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\WaitConditionLoop;
  33
  34 /**
  35  * interface is intended to be more or less compatible with
  36  * the PHP memcached client.
  37  *
  38  * backends for local hash array and SQL table included:
  39  * @code
  40  *   $bag = new HashBagOStuff();
  41  *   $bag = new SqlBagOStuff(); # connect to db first
  42  * @endcode
  43  *
  44  * @ingroup Cache
  45  */
  46 abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
  47         /** @var array[] Lock tracking */
  48         protected $locks = [];
  49         /** @var integer ERR_* class constant */
  50         protected $lastError = self::ERR_NONE;
  51         /** @var string */
  52         protected $keyspace = 'local';
  53         /** @var LoggerInterface */
  54         protected $logger;
  55         /** @var callback|null */
  56         protected $asyncHandler;
  57         /** @var integer Seconds */
  58         protected $syncTimeout;
  59
  60         /** @var bool */
  61         private $debugMode = false;
  62         /** @var array */
  63         private $duplicateKeyLookups = [];
  64         /** @var bool */
  65         private $reportDupes = false;
  66         /** @var bool */
  67         private $dupeTrackScheduled = false;
  68
  69         /** @var callable[] */
  70         protected $busyCallbacks = [];
  71
  72         /** @var integer[] Map of (ATTR_* class constant => QOS_* class constant) */
  73         protected $attrMap = [];
  74
  75         /** Possible values for getLastError() */
  76         const ERR_NONE = 0; // no error
  77         const ERR_NO_RESPONSE = 1; // no response
  78         const ERR_UNREACHABLE = 2; // can't connect
  79         const ERR_UNEXPECTED = 3; // response gave some error
  80
  81         /** Bitfield constants for get()/getMulti() */
  82         const READ_LATEST = 1; // use latest data for replicated stores
  83         const READ_VERIFIED = 2; // promise that caller can tell when keys are stale
  84         /** Bitfield constants for set()/merge() */
  85         const WRITE_SYNC = 1; // synchronously write to all locations for replicated stores
  86         const WRITE_CACHE_ONLY = 2; // Only change state of the in-memory cache
  87
  88         /**
  89          * $params include:
  90          *   - logger: Psr\Log\LoggerInterface instance
  91          *   - keyspace: Default keyspace for $this->makeKey()
  92          *   - asyncHandler: Callable to use for scheduling tasks after the web request ends.
  93          *      In CLI mode, it should run the task immediately.
  94          *   - reportDupes: Whether to emit warning log messages for all keys that were
  95          *      requested more than once (requires an asyncHandler).
  96          *   - syncTimeout: How long to wait with WRITE_SYNC in seconds.
  97          * @param array $params
  98          */
  99         public function __construct( array $params = [] ) {
 100                 if ( isset( $params['logger'] ) ) {
 101                         $this->setLogger( $params['logger'] );
 102                 } else {
 103                         $this->setLogger( new NullLogger() );
 104                 }
 105
 106                 if ( isset( $params['keyspace'] ) ) {
 107                         $this->keyspace = $params['keyspace'];
 108                 }
 109
 110                 $this->asyncHandler = isset( $params['asyncHandler'] )
 111                         ? $params['asyncHandler']
 112                         : null;
 113
 114                 if ( !empty( $params['reportDupes'] ) && is_callable( $this->asyncHandler ) ) {
 115                         $this->reportDupes = true;
 116                 }
 117
 118                 $this->syncTimeout = isset( $params['syncTimeout'] ) ? $params['syncTimeout'] : 3;
 119         }
 120
 121         /**
 122          * @param LoggerInterface $logger
 123          * @return null
 124          */
 125         public function setLogger( LoggerInterface $logger ) {
 126                 $this->logger = $logger;
 127         }
 128
 129         /**
 130          * @param bool $bool
 131          */
 132         public function setDebug( $bool ) {
 133                 $this->debugMode = $bool;
 134         }
 135
 136         /**
 137          * Get an item with the given key, regenerating and setting it if not found
 138          *
 139          * If the callback returns false, then nothing is stored.
 140          *
 141          * @param string $key
 142          * @param int $ttl Time-to-live (seconds)
 143          * @param callable $callback Callback that derives the new value
 144          * @param integer $flags Bitfield of BagOStuff::READ_* constants [optional]
 145          * @return mixed The cached value if found or the result of $callback otherwise
 146          * @since 1.27
 147          */
 148         final public function getWithSetCallback( $key, $ttl, $callback, $flags = 0 ) {
 149                 $value = $this->get( $key, $flags );
 150
 151                 if ( $value === false ) {
 152                         if ( !is_callable( $callback ) ) {
 153                                 throw new InvalidArgumentException( "Invalid cache miss callback provided." );
 154                         }
 155                         $value = call_user_func( $callback );
 156                         if ( $value !== false ) {
 157                                 $this->set( $key, $value, $ttl );
 158                         }
 159                 }
 160
 161                 return $value;
 162         }
 163
 164         /**
 165          * Get an item with the given key
 166          *
 167          * If the key includes a determistic input hash (e.g. the key can only have
 168          * the correct value) or complete staleness checks are handled by the caller
 169          * (e.g. nothing relies on the TTL), then the READ_VERIFIED flag should be set.
 170          * This lets tiered backends know they can safely upgrade a cached value to
 171          * higher tiers using standard TTLs.
 172          *
 173          * @param string $key
 174          * @param integer $flags Bitfield of BagOStuff::READ_* constants [optional]
 175          * @param integer $oldFlags [unused]
 176          * @return mixed Returns false on failure and if the item does not exist
 177          */
 178         public function get( $key, $flags = 0, $oldFlags = null ) {
 179                 // B/C for ( $key, &$casToken = null, $flags = 0 )
 180                 $flags = is_int( $oldFlags ) ? $oldFlags : $flags;
 181
 182                 $this->trackDuplicateKeys( $key );
 183
 184                 return $this->doGet( $key, $flags );
 185         }
 186
 187         /**
 188          * Track the number of times that a given key has been used.
 189          * @param string $key
 190          */
 191         private function trackDuplicateKeys( $key ) {
 192                 if ( !$this->reportDupes ) {
 193                         return;
 194                 }
 195
 196                 if ( !isset( $this->duplicateKeyLookups[$key] ) ) {
 197                         // Track that we have seen this key. This N-1 counting style allows
 198                         // easy filtering with array_filter() later.
 199                         $this->duplicateKeyLookups[$key] = 0;
 200                 } else {
 201                         $this->duplicateKeyLookups[$key] += 1;
 202
 203                         if ( $this->dupeTrackScheduled === false ) {
 204                                 $this->dupeTrackScheduled = true;
 205                                 // Schedule a callback that logs keys processed more than once by get().
 206                                 call_user_func( $this->asyncHandler, function () {
 207                                         $dups = array_filter( $this->duplicateKeyLookups );
 208                                         foreach ( $dups as $key => $count ) {
 209                                                 $this->logger->warning(
 210                                                         'Duplicate get(): "{key}" fetched {count} times',
 211                                                         // Count is N-1 of the actual lookup count
 212                                                         [ 'key' => $key, 'count' => $count + 1, ]
 213                                                 );
 214                                         }
 215                                 } );
 216                         }
 217                 }
 218         }
 219
 220         /**
 221          * @param string $key
 222          * @param integer $flags Bitfield of BagOStuff::READ_* constants [optional]
 223          * @return mixed Returns false on failure and if the item does not exist
 224          */
 225         abstract protected function doGet( $key, $flags = 0 );
 226
 227         /**
 228          * @note: This method is only needed if merge() uses mergeViaCas()
 229          *
 230          * @param string $key
 231          * @param mixed $casToken
 232          * @param integer $flags Bitfield of BagOStuff::READ_* constants [optional]
 233          * @return mixed Returns false on failure and if the item does not exist
 234          * @throws Exception
 235          */
 236         protected function getWithToken( $key, &$casToken, $flags = 0 ) {
 237                 throw new Exception( __METHOD__ . ' not implemented.' );
 238         }
 239
 240         /**
 241          * Set an item
 242          *
 243          * @param string $key
 244          * @param mixed $value
 245          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 246          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 247          * @return bool Success
 248          */
 249         abstract public function set( $key, $value, $exptime = 0, $flags = 0 );
 250
 251         /**
 252          * Delete an item
 253          *
 254          * @param string $key
 255          * @return bool True if the item was deleted or not found, false on failure
 256          */
 257         abstract public function delete( $key );
 258
 259         /**
 260          * Merge changes into the existing cache value (possibly creating a new one)
 261          *
 262          * The callback function returns the new value given the current value
 263          * (which will be false if not present), and takes the arguments:
 264          * (this BagOStuff, cache key, current value, TTL).
 265          * The TTL parameter is reference set to $exptime. It can be overriden in the callback.
 266          *
 267          * @param string $key
 268          * @param callable $callback Callback method to be executed
 269          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 270          * @param int $attempts The amount of times to attempt a merge in case of failure
 271          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 272          * @return bool Success
 273          * @throws InvalidArgumentException
 274          */
 275         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 276                 return $this->mergeViaLock( $key, $callback, $exptime, $attempts, $flags );
 277         }
 278
 279         /**
 280          * @see BagOStuff::merge()
 281          *
 282          * @param string $key
 283          * @param callable $callback Callback method to be executed
 284          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 285          * @param int $attempts The amount of times to attempt a merge in case of failure
 286          * @return bool Success
 287          */
 288         protected function mergeViaCas( $key, $callback, $exptime = 0, $attempts = 10 ) {
 289                 do {
 290                         $this->clearLastError();
 291                         $reportDupes = $this->reportDupes;
 292                         $this->reportDupes = false;
 293                         $casToken = null; // passed by reference
 294                         $currentValue = $this->getWithToken( $key, $casToken, self::READ_LATEST );
 295                         $this->reportDupes = $reportDupes;
 296
 297                         if ( $this->getLastError() ) {
 298                                 return false; // don't spam retries (retry only on races)
 299                         }
 300
 301                         // Derive the new value from the old value
 302                         $value = call_user_func( $callback, $this, $key, $currentValue, $exptime );
 303
 304                         $this->clearLastError();
 305                         if ( $value === false ) {
 306                                 $success = true; // do nothing
 307                         } elseif ( $currentValue === false ) {
 308                                 // Try to create the key, failing if it gets created in the meantime
 309                                 $success = $this->add( $key, $value, $exptime );
 310                         } else {
 311                                 // Try to update the key, failing if it gets changed in the meantime
 312                                 $success = $this->cas( $casToken, $key, $value, $exptime );
 313                         }
 314                         if ( $this->getLastError() ) {
 315                                 return false; // IO error; don't spam retries
 316                         }
 317                 } while ( !$success && --$attempts );
 318
 319                 return $success;
 320         }
 321
 322         /**
 323          * Check and set an item
 324          *
 325          * @param mixed $casToken
 326          * @param string $key
 327          * @param mixed $value
 328          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 329          * @return bool Success
 330          * @throws Exception
 331          */
 332         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 333                 throw new Exception( "CAS is not implemented in " . __CLASS__ );
 334         }
 335
 336         /**
 337          * @see BagOStuff::merge()
 338          *
 339          * @param string $key
 340          * @param callable $callback Callback method to be executed
 341          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 342          * @param int $attempts The amount of times to attempt a merge in case of failure
 343          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 344          * @return bool Success
 345          */
 346         protected function mergeViaLock( $key, $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 347                 if ( !$this->lock( $key, 6 ) ) {
 348                         return false;
 349                 }
 350
 351                 $this->clearLastError();
 352                 $reportDupes = $this->reportDupes;
 353                 $this->reportDupes = false;
 354                 $currentValue = $this->get( $key, self::READ_LATEST );
 355                 $this->reportDupes = $reportDupes;
 356
 357                 if ( $this->getLastError() ) {
 358                         $success = false;
 359                 } else {
 360                         // Derive the new value from the old value
 361                         $value = call_user_func( $callback, $this, $key, $currentValue, $exptime );
 362                         if ( $value === false ) {
 363                                 $success = true; // do nothing
 364                         } else {
 365                                 $success = $this->set( $key, $value, $exptime, $flags ); // set the new value
 366                         }
 367                 }
 368
 369                 if ( !$this->unlock( $key ) ) {
 370                         // this should never happen
 371                         trigger_error( "Could not release lock for key '$key'." );
 372                 }
 373
 374                 return $success;
 375         }
 376
 377         /**
 378          * Reset the TTL on a key if it exists
 379          *
 380          * @param string $key
 381          * @param int $expiry
 382          * @return bool Success Returns false if there is no key
 383          * @since 1.28
 384          */
 385         public function changeTTL( $key, $expiry = 0 ) {
 386                 $value = $this->get( $key );
 387
 388                 return ( $value === false ) ? false : $this->set( $key, $value, $expiry );
 389         }
 390
 391         /**
 392          * Acquire an advisory lock on a key string
 393          *
 394          * Note that if reentry is enabled, duplicate calls ignore $expiry
 395          *
 396          * @param string $key
 397          * @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
 398          * @param int $expiry Lock expiry [optional]; 1 day maximum
 399          * @param string $rclass Allow reentry if set and the current lock used this value
 400          * @return bool Success
 401          */
 402         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 403                 // Avoid deadlocks and allow lock reentry if specified
 404                 if ( isset( $this->locks[$key] ) ) {
 405                         if ( $rclass != '' && $this->locks[$key]['class'] === $rclass ) {
 406                                 ++$this->locks[$key]['depth'];
 407                                 return true;
 408                         } else {
 409                                 return false;
 410                         }
 411                 }
 412
 413                 $expiry = min( $expiry ?: INF, self::TTL_DAY );
 414                 $loop = new WaitConditionLoop(
 415                         function () use ( $key, $timeout, $expiry ) {
 416                                 $this->clearLastError();
 417                                 if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
 418                                         return true; // locked!
 419                                 } elseif ( $this->getLastError() ) {
 420                                         return WaitConditionLoop::CONDITION_ABORTED; // network partition?
 421                                 }
 422
 423                                 return WaitConditionLoop::CONDITION_CONTINUE;
 424                         },
 425                         $timeout
 426                 );
 427
 428                 $locked = ( $loop->invoke() === $loop::CONDITION_REACHED );
 429                 if ( $locked ) {
 430                         $this->locks[$key] = [ 'class' => $rclass, 'depth' => 1 ];
 431                 }
 432
 433                 return $locked;
 434         }
 435
 436         /**
 437          * Release an advisory lock on a key string
 438          *
 439          * @param string $key
 440          * @return bool Success
 441          */
 442         public function unlock( $key ) {
 443                 if ( isset( $this->locks[$key] ) && --$this->locks[$key]['depth'] <= 0 ) {
 444                         unset( $this->locks[$key] );
 445
 446                         return $this->delete( "{$key}:lock" );
 447                 }
 448
 449                 return true;
 450         }
 451
 452         /**
 453          * Get a lightweight exclusive self-unlocking lock
 454          *
 455          * Note that the same lock cannot be acquired twice.
 456          *
 457          * This is useful for task de-duplication or to avoid obtrusive
 458          * (though non-corrupting) DB errors like INSERT key conflicts
 459          * or deadlocks when using LOCK IN SHARE MODE.
 460          *
 461          * @param string $key
 462          * @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
 463          * @param int $expiry Lock expiry [optional]; 1 day maximum
 464          * @param string $rclass Allow reentry if set and the current lock used this value
 465          * @return ScopedCallback|null Returns null on failure
 466          * @since 1.26
 467          */
 468         final public function getScopedLock( $key, $timeout = 6, $expiry = 30, $rclass = '' ) {
 469                 $expiry = min( $expiry ?: INF, self::TTL_DAY );
 470
 471                 if ( !$this->lock( $key, $timeout, $expiry, $rclass ) ) {
 472                         return null;
 473                 }
 474
 475                 $lSince = microtime( true ); // lock timestamp
 476
 477                 return new ScopedCallback( function() use ( $key, $lSince, $expiry ) {
 478                         $latency = .050; // latency skew (err towards keeping lock present)
 479                         $age = ( microtime( true ) - $lSince + $latency );
 480                         if ( ( $age + $latency ) >= $expiry ) {
 481                                 $this->logger->warning( "Lock for $key held too long ($age sec)." );
 482                                 return; // expired; it's not "safe" to delete the key
 483                         }
 484                         $this->unlock( $key );
 485                 } );
 486         }
 487
 488         /**
 489          * Delete all objects expiring before a certain date.
 490          * @param string $date The reference date in MW format
 491          * @param callable|bool $progressCallback Optional, a function which will be called
 492          *     regularly during long-running operations with the percentage progress
 493          *     as the first parameter.
 494          *
 495          * @return bool Success, false if unimplemented
 496          */
 497         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 498                 // stub
 499                 return false;
 500         }
 501
 502         /**
 503          * Get an associative array containing the item for each of the keys that have items.
 504          * @param array $keys List of strings
 505          * @param integer $flags Bitfield; supports READ_LATEST [optional]
 506          * @return array
 507          */
 508         public function getMulti( array $keys, $flags = 0 ) {
 509                 $res = [];
 510                 foreach ( $keys as $key ) {
 511                         $val = $this->get( $key );
 512                         if ( $val !== false ) {
 513                                 $res[$key] = $val;
 514                         }
 515                 }
 516                 return $res;
 517         }
 518
 519         /**
 520          * Batch insertion
 521          * @param array $data $key => $value assoc array
 522          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 523          * @return bool Success
 524          * @since 1.24
 525          */
 526         public function setMulti( array $data, $exptime = 0 ) {
 527                 $res = true;
 528                 foreach ( $data as $key => $value ) {
 529                         if ( !$this->set( $key, $value, $exptime ) ) {
 530                                 $res = false;
 531                         }
 532                 }
 533                 return $res;
 534         }
 535
 536         /**
 537          * @param string $key
 538          * @param mixed $value
 539          * @param int $exptime
 540          * @return bool Success
 541          */
 542         public function add( $key, $value, $exptime = 0 ) {
 543                 if ( $this->get( $key ) === false ) {
 544                         return $this->set( $key, $value, $exptime );
 545                 }
 546                 return false; // key already set
 547         }
 548
 549         /**
 550          * Increase stored value of $key by $value while preserving its TTL
 551          * @param string $key Key to increase
 552          * @param int $value Value to add to $key (Default 1)
 553          * @return int|bool New value or false on failure
 554          */
 555         public function incr( $key, $value = 1 ) {
 556                 if ( !$this->lock( $key ) ) {
 557                         return false;
 558                 }
 559                 $n = $this->get( $key );
 560                 if ( $this->isInteger( $n ) ) { // key exists?
 561                         $n += intval( $value );
 562                         $this->set( $key, max( 0, $n ) ); // exptime?
 563                 } else {
 564                         $n = false;
 565                 }
 566                 $this->unlock( $key );
 567
 568                 return $n;
 569         }
 570
 571         /**
 572          * Decrease stored value of $key by $value while preserving its TTL
 573          * @param string $key
 574          * @param int $value
 575          * @return int|bool New value or false on failure
 576          */
 577         public function decr( $key, $value = 1 ) {
 578                 return $this->incr( $key, - $value );
 579         }
 580
 581         /**
 582          * Increase stored value of $key by $value while preserving its TTL
 583          *
 584          * This will create the key with value $init and TTL $ttl instead if not present
 585          *
 586          * @param string $key
 587          * @param int $ttl
 588          * @param int $value
 589          * @param int $init
 590          * @return int|bool New value or false on failure
 591          * @since 1.24
 592          */
 593         public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) {
 594                 $newValue = $this->incr( $key, $value );
 595                 if ( $newValue === false ) {
 596                         // No key set; initialize
 597                         $newValue = $this->add( $key, (int)$init, $ttl ) ? $init : false;
 598                 }
 599                 if ( $newValue === false ) {
 600                         // Raced out initializing; increment
 601                         $newValue = $this->incr( $key, $value );
 602                 }
 603
 604                 return $newValue;
 605         }
 606
 607         /**
 608          * Get the "last error" registered; clearLastError() should be called manually
 609          * @return int ERR_* constant for the "last error" registry
 610          * @since 1.23
 611          */
 612         public function getLastError() {
 613                 return $this->lastError;
 614         }
 615
 616         /**
 617          * Clear the "last error" registry
 618          * @since 1.23
 619          */
 620         public function clearLastError() {
 621                 $this->lastError = self::ERR_NONE;
 622         }
 623
 624         /**
 625          * Set the "last error" registry
 626          * @param int $err ERR_* constant
 627          * @since 1.23
 628          */
 629         protected function setLastError( $err ) {
 630                 $this->lastError = $err;
 631         }
 632
 633         /**
 634          * Let a callback be run to avoid wasting time on special blocking calls
 635          *
 636          * The callbacks may or may not be called ever, in any particular order.
 637          * They are likely to be invoked when something WRITE_SYNC is used used.
 638          * They should follow a caching pattern as shown below, so that any code
 639          * using the word will get it's result no matter what happens.
 640          * @code
 641          *     $result = null;
 642          *     $workCallback = function () use ( &$result ) {
 643          *         if ( !$result ) {
 644          *             $result = ....
 645          *         }
 646          *         return $result;
 647          *     }
 648          * @endcode
 649          *
 650          * @param callable $workCallback
 651          * @since 1.28
 652          */
 653         public function addBusyCallback( callable $workCallback ) {
 654                 $this->busyCallbacks[] = $workCallback;
 655         }
 656
 657         /**
 658          * Modify a cache update operation array for EventRelayer::notify()
 659          *
 660          * This is used for relayed writes, e.g. for broadcasting a change
 661          * to multiple data-centers. If the array contains a 'val' field
 662          * then the command involves setting a key to that value. Note that
 663          * for simplicity, 'val' is always a simple scalar value. This method
 664          * is used to possibly serialize the value and add any cache-specific
 665          * key/values needed for the relayer daemon (e.g. memcached flags).
 666          *
 667          * @param array $event
 668          * @return array
 669          * @since 1.26
 670          */
 671         public function modifySimpleRelayEvent( array $event ) {
 672                 return $event;
 673         }
 674
 675         /**
 676          * @param string $text
 677          */
 678         protected function debug( $text ) {
 679                 if ( $this->debugMode ) {
 680                         $this->logger->debug( "{class} debug: $text", [
 681                                 'class' => get_class( $this ),
 682                         ] );
 683                 }
 684         }
 685
 686         /**
 687          * Convert an optionally relative time to an absolute time
 688          * @param int $exptime
 689          * @return int
 690          */
 691         protected function convertExpiry( $exptime ) {
 692                 if ( $exptime != 0 && $exptime < ( 10 * self::TTL_YEAR ) ) {
 693                         return time() + $exptime;
 694                 } else {
 695                         return $exptime;
 696                 }
 697         }
 698
 699         /**
 700          * Convert an optionally absolute expiry time to a relative time. If an
 701          * absolute time is specified which is in the past, use a short expiry time.
 702          *
 703          * @param int $exptime
 704          * @return int
 705          */
 706         protected function convertToRelative( $exptime ) {
 707                 if ( $exptime >= ( 10 * self::TTL_YEAR ) ) {
 708                         $exptime -= time();
 709                         if ( $exptime <= 0 ) {
 710                                 $exptime = 1;
 711                         }
 712                         return $exptime;
 713                 } else {
 714                         return $exptime;
 715                 }
 716         }
 717
 718         /**
 719          * Check if a value is an integer
 720          *
 721          * @param mixed $value
 722          * @return bool
 723          */
 724         protected function isInteger( $value ) {
 725                 return ( is_int( $value ) || ctype_digit( $value ) );
 726         }
 727
 728         /**
 729          * Construct a cache key.
 730          *
 731          * @since 1.27
 732          * @param string $keyspace
 733          * @param array $args
 734          * @return string
 735          */
 736         public function makeKeyInternal( $keyspace, $args ) {
 737                 $key = $keyspace;
 738                 foreach ( $args as $arg ) {
 739                         $arg = str_replace( ':', '%3A', $arg );
 740                         $key = $key . ':' . $arg;
 741                 }
 742                 return strtr( $key, ' ', '_' );
 743         }
 744
 745         /**
 746          * Make a global cache key.
 747          *
 748          * @since 1.27
 749          * @param string ... Key component (variadic)
 750          * @return string
 751          */
 752         public function makeGlobalKey() {
 753                 return $this->makeKeyInternal( 'global', func_get_args() );
 754         }
 755
 756         /**
 757          * Make a cache key, scoped to this instance's keyspace.
 758          *
 759          * @since 1.27
 760          * @param string ... Key component (variadic)
 761          * @return string
 762          */
 763         public function makeKey() {
 764                 return $this->makeKeyInternal( $this->keyspace, func_get_args() );
 765         }
 766
 767         /**
 768          * @param integer $flag ATTR_* class constant
 769          * @return integer QOS_* class constant
 770          * @since 1.28
 771          */
 772         public function getQoS( $flag ) {
 773                 return isset( $this->attrMap[$flag] ) ? $this->attrMap[$flag] : self::QOS_UNKNOWN;
 774         }
 775
 776         /**
 777          * Merge the flag maps of one or more BagOStuff objects into a "lowest common denominator" map
 778          *
 779          * @param BagOStuff[] $bags
 780          * @return integer[] Resulting flag map (class ATTR_* constant => class QOS_* constant)
 781          */
 782         protected function mergeFlagMaps( array $bags ) {
 783                 $map = [];
 784                 foreach ( $bags as $bag ) {
 785                         foreach ( $bag->attrMap as $attr => $rank ) {
 786                                 if ( isset( $map[$attr] ) ) {
 787                                         $map[$attr] = min( $map[$attr], $rank );
 788                                 } else {
 789                                         $map[$attr] = $rank;
 790                                 }
 791                         }
 792                 }
 793
 794                 return $map;
 795         }
 796 }