includes/libs/objectcache/BagOStuff.php

   1 <?php
   2 /**
   3  * Copyright © 2003-2004 Brion Vibber <brion@pobox.com>
   4  * https://www.mediawiki.org/
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  19  * http://www.gnu.org/copyleft/gpl.html
  20  *
  21  * @file
  22  * @ingroup Cache
  23  */
  24
  25 /**
  26  * @defgroup Cache Cache
  27  */
  28
  29 use Psr\Log\LoggerAwareInterface;
  30 use Psr\Log\LoggerInterface;
  31 use Psr\Log\NullLogger;
  32 use Wikimedia\ScopedCallback;
  33 use Wikimedia\WaitConditionLoop;
  34
  35 /**
  36  * Class representing a cache/ephemeral data store
  37  *
  38  * This interface is intended to be more or less compatible with the PHP memcached client.
  39  *
  40  * Instances of this class should be created with an intended access scope, such as:
  41  *   - a) A single PHP thread on a server (e.g. stored in a PHP variable)
  42  *   - b) A single application server (e.g. stored in APC or sqlite)
  43  *   - c) All application servers in datacenter (e.g. stored in memcached or mysql)
  44  *   - d) All application servers in all datacenters (e.g. stored via mcrouter or dynomite)
  45  *
  46  * Callers should use the proper factory methods that yield BagOStuff instances. Site admins
  47  * should make sure the configuration for those factory methods matches their access scope.
  48  * BagOStuff subclasses have widely varying levels of support for replication features.
  49  *
  50  * For any given instance, methods like lock(), unlock(), merge(), and set() with WRITE_SYNC
  51  * should semantically operate over its entire access scope; any nodes/threads in that scope
  52  * should serialize appropriately when using them. Likewise, a call to get() with READ_LATEST
  53  * from one node in its access scope should reflect the prior changes of any other node its
  54  * access scope. Any get() should reflect the changes of any prior set() with WRITE_SYNC.
  55  *
  56  * Subclasses should override the default "segmentationSize" field with an appropriate value.
  57  * The value should not be larger than what the storage backend (by default) supports. It also
  58  * should be roughly informed by common performance bottlenecks (e.g. values over a certain size
  59  * having poor scalability). The same goes for the "segmentedValueMaxSize" member, which limits
  60  * the maximum size and chunk count (indirectly) of values.
  61  *
  62  * @ingroup Cache
  63  */
  64 abstract class BagOStuff implements IExpiringStore, IStoreKeyEncoder, LoggerAwareInterface {
  65         /** @var array[] Lock tracking */
  66         protected $locks = [];
  67         /** @var int ERR_* class constant */
  68         protected $lastError = self::ERR_NONE;
  69         /** @var string */
  70         protected $keyspace = 'local';
  71         /** @var LoggerInterface */
  72         protected $logger;
  73         /** @var callable|null */
  74         protected $asyncHandler;
  75         /** @var int Seconds */
  76         protected $syncTimeout;
  77         /** @var int Bytes; chunk size of segmented cache values */
  78         protected $segmentationSize;
  79         /** @var int Bytes; maximum total size of a segmented cache value */
  80         protected $segmentedValueMaxSize;
  81
  82         /** @var bool */
  83         private $debugMode = false;
  84         /** @var array */
  85         private $duplicateKeyLookups = [];
  86         /** @var bool */
  87         private $reportDupes = false;
  88         /** @var bool */
  89         private $dupeTrackScheduled = false;
  90
  91         /** @var callable[] */
  92         protected $busyCallbacks = [];
  93
  94         /** @var float|null */
  95         private $wallClockOverride;
  96
  97         /** @var int[] Map of (ATTR_* class constant => QOS_* class constant) */
  98         protected $attrMap = [];
  99
 100         /** Bitfield constants for get()/getMulti() */
 101         const READ_LATEST = 1; // use latest data for replicated stores
 102         const READ_VERIFIED = 2; // promise that caller can tell when keys are stale
 103         /** Bitfield constants for set()/merge() */
 104         const WRITE_SYNC = 4; // synchronously write to all locations for replicated stores
 105         const WRITE_CACHE_ONLY = 8; // Only change state of the in-memory cache
 106         const WRITE_ALLOW_SEGMENTS = 16; // Allow partitioning of the value if it is large
 107         const WRITE_PRUNE_SEGMENTS = 32; // Delete all partition segments of the value
 108
 109         /** @var string Component to use for key construction of blob segment keys */
 110         const SEGMENT_COMPONENT = 'segment';
 111
 112         /**
 113          * $params include:
 114          *   - logger: Psr\Log\LoggerInterface instance
 115          *   - keyspace: Default keyspace for $this->makeKey()
 116          *   - asyncHandler: Callable to use for scheduling tasks after the web request ends.
 117          *      In CLI mode, it should run the task immediately.
 118          *   - reportDupes: Whether to emit warning log messages for all keys that were
 119          *      requested more than once (requires an asyncHandler).
 120          *   - syncTimeout: How long to wait with WRITE_SYNC in seconds.
 121          *   - segmentationSize: The chunk size, in bytes, of segmented values. The value should
 122          *      not exceed the maximum size of values in the storage backend, as configured by
 123          *      the site administrator.
 124          *   - segmentedValueMaxSize: The maximum total size, in bytes, of segmented values.
 125          *      This should be configured to a reasonable size give the site traffic and the
 126          *      amount of I/O between application and cache servers that the network can handle.
 127          * @param array $params
 128          */
 129         public function __construct( array $params = [] ) {
 130                 $this->setLogger( $params['logger'] ?? new NullLogger() );
 131
 132                 if ( isset( $params['keyspace'] ) ) {
 133                         $this->keyspace = $params['keyspace'];
 134                 }
 135
 136                 $this->asyncHandler = $params['asyncHandler'] ?? null;
 137
 138                 if ( !empty( $params['reportDupes'] ) && is_callable( $this->asyncHandler ) ) {
 139                         $this->reportDupes = true;
 140                 }
 141
 142                 $this->syncTimeout = $params['syncTimeout'] ?? 3;
 143                 $this->segmentationSize = $params['segmentationSize'] ?? 8388608; // 8MiB
 144                 $this->segmentedValueMaxSize = $params['segmentedValueMaxSize'] ?? 67108864; // 64MiB
 145         }
 146
 147         /**
 148          * @param LoggerInterface $logger
 149          * @return void
 150          */
 151         public function setLogger( LoggerInterface $logger ) {
 152                 $this->logger = $logger;
 153         }
 154
 155         /**
 156          * @param bool $bool
 157          */
 158         public function setDebug( $bool ) {
 159                 $this->debugMode = $bool;
 160         }
 161
 162         /**
 163          * Get an item with the given key, regenerating and setting it if not found
 164          *
 165          * Nothing is stored nor deleted if the callback returns false
 166          *
 167          * @param string $key
 168          * @param int $ttl Time-to-live (seconds)
 169          * @param callable $callback Callback that derives the new value
 170          * @param int $flags Bitfield of BagOStuff::READ_* or BagOStuff::WRITE_* constants [optional]
 171          * @return mixed The cached value if found or the result of $callback otherwise
 172          * @since 1.27
 173          */
 174         final public function getWithSetCallback( $key, $ttl, $callback, $flags = 0 ) {
 175                 $value = $this->get( $key, $flags );
 176
 177                 if ( $value === false ) {
 178                         if ( !is_callable( $callback ) ) {
 179                                 throw new InvalidArgumentException( "Invalid cache miss callback provided." );
 180                         }
 181                         $value = call_user_func( $callback );
 182                         if ( $value !== false ) {
 183                                 $this->set( $key, $value, $ttl, $flags );
 184                         }
 185                 }
 186
 187                 return $value;
 188         }
 189
 190         /**
 191          * Get an item with the given key
 192          *
 193          * If the key includes a deterministic input hash (e.g. the key can only have
 194          * the correct value) or complete staleness checks are handled by the caller
 195          * (e.g. nothing relies on the TTL), then the READ_VERIFIED flag should be set.
 196          * This lets tiered backends know they can safely upgrade a cached value to
 197          * higher tiers using standard TTLs.
 198          *
 199          * @param string $key
 200          * @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
 201          * @return mixed Returns false on failure or if the item does not exist
 202          */
 203         public function get( $key, $flags = 0 ) {
 204                 $this->trackDuplicateKeys( $key );
 205
 206                 return $this->resolveSegments( $key, $this->doGet( $key, $flags ) );
 207         }
 208
 209         /**
 210          * Track the number of times that a given key has been used.
 211          * @param string $key
 212          */
 213         private function trackDuplicateKeys( $key ) {
 214                 if ( !$this->reportDupes ) {
 215                         return;
 216                 }
 217
 218                 if ( !isset( $this->duplicateKeyLookups[$key] ) ) {
 219                         // Track that we have seen this key. This N-1 counting style allows
 220                         // easy filtering with array_filter() later.
 221                         $this->duplicateKeyLookups[$key] = 0;
 222                 } else {
 223                         $this->duplicateKeyLookups[$key] += 1;
 224
 225                         if ( $this->dupeTrackScheduled === false ) {
 226                                 $this->dupeTrackScheduled = true;
 227                                 // Schedule a callback that logs keys processed more than once by get().
 228                                 call_user_func( $this->asyncHandler, function () {
 229                                         $dups = array_filter( $this->duplicateKeyLookups );
 230                                         foreach ( $dups as $key => $count ) {
 231                                                 $this->logger->warning(
 232                                                         'Duplicate get(): "{key}" fetched {count} times',
 233                                                         // Count is N-1 of the actual lookup count
 234                                                         [ 'key' => $key, 'count' => $count + 1, ]
 235                                                 );
 236                                         }
 237                                 } );
 238                         }
 239                 }
 240         }
 241
 242         /**
 243          * @param string $key
 244          * @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
 245          * @param mixed|null &$casToken Token to use for check-and-set comparisons
 246          * @return mixed Returns false on failure or if the item does not exist
 247          */
 248         abstract protected function doGet( $key, $flags = 0, &$casToken = null );
 249
 250         /**
 251          * Set an item
 252          *
 253          * @param string $key
 254          * @param mixed $value
 255          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 256          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 257          * @return bool Success
 258          */
 259         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
 260                 if (
 261                         ( $flags & self::WRITE_ALLOW_SEGMENTS ) != self::WRITE_ALLOW_SEGMENTS ||
 262                         is_infinite( $this->segmentationSize )
 263                 ) {
 264                         return $this->doSet( $key, $value, $exptime, $flags );
 265                 }
 266
 267                 $serialized = $this->serialize( $value );
 268                 $segmentSize = $this->getSegmentationSize();
 269                 $maxTotalSize = $this->getSegmentedValueMaxSize();
 270
 271                 $size = strlen( $serialized );
 272                 if ( $size <= $segmentSize ) {
 273                         // Since the work of serializing it was already done, just use it inline
 274                         return $this->doSet(
 275                                 $key,
 276                                 SerializedValueContainer::newUnified( $serialized ),
 277                                 $exptime,
 278                                 $flags
 279                         );
 280                 } elseif ( $size > $maxTotalSize ) {
 281                         $this->setLastError( "Key $key exceeded $maxTotalSize bytes." );
 282
 283                         return false;
 284                 }
 285
 286                 $chunksByKey = [];
 287                 $segmentHashes = [];
 288                 $count = intdiv( $size, $segmentSize ) + ( ( $size % $segmentSize ) ? 1 : 0 );
 289                 for ( $i = 0; $i < $count; ++$i ) {
 290                         $segment = substr( $serialized, $i * $segmentSize, $segmentSize );
 291                         $hash = sha1( $segment );
 292                         $chunkKey = $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $hash );
 293                         $chunksByKey[$chunkKey] = $segment;
 294                         $segmentHashes[] = $hash;
 295                 }
 296
 297                 $ok = $this->setMulti( $chunksByKey, $exptime, $flags );
 298                 if ( $ok ) {
 299                         // Only when all segments are stored should the main key be changed
 300                         $ok = $this->doSet(
 301                                 $key,
 302                                 SerializedValueContainer::newSegmented( $segmentHashes ),
 303                                 $exptime,
 304                                 $flags
 305                         );
 306                 }
 307
 308                 return $ok;
 309         }
 310
 311         /**
 312          * Set an item
 313          *
 314          * @param string $key
 315          * @param mixed $value
 316          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 317          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 318          * @return bool Success
 319          */
 320         abstract protected function doSet( $key, $value, $exptime = 0, $flags = 0 );
 321
 322         /**
 323          * Delete an item
 324          *
 325          * For large values written using WRITE_ALLOW_SEGMENTS, this only deletes the main
 326          * segment list key unless WRITE_PRUNE_SEGMENTS is in the flags. While deleting the segment
 327          * list key has the effect of functionally deleting the key, it leaves unused blobs in cache.
 328          *
 329          * @param string $key
 330          * @return bool True if the item was deleted or not found, false on failure
 331          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 332          */
 333         public function delete( $key, $flags = 0 ) {
 334                 if ( ( $flags & self::WRITE_PRUNE_SEGMENTS ) != self::WRITE_PRUNE_SEGMENTS ) {
 335                         return $this->doDelete( $key, $flags );
 336                 }
 337
 338                 $mainValue = $this->doGet( $key, self::READ_LATEST );
 339                 if ( !$this->doDelete( $key, $flags ) ) {
 340                         return false;
 341                 }
 342
 343                 if ( !SerializedValueContainer::isSegmented( $mainValue ) ) {
 344                         return true; // no segments to delete
 345                 }
 346
 347                 $orderedKeys = array_map(
 348                         function ( $segmentHash ) use ( $key ) {
 349                                 return $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $segmentHash );
 350                         },
 351                         $mainValue->{SerializedValueContainer::SEGMENTED_HASHES}
 352                 );
 353
 354                 return $this->deleteMulti( $orderedKeys, $flags );
 355         }
 356
 357         /**
 358          * Delete an item
 359          *
 360          * @param string $key
 361          * @return bool True if the item was deleted or not found, false on failure
 362          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 363          */
 364         abstract protected function doDelete( $key, $flags = 0 );
 365
 366         /**
 367          * Insert an item if it does not already exist
 368          *
 369          * @param string $key
 370          * @param mixed $value
 371          * @param int $exptime
 372          * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
 373          * @return bool Success
 374          */
 375         abstract public function add( $key, $value, $exptime = 0, $flags = 0 );
 376
 377         /**
 378          * Merge changes into the existing cache value (possibly creating a new one)
 379          *
 380          * The callback function returns the new value given the current value
 381          * (which will be false if not present), and takes the arguments:
 382          * (this BagOStuff, cache key, current value, TTL).
 383          * The TTL parameter is reference set to $exptime. It can be overriden in the callback.
 384          * Nothing is stored nor deleted if the callback returns false.
 385          *
 386          * @param string $key
 387          * @param callable $callback Callback method to be executed
 388          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 389          * @param int $attempts The amount of times to attempt a merge in case of failure
 390          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 391          * @return bool Success
 392          * @throws InvalidArgumentException
 393          */
 394         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 395                 return $this->mergeViaCas( $key, $callback, $exptime, $attempts, $flags );
 396         }
 397
 398         /**
 399          * @see BagOStuff::merge()
 400          *
 401          * @param string $key
 402          * @param callable $callback Callback method to be executed
 403          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 404          * @param int $attempts The amount of times to attempt a merge in case of failure
 405          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 406          * @return bool Success
 407          */
 408         protected function mergeViaCas( $key, $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 409                 do {
 410                         $casToken = null; // passed by reference
 411                         // Get the old value and CAS token from cache
 412                         $this->clearLastError();
 413                         $currentValue = $this->resolveSegments(
 414                                 $key,
 415                                 $this->doGet( $key, self::READ_LATEST, $casToken )
 416                         );
 417                         if ( $this->getLastError() ) {
 418                                 $this->logger->warning(
 419                                         __METHOD__ . ' failed due to I/O error on get() for {key}.',
 420                                         [ 'key' => $key ]
 421                                 );
 422
 423                                 return false; // don't spam retries (retry only on races)
 424                         }
 425
 426                         // Derive the new value from the old value
 427                         $value = call_user_func( $callback, $this, $key, $currentValue, $exptime );
 428                         $hadNoCurrentValue = ( $currentValue === false );
 429                         unset( $currentValue ); // free RAM in case the value is large
 430
 431                         $this->clearLastError();
 432                         if ( $value === false ) {
 433                                 $success = true; // do nothing
 434                         } elseif ( $hadNoCurrentValue ) {
 435                                 // Try to create the key, failing if it gets created in the meantime
 436                                 $success = $this->add( $key, $value, $exptime, $flags );
 437                         } else {
 438                                 // Try to update the key, failing if it gets changed in the meantime
 439                                 $success = $this->cas( $casToken, $key, $value, $exptime, $flags );
 440                         }
 441                         if ( $this->getLastError() ) {
 442                                 $this->logger->warning(
 443                                         __METHOD__ . ' failed due to I/O error for {key}.',
 444                                         [ 'key' => $key ]
 445                                 );
 446
 447                                 return false; // IO error; don't spam retries
 448                         }
 449
 450                 } while ( !$success && --$attempts );
 451
 452                 return $success;
 453         }
 454
 455         /**
 456          * Check and set an item
 457          *
 458          * @param mixed $casToken
 459          * @param string $key
 460          * @param mixed $value
 461          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 462          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 463          * @return bool Success
 464          */
 465         protected function cas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
 466                 if ( !$this->lock( $key, 0 ) ) {
 467                         return false; // non-blocking
 468                 }
 469
 470                 $curCasToken = null; // passed by reference
 471                 $this->doGet( $key, self::READ_LATEST, $curCasToken );
 472                 if ( $casToken === $curCasToken ) {
 473                         $success = $this->set( $key, $value, $exptime, $flags );
 474                 } else {
 475                         $this->logger->info(
 476                                 __METHOD__ . ' failed due to race condition for {key}.',
 477                                 [ 'key' => $key ]
 478                         );
 479
 480                         $success = false; // mismatched or failed
 481                 }
 482
 483                 $this->unlock( $key );
 484
 485                 return $success;
 486         }
 487
 488         /**
 489          * Change the expiration on a key if it exists
 490          *
 491          * If an expiry in the past is given then the key will immediately be expired
 492          *
 493          * For large values written using WRITE_ALLOW_SEGMENTS, this only changes the TTL of the
 494          * main segment list key. While lowering the TTL of the segment list key has the effect of
 495          * functionally lowering the TTL of the key, it might leave unused blobs in cache for longer.
 496          * Raising the TTL of such keys is not effective, since the expiration of a single segment
 497          * key effectively expires the entire value.
 498          *
 499          * @param string $key
 500          * @param int $exptime TTL or UNIX timestamp
 501          * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
 502          * @return bool Success Returns false on failure or if the item does not exist
 503          * @since 1.28
 504          */
 505         public function changeTTL( $key, $exptime = 0, $flags = 0 ) {
 506                 $expiry = $this->convertToExpiry( $exptime );
 507                 $delete = ( $expiry != 0 && $expiry < $this->getCurrentTime() );
 508
 509                 if ( !$this->lock( $key, 0 ) ) {
 510                         return false;
 511                 }
 512                 // Use doGet() to avoid having to trigger resolveSegments()
 513                 $blob = $this->doGet( $key, self::READ_LATEST );
 514                 if ( $blob ) {
 515                         if ( $delete ) {
 516                                 $ok = $this->doDelete( $key, $flags );
 517                         } else {
 518                                 $ok = $this->doSet( $key, $blob, $exptime, $flags );
 519                         }
 520                 } else {
 521                         $ok = false;
 522                 }
 523
 524                 $this->unlock( $key );
 525
 526                 return $ok;
 527         }
 528
 529         /**
 530          * Acquire an advisory lock on a key string
 531          *
 532          * Note that if reentry is enabled, duplicate calls ignore $expiry
 533          *
 534          * @param string $key
 535          * @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
 536          * @param int $expiry Lock expiry [optional]; 1 day maximum
 537          * @param string $rclass Allow reentry if set and the current lock used this value
 538          * @return bool Success
 539          */
 540         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 541                 // Avoid deadlocks and allow lock reentry if specified
 542                 if ( isset( $this->locks[$key] ) ) {
 543                         if ( $rclass != '' && $this->locks[$key]['class'] === $rclass ) {
 544                                 ++$this->locks[$key]['depth'];
 545                                 return true;
 546                         } else {
 547                                 return false;
 548                         }
 549                 }
 550
 551                 $fname = __METHOD__;
 552                 $expiry = min( $expiry ?: INF, self::TTL_DAY );
 553                 $loop = new WaitConditionLoop(
 554                         function () use ( $key, $expiry, $fname ) {
 555                                 $this->clearLastError();
 556                                 if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
 557                                         return WaitConditionLoop::CONDITION_REACHED; // locked!
 558                                 } elseif ( $this->getLastError() ) {
 559                                         $this->logger->warning(
 560                                                 $fname . ' failed due to I/O error for {key}.',
 561                                                 [ 'key' => $key ]
 562                                         );
 563
 564                                         return WaitConditionLoop::CONDITION_ABORTED; // network partition?
 565                                 }
 566
 567                                 return WaitConditionLoop::CONDITION_CONTINUE;
 568                         },
 569                         $timeout
 570                 );
 571
 572                 $code = $loop->invoke();
 573                 $locked = ( $code === $loop::CONDITION_REACHED );
 574                 if ( $locked ) {
 575                         $this->locks[$key] = [ 'class' => $rclass, 'depth' => 1 ];
 576                 } elseif ( $code === $loop::CONDITION_TIMED_OUT ) {
 577                         $this->logger->warning(
 578                                 "$fname failed due to timeout for {key}.",
 579                                 [ 'key' => $key, 'timeout' => $timeout ]
 580                         );
 581                 }
 582
 583                 return $locked;
 584         }
 585
 586         /**
 587          * Release an advisory lock on a key string
 588          *
 589          * @param string $key
 590          * @return bool Success
 591          */
 592         public function unlock( $key ) {
 593                 if ( !isset( $this->locks[$key] ) ) {
 594                         return false;
 595                 }
 596
 597                 if ( --$this->locks[$key]['depth'] <= 0 ) {
 598                         unset( $this->locks[$key] );
 599
 600                         $ok = $this->doDelete( "{$key}:lock" );
 601                         if ( !$ok ) {
 602                                 $this->logger->warning(
 603                                         __METHOD__ . ' failed to release lock for {key}.',
 604                                         [ 'key' => $key ]
 605                                 );
 606                         }
 607
 608                         return $ok;
 609                 }
 610
 611                 return true;
 612         }
 613
 614         /**
 615          * Get a lightweight exclusive self-unlocking lock
 616          *
 617          * Note that the same lock cannot be acquired twice.
 618          *
 619          * This is useful for task de-duplication or to avoid obtrusive
 620          * (though non-corrupting) DB errors like INSERT key conflicts
 621          * or deadlocks when using LOCK IN SHARE MODE.
 622          *
 623          * @param string $key
 624          * @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
 625          * @param int $expiry Lock expiry [optional]; 1 day maximum
 626          * @param string $rclass Allow reentry if set and the current lock used this value
 627          * @return ScopedCallback|null Returns null on failure
 628          * @since 1.26
 629          */
 630         final public function getScopedLock( $key, $timeout = 6, $expiry = 30, $rclass = '' ) {
 631                 $expiry = min( $expiry ?: INF, self::TTL_DAY );
 632
 633                 if ( !$this->lock( $key, $timeout, $expiry, $rclass ) ) {
 634                         return null;
 635                 }
 636
 637                 $lSince = $this->getCurrentTime(); // lock timestamp
 638
 639                 return new ScopedCallback( function () use ( $key, $lSince, $expiry ) {
 640                         $latency = 0.050; // latency skew (err towards keeping lock present)
 641                         $age = ( $this->getCurrentTime() - $lSince + $latency );
 642                         if ( ( $age + $latency ) >= $expiry ) {
 643                                 $this->logger->warning(
 644                                         "Lock for {key} held too long ({age} sec).",
 645                                         [ 'key' => $key, 'age' => $age ]
 646                                 );
 647                                 return; // expired; it's not "safe" to delete the key
 648                         }
 649                         $this->unlock( $key );
 650                 } );
 651         }
 652
 653         /**
 654          * Delete all objects expiring before a certain date.
 655          * @param string|int $timestamp The reference date in MW or TS_UNIX format
 656          * @param callable|null $progressCallback Optional, a function which will be called
 657          *     regularly during long-running operations with the percentage progress
 658          *     as the first parameter. [optional]
 659          * @param int $limit Maximum number of keys to delete [default: INF]
 660          *
 661          * @return bool Success, false if unimplemented
 662          */
 663         public function deleteObjectsExpiringBefore(
 664                 $timestamp,
 665                 callable $progressCallback = null,
 666                 $limit = INF
 667         ) {
 668                 // stub
 669                 return false;
 670         }
 671
 672         /**
 673          * Get an associative array containing the item for each of the keys that have items.
 674          * @param string[] $keys List of keys
 675          * @param int $flags Bitfield; supports READ_LATEST [optional]
 676          * @return array
 677          */
 678         public function getMulti( array $keys, $flags = 0 ) {
 679                 $valuesBykey = $this->doGetMulti( $keys, $flags );
 680                 foreach ( $valuesBykey as $key => $value ) {
 681                         // Resolve one blob at a time (avoids too much I/O at once)
 682                         $valuesBykey[$key] = $this->resolveSegments( $key, $value );
 683                 }
 684
 685                 return $valuesBykey;
 686         }
 687
 688         /**
 689          * Get an associative array containing the item for each of the keys that have items.
 690          * @param string[] $keys List of keys
 691          * @param int $flags Bitfield; supports READ_LATEST [optional]
 692          * @return array
 693          */
 694         protected function doGetMulti( array $keys, $flags = 0 ) {
 695                 $res = [];
 696                 foreach ( $keys as $key ) {
 697                         $val = $this->doGet( $key, $flags );
 698                         if ( $val !== false ) {
 699                                 $res[$key] = $val;
 700                         }
 701                 }
 702
 703                 return $res;
 704         }
 705
 706         /**
 707          * Batch insertion/replace
 708          *
 709          * This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O
 710          *
 711          * @param mixed[] $data Map of (key => value)
 712          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 713          * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
 714          * @return bool Success
 715          * @since 1.24
 716          */
 717         public function setMulti( array $data, $exptime = 0, $flags = 0 ) {
 718                 if ( ( $flags & self::WRITE_ALLOW_SEGMENTS ) === self::WRITE_ALLOW_SEGMENTS ) {
 719                         throw new InvalidArgumentException( __METHOD__ . ' got WRITE_ALLOW_SEGMENTS' );
 720                 }
 721
 722                 $res = true;
 723                 foreach ( $data as $key => $value ) {
 724                         $res = $this->doSet( $key, $value, $exptime, $flags ) && $res;
 725                 }
 726
 727                 return $res;
 728         }
 729
 730         /**
 731          * Batch deletion
 732          *
 733          * This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O
 734          *
 735          * @param string[] $keys List of keys
 736          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 737          * @return bool Success
 738          * @since 1.33
 739          */
 740         public function deleteMulti( array $keys, $flags = 0 ) {
 741                 $res = true;
 742                 foreach ( $keys as $key ) {
 743                         $res = $this->doDelete( $key, $flags ) && $res;
 744                 }
 745
 746                 return $res;
 747         }
 748
 749         /**
 750          * Increase stored value of $key by $value while preserving its TTL
 751          * @param string $key Key to increase
 752          * @param int $value Value to add to $key (default: 1) [optional]
 753          * @return int|bool New value or false on failure
 754          */
 755         abstract public function incr( $key, $value = 1 );
 756
 757         /**
 758          * Decrease stored value of $key by $value while preserving its TTL
 759          * @param string $key
 760          * @param int $value Value to subtract from $key (default: 1) [optional]
 761          * @return int|bool New value or false on failure
 762          */
 763         public function decr( $key, $value = 1 ) {
 764                 return $this->incr( $key, - $value );
 765         }
 766
 767         /**
 768          * Increase stored value of $key by $value while preserving its TTL
 769          *
 770          * This will create the key with value $init and TTL $ttl instead if not present
 771          *
 772          * @param string $key
 773          * @param int $ttl
 774          * @param int $value
 775          * @param int $init
 776          * @return int|bool New value or false on failure
 777          * @since 1.24
 778          */
 779         public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) {
 780                 $this->clearLastError();
 781                 $newValue = $this->incr( $key, $value );
 782                 if ( $newValue === false && !$this->getLastError() ) {
 783                         // No key set; initialize
 784                         $newValue = $this->add( $key, (int)$init, $ttl ) ? $init : false;
 785                         if ( $newValue === false && !$this->getLastError() ) {
 786                                 // Raced out initializing; increment
 787                                 $newValue = $this->incr( $key, $value );
 788                         }
 789                 }
 790
 791                 return $newValue;
 792         }
 793
 794         /**
 795          * Get and reassemble the chunks of blob at the given key
 796          *
 797          * @param string $key
 798          * @param mixed $mainValue
 799          * @return string|null|bool The combined string, false if missing, null on error
 800          */
 801         protected function resolveSegments( $key, $mainValue ) {
 802                 if ( SerializedValueContainer::isUnified( $mainValue ) ) {
 803                         return $this->unserialize( $mainValue->{SerializedValueContainer::UNIFIED_DATA} );
 804                 }
 805
 806                 if ( SerializedValueContainer::isSegmented( $mainValue ) ) {
 807                         $orderedKeys = array_map(
 808                                 function ( $segmentHash ) use ( $key ) {
 809                                         return $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $segmentHash );
 810                                 },
 811                                 $mainValue->{SerializedValueContainer::SEGMENTED_HASHES}
 812                         );
 813
 814                         $segmentsByKey = $this->doGetMulti( $orderedKeys );
 815
 816                         $parts = [];
 817                         foreach ( $orderedKeys as $segmentKey ) {
 818                                 if ( isset( $segmentsByKey[$segmentKey] ) ) {
 819                                         $parts[] = $segmentsByKey[$segmentKey];
 820                                 } else {
 821                                         return false; // missing segment
 822                                 }
 823                         }
 824
 825                         return $this->unserialize( implode( '', $parts ) );
 826                 }
 827
 828                 return $mainValue;
 829         }
 830
 831         /**
 832          * Get the "last error" registered; clearLastError() should be called manually
 833          * @return int ERR_* constant for the "last error" registry
 834          * @since 1.23
 835          */
 836         public function getLastError() {
 837                 return $this->lastError;
 838         }
 839
 840         /**
 841          * Clear the "last error" registry
 842          * @since 1.23
 843          */
 844         public function clearLastError() {
 845                 $this->lastError = self::ERR_NONE;
 846         }
 847
 848         /**
 849          * Set the "last error" registry
 850          * @param int $err ERR_* constant
 851          * @since 1.23
 852          */
 853         protected function setLastError( $err ) {
 854                 $this->lastError = $err;
 855         }
 856
 857         /**
 858          * Let a callback be run to avoid wasting time on special blocking calls
 859          *
 860          * The callbacks may or may not be called ever, in any particular order.
 861          * They are likely to be invoked when something WRITE_SYNC is used used.
 862          * They should follow a caching pattern as shown below, so that any code
 863          * using the work will get it's result no matter what happens.
 864          * @code
 865          *     $result = null;
 866          *     $workCallback = function () use ( &$result ) {
 867          *         if ( !$result ) {
 868          *             $result = ....
 869          *         }
 870          *         return $result;
 871          *     }
 872          * @endcode
 873          *
 874          * @param callable $workCallback
 875          * @since 1.28
 876          */
 877         public function addBusyCallback( callable $workCallback ) {
 878                 $this->busyCallbacks[] = $workCallback;
 879         }
 880
 881         /**
 882          * @param string $text
 883          */
 884         protected function debug( $text ) {
 885                 if ( $this->debugMode ) {
 886                         $this->logger->debug( "{class} debug: $text", [
 887                                 'class' => static::class,
 888                         ] );
 889                 }
 890         }
 891
 892         /**
 893          * @param int $exptime
 894          * @return bool
 895          */
 896         protected function expiryIsRelative( $exptime ) {
 897                 return ( $exptime != 0 && $exptime < ( 10 * self::TTL_YEAR ) );
 898         }
 899
 900         /**
 901          * Convert an optionally relative time to an absolute time
 902          * @param int $exptime
 903          * @return int
 904          */
 905         protected function convertToExpiry( $exptime ) {
 906                 if ( $this->expiryIsRelative( $exptime ) ) {
 907                         return (int)$this->getCurrentTime() + $exptime;
 908                 } else {
 909                         return $exptime;
 910                 }
 911         }
 912
 913         /**
 914          * Convert an optionally absolute expiry time to a relative time. If an
 915          * absolute time is specified which is in the past, use a short expiry time.
 916          *
 917          * @param int $exptime
 918          * @return int
 919          */
 920         protected function convertToRelative( $exptime ) {
 921                 if ( $exptime >= ( 10 * self::TTL_YEAR ) ) {
 922                         $exptime -= (int)$this->getCurrentTime();
 923                         if ( $exptime <= 0 ) {
 924                                 $exptime = 1;
 925                         }
 926                         return $exptime;
 927                 } else {
 928                         return $exptime;
 929                 }
 930         }
 931
 932         /**
 933          * Check if a value is an integer
 934          *
 935          * @param mixed $value
 936          * @return bool
 937          */
 938         protected function isInteger( $value ) {
 939                 if ( is_int( $value ) ) {
 940                         return true;
 941                 } elseif ( !is_string( $value ) ) {
 942                         return false;
 943                 }
 944
 945                 $integer = (int)$value;
 946
 947                 return ( $value === (string)$integer );
 948         }
 949
 950         /**
 951          * Construct a cache key.
 952          *
 953          * @since 1.27
 954          * @param string $keyspace
 955          * @param array $args
 956          * @return string Colon-delimited list of $keyspace followed by escaped components of $args
 957          */
 958         public function makeKeyInternal( $keyspace, $args ) {
 959                 $key = $keyspace;
 960                 foreach ( $args as $arg ) {
 961                         $key .= ':' . str_replace( ':', '%3A', $arg );
 962                 }
 963                 return strtr( $key, ' ', '_' );
 964         }
 965
 966         /**
 967          * Make a global cache key.
 968          *
 969          * @since 1.27
 970          * @param string $class Key class
 971          * @param string|null $component [optional] Key component (starting with a key collection name)
 972          * @return string Colon-delimited list of $keyspace followed by escaped components of $args
 973          */
 974         public function makeGlobalKey( $class, $component = null ) {
 975                 return $this->makeKeyInternal( 'global', func_get_args() );
 976         }
 977
 978         /**
 979          * Make a cache key, scoped to this instance's keyspace.
 980          *
 981          * @since 1.27
 982          * @param string $class Key class
 983          * @param string|null $component [optional] Key component (starting with a key collection name)
 984          * @return string Colon-delimited list of $keyspace followed by escaped components of $args
 985          */
 986         public function makeKey( $class, $component = null ) {
 987                 return $this->makeKeyInternal( $this->keyspace, func_get_args() );
 988         }
 989
 990         /**
 991          * @param int $flag ATTR_* class constant
 992          * @return int QOS_* class constant
 993          * @since 1.28
 994          */
 995         public function getQoS( $flag ) {
 996                 return $this->attrMap[$flag] ?? self::QOS_UNKNOWN;
 997         }
 998
 999         /**
1000          * @return int|float The chunk size, in bytes, of segmented objects (INF for no limit)
1001          * @since 1.34
1002          */
1003         public function getSegmentationSize() {
1004                 return $this->segmentationSize;
1005         }
1006
1007         /**
1008          * @return int|float Maximum total segmented object size in bytes (INF for no limit)
1009          * @since 1.34
1010          */
1011         public function getSegmentedValueMaxSize() {
1012                 return $this->segmentedValueMaxSize;
1013         }
1014
1015         /**
1016          * Merge the flag maps of one or more BagOStuff objects into a "lowest common denominator" map
1017          *
1018          * @param BagOStuff[] $bags
1019          * @return int[] Resulting flag map (class ATTR_* constant => class QOS_* constant)
1020          */
1021         protected function mergeFlagMaps( array $bags ) {
1022                 $map = [];
1023                 foreach ( $bags as $bag ) {
1024                         foreach ( $bag->attrMap as $attr => $rank ) {
1025                                 if ( isset( $map[$attr] ) ) {
1026                                         $map[$attr] = min( $map[$attr], $rank );
1027                                 } else {
1028                                         $map[$attr] = $rank;
1029                                 }
1030                         }
1031                 }
1032
1033                 return $map;
1034         }
1035
1036         /**
1037          * @internal For testing only
1038          * @return float UNIX timestamp
1039          * @codeCoverageIgnore
1040          */
1041         public function getCurrentTime() {
1042                 return $this->wallClockOverride ?: microtime( true );
1043         }
1044
1045         /**
1046          * @internal For testing only
1047          * @param float|null &$time Mock UNIX timestamp
1048          * @codeCoverageIgnore
1049          */
1050         public function setMockTime( &$time ) {
1051                 $this->wallClockOverride =& $time;
1052         }
1053
1054         /**
1055          * @param mixed $value
1056          * @return string|int String/integer representation
1057          * @note Special handling is usually needed for integers so incr()/decr() work
1058          */
1059         protected function serialize( $value ) {
1060                 return is_int( $value ) ? $value : serialize( $value );
1061         }
1062
1063         /**
1064          * @param string|int $value
1065          * @return mixed Original value or false on error
1066          * @note Special handling is usually needed for integers so incr()/decr() work
1067          */
1068         protected function unserialize( $value ) {
1069                 return $this->isInteger( $value ) ? (int)$value : unserialize( $value );
1070         }
1071 }