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