includes/libs/objectcache/MediumSpecificBagOStuff.php

   1 <?php
   2 /**
   3  * Storage medium specific cache for storing items.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Cache
  22  */
  23
  24 use Wikimedia\WaitConditionLoop;
  25
  26 /**
  27  * Storage medium specific cache for storing items (e.g. redis, memcached, ...)
  28  *
  29  * This should not be used for proxy classes that simply wrap other cache instances
  30  *
  31  * @ingroup Cache
  32  * @since 1.34
  33  */
  34 abstract class MediumSpecificBagOStuff extends BagOStuff {
  35         /** @var array[] Lock tracking */
  36         protected $locks = [];
  37         /** @var int ERR_* class constant */
  38         protected $lastError = self::ERR_NONE;
  39         /** @var string */
  40         protected $keyspace = 'local';
  41         /** @var int Seconds */
  42         protected $syncTimeout;
  43         /** @var int Bytes; chunk size of segmented cache values */
  44         protected $segmentationSize;
  45         /** @var int Bytes; maximum total size of a segmented cache value */
  46         protected $segmentedValueMaxSize;
  47
  48         /** @var array */
  49         private $duplicateKeyLookups = [];
  50         /** @var bool */
  51         private $reportDupes = false;
  52         /** @var bool */
  53         private $dupeTrackScheduled = false;
  54
  55         /** @var callable[] */
  56         protected $busyCallbacks = [];
  57
  58         /** @var string Component to use for key construction of blob segment keys */
  59         const SEGMENT_COMPONENT = 'segment';
  60
  61         /**
  62          * @see BagOStuff::__construct()
  63          * Additional $params options include:
  64          *   - logger: Psr\Log\LoggerInterface instance
  65          *   - keyspace: Default keyspace for $this->makeKey()
  66          *   - reportDupes: Whether to emit warning log messages for all keys that were
  67          *      requested more than once (requires an asyncHandler).
  68          *   - syncTimeout: How long to wait with WRITE_SYNC in seconds.
  69          *   - segmentationSize: The chunk size, in bytes, of segmented values. The value should
  70          *      not exceed the maximum size of values in the storage backend, as configured by
  71          *      the site administrator.
  72          *   - segmentedValueMaxSize: The maximum total size, in bytes, of segmented values.
  73          *      This should be configured to a reasonable size give the site traffic and the
  74          *      amount of I/O between application and cache servers that the network can handle.
  75          * @param array $params
  76          * @codingStandardsIgnoreStart
  77          * @phan-param array{logger?:Psr\Log\LoggerInterface,asyncHandler?:callable,keyspace?:string,reportDupes?:bool,syncTimeout?:int,segmentationSize?:int,segmentedValueMaxSize?:int} $params
  78          * @codingStandardsIgnoreEnd
  79          */
  80         public function __construct( array $params = [] ) {
  81                 parent::__construct( $params );
  82
  83                 if ( isset( $params['keyspace'] ) ) {
  84                         $this->keyspace = $params['keyspace'];
  85                 }
  86
  87                 if ( !empty( $params['reportDupes'] ) && is_callable( $this->asyncHandler ) ) {
  88                         $this->reportDupes = true;
  89                 }
  90
  91                 $this->syncTimeout = $params['syncTimeout'] ?? 3;
  92                 $this->segmentationSize = $params['segmentationSize'] ?? 8388608; // 8MiB
  93                 $this->segmentedValueMaxSize = $params['segmentedValueMaxSize'] ?? 67108864; // 64MiB
  94         }
  95
  96         /**
  97          * Get an item with the given key
  98          *
  99          * If the key includes a deterministic input hash (e.g. the key can only have
 100          * the correct value) or complete staleness checks are handled by the caller
 101          * (e.g. nothing relies on the TTL), then the READ_VERIFIED flag should be set.
 102          * This lets tiered backends know they can safely upgrade a cached value to
 103          * higher tiers using standard TTLs.
 104          *
 105          * @param string $key
 106          * @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
 107          * @return mixed Returns false on failure or if the item does not exist
 108          */
 109         public function get( $key, $flags = 0 ) {
 110                 $this->trackDuplicateKeys( $key );
 111
 112                 return $this->resolveSegments( $key, $this->doGet( $key, $flags ) );
 113         }
 114
 115         /**
 116          * Track the number of times that a given key has been used.
 117          * @param string $key
 118          */
 119         private function trackDuplicateKeys( $key ) {
 120                 if ( !$this->reportDupes ) {
 121                         return;
 122                 }
 123
 124                 if ( !isset( $this->duplicateKeyLookups[$key] ) ) {
 125                         // Track that we have seen this key. This N-1 counting style allows
 126                         // easy filtering with array_filter() later.
 127                         $this->duplicateKeyLookups[$key] = 0;
 128                 } else {
 129                         $this->duplicateKeyLookups[$key] += 1;
 130
 131                         if ( $this->dupeTrackScheduled === false ) {
 132                                 $this->dupeTrackScheduled = true;
 133                                 // Schedule a callback that logs keys processed more than once by get().
 134                                 call_user_func( $this->asyncHandler, function () {
 135                                         $dups = array_filter( $this->duplicateKeyLookups );
 136                                         foreach ( $dups as $key => $count ) {
 137                                                 $this->logger->warning(
 138                                                         'Duplicate get(): "{key}" fetched {count} times',
 139                                                         // Count is N-1 of the actual lookup count
 140                                                         [ 'key' => $key, 'count' => $count + 1, ]
 141                                                 );
 142                                         }
 143                                 } );
 144                         }
 145                 }
 146         }
 147
 148         /**
 149          * @param string $key
 150          * @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
 151          * @param mixed|null &$casToken Token to use for check-and-set comparisons
 152          * @return mixed Returns false on failure or if the item does not exist
 153          */
 154         abstract protected function doGet( $key, $flags = 0, &$casToken = null );
 155
 156         /**
 157          * Set an item
 158          *
 159          * @param string $key
 160          * @param mixed $value
 161          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 162          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 163          * @return bool Success
 164          */
 165         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
 166                 list( $entry, $usable ) = $this->makeValueOrSegmentList( $key, $value, $exptime, $flags );
 167                 // Only when all segments (if any) are stored should the main key be changed
 168                 return $usable ? $this->doSet( $key, $entry, $exptime, $flags ) : false;
 169         }
 170
 171         /**
 172          * Set an item
 173          *
 174          * @param string $key
 175          * @param mixed $value
 176          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 177          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 178          * @return bool Success
 179          */
 180         abstract protected function doSet( $key, $value, $exptime = 0, $flags = 0 );
 181
 182         /**
 183          * Delete an item
 184          *
 185          * For large values written using WRITE_ALLOW_SEGMENTS, this only deletes the main
 186          * segment list key unless WRITE_PRUNE_SEGMENTS is in the flags. While deleting the segment
 187          * list key has the effect of functionally deleting the key, it leaves unused blobs in cache.
 188          *
 189          * @param string $key
 190          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 191          * @return bool True if the item was deleted or not found, false on failure
 192          */
 193         public function delete( $key, $flags = 0 ) {
 194                 if ( !$this->fieldHasFlags( $flags, self::WRITE_PRUNE_SEGMENTS ) ) {
 195                         return $this->doDelete( $key, $flags );
 196                 }
 197
 198                 $mainValue = $this->doGet( $key, self::READ_LATEST );
 199                 if ( !$this->doDelete( $key, $flags ) ) {
 200                         return false;
 201                 }
 202
 203                 if ( !SerializedValueContainer::isSegmented( $mainValue ) ) {
 204                         return true; // no segments to delete
 205                 }
 206
 207                 $orderedKeys = array_map(
 208                         function ( $segmentHash ) use ( $key ) {
 209                                 return $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $segmentHash );
 210                         },
 211                         $mainValue->{SerializedValueContainer::SEGMENTED_HASHES}
 212                 );
 213
 214                 return $this->deleteMulti( $orderedKeys, $flags & ~self::WRITE_PRUNE_SEGMENTS );
 215         }
 216
 217         /**
 218          * Delete an item
 219          *
 220          * @param string $key
 221          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 222          * @return bool True if the item was deleted or not found, false on failure
 223          */
 224         abstract protected function doDelete( $key, $flags = 0 );
 225
 226         public function add( $key, $value, $exptime = 0, $flags = 0 ) {
 227                 list( $entry, $usable ) = $this->makeValueOrSegmentList( $key, $value, $exptime, $flags );
 228                 // Only when all segments (if any) are stored should the main key be changed
 229                 return $usable ? $this->doAdd( $key, $entry, $exptime, $flags ) : false;
 230         }
 231
 232         /**
 233          * Insert an item if it does not already exist
 234          *
 235          * @param string $key
 236          * @param mixed $value
 237          * @param int $exptime
 238          * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
 239          * @return bool Success
 240          */
 241         abstract protected function doAdd( $key, $value, $exptime = 0, $flags = 0 );
 242
 243         /**
 244          * Merge changes into the existing cache value (possibly creating a new one)
 245          *
 246          * The callback function returns the new value given the current value
 247          * (which will be false if not present), and takes the arguments:
 248          * (this BagOStuff, cache key, current value, TTL).
 249          * The TTL parameter is reference set to $exptime. It can be overriden in the callback.
 250          * Nothing is stored nor deleted if the callback returns false.
 251          *
 252          * @param string $key
 253          * @param callable $callback Callback method to be executed
 254          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 255          * @param int $attempts The amount of times to attempt a merge in case of failure
 256          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 257          * @return bool Success
 258          */
 259         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 260                 return $this->mergeViaCas( $key, $callback, $exptime, $attempts, $flags );
 261         }
 262
 263         /**
 264          * @param string $key
 265          * @param callable $callback Callback method to be executed
 266          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 267          * @param int $attempts The amount of times to attempt a merge in case of failure
 268          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 269          * @return bool Success
 270          * @see BagOStuff::merge()
 271          */
 272         final protected function mergeViaCas( $key, callable $callback, $exptime, $attempts, $flags ) {
 273                 $attemptsLeft = $attempts;
 274                 do {
 275                         $token = null; // passed by reference
 276                         // Get the old value and CAS token from cache
 277                         $this->clearLastError();
 278                         $currentValue = $this->resolveSegments(
 279                                 $key,
 280                                 $this->doGet( $key, $flags, $token )
 281                         );
 282                         if ( $this->getLastError() ) {
 283                                 // Don't spam slow retries due to network problems (retry only on races)
 284                                 $this->logger->warning(
 285                                         __METHOD__ . ' failed due to read I/O error on get() for {key}.',
 286                                         [ 'key' => $key ]
 287                                 );
 288                                 $success = false;
 289                                 break;
 290                         }
 291
 292                         // Derive the new value from the old value
 293                         $value = call_user_func( $callback, $this, $key, $currentValue, $exptime );
 294                         $keyWasNonexistant = ( $currentValue === false );
 295                         $valueMatchesOldValue = ( $value === $currentValue );
 296                         unset( $currentValue ); // free RAM in case the value is large
 297
 298                         $this->clearLastError();
 299                         if ( $value === false || $exptime < 0 ) {
 300                                 $success = true; // do nothing
 301                         } elseif ( $valueMatchesOldValue && $attemptsLeft !== $attempts ) {
 302                                 $success = true; // recently set by another thread to the same value
 303                         } elseif ( $keyWasNonexistant ) {
 304                                 // Try to create the key, failing if it gets created in the meantime
 305                                 $success = $this->add( $key, $value, $exptime, $flags );
 306                         } else {
 307                                 // Try to update the key, failing if it gets changed in the meantime
 308                                 $success = $this->cas( $token, $key, $value, $exptime, $flags );
 309                         }
 310                         if ( $this->getLastError() ) {
 311                                 // Don't spam slow retries due to network problems (retry only on races)
 312                                 $this->logger->warning(
 313                                         __METHOD__ . ' failed due to write I/O error for {key}.',
 314                                         [ 'key' => $key ]
 315                                 );
 316                                 $success = false;
 317                                 break;
 318                         }
 319
 320                 } while ( !$success && --$attemptsLeft );
 321
 322                 return $success;
 323         }
 324
 325         /**
 326          * Check and set an item
 327          *
 328          * @param mixed $casToken
 329          * @param string $key
 330          * @param mixed $value
 331          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 332          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 333          * @return bool Success
 334          */
 335         protected function cas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
 336                 if ( $casToken === null ) {
 337                         $this->logger->warning(
 338                                 __METHOD__ . ' got empty CAS token for {key}.',
 339                                 [ 'key' => $key ]
 340                         );
 341
 342                         return false; // caller may have meant to use add()?
 343                 }
 344
 345                 list( $entry, $usable ) = $this->makeValueOrSegmentList( $key, $value, $exptime, $flags );
 346                 // Only when all segments (if any) are stored should the main key be changed
 347                 return $usable ? $this->doCas( $casToken, $key, $entry, $exptime, $flags ) : false;
 348         }
 349
 350         /**
 351          * Check and set an item
 352          *
 353          * @param mixed $casToken
 354          * @param string $key
 355          * @param mixed $value
 356          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 357          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 358          * @return bool Success
 359          */
 360         protected function doCas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
 361                 // @TODO: the lock() call assumes that all other relavent sets() use one
 362                 if ( !$this->lock( $key, 0 ) ) {
 363                         return false; // non-blocking
 364                 }
 365
 366                 $curCasToken = null; // passed by reference
 367                 $this->clearLastError();
 368                 $this->doGet( $key, self::READ_LATEST, $curCasToken );
 369                 if ( is_object( $curCasToken ) ) {
 370                         // Using === does not work with objects since it checks for instance identity
 371                         throw new UnexpectedValueException( "CAS token cannot be an object" );
 372                 }
 373                 if ( $this->getLastError() ) {
 374                         // Fail if the old CAS token could not be read
 375                         $success = false;
 376                         $this->logger->warning(
 377                                 __METHOD__ . ' failed due to write I/O error for {key}.',
 378                                 [ 'key' => $key ]
 379                         );
 380                 } elseif ( $casToken === $curCasToken ) {
 381                         $success = $this->doSet( $key, $value, $exptime, $flags );
 382                 } else {
 383                         $success = false; // mismatched or failed
 384                         $this->logger->info(
 385                                 __METHOD__ . ' failed due to race condition for {key}.',
 386                                 [ 'key' => $key ]
 387                         );
 388                 }
 389
 390                 $this->unlock( $key );
 391
 392                 return $success;
 393         }
 394
 395         /**
 396          * Change the expiration on a key if it exists
 397          *
 398          * If an expiry in the past is given then the key will immediately be expired
 399          *
 400          * For large values written using WRITE_ALLOW_SEGMENTS, this only changes the TTL of the
 401          * main segment list key. While lowering the TTL of the segment list key has the effect of
 402          * functionally lowering the TTL of the key, it might leave unused blobs in cache for longer.
 403          * Raising the TTL of such keys is not effective, since the expiration of a single segment
 404          * key effectively expires the entire value.
 405          *
 406          * @param string $key
 407          * @param int $exptime TTL or UNIX timestamp
 408          * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
 409          * @return bool Success Returns false on failure or if the item does not exist
 410          * @since 1.28
 411          */
 412         public function changeTTL( $key, $exptime = 0, $flags = 0 ) {
 413                 return $this->doChangeTTL( $key, $exptime, $flags );
 414         }
 415
 416         /**
 417          * @param string $key
 418          * @param int $exptime
 419          * @param int $flags
 420          * @return bool
 421          */
 422         protected function doChangeTTL( $key, $exptime, $flags ) {
 423                 if ( !$this->lock( $key, 0 ) ) {
 424                         return false;
 425                 }
 426
 427                 $expiry = $this->getExpirationAsTimestamp( $exptime );
 428                 $delete = ( $expiry != self::TTL_INDEFINITE && $expiry < $this->getCurrentTime() );
 429
 430                 // Use doGet() to avoid having to trigger resolveSegments()
 431                 $blob = $this->doGet( $key, self::READ_LATEST );
 432                 if ( $blob ) {
 433                         if ( $delete ) {
 434                                 $ok = $this->doDelete( $key, $flags );
 435                         } else {
 436                                 $ok = $this->doSet( $key, $blob, $exptime, $flags );
 437                         }
 438                 } else {
 439                         $ok = false;
 440                 }
 441
 442                 $this->unlock( $key );
 443
 444                 return $ok;
 445         }
 446
 447         /**
 448          * Acquire an advisory lock on a key string
 449          *
 450          * Note that if reentry is enabled, duplicate calls ignore $expiry
 451          *
 452          * @param string $key
 453          * @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
 454          * @param int $expiry Lock expiry [optional]; 1 day maximum
 455          * @param string $rclass Allow reentry if set and the current lock used this value
 456          * @return bool Success
 457          */
 458         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 459                 // Avoid deadlocks and allow lock reentry if specified
 460                 if ( isset( $this->locks[$key] ) ) {
 461                         if ( $rclass != '' && $this->locks[$key]['class'] === $rclass ) {
 462                                 ++$this->locks[$key]['depth'];
 463                                 return true;
 464                         } else {
 465                                 return false;
 466                         }
 467                 }
 468
 469                 $fname = __METHOD__;
 470                 $expiry = min( $expiry ?: INF, self::TTL_DAY );
 471                 $loop = new WaitConditionLoop(
 472                         function () use ( $key, $expiry, $fname ) {
 473                                 $this->clearLastError();
 474                                 if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
 475                                         return WaitConditionLoop::CONDITION_REACHED; // locked!
 476                                 } elseif ( $this->getLastError() ) {
 477                                         $this->logger->warning(
 478                                                 $fname . ' failed due to I/O error for {key}.',
 479                                                 [ 'key' => $key ]
 480                                         );
 481
 482                                         return WaitConditionLoop::CONDITION_ABORTED; // network partition?
 483                                 }
 484
 485                                 return WaitConditionLoop::CONDITION_CONTINUE;
 486                         },
 487                         $timeout
 488                 );
 489
 490                 $code = $loop->invoke();
 491                 $locked = ( $code === $loop::CONDITION_REACHED );
 492                 if ( $locked ) {
 493                         $this->locks[$key] = [ 'class' => $rclass, 'depth' => 1 ];
 494                 } elseif ( $code === $loop::CONDITION_TIMED_OUT ) {
 495                         $this->logger->warning(
 496                                 "$fname failed due to timeout for {key}.",
 497                                 [ 'key' => $key, 'timeout' => $timeout ]
 498                         );
 499                 }
 500
 501                 return $locked;
 502         }
 503
 504         /**
 505          * Release an advisory lock on a key string
 506          *
 507          * @param string $key
 508          * @return bool Success
 509          */
 510         public function unlock( $key ) {
 511                 if ( !isset( $this->locks[$key] ) ) {
 512                         return false;
 513                 }
 514
 515                 if ( --$this->locks[$key]['depth'] <= 0 ) {
 516                         unset( $this->locks[$key] );
 517
 518                         $ok = $this->doDelete( "{$key}:lock" );
 519                         if ( !$ok ) {
 520                                 $this->logger->warning(
 521                                         __METHOD__ . ' failed to release lock for {key}.',
 522                                         [ 'key' => $key ]
 523                                 );
 524                         }
 525
 526                         return $ok;
 527                 }
 528
 529                 return true;
 530         }
 531
 532         /**
 533          * Delete all objects expiring before a certain date.
 534          * @param string|int $timestamp The reference date in MW or TS_UNIX format
 535          * @param callable|null $progress Optional, a function which will be called
 536          *     regularly during long-running operations with the percentage progress
 537          *     as the first parameter. [optional]
 538          * @param int $limit Maximum number of keys to delete [default: INF]
 539          *
 540          * @return bool Success; false if unimplemented
 541          */
 542         public function deleteObjectsExpiringBefore(
 543                 $timestamp,
 544                 callable $progress = null,
 545                 $limit = INF
 546         ) {
 547                 return false;
 548         }
 549
 550         /**
 551          * Get an associative array containing the item for each of the keys that have items.
 552          * @param string[] $keys List of keys; can be a map of (unused => key) for convenience
 553          * @param int $flags Bitfield; supports READ_LATEST [optional]
 554          * @return mixed[] Map of (key => value) for existing keys; preserves the order of $keys
 555          */
 556         public function getMulti( array $keys, $flags = 0 ) {
 557                 $foundByKey = $this->doGetMulti( $keys, $flags );
 558
 559                 $res = [];
 560                 foreach ( $keys as $key ) {
 561                         // Resolve one blob at a time (avoids too much I/O at once)
 562                         if ( array_key_exists( $key, $foundByKey ) ) {
 563                                 // A value should not appear in the key if a segment is missing
 564                                 $value = $this->resolveSegments( $key, $foundByKey[$key] );
 565                                 if ( $value !== false ) {
 566                                         $res[$key] = $value;
 567                                 }
 568                         }
 569                 }
 570
 571                 return $res;
 572         }
 573
 574         /**
 575          * Get an associative array containing the item for each of the keys that have items.
 576          * @param string[] $keys List of keys
 577          * @param int $flags Bitfield; supports READ_LATEST [optional]
 578          * @return array Map of (key => value) for existing keys
 579          */
 580         protected function doGetMulti( array $keys, $flags = 0 ) {
 581                 $res = [];
 582                 foreach ( $keys as $key ) {
 583                         $val = $this->doGet( $key, $flags );
 584                         if ( $val !== false ) {
 585                                 $res[$key] = $val;
 586                         }
 587                 }
 588
 589                 return $res;
 590         }
 591
 592         /**
 593          * Batch insertion/replace
 594          *
 595          * This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O
 596          *
 597          * @param mixed[] $data Map of (key => value)
 598          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 599          * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
 600          * @return bool Success
 601          * @since 1.24
 602          */
 603         public function setMulti( array $data, $exptime = 0, $flags = 0 ) {
 604                 if ( $this->fieldHasFlags( $flags, self::WRITE_ALLOW_SEGMENTS ) ) {
 605                         throw new InvalidArgumentException( __METHOD__ . ' got WRITE_ALLOW_SEGMENTS' );
 606                 }
 607
 608                 return $this->doSetMulti( $data, $exptime, $flags );
 609         }
 610
 611         /**
 612          * @param mixed[] $data Map of (key => value)
 613          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 614          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 615          * @return bool Success
 616          */
 617         protected function doSetMulti( array $data, $exptime = 0, $flags = 0 ) {
 618                 $res = true;
 619                 foreach ( $data as $key => $value ) {
 620                         $res = $this->doSet( $key, $value, $exptime, $flags ) && $res;
 621                 }
 622
 623                 return $res;
 624         }
 625
 626         /**
 627          * Batch deletion
 628          *
 629          * This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O
 630          *
 631          * @param string[] $keys List of keys
 632          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 633          * @return bool Success
 634          * @since 1.33
 635          */
 636         public function deleteMulti( array $keys, $flags = 0 ) {
 637                 if ( $this->fieldHasFlags( $flags, self::WRITE_PRUNE_SEGMENTS ) ) {
 638                         throw new InvalidArgumentException( __METHOD__ . ' got WRITE_PRUNE_SEGMENTS' );
 639                 }
 640
 641                 return $this->doDeleteMulti( $keys, $flags );
 642         }
 643
 644         /**
 645          * @param string[] $keys List of keys
 646          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 647          * @return bool Success
 648          */
 649         protected function doDeleteMulti( array $keys, $flags = 0 ) {
 650                 $res = true;
 651                 foreach ( $keys as $key ) {
 652                         $res = $this->doDelete( $key, $flags ) && $res;
 653                 }
 654                 return $res;
 655         }
 656
 657         /**
 658          * Change the expiration of multiple keys that exist
 659          *
 660          * @param string[] $keys List of keys
 661          * @param int $exptime TTL or UNIX timestamp
 662          * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
 663          * @return bool Success
 664          * @see BagOStuff::changeTTL()
 665          *
 666          * @since 1.34
 667          */
 668         public function changeTTLMulti( array $keys, $exptime, $flags = 0 ) {
 669                 $res = true;
 670                 foreach ( $keys as $key ) {
 671                         $res = $this->doChangeTTL( $key, $exptime, $flags ) && $res;
 672                 }
 673
 674                 return $res;
 675         }
 676
 677         public function incrWithInit( $key, $exptime, $value = 1, $init = null, $flags = 0 ) {
 678                 $init = is_int( $init ) ? $init : $value;
 679                 $this->clearLastError();
 680                 $newValue = $this->incr( $key, $value, $flags );
 681                 if ( $newValue === false && !$this->getLastError() ) {
 682                         // No key set; initialize
 683                         $newValue = $this->add( $key, (int)$init, $exptime, $flags ) ? $init : false;
 684                         if ( $newValue === false && !$this->getLastError() ) {
 685                                 // Raced out initializing; increment
 686                                 $newValue = $this->incr( $key, $value, $flags );
 687                         }
 688                 }
 689
 690                 return $newValue;
 691         }
 692
 693         /**
 694          * Get and reassemble the chunks of blob at the given key
 695          *
 696          * @param string $key
 697          * @param mixed $mainValue
 698          * @return string|null|bool The combined string, false if missing, null on error
 699          */
 700         final protected function resolveSegments( $key, $mainValue ) {
 701                 if ( SerializedValueContainer::isUnified( $mainValue ) ) {
 702                         return $this->unserialize( $mainValue->{SerializedValueContainer::UNIFIED_DATA} );
 703                 }
 704
 705                 if ( SerializedValueContainer::isSegmented( $mainValue ) ) {
 706                         $orderedKeys = array_map(
 707                                 function ( $segmentHash ) use ( $key ) {
 708                                         return $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $segmentHash );
 709                                 },
 710                                 $mainValue->{SerializedValueContainer::SEGMENTED_HASHES}
 711                         );
 712
 713                         $segmentsByKey = $this->doGetMulti( $orderedKeys );
 714
 715                         $parts = [];
 716                         foreach ( $orderedKeys as $segmentKey ) {
 717                                 if ( isset( $segmentsByKey[$segmentKey] ) ) {
 718                                         $parts[] = $segmentsByKey[$segmentKey];
 719                                 } else {
 720                                         return false; // missing segment
 721                                 }
 722                         }
 723
 724                         return $this->unserialize( implode( '', $parts ) );
 725                 }
 726
 727                 return $mainValue;
 728         }
 729
 730         /**
 731          * Get the "last error" registered; clearLastError() should be called manually
 732          * @return int ERR_* constant for the "last error" registry
 733          * @since 1.23
 734          */
 735         public function getLastError() {
 736                 return $this->lastError;
 737         }
 738
 739         /**
 740          * Clear the "last error" registry
 741          * @since 1.23
 742          */
 743         public function clearLastError() {
 744                 $this->lastError = self::ERR_NONE;
 745         }
 746
 747         /**
 748          * Set the "last error" registry
 749          * @param int $err ERR_* constant
 750          * @since 1.23
 751          */
 752         protected function setLastError( $err ) {
 753                 $this->lastError = $err;
 754         }
 755
 756         final public function addBusyCallback( callable $workCallback ) {
 757                 $this->busyCallbacks[] = $workCallback;
 758         }
 759
 760         /**
 761          * Determine the entry (inline or segment list) to store under a key to save the value
 762          *
 763          * @param string $key
 764          * @param mixed $value
 765          * @param int $exptime
 766          * @param int $flags
 767          * @return array (inline value or segment list, whether the entry is usable)
 768          * @since 1.34
 769          */
 770         final protected function makeValueOrSegmentList( $key, $value, $exptime, $flags ) {
 771                 $entry = $value;
 772                 $usable = true;
 773
 774                 if (
 775                         $this->fieldHasFlags( $flags, self::WRITE_ALLOW_SEGMENTS ) &&
 776                         !is_int( $value ) && // avoid breaking incr()/decr()
 777                         is_finite( $this->segmentationSize )
 778                 ) {
 779                         $segmentSize = $this->segmentationSize;
 780                         $maxTotalSize = $this->segmentedValueMaxSize;
 781
 782                         $serialized = $this->serialize( $value );
 783                         $size = strlen( $serialized );
 784                         if ( $size > $maxTotalSize ) {
 785                                 $this->logger->warning(
 786                                         "Value for {key} exceeds $maxTotalSize bytes; cannot segment.",
 787                                         [ 'key' => $key ]
 788                                 );
 789                         } elseif ( $size <= $segmentSize ) {
 790                                 // The serialized value was already computed, so just use it inline
 791                                 $entry = SerializedValueContainer::newUnified( $serialized );
 792                         } else {
 793                                 // Split the serialized value into chunks and store them at different keys
 794                                 $chunksByKey = [];
 795                                 $segmentHashes = [];
 796                                 $count = intdiv( $size, $segmentSize ) + ( ( $size % $segmentSize ) ? 1 : 0 );
 797                                 for ( $i = 0; $i < $count; ++$i ) {
 798                                         $segment = substr( $serialized, $i * $segmentSize, $segmentSize );
 799                                         $hash = sha1( $segment );
 800                                         $chunkKey = $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $hash );
 801                                         $chunksByKey[$chunkKey] = $segment;
 802                                         $segmentHashes[] = $hash;
 803                                 }
 804                                 $flags &= ~self::WRITE_ALLOW_SEGMENTS; // sanity
 805                                 $usable = $this->setMulti( $chunksByKey, $exptime, $flags );
 806                                 $entry = SerializedValueContainer::newSegmented( $segmentHashes );
 807                         }
 808                 }
 809
 810                 return [ $entry, $usable ];
 811         }
 812
 813         /**
 814          * @param int|float $exptime
 815          * @return bool Whether the expiry is non-infinite, and, negative or not a UNIX timestamp
 816          * @since 1.34
 817          */
 818         final protected function isRelativeExpiration( $exptime ) {
 819                 return ( $exptime !== self::TTL_INDEFINITE && $exptime < ( 10 * self::TTL_YEAR ) );
 820         }
 821
 822         /**
 823          * Convert an optionally relative timestamp to an absolute time
 824          *
 825          * The input value will be cast to an integer and interpreted as follows:
 826          *   - zero: no expiry; return zero (e.g. TTL_INDEFINITE)
 827          *   - negative: relative TTL; return UNIX timestamp offset by this value
 828          *   - positive (< 10 years): relative TTL; return UNIX timestamp offset by this value
 829          *   - positive (>= 10 years): absolute UNIX timestamp; return this value
 830          *
 831          * @param int $exptime
 832          * @return int Expiration timestamp or TTL_INDEFINITE for indefinite
 833          * @since 1.34
 834          */
 835         final protected function getExpirationAsTimestamp( $exptime ) {
 836                 if ( $exptime == self::TTL_INDEFINITE ) {
 837                         return $exptime;
 838                 }
 839
 840                 return $this->isRelativeExpiration( $exptime )
 841                         ? intval( $this->getCurrentTime() + $exptime )
 842                         : $exptime;
 843         }
 844
 845         /**
 846          * Convert an optionally absolute expiry time to a relative time. If an
 847          * absolute time is specified which is in the past, use a short expiry time.
 848          *
 849          * The input value will be cast to an integer and interpreted as follows:
 850          *   - zero: no expiry; return zero (e.g. TTL_INDEFINITE)
 851          *   - negative: relative TTL; return a short expiry time (1 second)
 852          *   - positive (< 10 years): relative TTL; return this value
 853          *   - positive (>= 10 years): absolute UNIX timestamp; return offset to current time
 854          *
 855          * @param int $exptime
 856          * @return int Relative TTL or TTL_INDEFINITE for indefinite
 857          * @since 1.34
 858          */
 859         final protected function getExpirationAsTTL( $exptime ) {
 860                 if ( $exptime == self::TTL_INDEFINITE ) {
 861                         return $exptime;
 862                 }
 863
 864                 return $this->isRelativeExpiration( $exptime )
 865                         ? $exptime
 866                         : (int)max( $exptime - $this->getCurrentTime(), 1 );
 867         }
 868
 869         /**
 870          * Check if a value is an integer
 871          *
 872          * @param mixed $value
 873          * @return bool
 874          */
 875         final protected function isInteger( $value ) {
 876                 if ( is_int( $value ) ) {
 877                         return true;
 878                 } elseif ( !is_string( $value ) ) {
 879                         return false;
 880                 }
 881
 882                 $integer = (int)$value;
 883
 884                 return ( $value === (string)$integer );
 885         }
 886
 887         public function makeKeyInternal( $keyspace, $args ) {
 888                 $key = $keyspace;
 889                 foreach ( $args as $arg ) {
 890                         $key .= ':' . str_replace( ':', '%3A', $arg );
 891                 }
 892                 return strtr( $key, ' ', '_' );
 893         }
 894
 895         /**
 896          * Make a global cache key.
 897          *
 898          * @param string $class Key class
 899          * @param string ...$components Key components (starting with a key collection name)
 900          * @return string Colon-delimited list of $keyspace followed by escaped components
 901          * @since 1.27
 902          */
 903         public function makeGlobalKey( $class, ...$components ) {
 904                 return $this->makeKeyInternal( 'global', func_get_args() );
 905         }
 906
 907         /**
 908          * Make a cache key, scoped to this instance's keyspace.
 909          *
 910          * @param string $class Key class
 911          * @param string ...$components Key components (starting with a key collection name)
 912          * @return string Colon-delimited list of $keyspace followed by escaped components
 913          * @since 1.27
 914          */
 915         public function makeKey( $class, ...$components ) {
 916                 return $this->makeKeyInternal( $this->keyspace, func_get_args() );
 917         }
 918
 919         /**
 920          * @param int $flag ATTR_* class constant
 921          * @return int QOS_* class constant
 922          * @since 1.28
 923          */
 924         public function getQoS( $flag ) {
 925                 return $this->attrMap[$flag] ?? self::QOS_UNKNOWN;
 926         }
 927
 928         public function getSegmentationSize() {
 929                 return $this->segmentationSize;
 930         }
 931
 932         public function getSegmentedValueMaxSize() {
 933                 return $this->segmentedValueMaxSize;
 934         }
 935
 936         /**
 937          * @param mixed $value
 938          * @return string|int String/integer representation
 939          * @note Special handling is usually needed for integers so incr()/decr() work
 940          */
 941         protected function serialize( $value ) {
 942                 return is_int( $value ) ? $value : serialize( $value );
 943         }
 944
 945         /**
 946          * @param string|int $value
 947          * @return mixed Original value or false on error
 948          * @note Special handling is usually needed for integers so incr()/decr() work
 949          */
 950         protected function unserialize( $value ) {
 951                 return $this->isInteger( $value ) ? (int)$value : unserialize( $value );
 952         }
 953
 954         /**
 955          * @param string $text
 956          */
 957         protected function debug( $text ) {
 958                 if ( $this->debugMode ) {
 959                         $this->logger->debug( "{class} debug: $text", [ 'class' => static::class ] );
 960                 }
 961         }
 962 }