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 = [];
  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 $instance;
  93
  94         /**
  95          * Get the signleton instance of this class
  96          *
  97          * @since 1.18
  98          * @return MessageCache
  99          */
 100         public static function singleton() {
 101                 if ( self::$instance === null ) {
 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                 global $wgUser;
 172
 173                 if ( !$this->mParserOptions ) {
 174                         if ( !$wgUser->isSafeToLoad() ) {
 175                                 // $wgUser isn't unstubbable yet, so don't try to get a
 176                                 // ParserOptions for it. And don't cache this ParserOptions
 177                                 // either.
 178                                 $po = ParserOptions::newFromAnon();
 179                                 $po->setEditSection( false );
 180                                 return $po;
 181                         }
 182
 183                         $this->mParserOptions = new ParserOptions;
 184                         $this->mParserOptions->setEditSection( false );
 185                 }
 186
 187                 return $this->mParserOptions;
 188         }
 189
 190         /**
 191          * Try to load the cache from APC.
 192          *
 193          * @param string $code Optional language code, see documenation of load().
 194          * @return array|bool The cache array, or false if not in cache.
 195          */
 196         protected function getLocalCache( $code ) {
 197                 $cacheKey = wfMemcKey( __CLASS__, $code );
 198
 199                 return $this->localCache->get( $cacheKey );
 200         }
 201
 202         /**
 203          * Save the cache to APC.
 204          *
 205          * @param string $code
 206          * @param array $cache The cache array
 207          */
 208         protected function saveToLocalCache( $code, $cache ) {
 209                 $cacheKey = wfMemcKey( __CLASS__, $code );
 210                 $this->localCache->set( $cacheKey, $cache );
 211         }
 212
 213         /**
 214          * Loads messages from caches or from database in this order:
 215          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 216          * (2) memcached
 217          * (3) from the database.
 218          *
 219          * When succesfully loading from (2) or (3), all higher level caches are
 220          * updated for the newest version.
 221          *
 222          * Nothing is loaded if member variable mDisable is true, either manually
 223          * set by calling code or if message loading fails (is this possible?).
 224          *
 225          * Returns true if cache is already populated or it was succesfully populated,
 226          * or false if populating empty cache fails. Also returns true if MessageCache
 227          * is disabled.
 228          *
 229          * @param bool|string $code Language to which load messages
 230          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 231          * @throws MWException
 232          * @return bool
 233          */
 234         function load( $code = false, $mode = null ) {
 235                 if ( !is_string( $code ) ) {
 236                         # This isn't really nice, so at least make a note about it and try to
 237                         # fall back
 238                         wfDebug( __METHOD__ . " called without providing a language code\n" );
 239                         $code = 'en';
 240                 }
 241
 242                 # Don't do double loading...
 243                 if ( isset( $this->mLoadedLanguages[$code] ) && $mode != self::FOR_UPDATE ) {
 244                         return true;
 245                 }
 246
 247                 # 8 lines of code just to say (once) that message cache is disabled
 248                 if ( $this->mDisable ) {
 249                         static $shownDisabled = false;
 250                         if ( !$shownDisabled ) {
 251                                 wfDebug( __METHOD__ . ": disabled\n" );
 252                                 $shownDisabled = true;
 253                         }
 254
 255                         return true;
 256                 }
 257
 258                 # Loading code starts
 259                 $success = false; # Keep track of success
 260                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 261                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 262
 263                 # Hash of the contents is stored in memcache, to detect if data-center cache
 264                 # or local cache goes out of date (e.g. due to replace() on some other server)
 265                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 266
 267                 # Try the local cache and check against the cluster hash key...
 268                 $cache = $this->getLocalCache( $code );
 269                 if ( !$cache ) {
 270                         $where[] = 'local cache is empty';
 271                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 272                         $where[] = 'local cache has the wrong hash';
 273                         $staleCache = $cache;
 274                 } elseif ( $this->isCacheExpired( $cache ) ) {
 275                         $where[] = 'local cache is expired';
 276                         $staleCache = $cache;
 277                 } elseif ( $hashVolatile ) {
 278                         $where[] = 'local cache validation key is expired/volatile';
 279                         $staleCache = $cache;
 280                 } else {
 281                         $where[] = 'got from local cache';
 282                         $success = true;
 283                         $this->mCache[$code] = $cache;
 284                 }
 285
 286                 if ( !$success ) {
 287                         $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 288                         # Try the global cache. If it is empty, try to acquire a lock. If
 289                         # the lock can't be acquired, wait for the other thread to finish
 290                         # and then try the global cache a second time.
 291                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 292                                 if ( $hashVolatile && $staleCache ) {
 293                                         # Do not bother fetching the whole cache blob to avoid I/O.
 294                                         # Instead, just try to get the non-blocking $statusKey lock
 295                                         # below, and use the local stale value if it was not acquired.
 296                                         $where[] = 'global cache is presumed expired';
 297                                 } else {
 298                                         $cache = $this->mMemc->get( $cacheKey );
 299                                         if ( !$cache ) {
 300                                                 $where[] = 'global cache is empty';
 301                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 302                                                 $where[] = 'global cache is expired';
 303                                                 $staleCache = $cache;
 304                                         } elseif ( $hashVolatile ) {
 305                                                 # DB results are slave lag prone until the holdoff TTL passes.
 306                                                 # By then, updates should be reflected in loadFromDBWithLock().
 307                                                 # One thread renerates the cache while others use old values.
 308                                                 $where[] = 'global cache is expired/volatile';
 309                                                 $staleCache = $cache;
 310                                         } else {
 311                                                 $where[] = 'got from global cache';
 312                                                 $this->mCache[$code] = $cache;
 313                                                 $this->saveToCaches( $cache, 'local-only', $code );
 314                                                 $success = true;
 315                                         }
 316                                 }
 317
 318                                 if ( $success ) {
 319                                         # Done, no need to retry
 320                                         break;
 321                                 }
 322
 323                                 # We need to call loadFromDB. Limit the concurrency to one process.
 324                                 # This prevents the site from going down when the cache expires.
 325                                 # Note that the DB slam protection lock here is non-blocking.
 326                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 327                                 if ( $loadStatus === true ) {
 328                                         $success = true;
 329                                         break;
 330                                 } elseif ( $staleCache ) {
 331                                         # Use the stale cache while some other thread constructs the new one
 332                                         $where[] = 'using stale cache';
 333                                         $this->mCache[$code] = $staleCache;
 334                                         $success = true;
 335                                         break;
 336                                 } elseif ( $failedAttempts > 0 ) {
 337                                         # Already blocked once, so avoid another lock/unlock cycle.
 338                                         # This case will typically be hit if memcached is down, or if
 339                                         # loadFromDB() takes longer than LOCK_WAIT.
 340                                         $where[] = "could not acquire status key.";
 341                                         break;
 342                                 } elseif ( $loadStatus === 'cantacquire' ) {
 343                                         # Wait for the other thread to finish, then retry. Normally,
 344                                         # the memcached get() will then yeild the other thread's result.
 345                                         $where[] = 'waited for other thread to complete';
 346                                         $this->getReentrantScopedLock( $cacheKey );
 347                                 } else {
 348                                         # Disable cache; $loadStatus is 'disabled'
 349                                         break;
 350                                 }
 351                         }
 352                 }
 353
 354                 if ( !$success ) {
 355                         $where[] = 'loading FAILED - cache is disabled';
 356                         $this->mDisable = true;
 357                         $this->mCache = false;
 358                         # This used to throw an exception, but that led to nasty side effects like
 359                         # the whole wiki being instantly down if the memcached server died
 360                 } else {
 361                         # All good, just record the success
 362                         $this->mLoadedLanguages[$code] = true;
 363                 }
 364
 365                 $info = implode( ', ', $where );
 366                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 367
 368                 return $success;
 369         }
 370
 371         /**
 372          * @param string $code
 373          * @param array $where List of wfDebug() comments
 374          * @param integer $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 375          * @return bool|string True on success or one of ("cantacquire", "disabled")
 376          */
 377         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 378                 global $wgUseLocalMessageCache;
 379
 380                 # If cache updates on all levels fail, give up on message overrides.
 381                 # This is to avoid easy site outages; see $saveSuccess comments below.
 382                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 383                 $status = $this->mMemc->get( $statusKey );
 384                 if ( $status === 'error' ) {
 385                         $where[] = "could not load; method is still globally disabled";
 386                         return 'disabled';
 387                 }
 388
 389                 # Now let's regenerate
 390                 $where[] = 'loading from database';
 391
 392                 # Lock the cache to prevent conflicting writes.
 393                 # This lock is non-blocking so stale cache can quickly be used.
 394                 # Note that load() will call a blocking getReentrantScopedLock()
 395                 # after this if it really need to wait for any current thread.
 396                 $cacheKey = wfMemcKey( 'messages', $code );
 397                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 398                 if ( !$scopedLock ) {
 399                         $where[] = 'could not acquire main lock';
 400                         return 'cantacquire';
 401                 }
 402
 403                 $cache = $this->loadFromDB( $code, $mode );
 404                 $this->mCache[$code] = $cache;
 405                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 406
 407                 if ( !$saveSuccess ) {
 408                         /**
 409                          * Cache save has failed.
 410                          *
 411                          * There are two main scenarios where this could be a problem:
 412                          * - The cache is more than the maximum size (typically 1MB compressed).
 413                          * - Memcached has no space remaining in the relevant slab class. This is
 414                          *   unlikely with recent versions of memcached.
 415                          *
 416                          * Either way, if there is a local cache, nothing bad will happen. If there
 417                          * is no local cache, disabling the message cache for all requests avoids
 418                          * incurring a loadFromDB() overhead on every request, and thus saves the
 419                          * wiki from complete downtime under moderate traffic conditions.
 420                          */
 421                         if ( !$wgUseLocalMessageCache ) {
 422                                 $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 423                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 424                         } else {
 425                                 $where[] = "could not save global cache";
 426                         }
 427                 }
 428
 429                 return true;
 430         }
 431
 432         /**
 433          * Loads cacheable messages from the database. Messages bigger than
 434          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 435          * on-demand from the database later.
 436          *
 437          * @param string $code Language code
 438          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 439          * @return array Loaded messages for storing in caches
 440          */
 441         function loadFromDB( $code, $mode = null ) {
 442                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 443
 444                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_SLAVE );
 445
 446                 $cache = [];
 447
 448                 # Common conditions
 449                 $conds = [
 450                         'page_is_redirect' => 0,
 451                         'page_namespace' => NS_MEDIAWIKI,
 452                 ];
 453
 454                 $mostused = [];
 455                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 456                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 457                                 $this->load( $wgLanguageCode );
 458                         }
 459                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 460                         foreach ( $mostused as $key => $value ) {
 461                                 $mostused[$key] = "$value/$code";
 462                         }
 463                 }
 464
 465                 if ( count( $mostused ) ) {
 466                         $conds['page_title'] = $mostused;
 467                 } elseif ( $code !== $wgLanguageCode ) {
 468                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 469                 } else {
 470                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 471                         # other than language code.
 472                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 473                 }
 474
 475                 # Conditions to fetch oversized pages to ignore them
 476                 $bigConds = $conds;
 477                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 478
 479                 # Load titles for all oversized pages in the MediaWiki namespace
 480                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 481                 foreach ( $res as $row ) {
 482                         $cache[$row->page_title] = '!TOO BIG';
 483                 }
 484
 485                 # Conditions to load the remaining pages with their contents
 486                 $smallConds = $conds;
 487                 $smallConds[] = 'page_latest=rev_id';
 488                 $smallConds[] = 'rev_text_id=old_id';
 489                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 490
 491                 $res = $dbr->select(
 492                         [ 'page', 'revision', 'text' ],
 493                         [ 'page_title', 'old_text', 'old_flags' ],
 494                         $smallConds,
 495                         __METHOD__ . "($code)-small"
 496                 );
 497
 498                 foreach ( $res as $row ) {
 499                         $text = Revision::getRevisionText( $row );
 500                         if ( $text === false ) {
 501                                 // Failed to fetch data; possible ES errors?
 502                                 // Store a marker to fetch on-demand as a workaround...
 503                                 $entry = '!TOO BIG';
 504                                 wfDebugLog(
 505                                         'MessageCache',
 506                                         __METHOD__
 507                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 508                                 );
 509                         } else {
 510                                 $entry = ' ' . $text;
 511                         }
 512                         $cache[$row->page_title] = $entry;
 513                 }
 514
 515                 $cache['VERSION'] = MSG_CACHE_VERSION;
 516                 ksort( $cache );
 517                 $cache['HASH'] = md5( serialize( $cache ) );
 518                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 519
 520                 return $cache;
 521         }
 522
 523         /**
 524          * Updates cache as necessary when message page is changed
 525          *
 526          * @param string|bool $title Name of the page changed (false if deleted)
 527          * @param mixed $text New contents of the page.
 528          */
 529         public function replace( $title, $text ) {
 530                 global $wgMaxMsgCacheEntrySize, $wgContLang, $wgLanguageCode;
 531
 532                 if ( $this->mDisable ) {
 533                         return;
 534                 }
 535
 536                 list( $msg, $code ) = $this->figureMessage( $title );
 537                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 538                         // Content language overrides do not use the /<code> suffix
 539                         return;
 540                 }
 541
 542                 // Note that if the cache is volatile, load() may trigger a DB fetch.
 543                 // In that case we reenter/reuse the existing cache key lock to avoid
 544                 // a self-deadlock. This is safe as no reads happen *directly* in this
 545                 // method between getReentrantScopedLock() and load() below. There is
 546                 // no risk of data "changing under our feet" for replace().
 547                 $cacheKey = wfMemcKey( 'messages', $code );
 548                 $scopedLock = $this->getReentrantScopedLock( $cacheKey );
 549                 $this->load( $code, self::FOR_UPDATE );
 550
 551                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 552                 if ( $text === false ) {
 553                         // Article was deleted
 554                         $this->mCache[$code][$title] = '!NONEXISTENT';
 555                         $this->wanCache->delete( $titleKey );
 556                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 557                         // Check for size
 558                         $this->mCache[$code][$title] = '!TOO BIG';
 559                         $this->wanCache->set( $titleKey, ' ' . $text, $this->mExpiry );
 560                 } else {
 561                         $this->mCache[$code][$title] = ' ' . $text;
 562                         $this->wanCache->delete( $titleKey );
 563                 }
 564
 565                 // Mark this cache as definitely "latest" (non-volatile) so
 566                 // load() calls do try to refresh the cache with slave data
 567                 $this->mCache[$code]['LATEST'] = time();
 568
 569                 // Update caches if the lock was acquired
 570                 if ( $scopedLock ) {
 571                         $this->saveToCaches( $this->mCache[$code], 'all', $code );
 572                 }
 573
 574                 ScopedCallback::consume( $scopedLock );
 575                 // Relay the purge to APC and other DCs
 576                 $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
 577
 578                 // Also delete cached sidebar... just in case it is affected
 579                 $codes = [ $code ];
 580                 if ( $code === 'en' ) {
 581                         // Delete all sidebars, like for example on action=purge on the
 582                         // sidebar messages
 583                         $codes = array_keys( Language::fetchLanguageNames() );
 584                 }
 585
 586                 foreach ( $codes as $code ) {
 587                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 588                         $this->wanCache->delete( $sidebarKey );
 589                 }
 590
 591                 // Update the message in the message blob store
 592                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 593                 $blobStore = $resourceloader->getMessageBlobStore();
 594                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 595
 596                 Hooks::run( 'MessageCacheReplace', [ $title, $text ] );
 597         }
 598
 599         /**
 600          * Is the given cache array expired due to time passing or a version change?
 601          *
 602          * @param array $cache
 603          * @return bool
 604          */
 605         protected function isCacheExpired( $cache ) {
 606                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 607                         return true;
 608                 }
 609                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 610                         return true;
 611                 }
 612                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 613                         return true;
 614                 }
 615
 616                 return false;
 617         }
 618
 619         /**
 620          * Shortcut to update caches.
 621          *
 622          * @param array $cache Cached messages with a version.
 623          * @param string $dest Either "local-only" to save to local caches only
 624          *   or "all" to save to all caches.
 625          * @param string|bool $code Language code (default: false)
 626          * @return bool
 627          */
 628         protected function saveToCaches( array $cache, $dest, $code = false ) {
 629                 if ( $dest === 'all' ) {
 630                         $cacheKey = wfMemcKey( 'messages', $code );
 631                         $success = $this->mMemc->set( $cacheKey, $cache );
 632                 } else {
 633                         $success = true;
 634                 }
 635
 636                 $this->setValidationHash( $code, $cache );
 637                 $this->saveToLocalCache( $code, $cache );
 638
 639                 return $success;
 640         }
 641
 642         /**
 643          * Get the md5 used to validate the local APC cache
 644          *
 645          * @param string $code
 646          * @return array (hash or false, bool expiry/volatility status)
 647          */
 648         protected function getValidationHash( $code ) {
 649                 $curTTL = null;
 650                 $value = $this->wanCache->get(
 651                         wfMemcKey( 'messages', $code, 'hash', 'v1' ),
 652                         $curTTL,
 653                         [ wfMemcKey( 'messages', $code ) ]
 654                 );
 655
 656                 if ( !$value ) {
 657                         // No hash found at all; cache must regenerate to be safe
 658                         $hash = false;
 659                         $expired = true;
 660                 } else {
 661                         $hash = $value['hash'];
 662                         if ( ( time() - $value['latest'] ) < WANObjectCache::HOLDOFF_TTL ) {
 663                                 // Cache was recently updated via replace() and should be up-to-date
 664                                 $expired = false;
 665                         } else {
 666                                 // See if the "check" key was bumped after the hash was generated
 667                                 $expired = ( $curTTL < 0 );
 668                         }
 669                 }
 670
 671                 return [ $hash, $expired ];
 672         }
 673
 674         /**
 675          * Set the md5 used to validate the local disk cache
 676          *
 677          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 678          * be treated as "volatile" by getValidationHash() for the next few seconds
 679          *
 680          * @param string $code
 681          * @param array $cache Cached messages with a version
 682          */
 683         protected function setValidationHash( $code, array $cache ) {
 684                 $this->wanCache->set(
 685                         wfMemcKey( 'messages', $code, 'hash', 'v1' ),
 686                         [
 687                                 'hash' => $cache['HASH'],
 688                                 'latest' => isset( $cache['LATEST'] ) ? $cache['LATEST'] : 0
 689                         ],
 690                         WANObjectCache::TTL_INDEFINITE
 691                 );
 692         }
 693
 694         /**
 695          * @param string $key A language message cache key that stores blobs
 696          * @param integer $timeout Wait timeout in seconds
 697          * @return null|ScopedCallback
 698          */
 699         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 700                 return $this->mMemc->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 701         }
 702
 703         /**
 704          * Get a message from either the content language or the user language.
 705          *
 706          * First, assemble a list of languages to attempt getting the message from. This
 707          * chain begins with the requested language and its fallbacks and then continues with
 708          * the content language and its fallbacks. For each language in the chain, the following
 709          * process will occur (in this order):
 710          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 711          *     Note: for the content language, there is no /lang subpage.
 712          *  2. Fetch from the static CDB cache.
 713          *  3. If available, check the database for fallback language overrides.
 714          *
 715          * This process provides a number of guarantees. When changing this code, make sure all
 716          * of these guarantees are preserved.
 717          *  * If the requested language is *not* the content language, then the CDB cache for that
 718          *    specific language will take precedence over the root database page ([[MW:msg]]).
 719          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 720          *    the message is available *anywhere* in the language for which it is a fallback.
 721          *
 722          * @param string $key The message key
 723          * @param bool $useDB If true, look for the message in the DB, false
 724          *   to use only the compiled l10n cache.
 725          * @param bool|string|object $langcode Code of the language to get the message for.
 726          *   - If string and a valid code, will create a standard language object
 727          *   - If string but not a valid code, will create a basic language object
 728          *   - If boolean and false, create object from the current users language
 729          *   - If boolean and true, create object from the wikis content language
 730          *   - If language object, use it as given
 731          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 732          *
 733          * @throws MWException When given an invalid key
 734          * @return string|bool False if the message doesn't exist, otherwise the
 735          *   message (which can be empty)
 736          */
 737         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 738                 if ( is_int( $key ) ) {
 739                         // Fix numerical strings that somehow become ints
 740                         // on their way here
 741                         $key = (string)$key;
 742                 } elseif ( !is_string( $key ) ) {
 743                         throw new MWException( 'Non-string key given' );
 744                 } elseif ( $key === '' ) {
 745                         // Shortcut: the empty key is always missing
 746                         return false;
 747                 }
 748
 749                 // For full keys, get the language code from the key
 750                 $pos = strrpos( $key, '/' );
 751                 if ( $isFullKey && $pos !== false ) {
 752                         $langcode = substr( $key, $pos + 1 );
 753                         $key = substr( $key, 0, $pos );
 754                 }
 755
 756                 // Normalise title-case input (with some inlining)
 757                 $lckey = MessageCache::normalizeKey( $key );
 758
 759                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 760
 761                 // Loop through each language in the fallback list until we find something useful
 762                 $lang = wfGetLangObj( $langcode );
 763                 $message = $this->getMessageFromFallbackChain(
 764                         $lang,
 765                         $lckey,
 766                         !$this->mDisable && $useDB
 767                 );
 768
 769                 // If we still have no message, maybe the key was in fact a full key so try that
 770                 if ( $message === false ) {
 771                         $parts = explode( '/', $lckey );
 772                         // We may get calls for things that are http-urls from sidebar
 773                         // Let's not load nonexistent languages for those
 774                         // They usually have more than one slash.
 775                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 776                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 777                                 if ( $message === null ) {
 778                                         $message = false;
 779                                 }
 780                         }
 781                 }
 782
 783                 // Post-processing if the message exists
 784                 if ( $message !== false ) {
 785                         // Fix whitespace
 786                         $message = str_replace(
 787                                 [
 788                                         # Fix for trailing whitespace, removed by textarea
 789                                         '&#32;',
 790                                         # Fix for NBSP, converted to space by firefox
 791                                         '&nbsp;',
 792                                         '&#160;',
 793                                         '&shy;'
 794                                 ],
 795                                 [
 796                                         ' ',
 797                                         "\xc2\xa0",
 798                                         "\xc2\xa0",
 799                                         "\xc2\xad"
 800                                 ],
 801                                 $message
 802                         );
 803                 }
 804
 805                 return $message;
 806         }
 807
 808         /**
 809          * Given a language, try and fetch messages from that language.
 810          *
 811          * Will also consider fallbacks of that language, the site language, and fallbacks for
 812          * the site language.
 813          *
 814          * @see MessageCache::get
 815          * @param Language|StubObject $lang Preferred language
 816          * @param string $lckey Lowercase key for the message (as for localisation cache)
 817          * @param bool $useDB Whether to include messages from the wiki database
 818          * @return string|bool The message, or false if not found
 819          */
 820         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 821                 global $wgLanguageCode, $wgContLang;
 822
 823                 $uckey = $wgContLang->ucfirst( $lckey );
 824                 $langcode = $lang->getCode();
 825                 $message = false;
 826
 827                 // First try the requested language.
 828                 if ( $useDB ) {
 829                         if ( $langcode === $wgLanguageCode ) {
 830                                 // Messages created in the content language will not have the /lang extension
 831                                 $message = $this->getMsgFromNamespace( $uckey, $langcode );
 832                         } else {
 833                                 $message = $this->getMsgFromNamespace( "$uckey/$langcode", $langcode );
 834                         }
 835                 }
 836
 837                 if ( $message !== false ) {
 838                         return $message;
 839                 }
 840
 841                 // Check the CDB cache
 842                 $message = $lang->getMessage( $lckey );
 843                 if ( $message !== null ) {
 844                         return $message;
 845                 }
 846
 847                 list( $fallbackChain, $siteFallbackChain ) =
 848                         Language::getFallbacksIncludingSiteLanguage( $langcode );
 849
 850                 // Next try checking the database for all of the fallback languages of the requested language.
 851                 if ( $useDB ) {
 852                         foreach ( $fallbackChain as $code ) {
 853                                 if ( $code === $wgLanguageCode ) {
 854                                         // Messages created in the content language will not have the /lang extension
 855                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 856                                 } else {
 857                                         $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 858                                 }
 859
 860                                 if ( $message !== false ) {
 861                                         // Found the message.
 862                                         return $message;
 863                                 }
 864                         }
 865                 }
 866
 867                 // Now try checking the site language.
 868                 if ( $useDB ) {
 869                         $message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
 870                         if ( $message !== false ) {
 871                                 return $message;
 872                         }
 873                 }
 874
 875                 $message = $wgContLang->getMessage( $lckey );
 876                 if ( $message !== null ) {
 877                         return $message;
 878                 }
 879
 880                 // Finally try the DB for the site language's fallbacks.
 881                 if ( $useDB ) {
 882                         foreach ( $siteFallbackChain as $code ) {
 883                                 $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 884                                 if ( $message === false && $code === $wgLanguageCode ) {
 885                                         // Messages created in the content language will not have the /lang extension
 886                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 887                                 }
 888
 889                                 if ( $message !== false ) {
 890                                         // Found the message.
 891                                         return $message;
 892                                 }
 893                         }
 894                 }
 895
 896                 return false;
 897         }
 898
 899         /**
 900          * Get a message from the MediaWiki namespace, with caching. The key must
 901          * first be converted to two-part lang/msg form if necessary.
 902          *
 903          * Unlike self::get(), this function doesn't resolve fallback chains, and
 904          * some callers require this behavior. LanguageConverter::parseCachedTable()
 905          * and self::get() are some examples in core.
 906          *
 907          * @param string $title Message cache key with initial uppercase letter.
 908          * @param string $code Code denoting the language to try.
 909          * @return string|bool The message, or false if it does not exist or on error
 910          */
 911         public function getMsgFromNamespace( $title, $code ) {
 912                 $this->load( $code );
 913                 if ( isset( $this->mCache[$code][$title] ) ) {
 914                         $entry = $this->mCache[$code][$title];
 915                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 916                                 // The message exists, so make sure a string
 917                                 // is returned.
 918                                 return (string)substr( $entry, 1 );
 919                         } elseif ( $entry === '!NONEXISTENT' ) {
 920                                 return false;
 921                         } elseif ( $entry === '!TOO BIG' ) {
 922                                 // Fall through and try invididual message cache below
 923                         }
 924                 } else {
 925                         // XXX: This is not cached in process cache, should it?
 926                         $message = false;
 927                         Hooks::run( 'MessagesPreLoad', [ $title, &$message ] );
 928                         if ( $message !== false ) {
 929                                 return $message;
 930                         }
 931
 932                         return false;
 933                 }
 934
 935                 # Try the individual message cache
 936                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 937                 $entry = $this->wanCache->get( $titleKey );
 938                 if ( $entry ) {
 939                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 940                                 $this->mCache[$code][$title] = $entry;
 941
 942                                 // The message exists, so make sure a string
 943                                 // is returned.
 944                                 return (string)substr( $entry, 1 );
 945                         } elseif ( $entry === '!NONEXISTENT' ) {
 946                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 947
 948                                 return false;
 949                         } else {
 950                                 # Corrupt/obsolete entry, delete it
 951                                 $this->wanCache->delete( $titleKey );
 952                         }
 953                 }
 954
 955                 # Try loading it from the database
 956                 $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 957                 if ( $revision ) {
 958                         $content = $revision->getContent();
 959                         if ( !$content ) {
 960                                 // A possibly temporary loading failure.
 961                                 wfDebugLog(
 962                                         'MessageCache',
 963                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
 964                                 );
 965                                 $message = null; // no negative caching
 966                         } else {
 967                                 // XXX: Is this the right way to turn a Content object into a message?
 968                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
 969                                 //       CssContent. MessageContent is *not* used for storing messages, it's
 970                                 //       only used for wrapping them when needed.
 971                                 $message = $content->getWikitextForTransclusion();
 972
 973                                 if ( $message === false || $message === null ) {
 974                                         wfDebugLog(
 975                                                 'MessageCache',
 976                                                 __METHOD__ . ": message content doesn't provide wikitext "
 977                                                         . "(content model: " . $content->getModel() . ")"
 978                                         );
 979
 980                                         $message = false; // negative caching
 981                                 } else {
 982                                         $this->mCache[$code][$title] = ' ' . $message;
 983                                         $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry );
 984                                 }
 985                         }
 986                 } else {
 987                         $message = false; // negative caching
 988                 }
 989
 990                 if ( $message === false ) { // negative caching
 991                         $this->mCache[$code][$title] = '!NONEXISTENT';
 992                         $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
 993                 }
 994
 995                 return $message;
 996         }
 997
 998         /**
 999          * @param string $message
1000          * @param bool $interface
1001          * @param string $language Language code
1002          * @param Title $title
1003          * @return string
1004          */
1005         function transform( $message, $interface = false, $language = null, $title = null ) {
1006                 // Avoid creating parser if nothing to transform
1007                 if ( strpos( $message, '{{' ) === false ) {
1008                         return $message;
1009                 }
1010
1011                 if ( $this->mInParser ) {
1012                         return $message;
1013                 }
1014
1015                 $parser = $this->getParser();
1016                 if ( $parser ) {
1017                         $popts = $this->getParserOptions();
1018                         $popts->setInterfaceMessage( $interface );
1019                         $popts->setTargetLanguage( $language );
1020
1021                         $userlang = $popts->setUserLang( $language );
1022                         $this->mInParser = true;
1023                         $message = $parser->transformMsg( $message, $popts, $title );
1024                         $this->mInParser = false;
1025                         $popts->setUserLang( $userlang );
1026                 }
1027
1028                 return $message;
1029         }
1030
1031         /**
1032          * @return Parser
1033          */
1034         function getParser() {
1035                 global $wgParser, $wgParserConf;
1036                 if ( !$this->mParser && isset( $wgParser ) ) {
1037                         # Do some initialisation so that we don't have to do it twice
1038                         $wgParser->firstCallInit();
1039                         # Clone it and store it
1040                         $class = $wgParserConf['class'];
1041                         if ( $class == 'ParserDiffTest' ) {
1042                                 # Uncloneable
1043                                 $this->mParser = new $class( $wgParserConf );
1044                         } else {
1045                                 $this->mParser = clone $wgParser;
1046                         }
1047                 }
1048
1049                 return $this->mParser;
1050         }
1051
1052         /**
1053          * @param string $text
1054          * @param Title $title
1055          * @param bool $linestart Whether or not this is at the start of a line
1056          * @param bool $interface Whether this is an interface message
1057          * @param Language|string $language Language code
1058          * @return ParserOutput|string
1059          */
1060         public function parse( $text, $title = null, $linestart = true,
1061                 $interface = false, $language = null
1062         ) {
1063                 if ( $this->mInParser ) {
1064                         return htmlspecialchars( $text );
1065                 }
1066
1067                 $parser = $this->getParser();
1068                 $popts = $this->getParserOptions();
1069                 $popts->setInterfaceMessage( $interface );
1070
1071                 if ( is_string( $language ) ) {
1072                         $language = Language::factory( $language );
1073                 }
1074                 $popts->setTargetLanguage( $language );
1075
1076                 if ( !$title || !$title instanceof Title ) {
1077                         global $wgTitle;
1078                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1079                                 wfGetAllCallers( 5 ) . ' with no title set.' );
1080                         $title = $wgTitle;
1081                 }
1082                 // Sometimes $wgTitle isn't set either...
1083                 if ( !$title ) {
1084                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1085                         # Create a ghost title in such case
1086                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1087                 }
1088
1089                 $this->mInParser = true;
1090                 $res = $parser->parse( $text, $title, $popts, $linestart );
1091                 $this->mInParser = false;
1092
1093                 return $res;
1094         }
1095
1096         function disable() {
1097                 $this->mDisable = true;
1098         }
1099
1100         function enable() {
1101                 $this->mDisable = false;
1102         }
1103
1104         /**
1105          * Clear all stored messages. Mainly used after a mass rebuild.
1106          */
1107         function clear() {
1108                 $langs = Language::fetchLanguageNames( null, 'mw' );
1109                 foreach ( array_keys( $langs ) as $code ) {
1110                         # Global and local caches
1111                         $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
1112                 }
1113
1114                 $this->mLoadedLanguages = [];
1115         }
1116
1117         /**
1118          * @param string $key
1119          * @return array
1120          */
1121         public function figureMessage( $key ) {
1122                 global $wgLanguageCode;
1123
1124                 $pieces = explode( '/', $key );
1125                 if ( count( $pieces ) < 2 ) {
1126                         return [ $key, $wgLanguageCode ];
1127                 }
1128
1129                 $lang = array_pop( $pieces );
1130                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1131                         return [ $key, $wgLanguageCode ];
1132                 }
1133
1134                 $message = implode( '/', $pieces );
1135
1136                 return [ $message, $lang ];
1137         }
1138
1139         /**
1140          * Get all message keys stored in the message cache for a given language.
1141          * If $code is the content language code, this will return all message keys
1142          * for which MediaWiki:msgkey exists. If $code is another language code, this
1143          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1144          * @param string $code Language code
1145          * @return array Array of message keys (strings)
1146          */
1147         public function getAllMessageKeys( $code ) {
1148                 global $wgContLang;
1149                 $this->load( $code );
1150                 if ( !isset( $this->mCache[$code] ) ) {
1151                         // Apparently load() failed
1152                         return null;
1153                 }
1154                 // Remove administrative keys
1155                 $cache = $this->mCache[$code];
1156                 unset( $cache['VERSION'] );
1157                 unset( $cache['EXPIRY'] );
1158                 // Remove any !NONEXISTENT keys
1159                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1160
1161                 // Keys may appear with a capital first letter. lcfirst them.
1162                 return array_map( [ $wgContLang, 'lcfirst' ], array_keys( $cache ) );
1163         }
1164 }