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::newAccelerator( 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                         # Cache save has failed.
 398                         # There are two main scenarios where this could be a problem:
 399                         #
 400                         #   - The cache is more than the maximum size (typically
 401                         #     1MB compressed).
 402                         #
 403                         #   - Memcached has no space remaining in the relevant slab
 404                         #     class. This is unlikely with recent versions of
 405                         #     memcached.
 406                         #
 407                         # Either way, if there is a local cache, nothing bad will
 408                         # happen. If there is no local cache, disabling the message
 409                         # cache for all requests avoids incurring a loadFromDB()
 410                         # overhead on every request, and thus saves the wiki from
 411                         # complete downtime under moderate traffic conditions.
 412                         if ( !$wgUseLocalMessageCache ) {
 413                                 $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 414                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 415                         } else {
 416                                 $where[] = "could not save global cache";
 417                         }
 418                 }
 419
 420                 return true;
 421         }
 422
 423         /**
 424          * Loads cacheable messages from the database. Messages bigger than
 425          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 426          * on-demand from the database later.
 427          *
 428          * @param string $code Language code
 429          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 430          * @return array Loaded messages for storing in caches
 431          */
 432         function loadFromDB( $code, $mode = null ) {
 433                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 434
 435                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_SLAVE );
 436
 437                 $cache = array();
 438
 439                 # Common conditions
 440                 $conds = array(
 441                         'page_is_redirect' => 0,
 442                         'page_namespace' => NS_MEDIAWIKI,
 443                 );
 444
 445                 $mostused = array();
 446                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 447                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 448                                 $this->load( $wgLanguageCode );
 449                         }
 450                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 451                         foreach ( $mostused as $key => $value ) {
 452                                 $mostused[$key] = "$value/$code";
 453                         }
 454                 }
 455
 456                 if ( count( $mostused ) ) {
 457                         $conds['page_title'] = $mostused;
 458                 } elseif ( $code !== $wgLanguageCode ) {
 459                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 460                 } else {
 461                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 462                         # other than language code.
 463                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 464                 }
 465
 466                 # Conditions to fetch oversized pages to ignore them
 467                 $bigConds = $conds;
 468                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 469
 470                 # Load titles for all oversized pages in the MediaWiki namespace
 471                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 472                 foreach ( $res as $row ) {
 473                         $cache[$row->page_title] = '!TOO BIG';
 474                 }
 475
 476                 # Conditions to load the remaining pages with their contents
 477                 $smallConds = $conds;
 478                 $smallConds[] = 'page_latest=rev_id';
 479                 $smallConds[] = 'rev_text_id=old_id';
 480                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 481
 482                 $res = $dbr->select(
 483                         array( 'page', 'revision', 'text' ),
 484                         array( 'page_title', 'old_text', 'old_flags' ),
 485                         $smallConds,
 486                         __METHOD__ . "($code)-small"
 487                 );
 488
 489                 foreach ( $res as $row ) {
 490                         $text = Revision::getRevisionText( $row );
 491                         if ( $text === false ) {
 492                                 // Failed to fetch data; possible ES errors?
 493                                 // Store a marker to fetch on-demand as a workaround...
 494                                 $entry = '!TOO BIG';
 495                                 wfDebugLog(
 496                                         'MessageCache',
 497                                         __METHOD__
 498                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 499                                 );
 500                         } else {
 501                                 $entry = ' ' . $text;
 502                         }
 503                         $cache[$row->page_title] = $entry;
 504                 }
 505
 506                 $cache['VERSION'] = MSG_CACHE_VERSION;
 507                 ksort( $cache );
 508                 $cache['HASH'] = md5( serialize( $cache ) );
 509                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 510
 511                 return $cache;
 512         }
 513
 514         /**
 515          * Updates cache as necessary when message page is changed
 516          *
 517          * @param string|bool $title Name of the page changed (false if deleted)
 518          * @param mixed $text New contents of the page.
 519          */
 520         public function replace( $title, $text ) {
 521                 global $wgMaxMsgCacheEntrySize, $wgContLang, $wgLanguageCode;
 522
 523                 if ( $this->mDisable ) {
 524                         return;
 525                 }
 526
 527                 list( $msg, $code ) = $this->figureMessage( $title );
 528                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 529                         // Content language overrides do not use the /<code> suffix
 530                         return;
 531                 }
 532
 533                 // Note that if the cache is volatile, load() may trigger a DB fetch.
 534                 // In that case we reenter/reuse the existing cache key lock to avoid
 535                 // a self-deadlock. This is safe as no reads happen *directly* in this
 536                 // method between getReentrantScopedLock() and load() below. There is
 537                 // no risk of data "changing under our feet" for replace().
 538                 $cacheKey = wfMemcKey( 'messages', $code );
 539                 $scopedLock = $this->getReentrantScopedLock( $cacheKey );
 540                 $this->load( $code, self::FOR_UPDATE );
 541
 542                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 543                 if ( $text === false ) {
 544                         // Article was deleted
 545                         $this->mCache[$code][$title] = '!NONEXISTENT';
 546                         $this->wanCache->delete( $titleKey );
 547                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 548                         // Check for size
 549                         $this->mCache[$code][$title] = '!TOO BIG';
 550                         $this->wanCache->set( $titleKey, ' ' . $text, $this->mExpiry );
 551                 } else {
 552                         $this->mCache[$code][$title] = ' ' . $text;
 553                         $this->wanCache->delete( $titleKey );
 554                 }
 555
 556                 // Mark this cache as definitely "latest" (non-volatile) so
 557                 // load() calls do try to refresh the cache with slave data
 558                 $this->mCache[$code]['LATEST'] = time();
 559
 560                 // Update caches if the lock was acquired
 561                 if ( $scopedLock ) {
 562                         $this->saveToCaches( $this->mCache[$code], 'all', $code );
 563                 }
 564
 565                 ScopedCallback::consume( $scopedLock );
 566                 // Relay the purge to APC and other DCs
 567                 $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
 568
 569                 // Also delete cached sidebar... just in case it is affected
 570                 $codes = array( $code );
 571                 if ( $code === 'en' ) {
 572                         // Delete all sidebars, like for example on action=purge on the
 573                         // sidebar messages
 574                         $codes = array_keys( Language::fetchLanguageNames() );
 575                 }
 576
 577                 foreach ( $codes as $code ) {
 578                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 579                         $this->wanCache->delete( $sidebarKey, 5 );
 580                 }
 581
 582                 // Update the message in the message blob store
 583                 $blobStore = new MessageBlobStore();
 584                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 585
 586                 Hooks::run( 'MessageCacheReplace', array( $title, $text ) );
 587         }
 588
 589         /**
 590          * Is the given cache array expired due to time passing or a version change?
 591          *
 592          * @param array $cache
 593          * @return bool
 594          */
 595         protected function isCacheExpired( $cache ) {
 596                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 597                         return true;
 598                 }
 599                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 600                         return true;
 601                 }
 602                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 603                         return true;
 604                 }
 605
 606                 return false;
 607         }
 608
 609         /**
 610          * Shortcut to update caches.
 611          *
 612          * @param array $cache Cached messages with a version.
 613          * @param string $dest Either "local-only" to save to local caches only
 614          *   or "all" to save to all caches.
 615          * @param string|bool $code Language code (default: false)
 616          * @return bool
 617          */
 618         protected function saveToCaches( array $cache, $dest, $code = false ) {
 619                 if ( $dest === 'all' ) {
 620                         $cacheKey = wfMemcKey( 'messages', $code );
 621                         $success = $this->mMemc->set( $cacheKey, $cache );
 622                 } else {
 623                         $success = true;
 624                 }
 625
 626                 $this->setValidationHash( $code, $cache );
 627                 $this->saveToLocalCache( $code, $cache );
 628
 629                 return $success;
 630         }
 631
 632         /**
 633          * Get the md5 used to validate the local APC cache
 634          *
 635          * @param string $code
 636          * @return array (hash or false, bool expiry/volatility status)
 637          */
 638         protected function getValidationHash( $code ) {
 639                 $curTTL = null;
 640                 $value = $this->wanCache->get(
 641                         wfMemcKey( 'messages', $code, 'hash', 'v1' ),
 642                         $curTTL,
 643                         array( wfMemcKey( 'messages', $code ) )
 644                 );
 645
 646                 if ( !$value ) {
 647                         // No hash found at all; cache must regenerate to be safe
 648                         $hash = false;
 649                         $expired = true;
 650                 } else {
 651                         $hash = $value['hash'];
 652                         if ( ( time() - $value['latest'] ) < WANObjectCache::HOLDOFF_TTL ) {
 653                                 // Cache was recently updated via replace() and should be up-to-date
 654                                 $expired = false;
 655                         } else {
 656                                 // See if the "check" key was bumped after the hash was generated
 657                                 $expired = ( $curTTL < 0 );
 658                         }
 659                 }
 660
 661                 return array( $hash, $expired );
 662         }
 663
 664         /**
 665          * Set the md5 used to validate the local disk cache
 666          *
 667          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 668          * be treated as "volatile" by getValidationHash() for the next few seconds
 669          *
 670          * @param string $code
 671          * @param array $cache Cached messages with a version
 672          */
 673         protected function setValidationHash( $code, array $cache ) {
 674                 $this->wanCache->set(
 675                         wfMemcKey( 'messages', $code, 'hash', 'v1' ),
 676                         array(
 677                                 'hash' => $cache['HASH'],
 678                                 'latest' => isset( $cache['LATEST'] ) ? $cache['LATEST'] : 0
 679                         ),
 680                         WANObjectCache::TTL_NONE
 681                 );
 682         }
 683
 684         /**
 685          * @param string $key A language message cache key that stores blobs
 686          * @param integer $timeout Wait timeout in seconds
 687          * @return null|ScopedCallback
 688          */
 689         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 690                 return $this->mMemc->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 691         }
 692
 693         /**
 694          * Get a message from either the content language or the user language.
 695          *
 696          * First, assemble a list of languages to attempt getting the message from. This
 697          * chain begins with the requested language and its fallbacks and then continues with
 698          * the content language and its fallbacks. For each language in the chain, the following
 699          * process will occur (in this order):
 700          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 701          *     Note: for the content language, there is no /lang subpage.
 702          *  2. Fetch from the static CDB cache.
 703          *  3. If available, check the database for fallback language overrides.
 704          *
 705          * This process provides a number of guarantees. When changing this code, make sure all
 706          * of these guarantees are preserved.
 707          *  * If the requested language is *not* the content language, then the CDB cache for that
 708          *    specific language will take precedence over the root database page ([[MW:msg]]).
 709          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 710          *    the message is available *anywhere* in the language for which it is a fallback.
 711          *
 712          * @param string $key The message key
 713          * @param bool $useDB If true, look for the message in the DB, false
 714          *   to use only the compiled l10n cache.
 715          * @param bool|string|object $langcode Code of the language to get the message for.
 716          *   - If string and a valid code, will create a standard language object
 717          *   - If string but not a valid code, will create a basic language object
 718          *   - If boolean and false, create object from the current users language
 719          *   - If boolean and true, create object from the wikis content language
 720          *   - If language object, use it as given
 721          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 722          *
 723          * @throws MWException When given an invalid key
 724          * @return string|bool False if the message doesn't exist, otherwise the
 725          *   message (which can be empty)
 726          */
 727         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 728                 global $wgContLang;
 729
 730                 if ( is_int( $key ) ) {
 731                         // Fix numerical strings that somehow become ints
 732                         // on their way here
 733                         $key = (string)$key;
 734                 } elseif ( !is_string( $key ) ) {
 735                         throw new MWException( 'Non-string key given' );
 736                 } elseif ( $key === '' ) {
 737                         // Shortcut: the empty key is always missing
 738                         return false;
 739                 }
 740
 741                 // For full keys, get the language code from the key
 742                 $pos = strrpos( $key, '/' );
 743                 if ( $isFullKey && $pos !== false ) {
 744                         $langcode = substr( $key, $pos + 1 );
 745                         $key = substr( $key, 0, $pos );
 746                 }
 747
 748                 // Normalise title-case input (with some inlining)
 749                 $lckey = MessageCache::normalizeKey( $key );
 750
 751                 Hooks::run( 'MessageCache::get', array( &$lckey ) );
 752
 753                 if ( ord( $lckey ) < 128 ) {
 754                         $uckey = ucfirst( $lckey );
 755                 } else {
 756                         $uckey = $wgContLang->ucfirst( $lckey );
 757                 }
 758
 759                 // Loop through each language in the fallback list until we find something useful
 760                 $lang = wfGetLangObj( $langcode );
 761                 $message = $this->getMessageFromFallbackChain(
 762                         $lang,
 763                         $lckey,
 764                         $uckey,
 765                         !$this->mDisable && $useDB
 766                 );
 767
 768                 // If we still have no message, maybe the key was in fact a full key so try that
 769                 if ( $message === false ) {
 770                         $parts = explode( '/', $lckey );
 771                         // We may get calls for things that are http-urls from sidebar
 772                         // Let's not load nonexistent languages for those
 773                         // They usually have more than one slash.
 774                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 775                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 776                                 if ( $message === null ) {
 777                                         $message = false;
 778                                 }
 779                         }
 780                 }
 781
 782                 // Post-processing if the message exists
 783                 if ( $message !== false ) {
 784                         // Fix whitespace
 785                         $message = str_replace(
 786                                 array(
 787                                         # Fix for trailing whitespace, removed by textarea
 788                                         '&#32;',
 789                                         # Fix for NBSP, converted to space by firefox
 790                                         '&nbsp;',
 791                                         '&#160;',
 792                                 ),
 793                                 array(
 794                                         ' ',
 795                                         "\xc2\xa0",
 796                                         "\xc2\xa0"
 797                                 ),
 798                                 $message
 799                         );
 800                 }
 801
 802                 return $message;
 803         }
 804
 805         /**
 806          * Given a language, try and fetch a message from that language, then the
 807          * fallbacks of that language, then the site language, then the fallbacks for the
 808          * site language.
 809          *
 810          * @param Language $lang Requested language
 811          * @param string $lckey Lowercase key for the message
 812          * @param string $uckey Uppercase key for the message
 813          * @param bool $useDB Whether to use the database
 814          *
 815          * @see MessageCache::get
 816          * @return string|bool The message, or false if not found
 817          */
 818         protected function getMessageFromFallbackChain( $lang, $lckey, $uckey, $useDB ) {
 819                 global $wgLanguageCode, $wgContLang;
 820
 821                 $langcode = $lang->getCode();
 822                 $message = false;
 823
 824                 // First try the requested language.
 825                 if ( $useDB ) {
 826                         if ( $langcode === $wgLanguageCode ) {
 827                                 // Messages created in the content language will not have the /lang extension
 828                                 $message = $this->getMsgFromNamespace( $uckey, $langcode );
 829                         } else {
 830                                 $message = $this->getMsgFromNamespace( "$uckey/$langcode", $langcode );
 831                         }
 832                 }
 833
 834                 if ( $message !== false ) {
 835                         return $message;
 836                 }
 837
 838                 // Check the CDB cache
 839                 $message = $lang->getMessage( $lckey );
 840                 if ( $message !== null ) {
 841                         return $message;
 842                 }
 843
 844                 list( $fallbackChain, $siteFallbackChain ) =
 845                         Language::getFallbacksIncludingSiteLanguage( $langcode );
 846
 847                 // Next try checking the database for all of the fallback languages of the requested language.
 848                 if ( $useDB ) {
 849                         foreach ( $fallbackChain as $code ) {
 850                                 if ( $code === $wgLanguageCode ) {
 851                                         // Messages created in the content language will not have the /lang extension
 852                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 853                                 } else {
 854                                         $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 855                                 }
 856
 857                                 if ( $message !== false ) {
 858                                         // Found the message.
 859                                         return $message;
 860                                 }
 861                         }
 862                 }
 863
 864                 // Now try checking the site language.
 865                 if ( $useDB ) {
 866                         $message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
 867                         if ( $message !== false ) {
 868                                 return $message;
 869                         }
 870                 }
 871
 872                 $message = $wgContLang->getMessage( $lckey );
 873                 if ( $message !== null ) {
 874                         return $message;
 875                 }
 876
 877                 // Finally try the DB for the site language's fallbacks.
 878                 if ( $useDB ) {
 879                         foreach ( $siteFallbackChain as $code ) {
 880                                 $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 881                                 if ( $message === false && $code === $wgLanguageCode ) {
 882                                         // Messages created in the content language will not have the /lang extension
 883                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 884                                 }
 885
 886                                 if ( $message !== false ) {
 887                                         // Found the message.
 888                                         return $message;
 889                                 }
 890                         }
 891                 }
 892
 893                 return false;
 894         }
 895
 896         /**
 897          * Get a message from the MediaWiki namespace, with caching. The key must
 898          * first be converted to two-part lang/msg form if necessary.
 899          *
 900          * Unlike self::get(), this function doesn't resolve fallback chains, and
 901          * some callers require this behavior. LanguageConverter::parseCachedTable()
 902          * and self::get() are some examples in core.
 903          *
 904          * @param string $title Message cache key with initial uppercase letter.
 905          * @param string $code Code denoting the language to try.
 906          * @return string|bool The message, or false if it does not exist or on error
 907          */
 908         function getMsgFromNamespace( $title, $code ) {
 909                 $this->load( $code );
 910                 if ( isset( $this->mCache[$code][$title] ) ) {
 911                         $entry = $this->mCache[$code][$title];
 912                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 913                                 // The message exists, so make sure a string
 914                                 // is returned.
 915                                 return (string)substr( $entry, 1 );
 916                         } elseif ( $entry === '!NONEXISTENT' ) {
 917                                 return false;
 918                         } elseif ( $entry === '!TOO BIG' ) {
 919                                 // Fall through and try invididual message cache below
 920                         }
 921                 } else {
 922                         // XXX: This is not cached in process cache, should it?
 923                         $message = false;
 924                         Hooks::run( 'MessagesPreLoad', array( $title, &$message ) );
 925                         if ( $message !== false ) {
 926                                 return $message;
 927                         }
 928
 929                         return false;
 930                 }
 931
 932                 # Try the individual message cache
 933                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 934                 $entry = $this->wanCache->get( $titleKey );
 935                 if ( $entry ) {
 936                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 937                                 $this->mCache[$code][$title] = $entry;
 938
 939                                 // The message exists, so make sure a string
 940                                 // is returned.
 941                                 return (string)substr( $entry, 1 );
 942                         } elseif ( $entry === '!NONEXISTENT' ) {
 943                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 944
 945                                 return false;
 946                         } else {
 947                                 # Corrupt/obsolete entry, delete it
 948                                 $this->wanCache->delete( $titleKey );
 949                         }
 950                 }
 951
 952                 # Try loading it from the database
 953                 $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 954                 if ( $revision ) {
 955                         $content = $revision->getContent();
 956                         if ( !$content ) {
 957                                 // A possibly temporary loading failure.
 958                                 wfDebugLog(
 959                                         'MessageCache',
 960                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
 961                                 );
 962                                 $message = null; // no negative caching
 963                         } else {
 964                                 // XXX: Is this the right way to turn a Content object into a message?
 965                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
 966                                 //       CssContent. MessageContent is *not* used for storing messages, it's
 967                                 //       only used for wrapping them when needed.
 968                                 $message = $content->getWikitextForTransclusion();
 969
 970                                 if ( $message === false || $message === null ) {
 971                                         wfDebugLog(
 972                                                 'MessageCache',
 973                                                 __METHOD__ . ": message content doesn't provide wikitext "
 974                                                         . "(content model: " . $content->getModel() . ")"
 975                                         );
 976
 977                                         $message = false; // negative caching
 978                                 } else {
 979                                         $this->mCache[$code][$title] = ' ' . $message;
 980                                         $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry );
 981                                 }
 982                         }
 983                 } else {
 984                         $message = false; // negative caching
 985                 }
 986
 987                 if ( $message === false ) { // negative caching
 988                         $this->mCache[$code][$title] = '!NONEXISTENT';
 989                         $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
 990                 }
 991
 992                 return $message;
 993         }
 994
 995         /**
 996          * @param string $message
 997          * @param bool $interface
 998          * @param string $language Language code
 999          * @param Title $title
1000          * @return string
1001          */
1002         function transform( $message, $interface = false, $language = null, $title = null ) {
1003                 // Avoid creating parser if nothing to transform
1004                 if ( strpos( $message, '{{' ) === false ) {
1005                         return $message;
1006                 }
1007
1008                 if ( $this->mInParser ) {
1009                         return $message;
1010                 }
1011
1012                 $parser = $this->getParser();
1013                 if ( $parser ) {
1014                         $popts = $this->getParserOptions();
1015                         $popts->setInterfaceMessage( $interface );
1016                         $popts->setTargetLanguage( $language );
1017
1018                         $userlang = $popts->setUserLang( $language );
1019                         $this->mInParser = true;
1020                         $message = $parser->transformMsg( $message, $popts, $title );
1021                         $this->mInParser = false;
1022                         $popts->setUserLang( $userlang );
1023                 }
1024
1025                 return $message;
1026         }
1027
1028         /**
1029          * @return Parser
1030          */
1031         function getParser() {
1032                 global $wgParser, $wgParserConf;
1033                 if ( !$this->mParser && isset( $wgParser ) ) {
1034                         # Do some initialisation so that we don't have to do it twice
1035                         $wgParser->firstCallInit();
1036                         # Clone it and store it
1037                         $class = $wgParserConf['class'];
1038                         if ( $class == 'ParserDiffTest' ) {
1039                                 # Uncloneable
1040                                 $this->mParser = new $class( $wgParserConf );
1041                         } else {
1042                                 $this->mParser = clone $wgParser;
1043                         }
1044                 }
1045
1046                 return $this->mParser;
1047         }
1048
1049         /**
1050          * @param string $text
1051          * @param Title $title
1052          * @param bool $linestart Whether or not this is at the start of a line
1053          * @param bool $interface Whether this is an interface message
1054          * @param string $language Language code
1055          * @return ParserOutput|string
1056          */
1057         public function parse( $text, $title = null, $linestart = true,
1058                 $interface = false, $language = null
1059         ) {
1060                 if ( $this->mInParser ) {
1061                         return htmlspecialchars( $text );
1062                 }
1063
1064                 $parser = $this->getParser();
1065                 $popts = $this->getParserOptions();
1066                 $popts->setInterfaceMessage( $interface );
1067                 $popts->setTargetLanguage( $language );
1068
1069                 if ( !$title || !$title instanceof Title ) {
1070                         global $wgTitle;
1071                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1072                                 wfGetAllCallers( 5 ) . ' with no title set.' );
1073                         $title = $wgTitle;
1074                 }
1075                 // Sometimes $wgTitle isn't set either...
1076                 if ( !$title ) {
1077                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1078                         # Create a ghost title in such case
1079                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1080                 }
1081
1082                 $this->mInParser = true;
1083                 $res = $parser->parse( $text, $title, $popts, $linestart );
1084                 $this->mInParser = false;
1085
1086                 return $res;
1087         }
1088
1089         function disable() {
1090                 $this->mDisable = true;
1091         }
1092
1093         function enable() {
1094                 $this->mDisable = false;
1095         }
1096
1097         /**
1098          * Clear all stored messages. Mainly used after a mass rebuild.
1099          */
1100         function clear() {
1101                 $langs = Language::fetchLanguageNames( null, 'mw' );
1102                 foreach ( array_keys( $langs ) as $code ) {
1103                         # Global and local caches
1104                         $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
1105                 }
1106
1107                 $this->mLoadedLanguages = array();
1108         }
1109
1110         /**
1111          * @param string $key
1112          * @return array
1113          */
1114         public function figureMessage( $key ) {
1115                 global $wgLanguageCode;
1116
1117                 $pieces = explode( '/', $key );
1118                 if ( count( $pieces ) < 2 ) {
1119                         return array( $key, $wgLanguageCode );
1120                 }
1121
1122                 $lang = array_pop( $pieces );
1123                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1124                         return array( $key, $wgLanguageCode );
1125                 }
1126
1127                 $message = implode( '/', $pieces );
1128
1129                 return array( $message, $lang );
1130         }
1131
1132         /**
1133          * Get all message keys stored in the message cache for a given language.
1134          * If $code is the content language code, this will return all message keys
1135          * for which MediaWiki:msgkey exists. If $code is another language code, this
1136          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1137          * @param string $code Language code
1138          * @return array Array of message keys (strings)
1139          */
1140         public function getAllMessageKeys( $code ) {
1141                 global $wgContLang;
1142                 $this->load( $code );
1143                 if ( !isset( $this->mCache[$code] ) ) {
1144                         // Apparently load() failed
1145                         return null;
1146                 }
1147                 // Remove administrative keys
1148                 $cache = $this->mCache[$code];
1149                 unset( $cache['VERSION'] );
1150                 unset( $cache['EXPIRY'] );
1151                 // Remove any !NONEXISTENT keys
1152                 $cache = array_diff( $cache, array( '!NONEXISTENT' ) );
1153
1154                 // Keys may appear with a capital first letter. lcfirst them.
1155                 return array_map( array( $wgContLang, 'lcfirst' ), array_keys( $cache ) );
1156         }
1157 }