$data['mVersion'] = self::VERSION;
$key = wfMemcKey( 'user', 'id', $this->mId );
- $opts = array( 'since' => wfGetDB( DB_SLAVE )->trxTimestamp() );
+ $opts = DatabaseBase::getCacheSetOptions( wfGetDB( DB_SLAVE ) );
ObjectCache::getMainWANInstance()->set( $key, $data, 3600, $opts );
}
$title = $page->getTitle();
$id = $title->getArticleID();
+ $dbr = wfGetDB( DB_SLAVE );
$dbrWatchlist = wfGetDB( DB_SLAVE, 'watchlist' );
+
+ $setOpts += DatabaseBase::getCacheSetOptions( $dbr, $dbrWatchlist );
+
$result = array();
// Number of page watchers
$result['visitingWatchers'] = $visitingWatchers;
}
- $dbr = wfGetDB( DB_SLAVE );
// Total number of edits
$edits = (int)$dbr->selectField(
'revision',
$fname
);
- $setOpts = array( 'since' => $dbr->trxTimestamp() );
-
return $result;
},
86400 * 7
public static function listExtensionActivatedTags() {
return ObjectCache::getMainWANInstance()->getWithSetCallback(
wfMemcKey( 'active-tags' ),
- function() {
+ function ( $oldValue, &$ttl, array &$setOpts ) {
+ $setOpts += DatabaseBase::getCacheSetOptions( wfGetDB( DB_SLAVE ) );
+
// Ask extensions which tags they consider active
$extensionActive = array();
Hooks::run( 'ChangeTagsListActive', array( &$extensionActive ) );
return ObjectCache::getMainWANInstance()->getWithSetCallback(
wfMemcKey( 'valid-tags-db' ),
- function() use ( $fname ) {
+ function ( $oldValue, &$ttl, array &$setOpts ) use ( $fname ) {
$dbr = wfGetDB( DB_SLAVE );
- $tags = $dbr->selectFieldValues(
- 'valid_tag', 'vt_tag', array(), $fname );
+
+ $setOpts += DatabaseBase::getCacheSetOptions( $dbr );
+
+ $tags = $dbr->selectFieldValues( 'valid_tag', 'vt_tag', array(), $fname );
return array_filter( array_unique( $tags ) );
},
public static function listExtensionDefinedTags() {
return ObjectCache::getMainWANInstance()->getWithSetCallback(
wfMemcKey( 'valid-tags-hook' ),
- function() {
+ function ( $oldValue, &$ttl, array &$setOpts ) {
+ $setOpts += DatabaseBase::getCacheSetOptions( wfGetDB( DB_SLAVE ) );
+
$tags = array();
Hooks::run( 'ListDefinedTags', array( &$tags ) );
return array_filter( array_unique( $tags ) );
$fname = __METHOD__;
$cachedStats = ObjectCache::getMainWANInstance()->getWithSetCallback(
wfMemcKey( 'change-tag-statistics' ),
- function() use ( $fname ) {
- $out = array();
-
+ function ( $oldValue, &$ttl, array &$setOpts ) use ( $fname ) {
$dbr = wfGetDB( DB_SLAVE, 'vslow' );
+
+ $setOpts += DatabaseBase::getCacheSetOptions( $dbr );
+
$res = $dbr->select(
'change_tag',
array( 'ct_tag', 'hitcount' => 'count(*)' ),
array( 'GROUP BY' => 'ct_tag', 'ORDER BY' => 'hitcount DESC' )
);
+ $out = array();
foreach ( $res as $row ) {
$out[$row->ct_tag] = $row->hitcount;
}
return $this->__call( __FUNCTION__, func_get_args() );
}
+ public function getSessionLagStatus() {
+ return $this->__call( __FUNCTION__, func_get_args() );
+ }
+
public function maxListLen() {
return $this->__call( __FUNCTION__, func_get_args() );
}
protected $mServer, $mUser, $mPassword, $mDBname;
+ /** @var BagOStuff APC cache */
+ protected $srvCache;
+
/** @var resource Database connection */
protected $mConn = null;
protected $mOpened = false;
*/
private $mTrxTimestamp = null;
+ /** @var float Lag estimate at the time of BEGIN */
+ private $mTrxSlaveLag = null;
+
/**
* Remembers the function name given for starting the most recent transaction via begin().
* Used to provide additional context for error reporting.
function __construct( array $params ) {
global $wgDBprefix, $wgDBmwschema, $wgCommandLineMode;
+ $this->mTrxAtomicLevels = new SplStack;
+ $this->srvCache = ObjectCache::newAccelerator( 'hash' );
+
$server = $params['host'];
$user = $params['user'];
$password = $params['password'];
$this->mTrxPreCommitCallbacks = array();
$this->mTrxShortId = wfRandomString( 12 );
$this->mTrxWriteDuration = 0.0;
+ // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
+ // Get an estimate of the slave lag before then, treating estimate staleness
+ // as lag itself just to be safe
+ $status = $this->getApproximateLagStatus();
+ $this->mTrxSlaveLag = $status['lag'] + ( microtime( true ) - $status['since'] );
}
/**
return true;
}
+ /**
+ * Get the slave lag when the current transaction started
+ * or a general lag estimate if not transaction is active
+ *
+ * This is useful when transactions might use snapshot isolation
+ * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
+ * is this lag plus transaction duration. If they don't, it is still
+ * safe to be pessimistic. In AUTO-COMMIT mode, this still gives an
+ * indication of the staleness of subsequent reads.
+ *
+ * @return array ('lag': seconds, 'since': UNIX timestamp of BEGIN)
+ * @since 1.27
+ */
+ public function getSessionLagStatus() {
+ return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
+ }
+
+ /**
+ * Get the slave lag when the current transaction started
+ *
+ * This is useful when transactions might use snapshot isolation
+ * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
+ * is this lag plus transaction duration. If they don't, it is still
+ * safe to be pessimistic. This returns null if there is no transaction.
+ *
+ * @return array|null ('lag': seconds, 'since': UNIX timestamp of BEGIN)
+ * @since 1.27
+ */
+ public function getTransactionLagStatus() {
+ return $this->mTrxLevel
+ ? array( 'lag' => $this->mTrxSlaveLag, 'since' => $this->trxTimestamp() )
+ : null;
+ }
+
+ /**
+ * Get a slave lag estimate for this server
+ *
+ * @return array ('lag': seconds, 'since': UNIX timestamp of estimate)
+ * @since 1.27
+ */
+ public function getApproximateLagStatus() {
+ return array(
+ 'lag' => $this->getLBInfo( 'slave' ) ? $this->getLag() : 0,
+ 'since' => microtime( true )
+ );
+ }
+
+ /**
+ * Merge the result of getSessionLagStatus() for several DBs
+ * using the most pessimistic values to estimate the lag of
+ * any data derived from them in combination
+ *
+ * This is information is useful for caching modules
+ *
+ * @see WANObjectCache::set()
+ * @see WANObjectCache::getWithSetCallback()
+ *
+ * @param IDatabase $db1
+ * @param IDatabase ...
+ * @return array ('lag': highest lag, 'since': lowest estimate UNIX timestamp)
+ * @since 1.27
+ */
+ public static function getCacheSetOptions( IDatabase $db1 ) {
+ $res = array( 'lag' => 0, 'since' => INF );
+ foreach ( func_get_args() as $db ) {
+ /** @var IDatabase $db */
+ $status = $db->getSessionLagStatus();
+ $res['lag'] = max( $res['lag'], $status['lag'] );
+ $res['since'] = min( $res['since'], $status['since'] );
+ }
+
+ return $res;
+ }
+
/**
* Get slave lag. Currently supported only by MySQL.
*
/** @var string Method to detect slave lag */
protected $lagDetectionMethod;
- /** @var BagOStuff APC cache */
- protected $srvCache;
-
/** @var string|null */
private $serverVersion = null;
$this->lagDetectionMethod = isset( $params['lagDetectionMethod'] )
? $params['lagDetectionMethod']
: 'Seconds_Behind_Master';
-
- $this->srvCache = ObjectCache::newAccelerator( 'hash' );
}
/**
return false;
}
+ public function getApproximateLagStatus() {
+ if ( $this->lagDetectionMethod === 'pt-heartbeat' ) {
+ // Disable caching since this is fast enough and we don't wan't
+ // to be *too* pessimistic by having both the cache TTL and the
+ // pt-heartbeat interval count as lag in getSessionLagStatus()
+ return parent::getApproximateLagStatus();
+ }
+
+ $key = wfGlobalCacheKey( 'mysql-lag', $this->getServer() );
+ $approxLag = $this->srvCache->get( $key );
+ if ( !$approxLag ) {
+ $approxLag = parent::getApproximateLagStatus();
+ $this->srvCache->set( $key, $approxLag, 1 );
+ }
+
+ return $approxLag;
+ }
+
/**
* Wait for the slave to catch up to a given master position.
* @todo Return values for this and base class are rubbish
*/
public function getLag();
+ /**
+ * Get the slave lag when the current transaction started
+ * or a general lag estimate if not transaction is active
+ *
+ * This is useful when transactions might use snapshot isolation
+ * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
+ * is this lag plus transaction duration. If they don't, it is still
+ * safe to be pessimistic. In AUTO-COMMIT mode, this still gives an
+ * indication of the staleness of subsequent reads.
+ *
+ * @return array ('lag': seconds, 'since': UNIX timestamp of BEGIN)
+ * @since 1.27
+ */
+ public function getSessionLagStatus();
+
/**
* Return the maximum number of items allowed in a list, or 0 for unlimited.
*
function ( $oldValue, &$ttl, array &$setOpts ) use ( $that, $title ) {
$dbr = $that->getSlaveDB(); // possibly remote DB
- $setOpts = array( 'since' => $dbr->trxTimestamp() );
+ $setOpts += DatabaseBase::getCacheSetOptions( $dbr );
if ( $title instanceof Title ) {
$row = $dbr->selectRow(
// Cache presence for 1 week and negatives for 1 day
$ttl = $this->fileExists ? 86400 * 7 : 86400;
- $opts = array( 'since' => wfGetDB( DB_SLAVE )->trxTimestamp() );
+ $opts = DatabaseBase::getCacheSetOptions( $this->repo->getSlaveDB() );
ObjectCache::getMainWANInstance()->set( $key, $cacheVal, $ttl, $opts );
}
function ( $oldValue, &$ttl, array &$setOpts ) use ( $prefix ) {
$dbr = wfGetDB( DB_SLAVE );
+ $setOpts += DatabaseBase::getCacheSetOptions( $dbr );
+
$row = $dbr->selectRow(
'interwiki',
Interwiki::selectFields(),
__METHOD__
);
- $setOpts = array( 'since' => $dbr->trxTimestamp() );
-
return $row ? (array)$row : '!NONEXISTENT';
},
$wgInterwikiExpiry
protected $lastRelayError = self::ERR_NONE;
/** Max time expected to pass between delete() and DB commit finishing */
- const MAX_COMMIT_DELAY = 1;
- /** Max expected replication lag for a reasonable storage setup */
- const MAX_REPLICA_LAG = 7;
+ const MAX_COMMIT_DELAY = 3;
+ /** Max replication lag before applying TTL_LAGGED to set() */
+ const MAX_REPLICA_LAG = 5;
/** Max time since snapshot transaction start to avoid no-op of set() */
- const MAX_SNAPSHOT_LAG = 6;
+ const MAX_SNAPSHOT_LAG = 5;
/** Seconds to tombstone keys on delete() */
- const HOLDOFF_TTL = 14; // MAX_COMMIT_DELAY + MAX_REPLICA_LAG + MAX_SNAPSHOT_LAG
+ const HOLDOFF_TTL = 14; // MAX_COMMIT_DELAY + MAX_REPLICA_LAG + MAX_SNAPSHOT_LAG + 1
/** Seconds to keep dependency purge keys around */
const CHECK_KEY_TTL = 31536000; // 1 year
const TTL_UNCACHEABLE = -1;
/** Idiom for getWithSetCallback() callbacks to 'lockTSE' logic */
const TSE_NONE = -1;
+ /** Max TTL to store keys when a data sourced is lagged */
+ const TTL_LAGGED = 30;
/** Cache format version number */
const VERSION = 1;
* Example usage:
* @code
* $dbr = wfGetDB( DB_SLAVE );
+ * $setOpts = DatabaseBase::getCacheSetOptions( $dbr );
* // Fetch the row from the DB
* $row = $dbr->selectRow( ... );
* $key = wfMemcKey( 'building', $buildingId );
- * // Give the age of the transaction snapshot the data came from
- * $opts = array( 'since' => $dbr->trxTimestamp() );
- * $cache->set( $key, $row, 86400, $opts );
+ * $cache->set( $key, $row, 86400, $setOpts );
* @endcode
*
* @param string $key Cache key
* @param mixed $value
* @param integer $ttl Seconds to live [0=forever]
* @param array $opts Options map:
+ * - lag : Seconds of slave lag. Typically, this is either the slave lag
+ * before the data was read or, if applicable, the slave lag before
+ * the snapshot-isolated transaction the data was read from started.
+ * [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.
final public function set( $key, $value, $ttl = 0, array $opts = array() ) {
$lockTSE = isset( $opts['lockTSE'] ) ? $opts['lockTSE'] : self::TSE_NONE;
$age = isset( $opts['since'] ) ? max( 0, microtime( true ) - $opts['since'] ) : 0;
+ $lag = isset( $opts['lag'] ) ? $opts['lag'] : 0;
+
+ if ( $lag > self::MAX_REPLICA_LAG ) {
+ // Too much lag detected; lower TTL so it converges faster
+ $ttl = $ttl ? min( $ttl, self::TTL_LAGGED ) : self::TTL_LAGGED;
+ }
if ( $age > self::MAX_SNAPSHOT_LAG ) {
if ( $lockTSE >= 0 ) {
* // Key to store the cached value under
* wfMemcKey( 'cat-attributes', $catId ),
* // Function that derives the new key value
- * function( $oldValue, &$ttl, array &$setOpts ) {
- * // Fetch row from the DB
+ * function ( $oldValue, &$ttl, array &$setOpts ) {
* $dbr = wfGetDB( DB_SLAVE );
- * $row = $dbr->selectRow( ... );
- *
- * // Set age of the transaction snapshot the data came from
- * $setOpts = array( 'since' => $dbr->trxTimestamp() );
+ * // Account for any snapshot/slave lag
+ * $setOpts += DatabaseBase::getCacheSetOptions( $dbr );
*
- * return $row;
+ * return $dbr->selectRow( ... );
* },
* // Time-to-live (seconds)
* 60
* // Key to store the cached value under
* wfMemcKey( 'site-cat-config' ),
* // Function that derives the new key value
- * function( $oldValue, &$ttl, array &$setOpts ) {
- * // Fetch row from the DB
+ * function ( $oldValue, &$ttl, array &$setOpts ) {
* $dbr = wfGetDB( DB_SLAVE );
- * $config = CatConfig::newFromRow( $dbr->selectRow( ... ) );
+ * // Account for any snapshot/slave lag
+ * $setOpts += DatabaseBase::getCacheSetOptions( $dbr );
*
- * // Set age of the transaction snapshot the data came from
- * $setOpts = array( 'since' => $dbr->trxTimestamp() );
- *
- * return $config;
+ * return CatConfig::newFromRow( $dbr->selectRow( ... ) );
* },
* // Time-to-live (seconds)
* 86400,
* // Key to store the cached value under
* wfMemcKey( 'cat-state', $cat->getId() ),
* // Function that derives the new key value
- * function( $oldValue, &$ttl, array &$setOpts ) {
+ * function ( $oldValue, &$ttl, array &$setOpts ) {
* // Determine new value from the DB
* $dbr = wfGetDB( DB_SLAVE );
- * $state = CatState::newFromResults( $dbr->select( ... ) );
- *
- * // Set age of the transaction snapshot the data came from
- * $setOpts = array( 'since' => $dbr->trxTimestamp() );
+ * // Account for any snapshot/slave lag
+ * $setOpts += DatabaseBase::getCacheSetOptions( $dbr );
*
- * return $state;
+ * return CatState::newFromResults( $dbr->select( ... ) );
* },
* // Time-to-live (seconds)
* 900,
* // Key to store the cached value under
* wfMemcKey( 'cat-last-actions', 100 ),
* // Function that derives the new key value
- * function( $oldValue, &$ttl, array &$setOpts ) {
+ * function ( $oldValue, &$ttl, array &$setOpts ) {
* $dbr = wfGetDB( DB_SLAVE );
+ * // Account for any snapshot/slave lag
+ * $setOpts += DatabaseBase::getCacheSetOptions( $dbr );
+ *
* // Start off with the last cached list
* $list = $oldValue ?: array();
* // 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
- * $list = array_slice( array_merge( $new, $list ), 0, 100 );
- *
- * // Set age of the transaction snapshot the data came from
- * $setOpts = array( 'since' => $dbr->trxTimestamp() );
- *
- * return $list;
+ * return array_slice( array_merge( $new, $list ), 0, 100 );
* },
* // Time-to-live (seconds)
* 10,
protected function mockDb() {
// Cant mock from DatabaseType or DatabaseBase, they dont
// have the full gamut of methods
+ // FIXME: the constructor normally sets mAtomicLevels and mSrvCache
$databaseMysql = $this->getMockBuilder( 'DatabaseMysql' )
->disableOriginalConstructor()
->getMock();
$databaseMysql->expects( $this->any() )
->method( 'isOpen' )
->will( $this->returnValue( true ) );
+ $databaseMysql->expects( $this->any() )
+ ->method( 'getApproximateLagStatus' )
+ ->will( $this->returnValue( array( 'lag' => 0, 'since' => 0 ) ) );
return $databaseMysql;
}
}
dépôts / lhc / web / wiklou.git / commitdiff