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 $date The reference date in MW format
 656          * @param callable|bool $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( $date, $progressCallback = false, $limit = INF ) {
 664                 // stub
 665                 return false;
 666         }
 667
 668         /**
 669          * Get an associative array containing the item for each of the keys that have items.
 670          * @param string[] $keys List of keys
 671          * @param int $flags Bitfield; supports READ_LATEST [optional]
 672          * @return array
 673          */
 674         public function getMulti( array $keys, $flags = 0 ) {
 675                 $valuesBykey = $this->doGetMulti( $keys, $flags );
 676                 foreach ( $valuesBykey as $key => $value ) {
 677                         // Resolve one blob at a time (avoids too much I/O at once)
 678                         $valuesBykey[$key] = $this->resolveSegments( $key, $value );
 679                 }
 680
 681                 return $valuesBykey;
 682         }
 683
 684         /**
 685          * Get an associative array containing the item for each of the keys that have items.
 686          * @param string[] $keys List of keys
 687          * @param int $flags Bitfield; supports READ_LATEST [optional]
 688          * @return array
 689          */
 690         protected function doGetMulti( array $keys, $flags = 0 ) {
 691                 $res = [];
 692                 foreach ( $keys as $key ) {
 693                         $val = $this->doGet( $key, $flags );
 694                         if ( $val !== false ) {
 695                                 $res[$key] = $val;
 696                         }
 697                 }
 698
 699                 return $res;
 700         }
 701
 702         /**
 703          * Batch insertion/replace
 704          *
 705          * This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O
 706          *
 707          * @param mixed[] $data Map of (key => value)
 708          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 709          * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
 710          * @return bool Success
 711          * @since 1.24
 712          */
 713         public function setMulti( array $data, $exptime = 0, $flags = 0 ) {
 714                 if ( ( $flags & self::WRITE_ALLOW_SEGMENTS ) === self::WRITE_ALLOW_SEGMENTS ) {
 715                         throw new InvalidArgumentException( __METHOD__ . ' got WRITE_ALLOW_SEGMENTS' );
 716                 }
 717
 718                 $res = true;
 719                 foreach ( $data as $key => $value ) {
 720                         $res = $this->doSet( $key, $value, $exptime, $flags ) && $res;
 721                 }
 722
 723                 return $res;
 724         }
 725
 726         /**
 727          * Batch deletion
 728          *
 729          * This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O
 730          *
 731          * @param string[] $keys List of keys
 732          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 733          * @return bool Success
 734          * @since 1.33
 735          */
 736         public function deleteMulti( array $keys, $flags = 0 ) {
 737                 $res = true;
 738                 foreach ( $keys as $key ) {
 739                         $res = $this->doDelete( $key, $flags ) && $res;
 740                 }
 741
 742                 return $res;
 743         }
 744
 745         /**
 746          * Increase stored value of $key by $value while preserving its TTL
 747          * @param string $key Key to increase
 748          * @param int $value Value to add to $key (default: 1) [optional]
 749          * @return int|bool New value or false on failure
 750          */
 751         abstract public function incr( $key, $value = 1 );
 752
 753         /**
 754          * Decrease stored value of $key by $value while preserving its TTL
 755          * @param string $key
 756          * @param int $value Value to subtract from $key (default: 1) [optional]
 757          * @return int|bool New value or false on failure
 758          */
 759         public function decr( $key, $value = 1 ) {
 760                 return $this->incr( $key, - $value );
 761         }
 762
 763         /**
 764          * Increase stored value of $key by $value while preserving its TTL
 765          *
 766          * This will create the key with value $init and TTL $ttl instead if not present
 767          *
 768          * @param string $key
 769          * @param int $ttl
 770          * @param int $value
 771          * @param int $init
 772          * @return int|bool New value or false on failure
 773          * @since 1.24
 774          */
 775         public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) {
 776                 $this->clearLastError();
 777                 $newValue = $this->incr( $key, $value );
 778                 if ( $newValue === false && !$this->getLastError() ) {
 779                         // No key set; initialize
 780                         $newValue = $this->add( $key, (int)$init, $ttl ) ? $init : false;
 781                         if ( $newValue === false && !$this->getLastError() ) {
 782                                 // Raced out initializing; increment
 783                                 $newValue = $this->incr( $key, $value );
 784                         }
 785                 }
 786
 787                 return $newValue;
 788         }
 789
 790         /**
 791          * Get and reassemble the chunks of blob at the given key
 792          *
 793          * @param string $key
 794          * @param mixed $mainValue
 795          * @return string|null|bool The combined string, false if missing, null on error
 796          */
 797         protected function resolveSegments( $key, $mainValue ) {
 798                 if ( SerializedValueContainer::isUnified( $mainValue ) ) {
 799                         return $this->unserialize( $mainValue->{SerializedValueContainer::UNIFIED_DATA} );
 800                 }
 801
 802                 if ( SerializedValueContainer::isSegmented( $mainValue ) ) {
 803                         $orderedKeys = array_map(
 804                                 function ( $segmentHash ) use ( $key ) {
 805                                         return $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $segmentHash );
 806                                 },
 807                                 $mainValue->{SerializedValueContainer::SEGMENTED_HASHES}
 808                         );
 809
 810                         $segmentsByKey = $this->doGetMulti( $orderedKeys );
 811
 812                         $parts = [];
 813                         foreach ( $orderedKeys as $segmentKey ) {
 814                                 if ( isset( $segmentsByKey[$segmentKey] ) ) {
 815                                         $parts[] = $segmentsByKey[$segmentKey];
 816                                 } else {
 817                                         return false; // missing segment
 818                                 }
 819                         }
 820
 821                         return $this->unserialize( implode( '', $parts ) );
 822                 }
 823
 824                 return $mainValue;
 825         }
 826
 827         /**
 828          * Get the "last error" registered; clearLastError() should be called manually
 829          * @return int ERR_* constant for the "last error" registry
 830          * @since 1.23
 831          */
 832         public function getLastError() {
 833                 return $this->lastError;
 834         }
 835
 836         /**
 837          * Clear the "last error" registry
 838          * @since 1.23
 839          */
 840         public function clearLastError() {
 841                 $this->lastError = self::ERR_NONE;
 842         }
 843
 844         /**
 845          * Set the "last error" registry
 846          * @param int $err ERR_* constant
 847          * @since 1.23
 848          */
 849         protected function setLastError( $err ) {
 850                 $this->lastError = $err;
 851         }
 852
 853         /**
 854          * Let a callback be run to avoid wasting time on special blocking calls
 855          *
 856          * The callbacks may or may not be called ever, in any particular order.
 857          * They are likely to be invoked when something WRITE_SYNC is used used.
 858          * They should follow a caching pattern as shown below, so that any code
 859          * using the work will get it's result no matter what happens.
 860          * @code
 861          *     $result = null;
 862          *     $workCallback = function () use ( &$result ) {
 863          *         if ( !$result ) {
 864          *             $result = ....
 865          *         }
 866          *         return $result;
 867          *     }
 868          * @endcode
 869          *
 870          * @param callable $workCallback
 871          * @since 1.28
 872          */
 873         public function addBusyCallback( callable $workCallback ) {
 874                 $this->busyCallbacks[] = $workCallback;
 875         }
 876
 877         /**
 878          * @param string $text
 879          */
 880         protected function debug( $text ) {
 881                 if ( $this->debugMode ) {
 882                         $this->logger->debug( "{class} debug: $text", [
 883                                 'class' => static::class,
 884                         ] );
 885                 }
 886         }
 887
 888         /**
 889          * @param int $exptime
 890          * @return bool
 891          */
 892         protected function expiryIsRelative( $exptime ) {
 893                 return ( $exptime != 0 && $exptime < ( 10 * self::TTL_YEAR ) );
 894         }
 895
 896         /**
 897          * Convert an optionally relative time to an absolute time
 898          * @param int $exptime
 899          * @return int
 900          */
 901         protected function convertToExpiry( $exptime ) {
 902                 if ( $this->expiryIsRelative( $exptime ) ) {
 903                         return (int)$this->getCurrentTime() + $exptime;
 904                 } else {
 905                         return $exptime;
 906                 }
 907         }
 908
 909         /**
 910          * Convert an optionally absolute expiry time to a relative time. If an
 911          * absolute time is specified which is in the past, use a short expiry time.
 912          *
 913          * @param int $exptime
 914          * @return int
 915          */
 916         protected function convertToRelative( $exptime ) {
 917                 if ( $exptime >= ( 10 * self::TTL_YEAR ) ) {
 918                         $exptime -= (int)$this->getCurrentTime();
 919                         if ( $exptime <= 0 ) {
 920                                 $exptime = 1;
 921                         }
 922                         return $exptime;
 923                 } else {
 924                         return $exptime;
 925                 }
 926         }
 927
 928         /**
 929          * Check if a value is an integer
 930          *
 931          * @param mixed $value
 932          * @return bool
 933          */
 934         protected function isInteger( $value ) {
 935                 if ( is_int( $value ) ) {
 936                         return true;
 937                 } elseif ( !is_string( $value ) ) {
 938                         return false;
 939                 }
 940
 941                 $integer = (int)$value;
 942
 943                 return ( $value === (string)$integer );
 944         }
 945
 946         /**
 947          * Construct a cache key.
 948          *
 949          * @since 1.27
 950          * @param string $keyspace
 951          * @param array $args
 952          * @return string Colon-delimited list of $keyspace followed by escaped components of $args
 953          */
 954         public function makeKeyInternal( $keyspace, $args ) {
 955                 $key = $keyspace;
 956                 foreach ( $args as $arg ) {
 957                         $key .= ':' . str_replace( ':', '%3A', $arg );
 958                 }
 959                 return strtr( $key, ' ', '_' );
 960         }
 961
 962         /**
 963          * Make a global cache key.
 964          *
 965          * @since 1.27
 966          * @param string $class Key class
 967          * @param string|null $component [optional] Key component (starting with a key collection name)
 968          * @return string Colon-delimited list of $keyspace followed by escaped components of $args
 969          */
 970         public function makeGlobalKey( $class, $component = null ) {
 971                 return $this->makeKeyInternal( 'global', func_get_args() );
 972         }
 973
 974         /**
 975          * Make a cache key, scoped to this instance's keyspace.
 976          *
 977          * @since 1.27
 978          * @param string $class Key class
 979          * @param string|null $component [optional] Key component (starting with a key collection name)
 980          * @return string Colon-delimited list of $keyspace followed by escaped components of $args
 981          */
 982         public function makeKey( $class, $component = null ) {
 983                 return $this->makeKeyInternal( $this->keyspace, func_get_args() );
 984         }
 985
 986         /**
 987          * @param int $flag ATTR_* class constant
 988          * @return int QOS_* class constant
 989          * @since 1.28
 990          */
 991         public function getQoS( $flag ) {
 992                 return $this->attrMap[$flag] ?? self::QOS_UNKNOWN;
 993         }
 994
 995         /**
 996          * @return int|float The chunk size, in bytes, of segmented objects (INF for no limit)
 997          * @since 1.34
 998          */
 999         public function getSegmentationSize() {
1000                 return $this->segmentationSize;
1001         }
1002
1003         /**
1004          * @return int|float Maximum total segmented object size in bytes (INF for no limit)
1005          * @since 1.34
1006          */
1007         public function getSegmentedValueMaxSize() {
1008                 return $this->segmentedValueMaxSize;
1009         }
1010
1011         /**
1012          * Merge the flag maps of one or more BagOStuff objects into a "lowest common denominator" map
1013          *
1014          * @param BagOStuff[] $bags
1015          * @return int[] Resulting flag map (class ATTR_* constant => class QOS_* constant)
1016          */
1017         protected function mergeFlagMaps( array $bags ) {
1018                 $map = [];
1019                 foreach ( $bags as $bag ) {
1020                         foreach ( $bag->attrMap as $attr => $rank ) {
1021                                 if ( isset( $map[$attr] ) ) {
1022                                         $map[$attr] = min( $map[$attr], $rank );
1023                                 } else {
1024                                         $map[$attr] = $rank;
1025                                 }
1026                         }
1027                 }
1028
1029                 return $map;
1030         }
1031
1032         /**
1033          * @internal For testing only
1034          * @return float UNIX timestamp
1035          * @codeCoverageIgnore
1036          */
1037         public function getCurrentTime() {
1038                 return $this->wallClockOverride ?: microtime( true );
1039         }
1040
1041         /**
1042          * @internal For testing only
1043          * @param float|null &$time Mock UNIX timestamp
1044          * @codeCoverageIgnore
1045          */
1046         public function setMockTime( &$time ) {
1047                 $this->wallClockOverride =& $time;
1048         }
1049
1050         /**
1051          * @param mixed $value
1052          * @return string|int String/integer representation
1053          * @note Special handling is usually needed for integers so incr()/decr() work
1054          */
1055         protected function serialize( $value ) {
1056                 return is_int( $value ) ? $value : serialize( $value );
1057         }
1058
1059         /**
1060          * @param string|int $value
1061          * @return mixed Original value or false on error
1062          * @note Special handling is usually needed for integers so incr()/decr() work
1063          */
1064         protected function unserialize( $value ) {
1065                 return $this->isInteger( $value ) ? (int)$value : unserialize( $value );
1066         }
1067 }