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 string $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          * @param string $serialized
 196          * @param string $hash
 197          * @param string $code
 198          */
 199         function saveToLocal( $serialized, $hash, $code ) {
 200                 global $wgCacheDirectory;
 201
 202                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 203                 wfMkdirParents( $wgCacheDirectory, null, __METHOD__ ); // might fail
 204
 205                 wfSuppressWarnings();
 206                 $file = fopen( $filename, 'w' );
 207                 wfRestoreWarnings();
 208
 209                 if ( !$file ) {
 210                         wfDebug( "Unable to open local cache file for writing\n" );
 211
 212                         return;
 213                 }
 214
 215                 fwrite( $file, $hash . $serialized );
 216                 fclose( $file );
 217                 wfSuppressWarnings();
 218                 chmod( $filename, 0666 );
 219                 wfRestoreWarnings();
 220         }
 221
 222         /**
 223          * Loads messages from caches or from database in this order:
 224          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 225          * (2) memcached
 226          * (3) from the database.
 227          *
 228          * When succesfully loading from (2) or (3), all higher level caches are
 229          * updated for the newest version.
 230          *
 231          * Nothing is loaded if member variable mDisable is true, either manually
 232          * set by calling code or if message loading fails (is this possible?).
 233          *
 234          * Returns true if cache is already populated or it was succesfully populated,
 235          * or false if populating empty cache fails. Also returns true if MessageCache
 236          * is disabled.
 237          *
 238          * @param bool|string $code Language to which load messages
 239          * @throws MWException
 240          * @return bool
 241          */
 242         function load( $code = false ) {
 243                 global $wgUseLocalMessageCache;
 244
 245                 if ( !is_string( $code ) ) {
 246                         # This isn't really nice, so at least make a note about it and try to
 247                         # fall back
 248                         wfDebug( __METHOD__ . " called without providing a language code\n" );
 249                         $code = 'en';
 250                 }
 251
 252                 # Don't do double loading...
 253                 if ( isset( $this->mLoadedLanguages[$code] ) ) {
 254                         return true;
 255                 }
 256
 257                 # 8 lines of code just to say (once) that message cache is disabled
 258                 if ( $this->mDisable ) {
 259                         static $shownDisabled = false;
 260                         if ( !$shownDisabled ) {
 261                                 wfDebug( __METHOD__ . ": disabled\n" );
 262                                 $shownDisabled = true;
 263                         }
 264
 265                         return true;
 266                 }
 267
 268                 # Loading code starts
 269                 wfProfileIn( __METHOD__ );
 270                 $success = false; # Keep track of success
 271                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 272                 $where = array(); # Debug info, delayed to avoid spamming debug log too much
 273                 $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 274
 275                 # Local cache
 276                 # Hash of the contents is stored in memcache, to detect if local cache goes
 277                 # out of date (e.g. due to replace() on some other server)
 278                 if ( $wgUseLocalMessageCache ) {
 279                         wfProfileIn( __METHOD__ . '-fromlocal' );
 280
 281                         $hash = $this->mMemc->get( wfMemcKey( 'messages', $code, 'hash' ) );
 282                         if ( $hash ) {
 283                                 $cache = $this->getLocalCache( $hash, $code );
 284                                 if ( !$cache ) {
 285                                         $where[] = 'local cache is empty or has the wrong hash';
 286                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 287                                         $where[] = 'local cache is expired';
 288                                         $staleCache = $cache;
 289                                 } else {
 290                                         $where[] = 'got from local cache';
 291                                         $success = true;
 292                                         $this->mCache[$code] = $cache;
 293                                 }
 294                         }
 295                         wfProfileOut( __METHOD__ . '-fromlocal' );
 296                 }
 297
 298                 if ( !$success ) {
 299                         # Try the global cache. If it is empty, try to acquire a lock. If
 300                         # the lock can't be acquired, wait for the other thread to finish
 301                         # and then try the global cache a second time.
 302                         for ( $failedAttempts = 0; $failedAttempts < 2; $failedAttempts++ ) {
 303                                 wfProfileIn( __METHOD__ . '-fromcache' );
 304                                 $cache = $this->mMemc->get( $cacheKey );
 305                                 if ( !$cache ) {
 306                                         $where[] = 'global cache is empty';
 307                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 308                                         $where[] = 'global cache is expired';
 309                                         $staleCache = $cache;
 310                                 } else {
 311                                         $where[] = 'got from global cache';
 312                                         $this->mCache[$code] = $cache;
 313                                         $this->saveToCaches( $cache, 'local-only', $code );
 314                                         $success = true;
 315                                 }
 316
 317                                 wfProfileOut( __METHOD__ . '-fromcache' );
 318
 319                                 if ( $success ) {
 320                                         # Done, no need to retry
 321                                         break;
 322                                 }
 323
 324                                 # We need to call loadFromDB. Limit the concurrency to a single
 325                                 # process. This prevents the site from going down when the cache
 326                                 # expires.
 327                                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 328                                 $acquired = $this->mMemc->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT );
 329                                 if ( $acquired ) {
 330                                         # Unlock the status key if there is an exception
 331                                         $that = $this;
 332                                         $statusUnlocker = new ScopedCallback( function () use ( $that, $statusKey ) {
 333                                                 $that->mMemc->delete( $statusKey );
 334                                         } );
 335
 336                                         # Now let's regenerate
 337                                         $where[] = 'loading from database';
 338
 339                                         # Lock the cache to prevent conflicting writes
 340                                         # If this lock fails, it doesn't really matter, it just means the
 341                                         # write is potentially non-atomic, e.g. the results of a replace()
 342                                         # may be discarded.
 343                                         if ( $this->lock( $cacheKey ) ) {
 344                                                 $mainUnlocker = new ScopedCallback( function () use ( $that, $cacheKey ) {
 345                                                         $that->unlock( $cacheKey );
 346                                                 } );
 347                                         } else {
 348                                                 $mainUnlocker = null;
 349                                                 $where[] = 'could not acquire main lock';
 350                                         }
 351
 352                                         $cache = $this->loadFromDB( $code );
 353                                         $this->mCache[$code] = $cache;
 354                                         $success = true;
 355                                         $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 356
 357                                         # Unlock
 358                                         ScopedCallback::consume( $mainUnlocker );
 359                                         ScopedCallback::consume( $statusUnlocker );
 360
 361                                         if ( !$saveSuccess ) {
 362                                                 # Cache save has failed.
 363                                                 # There are two main scenarios where this could be a problem:
 364                                                 #
 365                                                 #   - The cache is more than the maximum size (typically
 366                                                 #     1MB compressed).
 367                                                 #
 368                                                 #   - Memcached has no space remaining in the relevant slab
 369                                                 #     class. This is unlikely with recent versions of
 370                                                 #     memcached.
 371                                                 #
 372                                                 # Either way, if there is a local cache, nothing bad will
 373                                                 # happen. If there is no local cache, disabling the message
 374                                                 # cache for all requests avoids incurring a loadFromDB()
 375                                                 # overhead on every request, and thus saves the wiki from
 376                                                 # complete downtime under moderate traffic conditions.
 377                                                 if ( !$wgUseLocalMessageCache ) {
 378                                                         $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 379                                                         $where[] = 'could not save cache, disabled globally for 5 minutes';
 380                                                 } else {
 381                                                         $where[] = "could not save global cache";
 382                                                 }
 383                                         }
 384
 385                                         # Load from DB complete, no need to retry
 386                                         break;
 387                                 } elseif ( $staleCache ) {
 388                                         # Use the stale cache while some other thread constructs the new one
 389                                         $where[] = 'using stale cache';
 390                                         $this->mCache[$code] = $staleCache;
 391                                         $success = true;
 392                                         break;
 393                                 } elseif ( $failedAttempts > 0 ) {
 394                                         # Already retried once, still failed, so don't do another lock/unlock cycle
 395                                         # This case will typically be hit if memcached is down, or if
 396                                         # loadFromDB() takes longer than MSG_WAIT_TIMEOUT
 397                                         $where[] = "could not acquire status key.";
 398                                         break;
 399                                 } else {
 400                                         $status = $this->mMemc->get( $statusKey );
 401                                         if ( $status === 'error' ) {
 402                                                 # Disable cache
 403                                                 break;
 404                                         } else {
 405                                                 # Wait for the other thread to finish, then retry
 406                                                 $where[] = 'waited for other thread to complete';
 407                                                 $this->lock( $cacheKey );
 408                                                 $this->unlock( $cacheKey );
 409                                         }
 410                                 }
 411                         }
 412                 }
 413
 414                 if ( !$success ) {
 415                         $where[] = 'loading FAILED - cache is disabled';
 416                         $this->mDisable = true;
 417                         $this->mCache = false;
 418                         # This used to throw an exception, but that led to nasty side effects like
 419                         # the whole wiki being instantly down if the memcached server died
 420                 } else {
 421                         # All good, just record the success
 422                         $this->mLoadedLanguages[$code] = true;
 423                 }
 424                 $info = implode( ', ', $where );
 425                 wfDebug( __METHOD__ . ": Loading $code... $info\n" );
 426                 wfProfileOut( __METHOD__ );
 427
 428                 return $success;
 429         }
 430
 431         /**
 432          * Loads cacheable messages from the database. Messages bigger than
 433          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 434          * on-demand from the database later.
 435          *
 436          * @param string $code Language code.
 437          * @return array Loaded messages for storing in caches.
 438          */
 439         function loadFromDB( $code ) {
 440                 wfProfileIn( __METHOD__ );
 441                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 442                 $dbr = wfGetDB( DB_SLAVE );
 443                 $cache = array();
 444
 445                 # Common conditions
 446                 $conds = array(
 447                         'page_is_redirect' => 0,
 448                         'page_namespace' => NS_MEDIAWIKI,
 449                 );
 450
 451                 $mostused = array();
 452                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 453                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 454                                 $this->load( $wgLanguageCode );
 455                         }
 456                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 457                         foreach ( $mostused as $key => $value ) {
 458                                 $mostused[$key] = "$value/$code";
 459                         }
 460                 }
 461
 462                 if ( count( $mostused ) ) {
 463                         $conds['page_title'] = $mostused;
 464                 } elseif ( $code !== $wgLanguageCode ) {
 465                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 466                 } else {
 467                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 468                         # other than language code.
 469                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 470                 }
 471
 472                 # Conditions to fetch oversized pages to ignore them
 473                 $bigConds = $conds;
 474                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 475
 476                 # Load titles for all oversized pages in the MediaWiki namespace
 477                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 478                 foreach ( $res as $row ) {
 479                         $cache[$row->page_title] = '!TOO BIG';
 480                 }
 481
 482                 # Conditions to load the remaining pages with their contents
 483                 $smallConds = $conds;
 484                 $smallConds[] = 'page_latest=rev_id';
 485                 $smallConds[] = 'rev_text_id=old_id';
 486                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 487
 488                 $res = $dbr->select(
 489                         array( 'page', 'revision', 'text' ),
 490                         array( 'page_title', 'old_text', 'old_flags' ),
 491                         $smallConds,
 492                         __METHOD__ . "($code)-small"
 493                 );
 494
 495                 foreach ( $res as $row ) {
 496                         $text = Revision::getRevisionText( $row );
 497                         if ( $text === false ) {
 498                                 // Failed to fetch data; possible ES errors?
 499                                 // Store a marker to fetch on-demand as a workaround...
 500                                 $entry = '!TOO BIG';
 501                                 wfDebugLog(
 502                                         'MessageCache',
 503                                         __METHOD__
 504                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 505                                 );
 506                         } else {
 507                                 $entry = ' ' . $text;
 508                         }
 509                         $cache[$row->page_title] = $entry;
 510                 }
 511
 512                 $cache['VERSION'] = MSG_CACHE_VERSION;
 513                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 514                 wfProfileOut( __METHOD__ );
 515
 516                 return $cache;
 517         }
 518
 519         /**
 520          * Updates cache as necessary when message page is changed
 521          *
 522          * @param string $title Name of the page changed.
 523          * @param mixed $text New contents of the page.
 524          */
 525         public function replace( $title, $text ) {
 526                 global $wgMaxMsgCacheEntrySize;
 527                 wfProfileIn( __METHOD__ );
 528
 529                 if ( $this->mDisable ) {
 530                         wfProfileOut( __METHOD__ );
 531
 532                         return;
 533                 }
 534
 535                 list( $msg, $code ) = $this->figureMessage( $title );
 536
 537                 $cacheKey = wfMemcKey( 'messages', $code );
 538                 $this->load( $code );
 539                 $this->lock( $cacheKey );
 540
 541                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 542
 543                 if ( $text === false ) {
 544                         # Article was deleted
 545                         $this->mCache[$code][$title] = '!NONEXISTENT';
 546                         $this->mMemc->delete( $titleKey );
 547                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 548                         # Check for size
 549                         $this->mCache[$code][$title] = '!TOO BIG';
 550                         $this->mMemc->set( $titleKey, ' ' . $text, $this->mExpiry );
 551                 } else {
 552                         $this->mCache[$code][$title] = ' ' . $text;
 553                         $this->mMemc->delete( $titleKey );
 554                 }
 555
 556                 # Update caches
 557                 $this->saveToCaches( $this->mCache[$code], 'all', $code );
 558                 $this->unlock( $cacheKey );
 559
 560                 // Also delete cached sidebar... just in case it is affected
 561                 $codes = array( $code );
 562                 if ( $code === 'en' ) {
 563                         // Delete all sidebars, like for example on action=purge on the
 564                         // sidebar messages
 565                         $codes = array_keys( Language::fetchLanguageNames() );
 566                 }
 567
 568                 global $wgMemc;
 569                 foreach ( $codes as $code ) {
 570                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 571                         $wgMemc->delete( $sidebarKey );
 572                 }
 573
 574                 // Update the message in the message blob store
 575                 global $wgContLang;
 576                 MessageBlobStore::getInstance()->updateMessage( $wgContLang->lcfirst( $msg ) );
 577
 578                 wfRunHooks( 'MessageCacheReplace', array( $title, $text ) );
 579
 580                 wfProfileOut( __METHOD__ );
 581         }
 582
 583         /**
 584          * Is the given cache array expired due to time passing or a version change?
 585          *
 586          * @param array $cache
 587          * @return bool
 588          */
 589         protected function isCacheExpired( $cache ) {
 590                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 591                         return true;
 592                 }
 593                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 594                         return true;
 595                 }
 596                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 597                         return true;
 598                 }
 599
 600                 return false;
 601         }
 602
 603         /**
 604          * Shortcut to update caches.
 605          *
 606          * @param array $cache Cached messages with a version.
 607          * @param string $dest Either "local-only" to save to local caches only
 608          *   or "all" to save to all caches.
 609          * @param string|bool $code Language code (default: false)
 610          * @return bool
 611          */
 612         protected function saveToCaches( $cache, $dest, $code = false ) {
 613                 wfProfileIn( __METHOD__ );
 614                 global $wgUseLocalMessageCache;
 615
 616                 $cacheKey = wfMemcKey( 'messages', $code );
 617
 618                 if ( $dest === 'all' ) {
 619                         $success = $this->mMemc->set( $cacheKey, $cache );
 620                 } else {
 621                         $success = true;
 622                 }
 623
 624                 # Save to local cache
 625                 if ( $wgUseLocalMessageCache ) {
 626                         $serialized = serialize( $cache );
 627                         $hash = md5( $serialized );
 628                         $this->mMemc->set( wfMemcKey( 'messages', $code, 'hash' ), $hash );
 629                         $this->saveToLocal( $serialized, $hash, $code );
 630                 }
 631
 632                 wfProfileOut( __METHOD__ );
 633
 634                 return $success;
 635         }
 636
 637         /**
 638          * Represents a write lock on the messages key.
 639          *
 640          * Will retry MessageCache::MSG_WAIT_TIMEOUT times, each operations having
 641          * a timeout of MessageCache::MSG_LOCK_TIMEOUT.
 642          *
 643          * @param string $key
 644          * @return bool Success
 645          */
 646         function lock( $key ) {
 647                 $lockKey = $key . ':lock';
 648                 $acquired = false;
 649                 $testDone = false;
 650                 for ( $i = 0; $i < MSG_WAIT_TIMEOUT && !$acquired; $i++ ) {
 651                         $acquired = $this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT );
 652                         if ( $acquired ) {
 653                                 break;
 654                         }
 655
 656                         # Fail fast if memcached is totally down
 657                         if ( !$testDone ) {
 658                                 $testDone = true;
 659                                 if ( !$this->mMemc->set( wfMemcKey( 'test' ), 'test', 1 ) ) {
 660                                         break;
 661                                 }
 662                         }
 663                         sleep( 1 );
 664                 }
 665
 666                 return $acquired;
 667         }
 668
 669         function unlock( $key ) {
 670                 $lockKey = $key . ':lock';
 671                 $this->mMemc->delete( $lockKey );
 672         }
 673
 674         /**
 675          * Get a message from either the content language or the user language.
 676          *
 677          * First, assemble a list of languages to attempt getting the message from. This
 678          * chain begins with the requested language and its fallbacks and then continues with
 679          * the content language and its fallbacks. For each language in the chain, the following
 680          * process will occur (in this order):
 681          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 682          *     Note: for the content language, there is no /lang subpage.
 683          *  2. Fetch from the static CDB cache.
 684          *  3. If available, check the database for fallback language overrides.
 685          *
 686          * This process provides a number of guarantees. When changing this code, make sure all
 687          * of these guarantees are preserved.
 688          *  * If the requested language is *not* the content language, then the CDB cache for that
 689          *    specific language will take precedence over the root database page ([[MW:msg]]).
 690          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 691          *    the message is available *anywhere* in the language for which it is a fallback.
 692          *
 693          * @param string $key The message key
 694          * @param bool $useDB If true, look for the message in the DB, false
 695          *   to use only the compiled l10n cache.
 696          * @param bool|string|object $langcode Code of the language to get the message for.
 697          *   - If string and a valid code, will create a standard language object
 698          *   - If string but not a valid code, will create a basic language object
 699          *   - If boolean and false, create object from the current users language
 700          *   - If boolean and true, create object from the wikis content language
 701          *   - If language object, use it as given
 702          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 703          *
 704          * @throws MWException When given an invalid key
 705          * @return string|bool False if the message doesn't exist, otherwise the
 706          *   message (which can be empty)
 707          */
 708         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 709                 global $wgContLang;
 710
 711                 $section = new ProfileSection( __METHOD__ );
 712
 713                 if ( is_int( $key ) ) {
 714                         // Fix numerical strings that somehow become ints
 715                         // on their way here
 716                         $key = (string)$key;
 717                 } elseif ( !is_string( $key ) ) {
 718                         throw new MWException( 'Non-string key given' );
 719                 } elseif ( $key === '' ) {
 720                         // Shortcut: the empty key is always missing
 721                         return false;
 722                 }
 723
 724                 // For full keys, get the language code from the key
 725                 $pos = strrpos( $key, '/' );
 726                 if ( $isFullKey && $pos !== false ) {
 727                         $langcode = substr( $key, $pos + 1 );
 728                         $key = substr( $key, 0, $pos );
 729                 }
 730
 731                 // Normalise title-case input (with some inlining)
 732                 $lckey = strtr( $key, ' ', '_' );
 733                 if ( ord( $lckey ) < 128 ) {
 734                         $lckey[0] = strtolower( $lckey[0] );
 735                 } else {
 736                         $lckey = $wgContLang->lcfirst( $lckey );
 737                 }
 738
 739                 wfRunHooks( 'MessageCache::get', array( &$lckey ) );
 740
 741                 if ( ord( $lckey ) < 128 ) {
 742                         $uckey = ucfirst( $lckey );
 743                 } else {
 744                         $uckey = $wgContLang->ucfirst( $lckey );
 745                 }
 746
 747                 // Loop through each language in the fallback list until we find something useful
 748                 $lang = wfGetLangObj( $langcode );
 749                 $message = $this->getMessageFromFallbackChain(
 750                         $lang,
 751                         $lckey,
 752                         $uckey,
 753                         !$this->mDisable && $useDB
 754                 );
 755
 756                 // If we still have no message, maybe the key was in fact a full key so try that
 757                 if ( $message === false ) {
 758                         $parts = explode( '/', $lckey );
 759                         // We may get calls for things that are http-urls from sidebar
 760                         // Let's not load nonexistent languages for those
 761                         // They usually have more than one slash.
 762                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 763                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 764                                 if ( $message === null ) {
 765                                         $message = false;
 766                                 }
 767                         }
 768                 }
 769
 770                 // Post-processing if the message exists
 771                 if ( $message !== false ) {
 772                         // Fix whitespace
 773                         $message = str_replace(
 774                                 array(
 775                                         # Fix for trailing whitespace, removed by textarea
 776                                         '&#32;',
 777                                         # Fix for NBSP, converted to space by firefox
 778                                         '&nbsp;',
 779                                         '&#160;',
 780                                 ),
 781                                 array(
 782                                         ' ',
 783                                         "\xc2\xa0",
 784                                         "\xc2\xa0"
 785                                 ),
 786                                 $message
 787                         );
 788                 }
 789
 790                 return $message;
 791         }
 792
 793         /**
 794          * Given a language, try and fetch a message from that language, then the
 795          * fallbacks of that language, then the site language, then the fallbacks for the
 796          * site language.
 797          *
 798          * @param Language $lang Requested language
 799          * @param string $lckey Lowercase key for the message
 800          * @param string $uckey Uppercase key for the message
 801          * @param bool $useDB Whether to use the database
 802          *
 803          * @see MessageCache::get
 804          * @return string|bool The message, or false if not found
 805          */
 806         protected function getMessageFromFallbackChain( $lang, $lckey, $uckey, $useDB ) {
 807                 global $wgLanguageCode, $wgContLang;
 808
 809                 $langcode = $lang->getCode();
 810                 $message = false;
 811
 812                 // First try the requested language.
 813                 if ( $useDB ) {
 814                         if ( $langcode === $wgLanguageCode ) {
 815                                 // Messages created in the content language will not have the /lang extension
 816                                 $message = $this->getMsgFromNamespace( $uckey, $langcode );
 817                         } else {
 818                                 $message = $this->getMsgFromNamespace( "$uckey/$langcode", $langcode );
 819                         }
 820                 }
 821
 822                 if ( $message !== false ) {
 823                         return $message;
 824                 }
 825
 826                 // Check the CDB cache
 827                 $message = $lang->getMessage( $lckey );
 828                 if ( $message !== null ) {
 829                         return $message;
 830                 }
 831
 832                 list( $fallbackChain, $siteFallbackChain ) =
 833                         Language::getFallbacksIncludingSiteLanguage( $langcode );
 834
 835                 // Next try checking the database for all of the fallback languages of the requested language.
 836                 if ( $useDB ) {
 837                         foreach ( $fallbackChain as $code ) {
 838                                 if ( $code === $wgLanguageCode ) {
 839                                         // Messages created in the content language will not have the /lang extension
 840                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 841                                 } else {
 842                                         $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 843                                 }
 844
 845                                 if ( $message !== false ) {
 846                                         // Found the message.
 847                                         return $message;
 848                                 }
 849                         }
 850                 }
 851
 852                 // Now try checking the site language.
 853                 if ( $useDB ) {
 854                         $message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
 855                         if ( $message !== false ) {
 856                                 return $message;
 857                         }
 858                 }
 859
 860                 $message = $wgContLang->getMessage( $lckey );
 861                 if ( $message !== null ) {
 862                         return $message;
 863                 }
 864
 865                 // Finally try the DB for the site language's fallbacks.
 866                 if ( $useDB ) {
 867                         foreach ( $siteFallbackChain as $code ) {
 868                                 $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 869                                 if ( $message === false && $code === $wgLanguageCode ) {
 870                                         // Messages created in the content language will not have the /lang extension
 871                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 872                                 }
 873
 874                                 if ( $message !== false ) {
 875                                         // Found the message.
 876                                         return $message;
 877                                 }
 878                         }
 879                 }
 880
 881                 return false;
 882         }
 883
 884         /**
 885          * Get a message from the MediaWiki namespace, with caching. The key must
 886          * first be converted to two-part lang/msg form if necessary.
 887          *
 888          * Unlike self::get(), this function doesn't resolve fallback chains, and
 889          * some callers require this behavior. LanguageConverter::parseCachedTable()
 890          * and self::get() are some examples in core.
 891          *
 892          * @param string $title Message cache key with initial uppercase letter.
 893          * @param string $code Code denoting the language to try.
 894          * @return string|bool The message, or false if it does not exist or on error
 895          */
 896         function getMsgFromNamespace( $title, $code ) {
 897                 $this->load( $code );
 898                 if ( isset( $this->mCache[$code][$title] ) ) {
 899                         $entry = $this->mCache[$code][$title];
 900                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 901                                 // The message exists, so make sure a string
 902                                 // is returned.
 903                                 return (string)substr( $entry, 1 );
 904                         } elseif ( $entry === '!NONEXISTENT' ) {
 905                                 return false;
 906                         } elseif ( $entry === '!TOO BIG' ) {
 907                                 // Fall through and try invididual message cache below
 908                         }
 909                 } else {
 910                         // XXX: This is not cached in process cache, should it?
 911                         $message = false;
 912                         wfRunHooks( 'MessagesPreLoad', array( $title, &$message ) );
 913                         if ( $message !== false ) {
 914                                 return $message;
 915                         }
 916
 917                         return false;
 918                 }
 919
 920                 # Try the individual message cache
 921                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 922                 $entry = $this->mMemc->get( $titleKey );
 923                 if ( $entry ) {
 924                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 925                                 $this->mCache[$code][$title] = $entry;
 926
 927                                 // The message exists, so make sure a string
 928                                 // is returned.
 929                                 return (string)substr( $entry, 1 );
 930                         } elseif ( $entry === '!NONEXISTENT' ) {
 931                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 932
 933                                 return false;
 934                         } else {
 935                                 # Corrupt/obsolete entry, delete it
 936                                 $this->mMemc->delete( $titleKey );
 937                         }
 938                 }
 939
 940                 # Try loading it from the database
 941                 $revision = Revision::newFromTitle(
 942                         Title::makeTitle( NS_MEDIAWIKI, $title ), false, Revision::READ_LATEST
 943                 );
 944                 if ( $revision ) {
 945                         $content = $revision->getContent();
 946                         if ( !$content ) {
 947                                 // A possibly temporary loading failure.
 948                                 wfDebugLog(
 949                                         'MessageCache',
 950                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
 951                                 );
 952                                 $message = null; // no negative caching
 953                         } else {
 954                                 // XXX: Is this the right way to turn a Content object into a message?
 955                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
 956                                 //       CssContent. MessageContent is *not* used for storing messages, it's
 957                                 //       only used for wrapping them when needed.
 958                                 $message = $content->getWikitextForTransclusion();
 959
 960                                 if ( $message === false || $message === null ) {
 961                                         wfDebugLog(
 962                                                 'MessageCache',
 963                                                 __METHOD__ . ": message content doesn't provide wikitext "
 964                                                         . "(content model: " . $content->getContentHandler() . ")"
 965                                         );
 966
 967                                         $message = false; // negative caching
 968                                 } else {
 969                                         $this->mCache[$code][$title] = ' ' . $message;
 970                                         $this->mMemc->set( $titleKey, ' ' . $message, $this->mExpiry );
 971                                 }
 972                         }
 973                 } else {
 974                         $message = false; // negative caching
 975                 }
 976
 977                 if ( $message === false ) { // negative caching
 978                         $this->mCache[$code][$title] = '!NONEXISTENT';
 979                         $this->mMemc->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
 980                 }
 981
 982                 return $message;
 983         }
 984
 985         /**
 986          * @param string $message
 987          * @param bool $interface
 988          * @param string $language Language code
 989          * @param Title $title
 990          * @return string
 991          */
 992         function transform( $message, $interface = false, $language = null, $title = null ) {
 993                 // Avoid creating parser if nothing to transform
 994                 if ( strpos( $message, '{{' ) === false ) {
 995                         return $message;
 996                 }
 997
 998                 if ( $this->mInParser ) {
 999                         return $message;
1000                 }
1001
1002                 $parser = $this->getParser();
1003                 if ( $parser ) {
1004                         $popts = $this->getParserOptions();
1005                         $popts->setInterfaceMessage( $interface );
1006                         $popts->setTargetLanguage( $language );
1007
1008                         $userlang = $popts->setUserLang( $language );
1009                         $this->mInParser = true;
1010                         $message = $parser->transformMsg( $message, $popts, $title );
1011                         $this->mInParser = false;
1012                         $popts->setUserLang( $userlang );
1013                 }
1014
1015                 return $message;
1016         }
1017
1018         /**
1019          * @return Parser
1020          */
1021         function getParser() {
1022                 global $wgParser, $wgParserConf;
1023                 if ( !$this->mParser && isset( $wgParser ) ) {
1024                         # Do some initialisation so that we don't have to do it twice
1025                         $wgParser->firstCallInit();
1026                         # Clone it and store it
1027                         $class = $wgParserConf['class'];
1028                         if ( $class == 'ParserDiffTest' ) {
1029                                 # Uncloneable
1030                                 $this->mParser = new $class( $wgParserConf );
1031                         } else {
1032                                 $this->mParser = clone $wgParser;
1033                         }
1034                 }
1035
1036                 return $this->mParser;
1037         }
1038
1039         /**
1040          * @param string $text
1041          * @param Title $title
1042          * @param bool $linestart Whether or not this is at the start of a line
1043          * @param bool $interface Whether this is an interface message
1044          * @param string $language Language code
1045          * @return ParserOutput|string
1046          */
1047         public function parse( $text, $title = null, $linestart = true,
1048                 $interface = false, $language = null
1049         ) {
1050                 if ( $this->mInParser ) {
1051                         return htmlspecialchars( $text );
1052                 }
1053
1054                 $parser = $this->getParser();
1055                 $popts = $this->getParserOptions();
1056                 $popts->setInterfaceMessage( $interface );
1057                 $popts->setTargetLanguage( $language );
1058
1059                 wfProfileIn( __METHOD__ );
1060                 if ( !$title || !$title instanceof Title ) {
1061                         global $wgTitle;
1062                         $title = $wgTitle;
1063                 }
1064                 // Sometimes $wgTitle isn't set either...
1065                 if ( !$title ) {
1066                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1067                         # Create a ghost title in such case
1068                         $title = Title::newFromText( 'Dwimmerlaik' );
1069                 }
1070
1071                 $this->mInParser = true;
1072                 $res = $parser->parse( $text, $title, $popts, $linestart );
1073                 $this->mInParser = false;
1074
1075                 wfProfileOut( __METHOD__ );
1076
1077                 return $res;
1078         }
1079
1080         function disable() {
1081                 $this->mDisable = true;
1082         }
1083
1084         function enable() {
1085                 $this->mDisable = false;
1086         }
1087
1088         /**
1089          * Clear all stored messages. Mainly used after a mass rebuild.
1090          */
1091         function clear() {
1092                 $langs = Language::fetchLanguageNames( null, 'mw' );
1093                 foreach ( array_keys( $langs ) as $code ) {
1094                         # Global cache
1095                         $this->mMemc->delete( wfMemcKey( 'messages', $code ) );
1096                         # Invalidate all local caches
1097                         $this->mMemc->delete( wfMemcKey( 'messages', $code, 'hash' ) );
1098                 }
1099                 $this->mLoadedLanguages = array();
1100         }
1101
1102         /**
1103          * @param string $key
1104          * @return array
1105          */
1106         public function figureMessage( $key ) {
1107                 global $wgLanguageCode;
1108                 $pieces = explode( '/', $key );
1109                 if ( count( $pieces ) < 2 ) {
1110                         return array( $key, $wgLanguageCode );
1111                 }
1112
1113                 $lang = array_pop( $pieces );
1114                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1115                         return array( $key, $wgLanguageCode );
1116                 }
1117
1118                 $message = implode( '/', $pieces );
1119
1120                 return array( $message, $lang );
1121         }
1122
1123         /**
1124          * Get all message keys stored in the message cache for a given language.
1125          * If $code is the content language code, this will return all message keys
1126          * for which MediaWiki:msgkey exists. If $code is another language code, this
1127          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1128          * @param string $code Language code
1129          * @return array Array of message keys (strings)
1130          */
1131         public function getAllMessageKeys( $code ) {
1132                 global $wgContLang;
1133                 $this->load( $code );
1134                 if ( !isset( $this->mCache[$code] ) ) {
1135                         // Apparently load() failed
1136                         return null;
1137                 }
1138                 // Remove administrative keys
1139                 $cache = $this->mCache[$code];
1140                 unset( $cache['VERSION'] );
1141                 unset( $cache['EXPIRY'] );
1142                 // Remove any !NONEXISTENT keys
1143                 $cache = array_diff( $cache, array( '!NONEXISTENT' ) );
1144
1145                 // Keys may appear with a capital first letter. lcfirst them.
1146                 return array_map( array( $wgContLang, 'lcfirst' ), array_keys( $cache ) );
1147         }
1148 }