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', 2 );
  29
  30 /**
  31  * Message cache
  32  * Performs various MediaWiki namespace-related functions
  33  * @ingroup Cache
  34  */
  35 class MessageCache {
  36         const FOR_UPDATE = 1; // force message reload
  37
  38         /** How long to wait for memcached locks */
  39         const WAIT_SEC = 15;
  40         /** How long memcached locks last */
  41         const LOCK_TTL = 30;
  42
  43         /**
  44          * Process local cache of loaded messages that are defined in
  45          * MediaWiki namespace. First array level is a language code,
  46          * second level is message key and the values are either message
  47          * content prefixed with space, or !NONEXISTENT for negative
  48          * caching.
  49          * @var array $mCache
  50          */
  51         protected $mCache;
  52
  53         /**
  54          * Should  mean that database cannot be used, but check
  55          * @var bool $mDisable
  56          */
  57         protected $mDisable;
  58
  59         /**
  60          * Lifetime for cache, used by object caching.
  61          * Set on construction, see __construct().
  62          */
  63         protected $mExpiry;
  64
  65         /**
  66          * Message cache has its own parser which it uses to transform
  67          * messages.
  68          */
  69         protected $mParserOptions, $mParser;
  70
  71         /**
  72          * Variable for tracking which variables are already loaded
  73          * @var array $mLoadedLanguages
  74          */
  75         protected $mLoadedLanguages = array();
  76
  77         /**
  78          * @var bool $mInParser
  79          */
  80         protected $mInParser = false;
  81
  82         /** @var BagOStuff */
  83         protected $mMemc;
  84         /** @var WANObjectCache */
  85         protected $wanCache;
  86
  87         /**
  88          * Singleton instance
  89          *
  90          * @var MessageCache $instance
  91          */
  92         private static $instance;
  93
  94         /**
  95          * Get the signleton instance of this class
  96          *
  97          * @since 1.18
  98          * @return MessageCache
  99          */
 100         public static function singleton() {
 101                 if ( is_null( self::$instance ) ) {
 102                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
 103                         self::$instance = new self(
 104                                 wfGetMessageCacheStorage(),
 105                                 $wgUseDatabaseMessages,
 106                                 $wgMsgCacheExpiry
 107                         );
 108                 }
 109
 110                 return self::$instance;
 111         }
 112
 113         /**
 114          * Destroy the singleton instance
 115          *
 116          * @since 1.18
 117          */
 118         public static function destroyInstance() {
 119                 self::$instance = null;
 120         }
 121
 122         /**
 123          * Normalize message key input
 124          *
 125          * @param string $key Input message key to be normalized
 126          * @return string Normalized message key
 127          */
 128         public static function normalizeKey( $key ) {
 129                 global $wgContLang;
 130                 $lckey = strtr( $key, ' ', '_' );
 131                 if ( ord( $lckey ) < 128 ) {
 132                         $lckey[0] = strtolower( $lckey[0] );
 133                 } else {
 134                         $lckey = $wgContLang->lcfirst( $lckey );
 135                 }
 136
 137                 return $lckey;
 138         }
 139
 140         /**
 141          * @param BagOStuff $memCached A cache instance. If none, fall back to CACHE_NONE.
 142          * @param bool $useDB
 143          * @param int $expiry Lifetime for cache. @see $mExpiry.
 144          */
 145         function __construct( $memCached, $useDB, $expiry ) {
 146                 global $wgUseLocalMessageCache;
 147
 148                 if ( !$memCached ) {
 149                         $memCached = wfGetCache( CACHE_NONE );
 150                 }
 151
 152                 $this->mMemc = $memCached;
 153                 $this->mDisable = !$useDB;
 154                 $this->mExpiry = $expiry;
 155
 156                 if ( $wgUseLocalMessageCache ) {
 157                         $this->localCache = ObjectCache::getLocalServerInstance( CACHE_NONE );
 158                 } else {
 159                         $this->localCache = wfGetCache( CACHE_NONE );
 160                 }
 161
 162                 $this->wanCache = ObjectCache::getMainWANInstance();
 163         }
 164
 165         /**
 166          * ParserOptions is lazy initialised.
 167          *
 168          * @return ParserOptions
 169          */
 170         function getParserOptions() {
 171                 if ( !$this->mParserOptions ) {
 172                         $this->mParserOptions = new ParserOptions;
 173                         $this->mParserOptions->setEditSection( false );
 174                 }
 175
 176                 return $this->mParserOptions;
 177         }
 178
 179         /**
 180          * Try to load the cache from APC.
 181          *
 182          * @param string $code Optional language code, see documenation of load().
 183          * @return array|bool The cache array, or false if not in cache.
 184          */
 185         protected function getLocalCache( $code ) {
 186                 $cacheKey = wfMemcKey( __CLASS__, $code );
 187
 188                 return $this->localCache->get( $cacheKey );
 189         }
 190
 191         /**
 192          * Save the cache to APC.
 193          *
 194          * @param string $code
 195          * @param array $cache The cache array
 196          */
 197         protected function saveToLocalCache( $code, $cache ) {
 198                 $cacheKey = wfMemcKey( __CLASS__, $code );
 199                 $this->localCache->set( $cacheKey, $cache );
 200         }
 201
 202         /**
 203          * Loads messages from caches or from database in this order:
 204          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 205          * (2) memcached
 206          * (3) from the database.
 207          *
 208          * When succesfully loading from (2) or (3), all higher level caches are
 209          * updated for the newest version.
 210          *
 211          * Nothing is loaded if member variable mDisable is true, either manually
 212          * set by calling code or if message loading fails (is this possible?).
 213          *
 214          * Returns true if cache is already populated or it was succesfully populated,
 215          * or false if populating empty cache fails. Also returns true if MessageCache
 216          * is disabled.
 217          *
 218          * @param bool|string $code Language to which load messages
 219          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 220          * @throws MWException
 221          * @return bool
 222          */
 223         function load( $code = false, $mode = null ) {
 224                 if ( !is_string( $code ) ) {
 225                         # This isn't really nice, so at least make a note about it and try to
 226                         # fall back
 227                         wfDebug( __METHOD__ . " called without providing a language code\n" );
 228                         $code = 'en';
 229                 }
 230
 231                 # Don't do double loading...
 232                 if ( isset( $this->mLoadedLanguages[$code] ) && $mode != self::FOR_UPDATE ) {
 233                         return true;
 234                 }
 235
 236                 # 8 lines of code just to say (once) that message cache is disabled
 237                 if ( $this->mDisable ) {
 238                         static $shownDisabled = false;
 239                         if ( !$shownDisabled ) {
 240                                 wfDebug( __METHOD__ . ": disabled\n" );
 241                                 $shownDisabled = true;
 242                         }
 243
 244                         return true;
 245                 }
 246
 247                 # Loading code starts
 248                 $success = false; # Keep track of success
 249                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 250                 $where = array(); # Debug info, delayed to avoid spamming debug log too much
 251
 252                 # Hash of the contents is stored in memcache, to detect if data-center cache
 253                 # or local cache goes out of date (e.g. due to replace() on some other server)
 254                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 255
 256                 # Try the local cache and check against the cluster hash key...
 257                 $cache = $this->getLocalCache( $code );
 258                 if ( !$cache ) {
 259                         $where[] = 'local cache is empty';
 260                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 261                         $where[] = 'local cache has the wrong hash';
 262                         $staleCache = $cache;
 263                 } elseif ( $this->isCacheExpired( $cache ) ) {
 264                         $where[] = 'local cache is expired';
 265                         $staleCache = $cache;
 266                 } elseif ( $hashVolatile ) {
 267                         $where[] = 'local cache validation key is expired/volatile';
 268                         $staleCache = $cache;
 269                 } else {
 270                         $where[] = 'got from local cache';
 271                         $success = true;
 272                         $this->mCache[$code] = $cache;
 273                 }
 274
 275                 if ( !$success ) {
 276                         $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 277                         # Try the global cache. If it is empty, try to acquire a lock. If
 278                         # the lock can't be acquired, wait for the other thread to finish
 279                         # and then try the global cache a second time.
 280                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 281                                 if ( $hashVolatile && $staleCache ) {
 282                                         # Do not bother fetching the whole cache blob to avoid I/O.
 283                                         # Instead, just try to get the non-blocking $statusKey lock
 284                                         # below, and use the local stale value if it was not acquired.
 285                                         $where[] = 'global cache is presumed expired';
 286                                 } else {
 287                                         $cache = $this->mMemc->get( $cacheKey );
 288                                         if ( !$cache ) {
 289                                                 $where[] = 'global cache is empty';
 290                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 291                                                 $where[] = 'global cache is expired';
 292                                                 $staleCache = $cache;
 293                                         } elseif ( $hashVolatile ) {
 294                                                 # DB results are slave lag prone until the holdoff TTL passes.
 295                                                 # By then, updates should be reflected in loadFromDBWithLock().
 296                                                 # One thread renerates the cache while others use old values.
 297                                                 $where[] = 'global cache is expired/volatile';
 298                                                 $staleCache = $cache;
 299                                         } else {
 300                                                 $where[] = 'got from global cache';
 301                                                 $this->mCache[$code] = $cache;
 302                                                 $this->saveToCaches( $cache, 'local-only', $code );
 303                                                 $success = true;
 304                                         }
 305                                 }
 306
 307                                 if ( $success ) {
 308                                         # Done, no need to retry
 309                                         break;
 310                                 }
 311
 312                                 # We need to call loadFromDB. Limit the concurrency to one process.
 313                                 # This prevents the site from going down when the cache expires.
 314                                 # Note that the DB slam protection lock here is non-blocking.
 315                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 316                                 if ( $loadStatus === true ) {
 317                                         $success = true;
 318                                         break;
 319                                 } elseif ( $staleCache ) {
 320                                         # Use the stale cache while some other thread constructs the new one
 321                                         $where[] = 'using stale cache';
 322                                         $this->mCache[$code] = $staleCache;
 323                                         $success = true;
 324                                         break;
 325                                 } elseif ( $failedAttempts > 0 ) {
 326                                         # Already blocked once, so avoid another lock/unlock cycle.
 327                                         # This case will typically be hit if memcached is down, or if
 328                                         # loadFromDB() takes longer than LOCK_WAIT.
 329                                         $where[] = "could not acquire status key.";
 330                                         break;
 331                                 } elseif ( $loadStatus === 'cantacquire' ) {
 332                                         # Wait for the other thread to finish, then retry. Normally,
 333                                         # the memcached get() will then yeild the other thread's result.
 334                                         $where[] = 'waited for other thread to complete';
 335                                         $this->getReentrantScopedLock( $cacheKey );
 336                                 } else {
 337                                         # Disable cache; $loadStatus is 'disabled'
 338                                         break;
 339                                 }
 340                         }
 341                 }
 342
 343                 if ( !$success ) {
 344                         $where[] = 'loading FAILED - cache is disabled';
 345                         $this->mDisable = true;
 346                         $this->mCache = false;
 347                         # This used to throw an exception, but that led to nasty side effects like
 348                         # the whole wiki being instantly down if the memcached server died
 349                 } else {
 350                         # All good, just record the success
 351                         $this->mLoadedLanguages[$code] = true;
 352                 }
 353
 354                 $info = implode( ', ', $where );
 355                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 356
 357                 return $success;
 358         }
 359
 360         /**
 361          * @param string $code
 362          * @param array $where List of wfDebug() comments
 363          * @param integer $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 364          * @return bool|string True on success or one of ("cantacquire", "disabled")
 365          */
 366         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 367                 global $wgUseLocalMessageCache;
 368
 369                 # If cache updates on all levels fail, give up on message overrides.
 370                 # This is to avoid easy site outages; see $saveSuccess comments below.
 371                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 372                 $status = $this->mMemc->get( $statusKey );
 373                 if ( $status === 'error' ) {
 374                         $where[] = "could not load; method is still globally disabled";
 375                         return 'disabled';
 376                 }
 377
 378                 # Now let's regenerate
 379                 $where[] = 'loading from database';
 380
 381                 # Lock the cache to prevent conflicting writes.
 382                 # This lock is non-blocking so stale cache can quickly be used.
 383                 # Note that load() will call a blocking getReentrantScopedLock()
 384                 # after this if it really need to wait for any current thread.
 385                 $cacheKey = wfMemcKey( 'messages', $code );
 386                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 387                 if ( !$scopedLock ) {
 388                         $where[] = 'could not acquire main lock';
 389                         return 'cantacquire';
 390                 }
 391
 392                 $cache = $this->loadFromDB( $code, $mode );
 393                 $this->mCache[$code] = $cache;
 394                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 395
 396                 if ( !$saveSuccess ) {
 397                         /**
 398                          * Cache save has failed.
 399                          *
 400                          * There are two main scenarios where this could be a problem:
 401                          * - The cache is more than the maximum size (typically 1MB compressed).
 402                          * - Memcached has no space remaining in the relevant slab class. This is
 403                          *   unlikely with recent versions of memcached.
 404                          *
 405                          * Either way, if there is a local cache, nothing bad will happen. If there
 406                          * is no local cache, disabling the message cache for all requests avoids
 407                          * incurring a loadFromDB() overhead on every request, and thus saves the
 408                          * wiki from complete downtime under moderate traffic conditions.
 409                          */
 410                         if ( !$wgUseLocalMessageCache ) {
 411                                 $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 412                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 413                         } else {
 414                                 $where[] = "could not save global cache";
 415                         }
 416                 }
 417
 418                 return true;
 419         }
 420
 421         /**
 422          * Loads cacheable messages from the database. Messages bigger than
 423          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 424          * on-demand from the database later.
 425          *
 426          * @param string $code Language code
 427          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 428          * @return array Loaded messages for storing in caches
 429          */
 430         function loadFromDB( $code, $mode = null ) {
 431                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 432
 433                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_SLAVE );
 434
 435                 $cache = array();
 436
 437                 # Common conditions
 438                 $conds = array(
 439                         'page_is_redirect' => 0,
 440                         'page_namespace' => NS_MEDIAWIKI,
 441                 );
 442
 443                 $mostused = array();
 444                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 445                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 446                                 $this->load( $wgLanguageCode );
 447                         }
 448                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 449                         foreach ( $mostused as $key => $value ) {
 450                                 $mostused[$key] = "$value/$code";
 451                         }
 452                 }
 453
 454                 if ( count( $mostused ) ) {
 455                         $conds['page_title'] = $mostused;
 456                 } elseif ( $code !== $wgLanguageCode ) {
 457                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 458                 } else {
 459                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 460                         # other than language code.
 461                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 462                 }
 463
 464                 # Conditions to fetch oversized pages to ignore them
 465                 $bigConds = $conds;
 466                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 467
 468                 # Load titles for all oversized pages in the MediaWiki namespace
 469                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 470                 foreach ( $res as $row ) {
 471                         $cache[$row->page_title] = '!TOO BIG';
 472                 }
 473
 474                 # Conditions to load the remaining pages with their contents
 475                 $smallConds = $conds;
 476                 $smallConds[] = 'page_latest=rev_id';
 477                 $smallConds[] = 'rev_text_id=old_id';
 478                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 479
 480                 $res = $dbr->select(
 481                         array( 'page', 'revision', 'text' ),
 482                         array( 'page_title', 'old_text', 'old_flags' ),
 483                         $smallConds,
 484                         __METHOD__ . "($code)-small"
 485                 );
 486
 487                 foreach ( $res as $row ) {
 488                         $text = Revision::getRevisionText( $row );
 489                         if ( $text === false ) {
 490                                 // Failed to fetch data; possible ES errors?
 491                                 // Store a marker to fetch on-demand as a workaround...
 492                                 $entry = '!TOO BIG';
 493                                 wfDebugLog(
 494                                         'MessageCache',
 495                                         __METHOD__
 496                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 497                                 );
 498                         } else {
 499                                 $entry = ' ' . $text;
 500                         }
 501                         $cache[$row->page_title] = $entry;
 502                 }
 503
 504                 $cache['VERSION'] = MSG_CACHE_VERSION;
 505                 ksort( $cache );
 506                 $cache['HASH'] = md5( serialize( $cache ) );
 507                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 508
 509                 return $cache;
 510         }
 511
 512         /**
 513          * Updates cache as necessary when message page is changed
 514          *
 515          * @param string|bool $title Name of the page changed (false if deleted)
 516          * @param mixed $text New contents of the page.
 517          */
 518         public function replace( $title, $text ) {
 519                 global $wgMaxMsgCacheEntrySize, $wgContLang, $wgLanguageCode;
 520
 521                 if ( $this->mDisable ) {
 522                         return;
 523                 }
 524
 525                 list( $msg, $code ) = $this->figureMessage( $title );
 526                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 527                         // Content language overrides do not use the /<code> suffix
 528                         return;
 529                 }
 530
 531                 // Note that if the cache is volatile, load() may trigger a DB fetch.
 532                 // In that case we reenter/reuse the existing cache key lock to avoid
 533                 // a self-deadlock. This is safe as no reads happen *directly* in this
 534                 // method between getReentrantScopedLock() and load() below. There is
 535                 // no risk of data "changing under our feet" for replace().
 536                 $cacheKey = wfMemcKey( 'messages', $code );
 537                 $scopedLock = $this->getReentrantScopedLock( $cacheKey );
 538                 $this->load( $code, self::FOR_UPDATE );
 539
 540                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 541                 if ( $text === false ) {
 542                         // Article was deleted
 543                         $this->mCache[$code][$title] = '!NONEXISTENT';
 544                         $this->wanCache->delete( $titleKey );
 545                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 546                         // Check for size
 547                         $this->mCache[$code][$title] = '!TOO BIG';
 548                         $this->wanCache->set( $titleKey, ' ' . $text, $this->mExpiry );
 549                 } else {
 550                         $this->mCache[$code][$title] = ' ' . $text;
 551                         $this->wanCache->delete( $titleKey );
 552                 }
 553
 554                 // Mark this cache as definitely "latest" (non-volatile) so
 555                 // load() calls do try to refresh the cache with slave data
 556                 $this->mCache[$code]['LATEST'] = time();
 557
 558                 // Update caches if the lock was acquired
 559                 if ( $scopedLock ) {
 560                         $this->saveToCaches( $this->mCache[$code], 'all', $code );
 561                 }
 562
 563                 ScopedCallback::consume( $scopedLock );
 564                 // Relay the purge to APC and other DCs
 565                 $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
 566
 567                 // Also delete cached sidebar... just in case it is affected
 568                 $codes = array( $code );
 569                 if ( $code === 'en' ) {
 570                         // Delete all sidebars, like for example on action=purge on the
 571                         // sidebar messages
 572                         $codes = array_keys( Language::fetchLanguageNames() );
 573                 }
 574
 575                 foreach ( $codes as $code ) {
 576                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 577                         $this->wanCache->delete( $sidebarKey );
 578                 }
 579
 580                 // Update the message in the message blob store
 581                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 582                 $blobStore = $resourceloader->getMessageBlobStore();
 583                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 584
 585                 Hooks::run( 'MessageCacheReplace', array( $title, $text ) );
 586         }
 587
 588         /**
 589          * Is the given cache array expired due to time passing or a version change?
 590          *
 591          * @param array $cache
 592          * @return bool
 593          */
 594         protected function isCacheExpired( $cache ) {
 595                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 596                         return true;
 597                 }
 598                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 599                         return true;
 600                 }
 601                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 602                         return true;
 603                 }
 604
 605                 return false;
 606         }
 607
 608         /**
 609          * Shortcut to update caches.
 610          *
 611          * @param array $cache Cached messages with a version.
 612          * @param string $dest Either "local-only" to save to local caches only
 613          *   or "all" to save to all caches.
 614          * @param string|bool $code Language code (default: false)
 615          * @return bool
 616          */
 617         protected function saveToCaches( array $cache, $dest, $code = false ) {
 618                 if ( $dest === 'all' ) {
 619                         $cacheKey = wfMemcKey( 'messages', $code );
 620                         $success = $this->mMemc->set( $cacheKey, $cache );
 621                 } else {
 622                         $success = true;
 623                 }
 624
 625                 $this->setValidationHash( $code, $cache );
 626                 $this->saveToLocalCache( $code, $cache );
 627
 628                 return $success;
 629         }
 630
 631         /**
 632          * Get the md5 used to validate the local APC cache
 633          *
 634          * @param string $code
 635          * @return array (hash or false, bool expiry/volatility status)
 636          */
 637         protected function getValidationHash( $code ) {
 638                 $curTTL = null;
 639                 $value = $this->wanCache->get(
 640                         wfMemcKey( 'messages', $code, 'hash', 'v1' ),
 641                         $curTTL,
 642                         array( wfMemcKey( 'messages', $code ) )
 643                 );
 644
 645                 if ( !$value ) {
 646                         // No hash found at all; cache must regenerate to be safe
 647                         $hash = false;
 648                         $expired = true;
 649                 } else {
 650                         $hash = $value['hash'];
 651                         if ( ( time() - $value['latest'] ) < WANObjectCache::HOLDOFF_TTL ) {
 652                                 // Cache was recently updated via replace() and should be up-to-date
 653                                 $expired = false;
 654                         } else {
 655                                 // See if the "check" key was bumped after the hash was generated
 656                                 $expired = ( $curTTL < 0 );
 657                         }
 658                 }
 659
 660                 return array( $hash, $expired );
 661         }
 662
 663         /**
 664          * Set the md5 used to validate the local disk cache
 665          *
 666          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 667          * be treated as "volatile" by getValidationHash() for the next few seconds
 668          *
 669          * @param string $code
 670          * @param array $cache Cached messages with a version
 671          */
 672         protected function setValidationHash( $code, array $cache ) {
 673                 $this->wanCache->set(
 674                         wfMemcKey( 'messages', $code, 'hash', 'v1' ),
 675                         array(
 676                                 'hash' => $cache['HASH'],
 677                                 'latest' => isset( $cache['LATEST'] ) ? $cache['LATEST'] : 0
 678                         ),
 679                         WANObjectCache::TTL_INDEFINITE
 680                 );
 681         }
 682
 683         /**
 684          * @param string $key A language message cache key that stores blobs
 685          * @param integer $timeout Wait timeout in seconds
 686          * @return null|ScopedCallback
 687          */
 688         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 689                 return $this->mMemc->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 690         }
 691
 692         /**
 693          * Get a message from either the content language or the user language.
 694          *
 695          * First, assemble a list of languages to attempt getting the message from. This
 696          * chain begins with the requested language and its fallbacks and then continues with
 697          * the content language and its fallbacks. For each language in the chain, the following
 698          * process will occur (in this order):
 699          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 700          *     Note: for the content language, there is no /lang subpage.
 701          *  2. Fetch from the static CDB cache.
 702          *  3. If available, check the database for fallback language overrides.
 703          *
 704          * This process provides a number of guarantees. When changing this code, make sure all
 705          * of these guarantees are preserved.
 706          *  * If the requested language is *not* the content language, then the CDB cache for that
 707          *    specific language will take precedence over the root database page ([[MW:msg]]).
 708          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 709          *    the message is available *anywhere* in the language for which it is a fallback.
 710          *
 711          * @param string $key The message key
 712          * @param bool $useDB If true, look for the message in the DB, false
 713          *   to use only the compiled l10n cache.
 714          * @param bool|string|object $langcode Code of the language to get the message for.
 715          *   - If string and a valid code, will create a standard language object
 716          *   - If string but not a valid code, will create a basic language object
 717          *   - If boolean and false, create object from the current users language
 718          *   - If boolean and true, create object from the wikis content language
 719          *   - If language object, use it as given
 720          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 721          *
 722          * @throws MWException When given an invalid key
 723          * @return string|bool False if the message doesn't exist, otherwise the
 724          *   message (which can be empty)
 725          */
 726         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 727                 if ( is_int( $key ) ) {
 728                         // Fix numerical strings that somehow become ints
 729                         // on their way here
 730                         $key = (string)$key;
 731                 } elseif ( !is_string( $key ) ) {
 732                         throw new MWException( 'Non-string key given' );
 733                 } elseif ( $key === '' ) {
 734                         // Shortcut: the empty key is always missing
 735                         return false;
 736                 }
 737
 738                 // For full keys, get the language code from the key
 739                 $pos = strrpos( $key, '/' );
 740                 if ( $isFullKey && $pos !== false ) {
 741                         $langcode = substr( $key, $pos + 1 );
 742                         $key = substr( $key, 0, $pos );
 743                 }
 744
 745                 // Normalise title-case input (with some inlining)
 746                 $lckey = MessageCache::normalizeKey( $key );
 747
 748                 Hooks::run( 'MessageCache::get', array( &$lckey ) );
 749
 750                 // Loop through each language in the fallback list until we find something useful
 751                 $lang = wfGetLangObj( $langcode );
 752                 $message = $this->getMessageFromFallbackChain(
 753                         $lang,
 754                         $lckey,
 755                         !$this->mDisable && $useDB
 756                 );
 757
 758                 // If we still have no message, maybe the key was in fact a full key so try that
 759                 if ( $message === false ) {
 760                         $parts = explode( '/', $lckey );
 761                         // We may get calls for things that are http-urls from sidebar
 762                         // Let's not load nonexistent languages for those
 763                         // They usually have more than one slash.
 764                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 765                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 766                                 if ( $message === null ) {
 767                                         $message = false;
 768                                 }
 769                         }
 770                 }
 771
 772                 // Post-processing if the message exists
 773                 if ( $message !== false ) {
 774                         // Fix whitespace
 775                         $message = str_replace(
 776                                 array(
 777                                         # Fix for trailing whitespace, removed by textarea
 778                                         '&#32;',
 779                                         # Fix for NBSP, converted to space by firefox
 780                                         '&nbsp;',
 781                                         '&#160;',
 782                                 ),
 783                                 array(
 784                                         ' ',
 785                                         "\xc2\xa0",
 786                                         "\xc2\xa0"
 787                                 ),
 788                                 $message
 789                         );
 790                 }
 791
 792                 return $message;
 793         }
 794
 795         /**
 796          * Given a language, try and fetch messages from that language.
 797          *
 798          * Will also consider fallbacks of that language, the site language, and fallbacks for
 799          * the site language.
 800          *
 801          * @see MessageCache::get
 802          * @param Language|StubObject $lang Preferred language
 803          * @param string $lckey Lowercase key for the message (as for localisation cache)
 804          * @param bool $useDB Whether to include messages from the wiki database
 805          * @return string|bool The message, or false if not found
 806          */
 807         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 808                 global $wgLanguageCode, $wgContLang;
 809
 810                 $uckey = $wgContLang->ucfirst( $lckey );
 811                 $langcode = $lang->getCode();
 812                 $message = false;
 813
 814                 // First try the requested language.
 815                 if ( $useDB ) {
 816                         if ( $langcode === $wgLanguageCode ) {
 817                                 // Messages created in the content language will not have the /lang extension
 818                                 $message = $this->getMsgFromNamespace( $uckey, $langcode );
 819                         } else {
 820                                 $message = $this->getMsgFromNamespace( "$uckey/$langcode", $langcode );
 821                         }
 822                 }
 823
 824                 if ( $message !== false ) {
 825                         return $message;
 826                 }
 827
 828                 // Check the CDB cache
 829                 $message = $lang->getMessage( $lckey );
 830                 if ( $message !== null ) {
 831                         return $message;
 832                 }
 833
 834                 list( $fallbackChain, $siteFallbackChain ) =
 835                         Language::getFallbacksIncludingSiteLanguage( $langcode );
 836
 837                 // Next try checking the database for all of the fallback languages of the requested language.
 838                 if ( $useDB ) {
 839                         foreach ( $fallbackChain as $code ) {
 840                                 if ( $code === $wgLanguageCode ) {
 841                                         // Messages created in the content language will not have the /lang extension
 842                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 843                                 } else {
 844                                         $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 845                                 }
 846
 847                                 if ( $message !== false ) {
 848                                         // Found the message.
 849                                         return $message;
 850                                 }
 851                         }
 852                 }
 853
 854                 // Now try checking the site language.
 855                 if ( $useDB ) {
 856                         $message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
 857                         if ( $message !== false ) {
 858                                 return $message;
 859                         }
 860                 }
 861
 862                 $message = $wgContLang->getMessage( $lckey );
 863                 if ( $message !== null ) {
 864                         return $message;
 865                 }
 866
 867                 // Finally try the DB for the site language's fallbacks.
 868                 if ( $useDB ) {
 869                         foreach ( $siteFallbackChain as $code ) {
 870                                 $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 871                                 if ( $message === false && $code === $wgLanguageCode ) {
 872                                         // Messages created in the content language will not have the /lang extension
 873                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 874                                 }
 875
 876                                 if ( $message !== false ) {
 877                                         // Found the message.
 878                                         return $message;
 879                                 }
 880                         }
 881                 }
 882
 883                 return false;
 884         }
 885
 886         /**
 887          * Get a message from the MediaWiki namespace, with caching. The key must
 888          * first be converted to two-part lang/msg form if necessary.
 889          *
 890          * Unlike self::get(), this function doesn't resolve fallback chains, and
 891          * some callers require this behavior. LanguageConverter::parseCachedTable()
 892          * and self::get() are some examples in core.
 893          *
 894          * @param string $title Message cache key with initial uppercase letter.
 895          * @param string $code Code denoting the language to try.
 896          * @return string|bool The message, or false if it does not exist or on error
 897          */
 898         public function getMsgFromNamespace( $title, $code ) {
 899                 $this->load( $code );
 900                 if ( isset( $this->mCache[$code][$title] ) ) {
 901                         $entry = $this->mCache[$code][$title];
 902                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 903                                 // The message exists, so make sure a string
 904                                 // is returned.
 905                                 return (string)substr( $entry, 1 );
 906                         } elseif ( $entry === '!NONEXISTENT' ) {
 907                                 return false;
 908                         } elseif ( $entry === '!TOO BIG' ) {
 909                                 // Fall through and try invididual message cache below
 910                         }
 911                 } else {
 912                         // XXX: This is not cached in process cache, should it?
 913                         $message = false;
 914                         Hooks::run( 'MessagesPreLoad', array( $title, &$message ) );
 915                         if ( $message !== false ) {
 916                                 return $message;
 917                         }
 918
 919                         return false;
 920                 }
 921
 922                 # Try the individual message cache
 923                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 924                 $entry = $this->wanCache->get( $titleKey );
 925                 if ( $entry ) {
 926                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 927                                 $this->mCache[$code][$title] = $entry;
 928
 929                                 // The message exists, so make sure a string
 930                                 // is returned.
 931                                 return (string)substr( $entry, 1 );
 932                         } elseif ( $entry === '!NONEXISTENT' ) {
 933                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 934
 935                                 return false;
 936                         } else {
 937                                 # Corrupt/obsolete entry, delete it
 938                                 $this->wanCache->delete( $titleKey );
 939                         }
 940                 }
 941
 942                 # Try loading it from the database
 943                 $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 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->getModel() . ")"
 965                                         );
 966
 967                                         $message = false; // negative caching
 968                                 } else {
 969                                         $this->mCache[$code][$title] = ' ' . $message;
 970                                         $this->wanCache->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->wanCache->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( $language );
1058
1059                 if ( !$title || !$title instanceof Title ) {
1060                         global $wgTitle;
1061                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1062                                 wfGetAllCallers( 5 ) . ' with no title set.' );
1063                         $title = $wgTitle;
1064                 }
1065                 // Sometimes $wgTitle isn't set either...
1066                 if ( !$title ) {
1067                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1068                         # Create a ghost title in such case
1069                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1070                 }
1071
1072                 $this->mInParser = true;
1073                 $res = $parser->parse( $text, $title, $popts, $linestart );
1074                 $this->mInParser = false;
1075
1076                 return $res;
1077         }
1078
1079         function disable() {
1080                 $this->mDisable = true;
1081         }
1082
1083         function enable() {
1084                 $this->mDisable = false;
1085         }
1086
1087         /**
1088          * Clear all stored messages. Mainly used after a mass rebuild.
1089          */
1090         function clear() {
1091                 $langs = Language::fetchLanguageNames( null, 'mw' );
1092                 foreach ( array_keys( $langs ) as $code ) {
1093                         # Global and local caches
1094                         $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
1095                 }
1096
1097                 $this->mLoadedLanguages = array();
1098         }
1099
1100         /**
1101          * @param string $key
1102          * @return array
1103          */
1104         public function figureMessage( $key ) {
1105                 global $wgLanguageCode;
1106
1107                 $pieces = explode( '/', $key );
1108                 if ( count( $pieces ) < 2 ) {
1109                         return array( $key, $wgLanguageCode );
1110                 }
1111
1112                 $lang = array_pop( $pieces );
1113                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1114                         return array( $key, $wgLanguageCode );
1115                 }
1116
1117                 $message = implode( '/', $pieces );
1118
1119                 return array( $message, $lang );
1120         }
1121
1122         /**
1123          * Get all message keys stored in the message cache for a given language.
1124          * If $code is the content language code, this will return all message keys
1125          * for which MediaWiki:msgkey exists. If $code is another language code, this
1126          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1127          * @param string $code Language code
1128          * @return array Array of message keys (strings)
1129          */
1130         public function getAllMessageKeys( $code ) {
1131                 global $wgContLang;
1132                 $this->load( $code );
1133                 if ( !isset( $this->mCache[$code] ) ) {
1134                         // Apparently load() failed
1135                         return null;
1136                 }
1137                 // Remove administrative keys
1138                 $cache = $this->mCache[$code];
1139                 unset( $cache['VERSION'] );
1140                 unset( $cache['EXPIRY'] );
1141                 // Remove any !NONEXISTENT keys
1142                 $cache = array_diff( $cache, array( '!NONEXISTENT' ) );
1143
1144                 // Keys may appear with a capital first letter. lcfirst them.
1145                 return array_map( array( $wgContLang, 'lcfirst' ), array_keys( $cache ) );
1146         }
1147 }