnionSetCallback().
+ *
+ * *Only* use this method if the entity ID/key mapping is trivially 1:1 without exception.
+ * Key generation method must utitilize the *full* entity ID in the key (not a hash of it).
+ *
+ * Example usage:
+ * @code
+ * $poems = $cache->getMultiWithSetCallback(
+ * $cache->makeMultiKeys(
+ * $uuids,
+ * function ( $uuid ) use ( $cache ) {
+ * return $cache->makeKey( 'poem', $uuid );
+ * }
+ * ),
+ * $cache::TTL_DAY,
+ * function ( $uuid ) use ( $url ) {
+ * return $this->http->run( [ 'method' => 'GET', 'url' => "$url/$uuid" ] );
+ * }
+ * );
+ * $poemsByUUID = $cache->multiRemap( $uuids, $poems );
+ * @endcode
+ *
+ * @see WANObjectCache::makeMultiKeys()
+ * @see WANObjectCache::getMultiWithSetCallback()
+ * @see WANObjectCache::getMultiWithUnionSetCallback()
+ *
+ * @param string[]|int[] $ids Entity ID list makeMultiKeys()
+ * @param mixed[] $res Result of getMultiWithSetCallback()/getMultiWithUnionSetCallback()
+ * @return mixed[] Map of (ID => value); order of $ids is preserved
+ * @since 1.34
+ */
+ final public function multiRemap( array $ids, array $res ) {
+ if ( count( $ids ) !== count( $res ) ) {
+ // If makeMultiKeys() is called on a list of non-unique IDs, then the resulting
+ // ArrayIterator will have less entries due to "first appearance" de-duplication
+ $ids = array_keys( array_flip( $ids ) );
+ if ( count( $ids ) !== count( $res ) ) {
+ throw new UnexpectedValueException( "Multi-key result does not match ID list" );
+ }
+ }
+
+ return array_combine( $ids, $res );
+ }
+
+ /**
+ * Get the "last error" registered; clearLastError() should be called manually
+ * @return int ERR_* class constant for the "last error" registry
+ */
+ final public function getLastError() {
+ $code = $this->cache->getLastError();
+ switch ( $code ) {
+ case BagOStuff::ERR_NONE:
+ return self::ERR_NONE;
+ case BagOStuff::ERR_NO_RESPONSE:
+ return self::ERR_NO_RESPONSE;
+ case BagOStuff::ERR_UNREACHABLE:
+ return self::ERR_UNREACHABLE;
+ default:
+ return self::ERR_UNEXPECTED;
+ }
+ }
+
+ /**
+ * Clear the "last error" registry
+ */
+ final public function clearLastError() {
+ $this->cache->clearLastError();
+ }
+
+ /**
+ * Clear the in-process caches; useful for testing
+ *
+ * @since 1.27
+ */
+ public function clearProcessCache() {
+ $this->processCaches = [];
+ }
+
+ /**
+ * Enable or disable the use of brief caching for tombstoned keys
+ *
+ * When a key is purged via delete(), there normally is a period where caching
+ * is hold-off limited to an extremely short time. This method will disable that
+ * caching, forcing the callback to run for any of:
+ * - WANObjectCache::getWithSetCallback()
+ * - WANObjectCache::getMultiWithSetCallback()
+ * - WANObjectCache::getMultiWithUnionSetCallback()
+ *
+ * This is useful when both:
+ * - a) the database used by the callback is known to be up-to-date enough
+ * for some particular purpose (e.g. replica DB has applied transaction X)
+ * - b) the caller needs to exploit that fact, and therefore needs to avoid the
+ * use of inherently volatile and possibly stale interim keys
+ *
+ * @see WANObjectCache::delete()
+ * @param bool $enabled Whether to enable interim caching
+ * @since 1.31
+ */
+ final public function useInterimHoldOffCaching( $enabled ) {
+ $this->useInterimHoldOffCaching = $enabled;
+ }
+
+ /**
+ * @param int $flag ATTR_* class constant
+ * @return int QOS_* class constant
+ * @since 1.28
+ */
+ public function getQoS( $flag ) {
+ return $this->cache->getQoS( $flag );
+ }
+
+ /**
+ * Get a TTL that is higher for objects that have not changed recently
+ *
+ * This is useful for keys that get explicit purges and DB or purge relay
+ * lag is a potential concern (especially how it interacts with CDN cache)
+ *
+ * Example usage:
+ * @code
+ * // Last-modified time of page
+ * $mtime = wfTimestamp( TS_UNIX, $page->getTimestamp() );
+ * // Get adjusted TTL. If $mtime is 3600 seconds ago and $minTTL/$factor left at
+ * // defaults, then $ttl is 3600 * .2 = 720. If $minTTL was greater than 720, then
+ * // $ttl would be $minTTL. If $maxTTL was smaller than 720, $ttl would be $maxTTL.
+ * $ttl = $cache->adaptiveTTL( $mtime, $cache::TTL_DAY );
+ * @endcode
+ *
+ * Another use case is when there are no applicable "last modified" fields in the DB,
+ * and there are too many dependencies for explicit purges to be viable, and the rate of
+ * change to relevant content is unstable, and it is highly valued to have the cached value
+ * be as up-to-date as possible.
+ *
+ * Example usage:
+ * @code
+ * $query = "<some complex query>";
+ * $idListFromComplexQuery = $cache->getWithSetCallback(
+ * $cache->makeKey( 'complex-graph-query', $hashOfQuery ),
+ * GraphQueryClass::STARTING_TTL,
+ * function ( $oldValue, &$ttl, array &$setOpts, $oldAsOf ) use ( $query, $cache ) {
+ * $gdb = $this->getReplicaGraphDbConnection();
+ * // Account for any snapshot/replica DB lag
+ * $setOpts += GraphDatabase::getCacheSetOptions( $gdb );
+ *
+ * $newList = iterator_to_array( $gdb->query( $query ) );
+ * sort( $newList, SORT_NUMERIC ); // normalize
+ *
+ * $minTTL = GraphQueryClass::MIN_TTL;
+ * $maxTTL = GraphQueryClass::MAX_TTL;
+ * if ( $oldValue !== false ) {
+ * // Note that $oldAsOf is the last time this callback ran
+ * $ttl = ( $newList === $oldValue )
+ * // No change: cache for 150% of the age of $oldValue
+ * ? $cache->adaptiveTTL( $oldAsOf, $maxTTL, $minTTL, 1.5 )
+ * // Changed: cache for 50% of the age of $oldValue
+ * : $cache->adaptiveTTL( $oldAsOf, $maxTTL, $minTTL, .5 );
+ * }
+ *
+ * return $newList;
+ * },
+ * [
+ * // Keep stale values around for doing comparisons for TTL calculations.
+ * // High values improve long-tail keys hit-rates, though might waste space.
+ * 'staleTTL' => GraphQueryClass::GRACE_TTL
+ * ]
+ * );
+ * @endcode
+ *
+ * @param int|float $mtime UNIX timestamp
+ * @param int $maxTTL Maximum TTL (seconds)
+ * @param int $minTTL Minimum TTL (seconds); Default: 30
+ * @param float $factor Value in the range (0,1); Default: .2
+ * @return int Adaptive TTL
+ * @since 1.28
+ */
+ public function adaptiveTTL( $mtime, $maxTTL, $minTTL = 30, $factor = 0.2 ) {
+ if ( is_float( $mtime ) || ctype_digit( $mtime ) ) {
+ $mtime = (int)$mtime; // handle fractional seconds and string integers
+ }
+
+ if ( !is_int( $mtime ) || $mtime <= 0 ) {
+ return $minTTL; // no last-modified time provided
+ }
+
+ $age = $this->getCurrentTime() - $mtime;
+
+ return (int)min( $maxTTL, max( $minTTL, $factor * $age ) );
+ }
+
+ /**
+ * @return int Number of warmup key cache misses last round
+ * @since 1.30
+ */
+ final public function getWarmupKeyMisses() {
+ return $this->warmupKeyMisses;
+ }
+
+ /**
+ * Do the actual async bus purge of a key
+ *
+ * This must set the key to "PURGED:<UNIX timestamp>:<holdoff>"
+ *
+ * @param string $key Cache key
+ * @param int $ttl Seconds to keep the tombstone around
+ * @param int $holdoff HOLDOFF_* constant controlling how long to ignore sets for this key
+ * @return bool Success
+ */
+ protected function relayPurge( $key, $ttl, $holdoff ) {
+ if ( $this->mcrouterAware ) {
+ // See https://github.com/facebook/mcrouter/wiki/Multi-cluster-broadcast-setup
+ // Wildcards select all matching routes, e.g. the WAN cluster on all DCs
+ $ok = $this->cache->set(
+ "/*/{$this->cluster}/{$key}",
+ $this->makePurgeValue( $this->getCurrentTime(), self::HOLDOFF_TTL_NONE ),
+ $ttl
+ );
+ } else {
+ // This handles the mcrouter and the single-DC case
+ $ok = $this->cache->set(
+ $key,
+ $this->makePurgeValue( $this->getCurrentTime(), self::HOLDOFF_TTL_NONE ),
+ $ttl
+ );
+ }
+
+ return $ok;
+ }
+
+ /**
+ * Do the actual async bus delete of a key
+ *
+ * @param string $key Cache key
+ * @return bool Success
+ */
+ protected function relayDelete( $key ) {
+ if ( $this->mcrouterAware ) {
+ // See https://github.com/facebook/mcrouter/wiki/Multi-cluster-broadcast-setup
+ // Wildcards select all matching routes, e.g. the WAN cluster on all DCs
+ $ok = $this->cache->delete( "/*/{$this->cluster}/{$key}" );
+ } else {
+ // Some other proxy handles broadcasting or there is only one datacenter
+ $ok = $this->cache->delete( $key );
+ }
+
+ return $ok;
+ }
+
+ /**
+ * @param string $key
+ * @param int $ttl Seconds to live
+ * @param callable $callback
+ * @param array $opts
+ * @return bool Success
+ * @note Callable type hints are not used to avoid class-autoloading
+ */
+ private function scheduleAsyncRefresh( $key, $ttl, $callback, $opts ) {
+ if ( !$this->asyncHandler ) {
+ return false;
+ }
+ // Update the cache value later, such during post-send of an HTTP request
+ $func = $this->asyncHandler;
+ $func( function () use ( $key, $ttl, $callback, $opts ) {
+ $opts['minAsOf'] = INF; // force a refresh
+ $this->fetchOrRegenerate( $key, $ttl, $callback, $opts );
+ } );
+
+ return true;
+ }
+
+ /**
+ * Check if a key is fresh or in the grace window and thus due for randomized reuse
+ *
+ * If $curTTL > 0 (e.g. not expired) this returns true. Otherwise, the chance of returning
+ * true decrease steadily from 100% to 0% as the |$curTTL| moves from 0 to $graceTTL seconds.
+ * This handles widely varying levels of cache access traffic.
+ *
+ * If $curTTL <= -$graceTTL (e.g. already expired), then this returns false.
+ *
+ * @param float $curTTL Approximate TTL left on the key if present
+ * @param int $graceTTL Consider using stale values if $curTTL is greater than this
+ * @return bool
+ */
+ private function isAliveOrInGracePeriod( $curTTL, $graceTTL ) {
+ if ( $curTTL > 0 ) {
+ return true;
+ } elseif ( $graceTTL <= 0 ) {
+ return false;
+ }
+
+ $ageStale = abs( $curTTL ); // seconds of staleness
+ $curGTTL = ( $graceTTL - $ageStale ); // current grace-time-to-live
+ if ( $curGTTL <= 0 ) {
+ return false; // already out of grace period
+ }
+
+ // Chance of using a stale value is the complement of the chance of refreshing it
+ return !$this->worthRefreshExpiring( $curGTTL, $graceTTL );
+ }
+
+ /**
+ * Check if a key is nearing expiration and thus due for randomized regeneration
+ *
+ * This returns false if $curTTL >= $lowTTL. Otherwise, the chance of returning true
+ * increases steadily from 0% to 100% as the $curTTL moves from $lowTTL to 0 seconds.
+ * This handles widely varying levels of cache access traffic.
+ *
+ * If $curTTL <= 0 (e.g. already expired), then this returns false.
+ *
+ * @param float $curTTL Approximate TTL left on the key if present
+ * @param float $lowTTL Consider a refresh when $curTTL is less than this
+ * @return bool
+ */
+ protected function worthRefreshExpiring( $curTTL, $lowTTL ) {
+ if ( $lowTTL <= 0 ) {
+ return false;
+ } elseif ( $curTTL >= $lowTTL ) {
+ return false;
+ } elseif ( $curTTL <= 0 ) {
+ return false;
+ }
+
+ $chance = ( 1 - $curTTL / $lowTTL );
+
+ return mt_rand( 1, 1e9 ) <= 1e9 * $chance;
+ }
+
+ /**
+ * Check if a key is due for randomized regeneration due to its popularity
+ *
+ * This is used so that popular keys can preemptively refresh themselves for higher
+ * consistency (especially in the case of purge loss/delay). Unpopular keys can remain
+ * in cache with their high nominal TTL. This means popular keys keep good consistency,
+ * whether the data changes frequently or not, and long-tail keys get to stay in cache
+ * and get hits too. Similar to worthRefreshExpiring(), randomization is used.
+ *
+ * @param float $asOf UNIX timestamp of the value
+ * @param int $ageNew Age of key when this might recommend refreshing (seconds)
+ * @param int $timeTillRefresh Age of key when it should be refreshed if popular (seconds)
+ * @param float $now The current UNIX timestamp
+ * @return bool
+ */
+ protected function worthRefreshPopular( $asOf, $ageNew, $timeTillRefresh, $now ) {
+ if ( $ageNew < 0 || $timeTillRefresh <= 0 ) {
+ return false;
+ }
+
+ $age = $now - $asOf;
+ $timeOld = $age - $ageNew;
+ if ( $timeOld <= 0 ) {
+ return false;
+ }
+
+ $popularHitsPerSec = 1;
+ // Lifecycle is: new, ramp-up refresh chance, full refresh chance.
+ // Note that the "expected # of refreshes" for the ramp-up time range is half
+ // of what it would be if P(refresh) was at its full value during that time range.
+ $refreshWindowSec = max( $timeTillRefresh - $ageNew - self::$RAMPUP_TTL / 2, 1 );
+ // P(refresh) * (# hits in $refreshWindowSec) = (expected # of refreshes)
+ // P(refresh) * ($refreshWindowSec * $popularHitsPerSec) = 1 (by definition)
+ // P(refresh) = 1/($refreshWindowSec * $popularHitsPerSec)
+ $chance = 1 / ( $popularHitsPerSec * $refreshWindowSec );
+
+ // Ramp up $chance from 0 to its nominal value over RAMPUP_TTL seconds to avoid stampedes
+ $chance *= ( $timeOld <= self::$RAMPUP_TTL ) ? $timeOld / self::$RAMPUP_TTL : 1;
+
+ return mt_rand( 1, 1e9 ) <= 1e9 * $chance;
+ }
+
+ /**
+ * Check if $value is not false, versioned (if needed), and not older than $minTime (if set)
+ *
+ * @param array|bool $value
+ * @param float $asOf The time $value was generated
+ * @param float $minAsOf Minimum acceptable "as of" timestamp
+ * @param float|null $purgeTime The last time the value was invalidated
+ * @return bool
+ */
+ protected function isValid( $value, $asOf, $minAsOf, $purgeTime = null ) {
+ // Avoid reading any key not generated after the latest delete() or touch
+ $safeMinAsOf = max( $minAsOf, $purgeTime + self::$TINY_POSTIVE );
+
+ if ( $value === false ) {
+ return false;
+ } elseif ( $safeMinAsOf > 0 && $asOf < $minAsOf ) {
+ return false;
+ }
+
+ return true;
+ }
+
+ /**
+ * @param mixed $value
+ * @param int $ttl Seconds to live or zero for "indefinite"
+ * @param int|null $version Value version number or null if not versioned
+ * @param float $now Unix Current timestamp just before calling set()
+ * @param float $walltime How long it took to generate the value in seconds
+ * @return array
+ */
+ private function wrap( $value, $ttl, $version, $now, $walltime ) {
+ // Returns keys in ascending integer order for PHP7 array packing:
+ // https://nikic.github.io/2014/12/22/PHPs-new-hashtable-implementation.html
+ $wrapped = [
+ self::$FLD_FORMAT_VERSION => self::$VERSION,
+ self::$FLD_VALUE => $value,
+ self::$FLD_TTL => $ttl,
+ self::$FLD_TIME => $now
+ ];
+ if ( $version !== null ) {
+ $wrapped[self::$FLD_VALUE_VERSION] = $version;
+ }
+ if ( $walltime >= self::$GENERATION_SLOW_SEC ) {
+ $wrapped[self::$FLD_GENERATION_TIME] = $walltime;
+ }
+
+ return $wrapped;
+ }
+
+ /**
+ * @param array|string|bool $wrapped The entry at a cache key
+ * @param float $now Unix Current timestamp (preferrably pre-query)
+ * @return array (value or false if absent/tombstoned/malformed, value metadata map).
+ * The cache key metadata includes the following metadata:
+ * - asOf: UNIX timestamp of the value or null if there is no value
+ * - curTTL: remaining time-to-live (negative if tombstoned) or null if there is no value
+ * - version: value version number or null if the if there is no value
+ * - tombAsOf: UNIX timestamp of the tombstone or null if there is no tombstone
+ */
+ private function unwrap( $wrapped, $now ) {
+ $value = false;
+ $info = [ 'asOf' => null, 'curTTL' => null, 'version' => null, 'tombAsOf' => null ];
+
+ if ( is_array( $wrapped ) ) {
+ // Entry expected to be a cached value; validate it
+ if (
+ ( $wrapped[self::$FLD_FORMAT_VERSION] ?? null ) === self::$VERSION &&
+ $wrapped[self::$FLD_TIME] >= $this->epoch
+ ) {
+ if ( $wrapped[self::$FLD_TTL] > 0 ) {
+ // Get the approximate time left on the key
+ $age = $now - $wrapped[self::$FLD_TIME];
+ $curTTL = max( $wrapped[self::$FLD_TTL] - $age, 0.0 );
+ } else {
+ // Key had no TTL, so the time left is unbounded
+ $curTTL = INF;
+ }
+ $value = $wrapped[self::$FLD_VALUE];
+ $info['version'] = $wrapped[self::$FLD_VALUE_VERSION] ?? null;
+ $info['asOf'] = $wrapped[self::$FLD_TIME];
+ $info['curTTL'] = $curTTL;
+ }
+ } else {
+ // Entry expected to be a tombstone; parse it
+ $purge = $this->parsePurgeValue( $wrapped );
+ if ( $purge !== false ) {
+ // Tombstoned keys should always have a negative current $ttl
+ $info['curTTL'] = min( $purge[self::$PURGE_TIME] - $now, self::$TINY_NEGATIVE );
+ $info['tombAsOf'] = $purge[self::$PURGE_TIME];
+ }
+ }
+
+ return [ $value, $info ];
+ }
+
+ /**
+ * @param string[] $keys
+ * @param string $prefix
+ * @return string[] Prefix keys; the order of $keys is preserved
+ */
+ protected static function prefixCacheKeys( array $keys, $prefix ) {
+ $res = [];
+ foreach ( $keys as $key ) {
+ $res[] = $prefix . $key;
+ }
+
+ return $res;
+ }
+
+ /**
+ * @param string $key String of the format <scope>:<class>[:<class or variable>]...
+ * @return string A collection name to describe this class of key
+ */
+ private function determineKeyClassForStats( $key ) {
+ $parts = explode( ':', $key, 3 );
+
+ return $parts[1] ?? $parts[0]; // sanity
+ }
+
+ /**
+ * @param string|array|bool $value Possible string of the form "PURGED:<timestamp>:<holdoff>"
+ * @return array|bool Array containing a UNIX timestamp (float) and holdoff period (integer),
+ * or false if value isn't a valid purge value
+ */
+ private function parsePurgeValue( $value ) {
+ if ( !is_string( $value ) ) {
+ return false;
+ }
+
+ $segments = explode( ':', $value, 3 );
+ if (
+ !isset( $segments[0] ) ||
+ !isset( $segments[1] ) ||
+ "{$segments[0]}:" !== self::$PURGE_VAL_PREFIX
+ ) {
+ return false;
+ }
+
+ if ( !isset( $segments[2] ) ) {
+ // Back-compat with old purge values without holdoff
+ $segments[2] = self::HOLDOFF_TTL;
+ }
+
+ if ( $segments[1] < $this->epoch ) {
+ // Values this old are ignored
+ return false;
+ }
+
+ return [
+ self::$PURGE_TIME => (float)$segments[1],
+ self::$PURGE_HOLDOFF => (int)$segments[2],
+ ];
+ }
+
+ /**
+ * @param float $timestamp
+ * @param int $holdoff In seconds
+ * @return string Wrapped purge value
+ */
+ private function makePurgeValue( $timestamp, $holdoff ) {
+ return self::$PURGE_VAL_PREFIX . (float)$timestamp . ':' . (int)$holdoff;
+ }
+
+ /**
+ * @param string $group
+ * @return MapCacheLRU
+ */
+ private function getProcessCache( $group ) {
+ if ( !isset( $this->processCaches[$group] ) ) {
+ list( , $size ) = explode( ':', $group );
+ $this->processCaches[$group] = new MapCacheLRU( (int)$size );
+ }
+
+ return $this->processCaches[$group];
+ }
+
+ /**
+ * @param string $key
+ * @param int $version
+ * @return string
+ */
+ private function getProcessCacheKey( $key, $version ) {
+ return $key . ' ' . (int)$version;
+ }
+
+ /**
+ * @param ArrayIterator $keys
+ * @param array $opts
+ * @return string[] Map of (ID => cache key)
+ */
+ private function getNonProcessCachedMultiKeys( ArrayIterator $keys, array $opts ) {
+ $pcTTL = $opts['pcTTL'] ?? self::TTL_UNCACHEABLE;
+
+ $keysMissing = [];
+ if ( $pcTTL > 0 && $this->callbackDepth == 0 ) {
+ $version = $opts['version'] ?? null;
+ $pCache = $this->getProcessCache( $opts['pcGroup'] ?? self::PC_PRIMARY );
+ foreach ( $keys as $key => $id ) {
+ if ( !$pCache->has( $this->getProcessCacheKey( $key, $version ), $pcTTL ) ) {
+ $keysMissing[$id] = $key;
+ }
+ }
+ }
+
+ return $keysMissing;
+ }
+
+ /**
+ * @param string[] $keys
+ * @param string[]|string[][] $checkKeys
+ * @return string[] List of cache keys
+ */
+ private function getRawKeysForWarmup( array $keys, array $checkKeys ) {
+ if ( !$keys ) {
+ return [];
+ }
+
+ $keysWarmUp = [];
+ // Get all the value keys to fetch...
+ foreach ( $keys as $key ) {
+ $keysWarmUp[] = self::$VALUE_KEY_PREFIX . $key;
+ }
+ // Get all the check keys to fetch...
+ foreach ( $checkKeys as $i => $checkKeyOrKeys ) {
+ if ( is_int( $i ) ) {
+ // Single check key that applies to all value keys
+ $keysWarmUp[] = self::$TIME_KEY_PREFIX . $checkKeyOrKeys;
+ } else {
+ // List of check keys that apply to value key $i
+ $keysWarmUp = array_merge(
+ $keysWarmUp,
+ self::prefixCacheKeys( $checkKeyOrKeys, self::$TIME_KEY_PREFIX )
+ );
+ }
+ }
+
+ $warmupCache = $this->cache->getMulti( $keysWarmUp );
+ $warmupCache += array_fill_keys( $keysWarmUp, false );
+
+ return $warmupCache;
+ }
+
+ /**
+ * @return float UNIX timestamp
+ * @codeCoverageIgnore
+ */
+ protected function getCurrentTime() {
+ if ( $this->wallClockOverride ) {
+ return $this->wallClockOverride;
+ }
+
+ $clockTime = (float)time(); // call this first
+ // microtime() uses an initial gettimeofday() call added to usage clocks.
+ // This can severely drift from time() and the microtime() value of other threads
+ // due to undercounting of the amount of time elapsed. Instead of seeing the current
+ // time as being in the past, use the value of time(). This avoids setting cache values
+ // that will immediately be seen as expired and possibly cause stampedes.
+ return max( microtime( true ), $clockTime );
+ }
+
+ /**
+ * @param float|null &$time Mock UNIX timestamp for testing
+ * @codeCoverageIgnore
+ */
+ public function setMockTime( &$time ) {
+ $this->wallClockOverride =& $time;
+ $this->cache->setMockTime( $time );
+ }
+}
+++ /dev/null
-<?php
-/**
- * Object caching using WinCache.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
- * http://www.gnu.org/copyleft/gpl.html
- *
- * @file
- * @ingroup Cache
- */
-
-/**
- * Wrapper for WinCache object caching functions; identical interface
- * to the APC wrapper
- *
- * @ingroup Cache
- */
-class WinCacheBagOStuff extends MediumSpecificBagOStuff {
- protected function doGet( $key, $flags = 0, &$casToken = null ) {
- $casToken = null;
-
- $blob = wincache_ucache_get( $key );
- if ( !is_string( $blob ) && !is_int( $blob ) ) {
- return false;
- }
-
- $value = $this->unserialize( $blob );
- if ( $value !== false ) {
- $casToken = (string)$blob; // don't bother hashing this
- }
-
- return $value;
- }
-
- protected function cas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
- if ( !wincache_lock( $key ) ) { // optimize with FIFO lock
- return false;
- }
-
- $curCasToken = null; // passed by reference
- $this->doGet( $key, self::READ_LATEST, $curCasToken );
- if ( $casToken === $curCasToken ) {
- $success = $this->set( $key, $value, $exptime, $flags );
- } else {
- $this->logger->info(
- __METHOD__ . ' failed due to race condition for {key}.',
- [ 'key' => $key ]
- );
-
- $success = false; // mismatched or failed
- }
-
- wincache_unlock( $key );
-
- return $success;
- }
-
- protected function doSet( $key, $value, $exptime = 0, $flags = 0 ) {
- $result = wincache_ucache_set( $key, $this->serialize( $value ), $exptime );
-
- // false positive, wincache_ucache_set returns an empty array
- // in some circumstances.
- // @phan-suppress-next-line PhanTypeComparisonToArray
- return ( $result === [] || $result === true );
- }
-
- public function add( $key, $value, $exptime = 0, $flags = 0 ) {
- if ( wincache_ucache_exists( $key ) ) {
- return false; // avoid warnings
- }
-
- $result = wincache_ucache_add( $key, $this->serialize( $value ), $exptime );
-
- // false positive, wincache_ucache_add returns an empty array
- // in some circumstances.
- // @phan-suppress-next-line PhanTypeComparisonToArray
- return ( $result === [] || $result === true );
- }
-
- protected function doDelete( $key, $flags = 0 ) {
- wincache_ucache_delete( $key );
-
- return true;
- }
-
- /**
- * Construct a cache key.
- *
- * @since 1.27
- * @param string $keyspace
- * @param array $args
- * @return string
- */
- public function makeKeyInternal( $keyspace, $args ) {
- // WinCache keys have a maximum length of 150 characters. From that,
- // subtract the number of characters we need for the keyspace and for
- // the separator character needed for each argument. To handle some
- // custom prefixes used by thing like WANObjectCache, limit to 125.
- // NOTE: Same as in memcached, except the max key length there is 255.
- $charsLeft = 125 - strlen( $keyspace ) - count( $args );
-
- $args = array_map(
- function ( $arg ) use ( &$charsLeft ) {
- // 33 = 32 characters for the MD5 + 1 for the '#' prefix.
- if ( $charsLeft > 33 && strlen( $arg ) > $charsLeft ) {
- $arg = '#' . md5( $arg );
- }
-
- $charsLeft -= strlen( $arg );
- return $arg;
- },
- $args
- );
-
- if ( $charsLeft < 0 ) {
- return $keyspace . ':BagOStuff-long-key:##' . md5( implode( ':', $args ) );
- }
-
- return $keyspace . ':' . implode( ':', $args );
- }
-
- /**
- * Increase stored value of $key by $value while preserving its original TTL
- * @param string $key Key to increase
- * @param int $value Value to add to $key (Default 1)
- * @return int|bool New value or false on failure
- */
- public function incr( $key, $value = 1 ) {
- if ( !wincache_lock( $key ) ) { // optimize with FIFO lock
- return false;
- }
-
- $n = $this->doGet( $key );
- if ( $this->isInteger( $n ) ) {
- $n = max( $n + (int)$value, 0 );
- $oldTTL = wincache_ucache_info( false, $key )["ucache_entries"][1]["ttl_seconds"];
- $this->set( $key, $n, $oldTTL );
- } else {
- $n = false;
- }
-
- wincache_unlock( $key );
-
- return $n;
- }
-}
dépôts / lhc / web / wiklou.git / commitdiff