includes/cache/MessageCache.php

   1 <?php
   2 /**
   3  * Localisation messages cache.
   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 /**
  25  * MediaWiki message cache structure version.
  26  * Bump this whenever the message cache format has changed.
  27  */
  28 define( 'MSG_CACHE_VERSION', 1 );
  29
  30 /**
  31  * Memcached timeout when loading a key.
  32  * See MessageCache::load()
  33  */
  34 define( 'MSG_LOAD_TIMEOUT', 60 );
  35
  36 /**
  37  * Memcached timeout when locking a key for a writing operation.
  38  * See MessageCache::lock()
  39  */
  40 define( 'MSG_LOCK_TIMEOUT', 30 );
  41 /**
  42  * Number of times we will try to acquire a lock from Memcached.
  43  * This comes in addition to MSG_LOCK_TIMEOUT.
  44  */
  45 define( 'MSG_WAIT_TIMEOUT', 30 );
  46
  47 /**
  48  * Message cache
  49  * Performs various MediaWiki namespace-related functions
  50  * @ingroup Cache
  51  */
  52 class MessageCache {
  53         /**
  54          * Process local cache of loaded messages that are defined in
  55          * MediaWiki namespace. First array level is a language code,
  56          * second level is message key and the values are either message
  57          * content prefixed with space, or !NONEXISTENT for negative
  58          * caching.
  59          */
  60         protected $mCache;
  61
  62         /**
  63          * Should  mean that database cannot be used, but check
  64          * @var bool $mDisable
  65          */
  66         protected $mDisable;
  67
  68         /**
  69          * Lifetime for cache, used by object caching.
  70          * Set on construction, see __construct().
  71          */
  72         protected $mExpiry;
  73
  74         /**
  75          * Message cache has it's own parser which it uses to transform
  76          * messages.
  77          */
  78         protected $mParserOptions, $mParser;
  79
  80         /**
  81          * Variable for tracking which variables are already loaded
  82          * @var array $mLoadedLanguages
  83          */
  84         protected $mLoadedLanguages = array();
  85
  86         /**
  87          * Singleton instance
  88          *
  89          * @var MessageCache $instance
  90          */
  91         private static $instance;
  92
  93         /**
  94          * @var bool $mInParser
  95          */
  96         protected $mInParser = false;
  97
  98         /**
  99          * Get the signleton instance of this class
 100          *
 101          * @since 1.18
 102          * @return MessageCache
 103          */
 104         public static function singleton() {
 105                 if ( is_null( self::$instance ) ) {
 106                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
 107                         self::$instance = new self(
 108                                 wfGetMessageCacheStorage(),
 109                                 $wgUseDatabaseMessages,
 110                                 $wgMsgCacheExpiry
 111                         );
 112                 }
 113
 114                 return self::$instance;
 115         }
 116
 117         /**
 118          * Destroy the singleton instance
 119          *
 120          * @since 1.18
 121          */
 122         public static function destroyInstance() {
 123                 self::$instance = null;
 124         }
 125
 126         /**
 127          * @param BagOStuff $memCached A cache instance. If none, fall back to CACHE_NONE.
 128          * @param bool $useDB
 129          * @param int $expiry Lifetime for cache. @see $mExpiry.
 130          */
 131         function __construct( $memCached, $useDB, $expiry ) {
 132                 if ( !$memCached ) {
 133                         $memCached = wfGetCache( CACHE_NONE );
 134                 }
 135
 136                 $this->mMemc = $memCached;
 137                 $this->mDisable = !$useDB;
 138                 $this->mExpiry = $expiry;
 139         }
 140
 141         /**
 142          * ParserOptions is lazy initialised.
 143          *
 144          * @return ParserOptions
 145          */
 146         function getParserOptions() {
 147                 if ( !$this->mParserOptions ) {
 148                         $this->mParserOptions = new ParserOptions;
 149                         $this->mParserOptions->setEditSection( false );
 150                 }
 151
 152                 return $this->mParserOptions;
 153         }
 154
 155         /**
 156          * Try to load the cache from a local file.
 157          *
 158          * @param string $hash the hash of contents, to check validity.
 159          * @param Mixed $code Optional language code, see documenation of load().
 160          * @return array The cache array
 161          */
 162         function getLocalCache( $hash, $code ) {
 163                 global $wgCacheDirectory;
 164
 165                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 166
 167                 # Check file existence
 168                 wfSuppressWarnings();
 169                 $file = fopen( $filename, 'r' );
 170                 wfRestoreWarnings();
 171                 if ( !$file ) {
 172                         return false; // No cache file
 173                 }
 174
 175                 // Check to see if the file has the hash specified
 176                 $localHash = fread( $file, 32 );
 177                 if ( $hash === $localHash ) {
 178                         // All good, get the rest of it
 179                         $serialized = '';
 180                         while ( !feof( $file ) ) {
 181                                 $serialized .= fread( $file, 100000 );
 182                         }
 183                         fclose( $file );
 184
 185                         return unserialize( $serialized );
 186                 } else {
 187                         fclose( $file );
 188
 189                         return false; // Wrong hash
 190                 }
 191         }
 192
 193         /**
 194          * Save the cache to a local file.
 195          */
 196         function saveToLocal( $serialized, $hash, $code ) {
 197                 global $wgCacheDirectory;
 198
 199                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 200                 wfMkdirParents( $wgCacheDirectory, null, __METHOD__ ); // might fail
 201
 202                 wfSuppressWarnings();
 203                 $file = fopen( $filename, 'w' );
 204                 wfRestoreWarnings();
 205
 206                 if ( !$file ) {
 207                         wfDebug( "Unable to open local cache file for writing\n" );
 208
 209                         return;
 210                 }
 211
 212                 fwrite( $file, $hash . $serialized );
 213                 fclose( $file );
 214                 wfSuppressWarnings();
 215                 chmod( $filename, 0666 );
 216                 wfRestoreWarnings();
 217         }
 218
 219         /**
 220          * Loads messages from caches or from database in this order:
 221          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 222          * (2) memcached
 223          * (3) from the database.
 224          *
 225          * When succesfully loading from (2) or (3), all higher level caches are
 226          * updated for the newest version.
 227          *
 228          * Nothing is loaded if member variable mDisable is true, either manually
 229          * set by calling code or if message loading fails (is this possible?).
 230          *
 231          * Returns true if cache is already populated or it was succesfully populated,
 232          * or false if populating empty cache fails. Also returns true if MessageCache
 233          * is disabled.
 234          *
 235          * @param bool|String $code Language to which load messages
 236          * @throws MWException
 237          * @return bool
 238          */
 239         function load( $code = false ) {
 240                 global $wgUseLocalMessageCache;
 241
 242                 if ( !is_string( $code ) ) {
 243                         # This isn't really nice, so at least make a note about it and try to
 244                         # fall back
 245                         wfDebug( __METHOD__ . " called without providing a language code\n" );
 246                         $code = 'en';
 247                 }
 248
 249                 # Don't do double loading...
 250                 if ( isset( $this->mLoadedLanguages[$code] ) ) {
 251                         return true;
 252                 }
 253
 254                 # 8 lines of code just to say (once) that message cache is disabled
 255                 if ( $this->mDisable ) {
 256                         static $shownDisabled = false;
 257                         if ( !$shownDisabled ) {
 258                                 wfDebug( __METHOD__ . ": disabled\n" );
 259                                 $shownDisabled = true;
 260                         }
 261
 262                         return true;
 263                 }
 264
 265                 # Loading code starts
 266                 wfProfileIn( __METHOD__ );
 267                 $success = false; # Keep track of success
 268                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 269                 $where = array(); # Debug info, delayed to avoid spamming debug log too much
 270                 $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 271
 272                 # Local cache
 273                 # Hash of the contents is stored in memcache, to detect if local cache goes
 274                 # out of date (e.g. due to replace() on some other server)
 275                 if ( $wgUseLocalMessageCache ) {
 276                         wfProfileIn( __METHOD__ . '-fromlocal' );
 277
 278                         $hash = $this->mMemc->get( wfMemcKey( 'messages', $code, 'hash' ) );
 279                         if ( $hash ) {
 280                                 $cache = $this->getLocalCache( $hash, $code );
 281                                 if ( !$cache ) {
 282                                         $where[] = 'local cache is empty or has the wrong hash';
 283                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 284                                         $where[] = 'local cache is expired';
 285                                         $staleCache = $cache;
 286                                 } else {
 287                                         $where[] = 'got from local cache';
 288                                         $success = true;
 289                                         $this->mCache[$code] = $cache;
 290                                 }
 291                         }
 292                         wfProfileOut( __METHOD__ . '-fromlocal' );
 293                 }
 294
 295                 if ( !$success ) {
 296                         # Try the global cache. If it is empty, try to acquire a lock. If
 297                         # the lock can't be acquired, wait for the other thread to finish
 298                         # and then try the global cache a second time.
 299                         for ( $failedAttempts = 0; $failedAttempts < 2; $failedAttempts++ ) {
 300                                 wfProfileIn( __METHOD__ . '-fromcache' );
 301                                 $cache = $this->mMemc->get( $cacheKey );
 302                                 if ( !$cache ) {
 303                                         $where[] = 'global cache is empty';
 304                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 305                                         $where[] = 'global cache is expired';
 306                                         $staleCache = $cache;
 307                                 } else {
 308                                         $where[] = 'got from global cache';
 309                                         $this->mCache[$code] = $cache;
 310                                         $this->saveToCaches( $cache, 'local-only', $code );
 311                                         $success = true;
 312                                 }
 313
 314                                 wfProfileOut( __METHOD__ . '-fromcache' );
 315
 316                                 if ( $success ) {
 317                                         # Done, no need to retry
 318                                         break;
 319                                 }
 320
 321                                 # We need to call loadFromDB. Limit the concurrency to a single
 322                                 # process. This prevents the site from going down when the cache
 323                                 # expires.
 324                                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 325                                 $acquired = $this->mMemc->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT );
 326                                 if ( $acquired ) {
 327                                         # Unlock the status key if there is an exception
 328                                         $that = $this;
 329                                         $statusUnlocker = new ScopedCallback( function () use ( $that, $statusKey ) {
 330                                                 $that->mMemc->delete( $statusKey );
 331                                         } );
 332
 333                                         # Now let's regenerate
 334                                         $where[] = 'loading from database';
 335
 336                                         # Lock the cache to prevent conflicting writes
 337                                         # If this lock fails, it doesn't really matter, it just means the
 338                                         # write is potentially non-atomic, e.g. the results of a replace()
 339                                         # may be discarded.
 340                                         if ( $this->lock( $cacheKey ) ) {
 341                                                 $mainUnlocker = new ScopedCallback( function () use ( $that, $cacheKey ) {
 342                                                         $that->unlock( $cacheKey );
 343                                                 } );
 344                                         } else {
 345                                                 $mainUnlocker = null;
 346                                                 $where[] = 'could not acquire main lock';
 347                                         }
 348
 349                                         $cache = $this->loadFromDB( $code );
 350                                         $this->mCache[$code] = $cache;
 351                                         $success = true;
 352                                         $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 353
 354                                         # Unlock
 355                                         ScopedCallback::consume( $mainUnlocker );
 356                                         ScopedCallback::consume( $statusUnlocker );
 357
 358                                         if ( !$saveSuccess ) {
 359                                                 # Cache save has failed.
 360                                                 # There are two main scenarios where this could be a problem:
 361                                                 #
 362                                                 #   - The cache is more than the maximum size (typically
 363                                                 #     1MB compressed).
 364                                                 #
 365                                                 #   - Memcached has no space remaining in the relevant slab
 366                                                 #     class. This is unlikely with recent versions of
 367                                                 #     memcached.
 368                                                 #
 369                                                 # Either way, if there is a local cache, nothing bad will
 370                                                 # happen. If there is no local cache, disabling the message
 371                                                 # cache for all requests avoids incurring a loadFromDB()
 372                                                 # overhead on every request, and thus saves the wiki from
 373                                                 # complete downtime under moderate traffic conditions.
 374                                                 if ( !$wgUseLocalMessageCache ) {
 375                                                         $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 376                                                         $where[] = 'could not save cache, disabled globally for 5 minutes';
 377                                                 } else {
 378                                                         $where[] = "could not save global cache";
 379                                                 }
 380                                         }
 381
 382                                         # Load from DB complete, no need to retry
 383                                         break;
 384                                 } elseif ( $staleCache ) {
 385                                         # Use the stale cache while some other thread constructs the new one
 386                                         $where[] = 'using stale cache';
 387                                         $this->mCache[$code] = $staleCache;
 388                                         $success = true;
 389                                         break;
 390                                 } elseif ( $failedAttempts > 0 ) {
 391                                         # Already retried once, still failed, so don't do another lock/unlock cycle
 392                                         # This case will typically be hit if memcached is down, or if
 393                                         # loadFromDB() takes longer than MSG_WAIT_TIMEOUT
 394                                         $where[] = "could not acquire status key.";
 395                                         break;
 396                                 } else {
 397                                         $status = $this->mMemc->get( $statusKey );
 398                                         if ( $status === 'error' ) {
 399                                                 # Disable cache
 400                                                 break;
 401                                         } else {
 402                                                 # Wait for the other thread to finish, then retry
 403                                                 $where[] = 'waited for other thread to complete';
 404                                                 $this->lock( $cacheKey );
 405                                                 $this->unlock( $cacheKey );
 406                                         }
 407                                 }
 408                         }
 409                 }
 410
 411                 if ( !$success ) {
 412                         $where[] = 'loading FAILED - cache is disabled';
 413                         $this->mDisable = true;
 414                         $this->mCache = false;
 415                         # This used to throw an exception, but that led to nasty side effects like
 416                         # the whole wiki being instantly down if the memcached server died
 417                 } else {
 418                         # All good, just record the success
 419                         $this->mLoadedLanguages[$code] = true;
 420                 }
 421                 $info = implode( ', ', $where );
 422                 wfDebug( __METHOD__ . ": Loading $code... $info\n" );
 423                 wfProfileOut( __METHOD__ );
 424
 425                 return $success;
 426         }
 427
 428         /**
 429          * Loads cacheable messages from the database. Messages bigger than
 430          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 431          * on-demand from the database later.
 432          *
 433          * @param string $code Language code.
 434          * @return array Loaded messages for storing in caches.
 435          */
 436         function loadFromDB( $code ) {
 437                 wfProfileIn( __METHOD__ );
 438                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 439                 $dbr = wfGetDB( DB_SLAVE );
 440                 $cache = array();
 441
 442                 # Common conditions
 443                 $conds = array(
 444                         'page_is_redirect' => 0,
 445                         'page_namespace' => NS_MEDIAWIKI,
 446                 );
 447
 448                 $mostused = array();
 449                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 450                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 451                                 $this->load( $wgLanguageCode );
 452                         }
 453                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 454                         foreach ( $mostused as $key => $value ) {
 455                                 $mostused[$key] = "$value/$code";
 456                         }
 457                 }
 458
 459                 if ( count( $mostused ) ) {
 460                         $conds['page_title'] = $mostused;
 461                 } elseif ( $code !== $wgLanguageCode ) {
 462                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 463                 } else {
 464                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 465                         # other than language code.
 466                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 467                 }
 468
 469                 # Conditions to fetch oversized pages to ignore them
 470                 $bigConds = $conds;
 471                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 472
 473                 # Load titles for all oversized pages in the MediaWiki namespace
 474                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 475                 foreach ( $res as $row ) {
 476                         $cache[$row->page_title] = '!TOO BIG';
 477                 }
 478
 479                 # Conditions to load the remaining pages with their contents
 480                 $smallConds = $conds;
 481                 $smallConds[] = 'page_latest=rev_id';
 482                 $smallConds[] = 'rev_text_id=old_id';
 483                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 484
 485                 $res = $dbr->select(
 486                         array( 'page', 'revision', 'text' ),
 487                         array( 'page_title', 'old_text', 'old_flags' ),
 488                         $smallConds,
 489                         __METHOD__ . "($code)-small"
 490                 );
 491
 492                 foreach ( $res as $row ) {
 493                         $text = Revision::getRevisionText( $row );
 494                         if ( $text === false ) {
 495                                 // Failed to fetch data; possible ES errors?
 496                                 // Store a marker to fetch on-demand as a workaround...
 497                                 $entry = '!TOO BIG';
 498                                 wfDebugLog(
 499                                         'MessageCache',
 500                                         __METHOD__
 501                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 502                                 );
 503                         } else {
 504                                 $entry = ' ' . $text;
 505                         }
 506                         $cache[$row->page_title] = $entry;
 507                 }
 508
 509                 $cache['VERSION'] = MSG_CACHE_VERSION;
 510                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 511                 wfProfileOut( __METHOD__ );
 512
 513                 return $cache;
 514         }
 515
 516         /**
 517          * Updates cache as necessary when message page is changed
 518          *
 519          * @param string $title Name of the page changed.
 520          * @param mixed $text New contents of the page.
 521          */
 522         public function replace( $title, $text ) {
 523                 global $wgMaxMsgCacheEntrySize;
 524                 wfProfileIn( __METHOD__ );
 525
 526                 if ( $this->mDisable ) {
 527                         wfProfileOut( __METHOD__ );
 528
 529                         return;
 530                 }
 531
 532                 list( $msg, $code ) = $this->figureMessage( $title );
 533
 534                 $cacheKey = wfMemcKey( 'messages', $code );
 535                 $this->load( $code );
 536                 $this->lock( $cacheKey );
 537
 538                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 539
 540                 if ( $text === false ) {
 541                         # Article was deleted
 542                         $this->mCache[$code][$title] = '!NONEXISTENT';
 543                         $this->mMemc->delete( $titleKey );
 544                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 545                         # Check for size
 546                         $this->mCache[$code][$title] = '!TOO BIG';
 547                         $this->mMemc->set( $titleKey, ' ' . $text, $this->mExpiry );
 548                 } else {
 549                         $this->mCache[$code][$title] = ' ' . $text;
 550                         $this->mMemc->delete( $titleKey );
 551                 }
 552
 553                 # Update caches
 554                 $this->saveToCaches( $this->mCache[$code], 'all', $code );
 555                 $this->unlock( $cacheKey );
 556
 557                 // Also delete cached sidebar... just in case it is affected
 558                 $codes = array( $code );
 559                 if ( $code === 'en' ) {
 560                         // Delete all sidebars, like for example on action=purge on the
 561                         // sidebar messages
 562                         $codes = array_keys( Language::fetchLanguageNames() );
 563                 }
 564
 565                 global $wgMemc;
 566                 foreach ( $codes as $code ) {
 567                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 568                         $wgMemc->delete( $sidebarKey );
 569                 }
 570
 571                 // Update the message in the message blob store
 572                 global $wgContLang;
 573                 MessageBlobStore::updateMessage( $wgContLang->lcfirst( $msg ) );
 574
 575                 wfRunHooks( 'MessageCacheReplace', array( $title, $text ) );
 576
 577                 wfProfileOut( __METHOD__ );
 578         }
 579
 580         /**
 581          * Is the given cache array expired due to time passing or a version change?
 582          *
 583          * @param $cache
 584          * @return bool
 585          */
 586         protected function isCacheExpired( $cache ) {
 587                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 588                         return true;
 589                 }
 590                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 591                         return true;
 592                 }
 593                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 594                         return true;
 595                 }
 596
 597                 return false;
 598         }
 599
 600         /**
 601          * Shortcut to update caches.
 602          *
 603          * @param array $cache Cached messages with a version.
 604          * @param string $dest Either "local-only" to save to local caches only
 605          *   or "all" to save to all caches.
 606          * @param string|bool $code Language code (default: false)
 607          * @return bool
 608          */
 609         protected function saveToCaches( $cache, $dest, $code = false ) {
 610                 wfProfileIn( __METHOD__ );
 611                 global $wgUseLocalMessageCache;
 612
 613                 $cacheKey = wfMemcKey( 'messages', $code );
 614
 615                 if ( $dest === 'all' ) {
 616                         $success = $this->mMemc->set( $cacheKey, $cache );
 617                 } else {
 618                         $success = true;
 619                 }
 620
 621                 # Save to local cache
 622                 if ( $wgUseLocalMessageCache ) {
 623                         $serialized = serialize( $cache );
 624                         $hash = md5( $serialized );
 625                         $this->mMemc->set( wfMemcKey( 'messages', $code, 'hash' ), $hash );
 626                         $this->saveToLocal( $serialized, $hash, $code );
 627                 }
 628
 629                 wfProfileOut( __METHOD__ );
 630
 631                 return $success;
 632         }
 633
 634         /**
 635          * Represents a write lock on the messages key.
 636          *
 637          * Will retry MessageCache::MSG_WAIT_TIMEOUT times, each operations having
 638          * a timeout of MessageCache::MSG_LOCK_TIMEOUT.
 639          *
 640          * @param string $key
 641          * @return Boolean: success
 642          */
 643         function lock( $key ) {
 644                 $lockKey = $key . ':lock';
 645                 $acquired = false;
 646                 $testDone = false;
 647                 for ( $i = 0; $i < MSG_WAIT_TIMEOUT && !$acquired; $i++ ) {
 648                         $acquired = $this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT );
 649                         if ( $acquired ) {
 650                                 break;
 651                         }
 652
 653                         # Fail fast if memcached is totally down
 654                         if ( !$testDone ) {
 655                                 $testDone = true;
 656                                 if ( !$this->mMemc->set( wfMemcKey( 'test' ), 'test', 1 ) ) {
 657                                         break;
 658                                 }
 659                         }
 660                         sleep( 1 );
 661                 }
 662
 663                 return $acquired;
 664         }
 665
 666         function unlock( $key ) {
 667                 $lockKey = $key . ':lock';
 668                 $this->mMemc->delete( $lockKey );
 669         }
 670
 671         /**
 672          * Get a message from either the content language or the user language.
 673          *
 674          * First, assemble a list of languages to attempt getting the message from. This
 675          * chain begins with the requested language and its fallbacks and then continues with
 676          * the content language and its fallbacks. For each language in the chain, the following
 677          * process will occur (in this order):
 678          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 679          *     Note: for the content language, there is no /lang subpage.
 680          *  2. Fetch from the static CDB cache.
 681          *  3. If available, check the database for fallback language overrides.
 682          *
 683          * This process provides a number of guarantees. When changing this code, make sure all
 684          * of these guarantees are preserved.
 685          *  * If the requested language is *not* the content language, then the CDB cache for that
 686          *    specific language will take precedence over the root database page ([[MW:msg]]).
 687          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 688          *    the message is available *anywhere* in the language for which it is a fallback.
 689          *
 690          * @param string $key the message key
 691          * @param bool $useDB If true, look for the message in the DB, false
 692          *                    to use only the compiled l10n cache.
 693          * @param bool|string|object $langcode Code of the language to get the message for.
 694          *        - If string and a valid code, will create a standard language object
 695          *        - If string but not a valid code, will create a basic language object
 696          *        - If boolean and false, create object from the current users language
 697          *        - If boolean and true, create object from the wikis content language
 698          *        - If language object, use it as given
 699          * @param bool $isFullKey specifies whether $key is a two part key
 700          *                   "msg/lang".
 701          *
 702          * @throws MWException when given an invalid key
 703          * @return string|bool False if the message doesn't exist, otherwise the
 704          *   message (which can be empty)
 705          */
 706         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 707                 global $wgContLang;
 708
 709                 $section = new ProfileSection( __METHOD__ );
 710
 711                 if ( is_int( $key ) ) {
 712                         // Fix numerical strings that somehow become ints
 713                         // on their way here
 714                         $key = (string)$key;
 715                 } elseif ( !is_string( $key ) ) {
 716                         throw new MWException( 'Non-string key given' );
 717                 } elseif ( $key === '' ) {
 718                         // Shortcut: the empty key is always missing
 719                         return false;
 720                 }
 721
 722                 // For full keys, get the language code from the key
 723                 $pos = strrpos( $key, '/' );
 724                 if ( $isFullKey && $pos !== false ) {
 725                         $langcode = substr( $key, $pos + 1 );
 726                         $key = substr( $key, 0, $pos );
 727                 }
 728
 729                 // Normalise title-case input (with some inlining)
 730                 $lckey = strtr( $key, ' ', '_' );
 731                 if ( ord( $key ) < 128 ) {
 732                         $lckey[0] = strtolower( $lckey[0] );
 733                         $uckey = ucfirst( $lckey );
 734                 } else {
 735                         $lckey = $wgContLang->lcfirst( $lckey );
 736                         $uckey = $wgContLang->ucfirst( $lckey );
 737                 }
 738
 739                 // Loop through each language in the fallback list until we find something useful
 740                 $lang = wfGetLangObj( $langcode );
 741                 $message = $this->getMessageFromFallbackChain(
 742                         $lang,
 743                         $lckey,
 744                         $uckey,
 745                         !$this->mDisable && $useDB
 746                 );
 747
 748                 // If we still have no message, maybe the key was in fact a full key so try that
 749                 if ( $message === false ) {
 750                         $parts = explode( '/', $lckey );
 751                         // We may get calls for things that are http-urls from sidebar
 752                         // Let's not load nonexistent languages for those
 753                         // They usually have more than one slash.
 754                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 755                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 756                                 if ( $message === null ) {
 757                                         $message = false;
 758                                 }
 759                         }
 760                 }
 761
 762                 // Post-processing if the message exists
 763                 if ( $message !== false ) {
 764                         // Fix whitespace
 765                         $message = str_replace(
 766                                 array(
 767                                         # Fix for trailing whitespace, removed by textarea
 768                                         '&#32;',
 769                                         # Fix for NBSP, converted to space by firefox
 770                                         '&nbsp;',
 771                                         '&#160;',
 772                                 ),
 773                                 array(
 774                                         ' ',
 775                                         "\xc2\xa0",
 776                                         "\xc2\xa0"
 777                                 ),
 778                                 $message
 779                         );
 780                 }
 781
 782                 return $message;
 783         }
 784
 785         /**
 786          * Given a language, try and fetch a message from that language, then the
 787          * fallbacks of that language, then the site language, then the fallbacks for the
 788          * site language.
 789          *
 790          * @param Language $lang Requested language
 791          * @param string $lckey Lowercase key for the message
 792          * @param string $uckey Uppercase key for the message
 793          * @param bool $useDB Whether to use the database
 794          *
 795          * @see MessageCache::get
 796          * @return string|bool The message, or false if not found
 797          */
 798         protected function getMessageFromFallbackChain( $lang, $lckey, $uckey, $useDB ) {
 799                 global $wgLanguageCode, $wgContLang;
 800
 801                 $langcode = $lang->getCode();
 802                 $message = false;
 803
 804                 // First try the requested language.
 805                 if ( $useDB ) {
 806                         if ( $langcode === $wgLanguageCode ) {
 807                                 // Messages created in the content language will not have the /lang extension
 808                                 $message = $this->getMsgFromNamespace( $uckey, $langcode );
 809                         } else {
 810                                 $message = $this->getMsgFromNamespace( "$uckey/$langcode", $langcode );
 811                         }
 812                 }
 813
 814                 if ( $message !== false ) {
 815                         return $message;
 816                 }
 817
 818                 // Check the CDB cache
 819                 $message = $lang->getMessage( $lckey );
 820                 if ( $message !== null ) {
 821                         return $message;
 822                 }
 823
 824                 list( $fallbackChain, $siteFallbackChain ) =
 825                         Language::getFallbacksIncludingSiteLanguage( $langcode );
 826
 827                 // Next try checking the database for all of the fallback languages of the requested language.
 828                 if ( $useDB ) {
 829                         foreach ( $fallbackChain as $code ) {
 830                                 if ( $code === $wgLanguageCode ) {
 831                                         // Messages created in the content language will not have the /lang extension
 832                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 833                                 } else {
 834                                         $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 835                                 }
 836
 837                                 if ( $message !== false ) {
 838                                         // Found the message.
 839                                         return $message;
 840                                 }
 841                         }
 842                 }
 843
 844                 // Now try checking the site language.
 845                 if ( $useDB ) {
 846                         $message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
 847                         if ( $message !== false ) {
 848                                 return $message;
 849                         }
 850                 }
 851
 852                 $message = $wgContLang->getMessage( $lckey );
 853                 if ( $message !== null ) {
 854                         return $message;
 855                 }
 856
 857                 // Finally try the DB for the site language's fallbacks.
 858                 if ( $useDB ) {
 859                         foreach ( $siteFallbackChain as $code ) {
 860                                 $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 861                                 if ( $message === false && $code === $wgLanguageCode ) {
 862                                         // Messages created in the content language will not have the /lang extension
 863                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 864                                 }
 865
 866                                 if ( $message !== false ) {
 867                                         // Found the message.
 868                                         return $message;
 869                                 }
 870                         }
 871                 }
 872
 873                 return false;
 874         }
 875
 876         /**
 877          * Get a message from the MediaWiki namespace, with caching. The key must
 878          * first be converted to two-part lang/msg form if necessary.
 879          *
 880          * Unlike self::get(), this function doesn't resolve fallback chains, and
 881          * some callers require this behavior. LanguageConverter::parseCachedTable()
 882          * and self::get() are some examples in core.
 883          *
 884          * @param string $title Message cache key with initial uppercase letter.
 885          * @param string $code Code denoting the language to try.
 886          * @return string|bool The message, or false if it does not exist or on error
 887          */
 888         function getMsgFromNamespace( $title, $code ) {
 889                 $this->load( $code );
 890                 if ( isset( $this->mCache[$code][$title] ) ) {
 891                         $entry = $this->mCache[$code][$title];
 892                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 893                                 // The message exists, so make sure a string
 894                                 // is returned.
 895                                 return (string)substr( $entry, 1 );
 896                         } elseif ( $entry === '!NONEXISTENT' ) {
 897                                 return false;
 898                         } elseif ( $entry === '!TOO BIG' ) {
 899                                 // Fall through and try invididual message cache below
 900                         }
 901                 } else {
 902                         // XXX: This is not cached in process cache, should it?
 903                         $message = false;
 904                         wfRunHooks( 'MessagesPreLoad', array( $title, &$message ) );
 905                         if ( $message !== false ) {
 906                                 return $message;
 907                         }
 908
 909                         return false;
 910                 }
 911
 912                 # Try the individual message cache
 913                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 914                 $entry = $this->mMemc->get( $titleKey );
 915                 if ( $entry ) {
 916                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 917                                 $this->mCache[$code][$title] = $entry;
 918
 919                                 // The message exists, so make sure a string
 920                                 // is returned.
 921                                 return (string)substr( $entry, 1 );
 922                         } elseif ( $entry === '!NONEXISTENT' ) {
 923                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 924
 925                                 return false;
 926                         } else {
 927                                 # Corrupt/obsolete entry, delete it
 928                                 $this->mMemc->delete( $titleKey );
 929                         }
 930                 }
 931
 932                 # Try loading it from the database
 933                 $revision = Revision::newFromTitle(
 934                         Title::makeTitle( NS_MEDIAWIKI, $title ), false, Revision::READ_LATEST
 935                 );
 936                 if ( $revision ) {
 937                         $content = $revision->getContent();
 938                         if ( !$content ) {
 939                                 // A possibly temporary loading failure.
 940                                 wfDebugLog(
 941                                         'MessageCache',
 942                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
 943                                 );
 944                                 $message = null; // no negative caching
 945                         } else {
 946                                 // XXX: Is this the right way to turn a Content object into a message?
 947                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
 948                                 //       CssContent. MessageContent is *not* used for storing messages, it's
 949                                 //       only used for wrapping them when needed.
 950                                 $message = $content->getWikitextForTransclusion();
 951
 952                                 if ( $message === false || $message === null ) {
 953                                         wfDebugLog(
 954                                                 'MessageCache',
 955                                                 __METHOD__ . ": message content doesn't provide wikitext "
 956                                                         . "(content model: " . $content->getContentHandler() . ")"
 957                                         );
 958
 959                                         $message = false; // negative caching
 960                                 } else {
 961                                         $this->mCache[$code][$title] = ' ' . $message;
 962                                         $this->mMemc->set( $titleKey, ' ' . $message, $this->mExpiry );
 963                                 }
 964                         }
 965                 } else {
 966                         $message = false; // negative caching
 967                 }
 968
 969                 if ( $message === false ) { // negative caching
 970                         $this->mCache[$code][$title] = '!NONEXISTENT';
 971                         $this->mMemc->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
 972                 }
 973
 974                 return $message;
 975         }
 976
 977         /**
 978          * @param string $message
 979          * @param bool $interface
 980          * @param string $language Language code
 981          * @param Title $title
 982          * @return string
 983          */
 984         function transform( $message, $interface = false, $language = null, $title = null ) {
 985                 // Avoid creating parser if nothing to transform
 986                 if ( strpos( $message, '{{' ) === false ) {
 987                         return $message;
 988                 }
 989
 990                 if ( $this->mInParser ) {
 991                         return $message;
 992                 }
 993
 994                 $parser = $this->getParser();
 995                 if ( $parser ) {
 996                         $popts = $this->getParserOptions();
 997                         $popts->setInterfaceMessage( $interface );
 998                         $popts->setTargetLanguage( $language );
 999
1000                         $userlang = $popts->setUserLang( $language );
1001                         $this->mInParser = true;
1002                         $message = $parser->transformMsg( $message, $popts, $title );
1003                         $this->mInParser = false;
1004                         $popts->setUserLang( $userlang );
1005                 }
1006
1007                 return $message;
1008         }
1009
1010         /**
1011          * @return Parser
1012          */
1013         function getParser() {
1014                 global $wgParser, $wgParserConf;
1015                 if ( !$this->mParser && isset( $wgParser ) ) {
1016                         # Do some initialisation so that we don't have to do it twice
1017                         $wgParser->firstCallInit();
1018                         # Clone it and store it
1019                         $class = $wgParserConf['class'];
1020                         if ( $class == 'Parser_DiffTest' ) {
1021                                 # Uncloneable
1022                                 $this->mParser = new $class( $wgParserConf );
1023                         } else {
1024                                 $this->mParser = clone $wgParser;
1025                         }
1026                 }
1027
1028                 return $this->mParser;
1029         }
1030
1031         /**
1032          * @param string $text
1033          * @param Title $title
1034          * @param bool $linestart Whether or not this is at the start of a line
1035          * @param bool $interface Whether this is an interface message
1036          * @param string $language Language code
1037          * @return ParserOutput|string
1038          */
1039         public function parse( $text, $title = null, $linestart = true,
1040                 $interface = false, $language = null
1041         ) {
1042                 if ( $this->mInParser ) {
1043                         return htmlspecialchars( $text );
1044                 }
1045
1046                 $parser = $this->getParser();
1047                 $popts = $this->getParserOptions();
1048                 $popts->setInterfaceMessage( $interface );
1049                 $popts->setTargetLanguage( $language );
1050
1051                 wfProfileIn( __METHOD__ );
1052                 if ( !$title || !$title instanceof Title ) {
1053                         global $wgTitle;
1054                         $title = $wgTitle;
1055                 }
1056                 // Sometimes $wgTitle isn't set either...
1057                 if ( !$title ) {
1058                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1059                         # Create a ghost title in such case
1060                         $title = Title::newFromText( 'Dwimmerlaik' );
1061                 }
1062
1063                 $this->mInParser = true;
1064                 $res = $parser->parse( $text, $title, $popts, $linestart );
1065                 $this->mInParser = false;
1066
1067                 wfProfileOut( __METHOD__ );
1068
1069                 return $res;
1070         }
1071
1072         function disable() {
1073                 $this->mDisable = true;
1074         }
1075
1076         function enable() {
1077                 $this->mDisable = false;
1078         }
1079
1080         /**
1081          * Clear all stored messages. Mainly used after a mass rebuild.
1082          */
1083         function clear() {
1084                 $langs = Language::fetchLanguageNames( null, 'mw' );
1085                 foreach ( array_keys( $langs ) as $code ) {
1086                         # Global cache
1087                         $this->mMemc->delete( wfMemcKey( 'messages', $code ) );
1088                         # Invalidate all local caches
1089                         $this->mMemc->delete( wfMemcKey( 'messages', $code, 'hash' ) );
1090                 }
1091                 $this->mLoadedLanguages = array();
1092         }
1093
1094         /**
1095          * @param $key
1096          * @return array
1097          */
1098         public function figureMessage( $key ) {
1099                 global $wgLanguageCode;
1100                 $pieces = explode( '/', $key );
1101                 if ( count( $pieces ) < 2 ) {
1102                         return array( $key, $wgLanguageCode );
1103                 }
1104
1105                 $lang = array_pop( $pieces );
1106                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1107                         return array( $key, $wgLanguageCode );
1108                 }
1109
1110                 $message = implode( '/', $pieces );
1111
1112                 return array( $message, $lang );
1113         }
1114
1115         /**
1116          * Get all message keys stored in the message cache for a given language.
1117          * If $code is the content language code, this will return all message keys
1118          * for which MediaWiki:msgkey exists. If $code is another language code, this
1119          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1120          * @param string $code Language code
1121          * @return array of message keys (strings)
1122          */
1123         public function getAllMessageKeys( $code ) {
1124                 global $wgContLang;
1125                 $this->load( $code );
1126                 if ( !isset( $this->mCache[$code] ) ) {
1127                         // Apparently load() failed
1128                         return null;
1129                 }
1130                 // Remove administrative keys
1131                 $cache = $this->mCache[$code];
1132                 unset( $cache['VERSION'] );
1133                 unset( $cache['EXPIRY'] );
1134                 // Remove any !NONEXISTENT keys
1135                 $cache = array_diff( $cache, array( '!NONEXISTENT' ) );
1136
1137                 // Keys may appear with a capital first letter. lcfirst them.
1138                 return array_map( array( $wgContLang, 'lcfirst' ), array_keys( $cache ) );
1139         }
1140 }