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 use MediaWiki\MediaWikiServices;
  24 use Wikimedia\ScopedCallback;
  25 use MediaWiki\Logger\LoggerFactory;
  26 use Wikimedia\Rdbms\Database;
  27
  28 /**
  29  * MediaWiki message cache structure version.
  30  * Bump this whenever the message cache format has changed.
  31  */
  32 define( 'MSG_CACHE_VERSION', 2 );
  33
  34 /**
  35  * Cache of messages that are defined by MediaWiki namespace pages or by hooks
  36  *
  37  * Performs various MediaWiki namespace-related functions
  38  * @ingroup Cache
  39  */
  40 class MessageCache {
  41         const FOR_UPDATE = 1; // force message reload
  42
  43         /** How long to wait for memcached locks */
  44         const WAIT_SEC = 15;
  45         /** How long memcached locks last */
  46         const LOCK_TTL = 30;
  47
  48         /**
  49          * Process local cache of loaded messages that are defined in
  50          * MediaWiki namespace. First array level is a language code,
  51          * second level is message key and the values are either message
  52          * content prefixed with space, or !NONEXISTENT for negative
  53          * caching.
  54          * @var array $mCache
  55          */
  56         protected $mCache;
  57
  58         /**
  59          * @var bool[] Map of (language code => boolean)
  60          */
  61         protected $mCacheVolatile = [];
  62
  63         /**
  64          * Should mean that database cannot be used, but check
  65          * @var bool $mDisable
  66          */
  67         protected $mDisable;
  68
  69         /**
  70          * Lifetime for cache, used by object caching.
  71          * Set on construction, see __construct().
  72          */
  73         protected $mExpiry;
  74
  75         /**
  76          * Message cache has its own parser which it uses to transform messages
  77          * @var ParserOptions
  78          */
  79         protected $mParserOptions;
  80         /** @var Parser */
  81         protected $mParser;
  82
  83         /**
  84          * Variable for tracking which variables are already loaded
  85          * @var array $mLoadedLanguages
  86          */
  87         protected $mLoadedLanguages = [];
  88
  89         /**
  90          * @var bool $mInParser
  91          */
  92         protected $mInParser = false;
  93
  94         /** @var WANObjectCache */
  95         protected $wanCache;
  96         /** @var BagOStuff */
  97         protected $clusterCache;
  98         /** @var BagOStuff */
  99         protected $srvCache;
 100
 101         /**
 102          * Singleton instance
 103          *
 104          * @var MessageCache $instance
 105          */
 106         private static $instance;
 107
 108         /**
 109          * Get the signleton instance of this class
 110          *
 111          * @since 1.18
 112          * @return MessageCache
 113          */
 114         public static function singleton() {
 115                 if ( self::$instance === null ) {
 116                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry, $wgUseLocalMessageCache;
 117                         self::$instance = new self(
 118                                 MediaWikiServices::getInstance()->getMainWANObjectCache(),
 119                                 wfGetMessageCacheStorage(),
 120                                 $wgUseLocalMessageCache
 121                                         ? MediaWikiServices::getInstance()->getLocalServerObjectCache()
 122                                         : new EmptyBagOStuff(),
 123                                 $wgUseDatabaseMessages,
 124                                 $wgMsgCacheExpiry
 125                         );
 126                 }
 127
 128                 return self::$instance;
 129         }
 130
 131         /**
 132          * Destroy the singleton instance
 133          *
 134          * @since 1.18
 135          */
 136         public static function destroyInstance() {
 137                 self::$instance = null;
 138         }
 139
 140         /**
 141          * Normalize message key input
 142          *
 143          * @param string $key Input message key to be normalized
 144          * @return string Normalized message key
 145          */
 146         public static function normalizeKey( $key ) {
 147                 global $wgContLang;
 148
 149                 $lckey = strtr( $key, ' ', '_' );
 150                 if ( ord( $lckey ) < 128 ) {
 151                         $lckey[0] = strtolower( $lckey[0] );
 152                 } else {
 153                         $lckey = $wgContLang->lcfirst( $lckey );
 154                 }
 155
 156                 return $lckey;
 157         }
 158
 159         /**
 160          * @param WANObjectCache $wanCache
 161          * @param BagOStuff $clusterCache
 162          * @param BagOStuff $serverCache
 163          * @param bool $useDB Whether to look for message overrides (e.g. MediaWiki: pages)
 164          * @param int $expiry Lifetime for cache. @see $mExpiry.
 165          */
 166         public function __construct(
 167                 WANObjectCache $wanCache,
 168                 BagOStuff $clusterCache,
 169                 BagOStuff $serverCache,
 170                 $useDB,
 171                 $expiry
 172         ) {
 173                 $this->wanCache = $wanCache;
 174                 $this->clusterCache = $clusterCache;
 175                 $this->srvCache = $serverCache;
 176
 177                 $this->mDisable = !$useDB;
 178                 $this->mExpiry = $expiry;
 179         }
 180
 181         /**
 182          * ParserOptions is lazy initialised.
 183          *
 184          * @return ParserOptions
 185          */
 186         function getParserOptions() {
 187                 global $wgUser;
 188
 189                 if ( !$this->mParserOptions ) {
 190                         if ( !$wgUser->isSafeToLoad() ) {
 191                                 // $wgUser isn't unstubbable yet, so don't try to get a
 192                                 // ParserOptions for it. And don't cache this ParserOptions
 193                                 // either.
 194                                 $po = ParserOptions::newFromAnon();
 195                                 $po->setAllowUnsafeRawHtml( false );
 196                                 return $po;
 197                         }
 198
 199                         $this->mParserOptions = new ParserOptions;
 200                         // Messages may take parameters that could come
 201                         // from malicious sources. As a precaution, disable
 202                         // the <html> parser tag when parsing messages.
 203                         $this->mParserOptions->setAllowUnsafeRawHtml( false );
 204                 }
 205
 206                 return $this->mParserOptions;
 207         }
 208
 209         /**
 210          * Try to load the cache from APC.
 211          *
 212          * @param string $code Optional language code, see documenation of load().
 213          * @return array|bool The cache array, or false if not in cache.
 214          */
 215         protected function getLocalCache( $code ) {
 216                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 217
 218                 return $this->srvCache->get( $cacheKey );
 219         }
 220
 221         /**
 222          * Save the cache to APC.
 223          *
 224          * @param string $code
 225          * @param array $cache The cache array
 226          */
 227         protected function saveToLocalCache( $code, $cache ) {
 228                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 229                 $this->srvCache->set( $cacheKey, $cache );
 230         }
 231
 232         /**
 233          * Loads messages from caches or from database in this order:
 234          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 235          * (2) memcached
 236          * (3) from the database.
 237          *
 238          * When succesfully loading from (2) or (3), all higher level caches are
 239          * updated for the newest version.
 240          *
 241          * Nothing is loaded if member variable mDisable is true, either manually
 242          * set by calling code or if message loading fails (is this possible?).
 243          *
 244          * Returns true if cache is already populated or it was succesfully populated,
 245          * or false if populating empty cache fails. Also returns true if MessageCache
 246          * is disabled.
 247          *
 248          * @param string $code Language to which load messages
 249          * @param int $mode Use MessageCache::FOR_UPDATE to skip process cache [optional]
 250          * @throws MWException
 251          * @return bool
 252          */
 253         protected function load( $code, $mode = null ) {
 254                 if ( !is_string( $code ) ) {
 255                         throw new InvalidArgumentException( "Missing language code" );
 256                 }
 257
 258                 # Don't do double loading...
 259                 if ( isset( $this->mLoadedLanguages[$code] ) && $mode != self::FOR_UPDATE ) {
 260                         return true;
 261                 }
 262
 263                 # 8 lines of code just to say (once) that message cache is disabled
 264                 if ( $this->mDisable ) {
 265                         static $shownDisabled = false;
 266                         if ( !$shownDisabled ) {
 267                                 wfDebug( __METHOD__ . ": disabled\n" );
 268                                 $shownDisabled = true;
 269                         }
 270
 271                         return true;
 272                 }
 273
 274                 # Loading code starts
 275                 $success = false; # Keep track of success
 276                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 277                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 278
 279                 # Hash of the contents is stored in memcache, to detect if data-center cache
 280                 # or local cache goes out of date (e.g. due to replace() on some other server)
 281                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 282                 $this->mCacheVolatile[$code] = $hashVolatile;
 283
 284                 # Try the local cache and check against the cluster hash key...
 285                 $cache = $this->getLocalCache( $code );
 286                 if ( !$cache ) {
 287                         $where[] = 'local cache is empty';
 288                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 289                         $where[] = 'local cache has the wrong hash';
 290                         $staleCache = $cache;
 291                 } elseif ( $this->isCacheExpired( $cache ) ) {
 292                         $where[] = 'local cache is expired';
 293                         $staleCache = $cache;
 294                 } elseif ( $hashVolatile ) {
 295                         $where[] = 'local cache validation key is expired/volatile';
 296                         $staleCache = $cache;
 297                 } else {
 298                         $where[] = 'got from local cache';
 299                         $success = true;
 300                         $this->mCache[$code] = $cache;
 301                 }
 302
 303                 if ( !$success ) {
 304                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 305                         # Try the global cache. If it is empty, try to acquire a lock. If
 306                         # the lock can't be acquired, wait for the other thread to finish
 307                         # and then try the global cache a second time.
 308                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 309                                 if ( $hashVolatile && $staleCache ) {
 310                                         # Do not bother fetching the whole cache blob to avoid I/O.
 311                                         # Instead, just try to get the non-blocking $statusKey lock
 312                                         # below, and use the local stale value if it was not acquired.
 313                                         $where[] = 'global cache is presumed expired';
 314                                 } else {
 315                                         $cache = $this->clusterCache->get( $cacheKey );
 316                                         if ( !$cache ) {
 317                                                 $where[] = 'global cache is empty';
 318                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 319                                                 $where[] = 'global cache is expired';
 320                                                 $staleCache = $cache;
 321                                         } elseif ( $hashVolatile ) {
 322                                                 # DB results are replica DB lag prone until the holdoff TTL passes.
 323                                                 # By then, updates should be reflected in loadFromDBWithLock().
 324                                                 # One thread renerates the cache while others use old values.
 325                                                 $where[] = 'global cache is expired/volatile';
 326                                                 $staleCache = $cache;
 327                                         } else {
 328                                                 $where[] = 'got from global cache';
 329                                                 $this->mCache[$code] = $cache;
 330                                                 $this->saveToCaches( $cache, 'local-only', $code );
 331                                                 $success = true;
 332                                         }
 333                                 }
 334
 335                                 if ( $success ) {
 336                                         # Done, no need to retry
 337                                         break;
 338                                 }
 339
 340                                 # We need to call loadFromDB. Limit the concurrency to one process.
 341                                 # This prevents the site from going down when the cache expires.
 342                                 # Note that the DB slam protection lock here is non-blocking.
 343                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 344                                 if ( $loadStatus === true ) {
 345                                         $success = true;
 346                                         break;
 347                                 } elseif ( $staleCache ) {
 348                                         # Use the stale cache while some other thread constructs the new one
 349                                         $where[] = 'using stale cache';
 350                                         $this->mCache[$code] = $staleCache;
 351                                         $success = true;
 352                                         break;
 353                                 } elseif ( $failedAttempts > 0 ) {
 354                                         # Already blocked once, so avoid another lock/unlock cycle.
 355                                         # This case will typically be hit if memcached is down, or if
 356                                         # loadFromDB() takes longer than LOCK_WAIT.
 357                                         $where[] = "could not acquire status key.";
 358                                         break;
 359                                 } elseif ( $loadStatus === 'cantacquire' ) {
 360                                         # Wait for the other thread to finish, then retry. Normally,
 361                                         # the memcached get() will then yeild the other thread's result.
 362                                         $where[] = 'waited for other thread to complete';
 363                                         $this->getReentrantScopedLock( $cacheKey );
 364                                 } else {
 365                                         # Disable cache; $loadStatus is 'disabled'
 366                                         break;
 367                                 }
 368                         }
 369                 }
 370
 371                 if ( !$success ) {
 372                         $where[] = 'loading FAILED - cache is disabled';
 373                         $this->mDisable = true;
 374                         $this->mCache = false;
 375                         wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
 376                         # This used to throw an exception, but that led to nasty side effects like
 377                         # the whole wiki being instantly down if the memcached server died
 378                 } else {
 379                         # All good, just record the success
 380                         $this->mLoadedLanguages[$code] = true;
 381                 }
 382
 383                 $info = implode( ', ', $where );
 384                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 385
 386                 return $success;
 387         }
 388
 389         /**
 390          * @param string $code
 391          * @param array &$where List of wfDebug() comments
 392          * @param int $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 393          * @return bool|string True on success or one of ("cantacquire", "disabled")
 394          */
 395         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 396                 # If cache updates on all levels fail, give up on message overrides.
 397                 # This is to avoid easy site outages; see $saveSuccess comments below.
 398                 $statusKey = $this->clusterCache->makeKey( 'messages', $code, 'status' );
 399                 $status = $this->clusterCache->get( $statusKey );
 400                 if ( $status === 'error' ) {
 401                         $where[] = "could not load; method is still globally disabled";
 402                         return 'disabled';
 403                 }
 404
 405                 # Now let's regenerate
 406                 $where[] = 'loading from database';
 407
 408                 # Lock the cache to prevent conflicting writes.
 409                 # This lock is non-blocking so stale cache can quickly be used.
 410                 # Note that load() will call a blocking getReentrantScopedLock()
 411                 # after this if it really need to wait for any current thread.
 412                 $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 413                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 414                 if ( !$scopedLock ) {
 415                         $where[] = 'could not acquire main lock';
 416                         return 'cantacquire';
 417                 }
 418
 419                 $cache = $this->loadFromDB( $code, $mode );
 420                 $this->mCache[$code] = $cache;
 421                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 422
 423                 if ( !$saveSuccess ) {
 424                         /**
 425                          * Cache save has failed.
 426                          *
 427                          * There are two main scenarios where this could be a problem:
 428                          * - The cache is more than the maximum size (typically 1MB compressed).
 429                          * - Memcached has no space remaining in the relevant slab class. This is
 430                          *   unlikely with recent versions of memcached.
 431                          *
 432                          * Either way, if there is a local cache, nothing bad will happen. If there
 433                          * is no local cache, disabling the message cache for all requests avoids
 434                          * incurring a loadFromDB() overhead on every request, and thus saves the
 435                          * wiki from complete downtime under moderate traffic conditions.
 436                          */
 437                         if ( $this->srvCache instanceof EmptyBagOStuff ) {
 438                                 $this->clusterCache->set( $statusKey, 'error', 60 * 5 );
 439                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 440                         } else {
 441                                 $where[] = "could not save global cache";
 442                         }
 443                 }
 444
 445                 return true;
 446         }
 447
 448         /**
 449          * Loads cacheable messages from the database. Messages bigger than
 450          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 451          * on-demand from the database later.
 452          *
 453          * @param string $code Language code
 454          * @param int $mode Use MessageCache::FOR_UPDATE to skip process cache
 455          * @return array Loaded messages for storing in caches
 456          */
 457         protected function loadFromDB( $code, $mode = null ) {
 458                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 459
 460                 // (T164666) The query here performs really poorly on WMF's
 461                 // contributions replicas. We don't have a way to say "any group except
 462                 // contributions", so for the moment let's specify 'api'.
 463                 // @todo: Get rid of this hack.
 464                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA, 'api' );
 465
 466                 $cache = [];
 467
 468                 # Common conditions
 469                 $conds = [
 470                         'page_is_redirect' => 0,
 471                         'page_namespace' => NS_MEDIAWIKI,
 472                 ];
 473
 474                 $mostused = [];
 475                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 476                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 477                                 $this->load( $wgLanguageCode );
 478                         }
 479                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 480                         foreach ( $mostused as $key => $value ) {
 481                                 $mostused[$key] = "$value/$code";
 482                         }
 483                 }
 484
 485                 if ( count( $mostused ) ) {
 486                         $conds['page_title'] = $mostused;
 487                 } elseif ( $code !== $wgLanguageCode ) {
 488                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 489                 } else {
 490                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 491                         # other than language code.
 492                         $conds[] = 'page_title NOT' .
 493                                 $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 494                 }
 495
 496                 # Conditions to fetch oversized pages to ignore them
 497                 $bigConds = $conds;
 498                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 499
 500                 # Load titles for all oversized pages in the MediaWiki namespace
 501                 $res = $dbr->select(
 502                         'page',
 503                         [ 'page_title', 'page_latest' ],
 504                         $bigConds,
 505                         __METHOD__ . "($code)-big"
 506                 );
 507                 foreach ( $res as $row ) {
 508                         $cache[$row->page_title] = '!TOO BIG';
 509                         // At least include revision ID so page changes are reflected in the hash
 510                         $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 511                 }
 512
 513                 # Conditions to load the remaining pages with their contents
 514                 $smallConds = $conds;
 515                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 516
 517                 $res = $dbr->select(
 518                         [ 'page', 'revision', 'text' ],
 519                         [ 'page_title', 'old_id', 'old_text', 'old_flags' ],
 520                         $smallConds,
 521                         __METHOD__ . "($code)-small",
 522                         [],
 523                         [
 524                                 'revision' => [ 'JOIN', 'page_latest=rev_id' ],
 525                                 'text' => [ 'JOIN', 'rev_text_id=old_id' ],
 526                         ]
 527                 );
 528
 529                 foreach ( $res as $row ) {
 530                         $text = Revision::getRevisionText( $row );
 531                         if ( $text === false ) {
 532                                 // Failed to fetch data; possible ES errors?
 533                                 // Store a marker to fetch on-demand as a workaround...
 534                                 // TODO Use a differnt marker
 535                                 $entry = '!TOO BIG';
 536                                 wfDebugLog(
 537                                         'MessageCache',
 538                                         __METHOD__
 539                                         . ": failed to load message page text for {$row->page_title} ($code)"
 540                                 );
 541                         } else {
 542                                 $entry = ' ' . $text;
 543                         }
 544                         $cache[$row->page_title] = $entry;
 545                 }
 546
 547                 $cache['VERSION'] = MSG_CACHE_VERSION;
 548                 ksort( $cache );
 549
 550                 # Hash for validating local cache (APC). No need to take into account
 551                 # messages larger than $wgMaxMsgCacheEntrySize, since those are only
 552                 # stored and fetched from memcache.
 553                 $cache['HASH'] = md5( serialize( $cache ) );
 554                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 555
 556                 return $cache;
 557         }
 558
 559         /**
 560          * Updates cache as necessary when message page is changed
 561          *
 562          * @param string $title Message cache key with initial uppercase letter
 563          * @param string|bool $text New contents of the page (false if deleted)
 564          */
 565         public function replace( $title, $text ) {
 566                 global $wgLanguageCode;
 567
 568                 if ( $this->mDisable ) {
 569                         return;
 570                 }
 571
 572                 list( $msg, $code ) = $this->figureMessage( $title );
 573                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 574                         // Content language overrides do not use the /<code> suffix
 575                         return;
 576                 }
 577
 578                 // (a) Update the process cache with the new message text
 579                 if ( $text === false ) {
 580                         // Page deleted
 581                         $this->mCache[$code][$title] = '!NONEXISTENT';
 582                 } else {
 583                         // Ignore $wgMaxMsgCacheEntrySize so the process cache is up to date
 584                         $this->mCache[$code][$title] = ' ' . $text;
 585                 }
 586
 587                 // (b) Update the shared caches in a deferred update with a fresh DB snapshot
 588                 DeferredUpdates::addCallableUpdate(
 589                         function () use ( $title, $msg, $code ) {
 590                                 global $wgContLang, $wgMaxMsgCacheEntrySize;
 591                                 // Allow one caller at a time to avoid race conditions
 592                                 $scopedLock = $this->getReentrantScopedLock(
 593                                         $this->clusterCache->makeKey( 'messages', $code )
 594                                 );
 595                                 if ( !$scopedLock ) {
 596                                         LoggerFactory::getInstance( 'MessageCache' )->error(
 597                                                 __METHOD__ . ': could not acquire lock to update {title} ({code})',
 598                                                 [ 'title' => $title, 'code' => $code ] );
 599                                         return;
 600                                 }
 601                                 // Load the messages from the master DB to avoid race conditions
 602                                 $cache = $this->loadFromDB( $code, self::FOR_UPDATE );
 603                                 $this->mCache[$code] = $cache;
 604                                 // Load the process cache values and set the per-title cache keys
 605                                 $page = WikiPage::factory( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 606                                 $page->loadPageData( $page::READ_LATEST );
 607                                 $text = $this->getMessageTextFromContent( $page->getContent() );
 608                                 // Check if an individual cache key should exist and update cache accordingly
 609                                 if ( is_string( $text ) && strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 610                                         $titleKey = $this->bigMessageCacheKey( $this->mCache[$code]['HASH'], $title );
 611                                         $this->wanCache->set( $titleKey, ' ' . $text, $this->mExpiry );
 612                                 }
 613                                 // Mark this cache as definitely being "latest" (non-volatile) so
 614                                 // load() calls do try to refresh the cache with replica DB data
 615                                 $this->mCache[$code]['LATEST'] = time();
 616                                 // Pre-emptively update the local datacenter cache so things like edit filter and
 617                                 // blacklist changes are reflected immediately; these often use MediaWiki: pages.
 618                                 // The datacenter handling replace() calls should be the same one handling edits
 619                                 // as they require HTTP POST.
 620                                 $this->saveToCaches( $this->mCache[$code], 'all', $code );
 621                                 // Release the lock now that the cache is saved
 622                                 ScopedCallback::consume( $scopedLock );
 623
 624                                 // Relay the purge. Touching this check key expires cache contents
 625                                 // and local cache (APC) validation hash across all datacenters.
 626                                 $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
 627
 628                                 // Purge the message in the message blob store
 629                                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 630                                 $blobStore = $resourceloader->getMessageBlobStore();
 631                                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 632
 633                                 Hooks::run( 'MessageCacheReplace', [ $title, $text ] );
 634                         },
 635                         DeferredUpdates::PRESEND
 636                 );
 637         }
 638
 639         /**
 640          * Is the given cache array expired due to time passing or a version change?
 641          *
 642          * @param array $cache
 643          * @return bool
 644          */
 645         protected function isCacheExpired( $cache ) {
 646                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 647                         return true;
 648                 }
 649                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 650                         return true;
 651                 }
 652                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 653                         return true;
 654                 }
 655
 656                 return false;
 657         }
 658
 659         /**
 660          * Shortcut to update caches.
 661          *
 662          * @param array $cache Cached messages with a version.
 663          * @param string $dest Either "local-only" to save to local caches only
 664          *   or "all" to save to all caches.
 665          * @param string|bool $code Language code (default: false)
 666          * @return bool
 667          */
 668         protected function saveToCaches( array $cache, $dest, $code = false ) {
 669                 if ( $dest === 'all' ) {
 670                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 671                         $success = $this->clusterCache->set( $cacheKey, $cache );
 672                         $this->setValidationHash( $code, $cache );
 673                 } else {
 674                         $success = true;
 675                 }
 676
 677                 $this->saveToLocalCache( $code, $cache );
 678
 679                 return $success;
 680         }
 681
 682         /**
 683          * Get the md5 used to validate the local APC cache
 684          *
 685          * @param string $code
 686          * @return array (hash or false, bool expiry/volatility status)
 687          */
 688         protected function getValidationHash( $code ) {
 689                 $curTTL = null;
 690                 $value = $this->wanCache->get(
 691                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 692                         $curTTL,
 693                         [ $this->getCheckKey( $code ) ]
 694                 );
 695
 696                 if ( $value ) {
 697                         $hash = $value['hash'];
 698                         if ( ( time() - $value['latest'] ) < WANObjectCache::TTL_MINUTE ) {
 699                                 // Cache was recently updated via replace() and should be up-to-date.
 700                                 // That method is only called in the primary datacenter and uses FOR_UPDATE.
 701                                 // Also, it is unlikely that the current datacenter is *now* secondary one.
 702                                 $expired = false;
 703                         } else {
 704                                 // See if the "check" key was bumped after the hash was generated
 705                                 $expired = ( $curTTL < 0 );
 706                         }
 707                 } else {
 708                         // No hash found at all; cache must regenerate to be safe
 709                         $hash = false;
 710                         $expired = true;
 711                 }
 712
 713                 return [ $hash, $expired ];
 714         }
 715
 716         /**
 717          * Set the md5 used to validate the local disk cache
 718          *
 719          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 720          * be treated as "volatile" by getValidationHash() for the next few seconds.
 721          * This is triggered when $cache is generated using FOR_UPDATE mode.
 722          *
 723          * @param string $code
 724          * @param array $cache Cached messages with a version
 725          */
 726         protected function setValidationHash( $code, array $cache ) {
 727                 $this->wanCache->set(
 728                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 729                         [
 730                                 'hash' => $cache['HASH'],
 731                                 'latest' => $cache['LATEST'] ?? 0
 732                         ],
 733                         WANObjectCache::TTL_INDEFINITE
 734                 );
 735         }
 736
 737         /**
 738          * @param string $key A language message cache key that stores blobs
 739          * @param int $timeout Wait timeout in seconds
 740          * @return null|ScopedCallback
 741          */
 742         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 743                 return $this->clusterCache->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 744         }
 745
 746         /**
 747          * Get a message from either the content language or the user language.
 748          *
 749          * First, assemble a list of languages to attempt getting the message from. This
 750          * chain begins with the requested language and its fallbacks and then continues with
 751          * the content language and its fallbacks. For each language in the chain, the following
 752          * process will occur (in this order):
 753          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 754          *     Note: for the content language, there is no /lang subpage.
 755          *  2. Fetch from the static CDB cache.
 756          *  3. If available, check the database for fallback language overrides.
 757          *
 758          * This process provides a number of guarantees. When changing this code, make sure all
 759          * of these guarantees are preserved.
 760          *  * If the requested language is *not* the content language, then the CDB cache for that
 761          *    specific language will take precedence over the root database page ([[MW:msg]]).
 762          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 763          *    the message is available *anywhere* in the language for which it is a fallback.
 764          *
 765          * @param string $key The message key
 766          * @param bool $useDB If true, look for the message in the DB, false
 767          *   to use only the compiled l10n cache.
 768          * @param bool|string|object $langcode Code of the language to get the message for.
 769          *   - If string and a valid code, will create a standard language object
 770          *   - If string but not a valid code, will create a basic language object
 771          *   - If boolean and false, create object from the current users language
 772          *   - If boolean and true, create object from the wikis content language
 773          *   - If language object, use it as given
 774          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 775          *
 776          * @throws MWException When given an invalid key
 777          * @return string|bool False if the message doesn't exist, otherwise the
 778          *   message (which can be empty)
 779          */
 780         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 781                 if ( is_int( $key ) ) {
 782                         // Fix numerical strings that somehow become ints
 783                         // on their way here
 784                         $key = (string)$key;
 785                 } elseif ( !is_string( $key ) ) {
 786                         throw new MWException( 'Non-string key given' );
 787                 } elseif ( $key === '' ) {
 788                         // Shortcut: the empty key is always missing
 789                         return false;
 790                 }
 791
 792                 // For full keys, get the language code from the key
 793                 $pos = strrpos( $key, '/' );
 794                 if ( $isFullKey && $pos !== false ) {
 795                         $langcode = substr( $key, $pos + 1 );
 796                         $key = substr( $key, 0, $pos );
 797                 }
 798
 799                 // Normalise title-case input (with some inlining)
 800                 $lckey = self::normalizeKey( $key );
 801
 802                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 803
 804                 // Loop through each language in the fallback list until we find something useful
 805                 $lang = wfGetLangObj( $langcode );
 806                 $message = $this->getMessageFromFallbackChain(
 807                         $lang,
 808                         $lckey,
 809                         !$this->mDisable && $useDB
 810                 );
 811
 812                 // If we still have no message, maybe the key was in fact a full key so try that
 813                 if ( $message === false ) {
 814                         $parts = explode( '/', $lckey );
 815                         // We may get calls for things that are http-urls from sidebar
 816                         // Let's not load nonexistent languages for those
 817                         // They usually have more than one slash.
 818                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 819                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 820                                 if ( $message === null ) {
 821                                         $message = false;
 822                                 }
 823                         }
 824                 }
 825
 826                 // Post-processing if the message exists
 827                 if ( $message !== false ) {
 828                         // Fix whitespace
 829                         $message = str_replace(
 830                                 [
 831                                         # Fix for trailing whitespace, removed by textarea
 832                                         '&#32;',
 833                                         # Fix for NBSP, converted to space by firefox
 834                                         '&nbsp;',
 835                                         '&#160;',
 836                                         '&shy;'
 837                                 ],
 838                                 [
 839                                         ' ',
 840                                         "\u{00A0}",
 841                                         "\u{00A0}",
 842                                         "\u{00AD}"
 843                                 ],
 844                                 $message
 845                         );
 846                 }
 847
 848                 return $message;
 849         }
 850
 851         /**
 852          * Given a language, try and fetch messages from that language.
 853          *
 854          * Will also consider fallbacks of that language, the site language, and fallbacks for
 855          * the site language.
 856          *
 857          * @see MessageCache::get
 858          * @param Language|StubObject $lang Preferred language
 859          * @param string $lckey Lowercase key for the message (as for localisation cache)
 860          * @param bool $useDB Whether to include messages from the wiki database
 861          * @return string|bool The message, or false if not found
 862          */
 863         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 864                 global $wgContLang;
 865
 866                 $alreadyTried = [];
 867
 868                 // First try the requested language.
 869                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 870                 if ( $message !== false ) {
 871                         return $message;
 872                 }
 873
 874                 // Now try checking the site language.
 875                 $message = $this->getMessageForLang( $wgContLang, $lckey, $useDB, $alreadyTried );
 876                 return $message;
 877         }
 878
 879         /**
 880          * Given a language, try and fetch messages from that language and its fallbacks.
 881          *
 882          * @see MessageCache::get
 883          * @param Language|StubObject $lang Preferred language
 884          * @param string $lckey Lowercase key for the message (as for localisation cache)
 885          * @param bool $useDB Whether to include messages from the wiki database
 886          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 887          * @return string|bool The message, or false if not found
 888          */
 889         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 890                 global $wgContLang;
 891
 892                 $langcode = $lang->getCode();
 893
 894                 // Try checking the database for the requested language
 895                 if ( $useDB ) {
 896                         $uckey = $wgContLang->ucfirst( $lckey );
 897
 898                         if ( !isset( $alreadyTried[$langcode] ) ) {
 899                                 $message = $this->getMsgFromNamespace(
 900                                         $this->getMessagePageName( $langcode, $uckey ),
 901                                         $langcode
 902                                 );
 903
 904                                 if ( $message !== false ) {
 905                                         return $message;
 906                                 }
 907                                 $alreadyTried[$langcode] = true;
 908                         }
 909                 } else {
 910                         $uckey = null;
 911                 }
 912
 913                 // Check the CDB cache
 914                 $message = $lang->getMessage( $lckey );
 915                 if ( $message !== null ) {
 916                         return $message;
 917                 }
 918
 919                 // Try checking the database for all of the fallback languages
 920                 if ( $useDB ) {
 921                         $fallbackChain = Language::getFallbacksFor( $langcode );
 922
 923                         foreach ( $fallbackChain as $code ) {
 924                                 if ( isset( $alreadyTried[$code] ) ) {
 925                                         continue;
 926                                 }
 927
 928                                 $message = $this->getMsgFromNamespace(
 929                                         $this->getMessagePageName( $code, $uckey ), $code );
 930
 931                                 if ( $message !== false ) {
 932                                         return $message;
 933                                 }
 934                                 $alreadyTried[$code] = true;
 935                         }
 936                 }
 937
 938                 return false;
 939         }
 940
 941         /**
 942          * Get the message page name for a given language
 943          *
 944          * @param string $langcode
 945          * @param string $uckey Uppercase key for the message
 946          * @return string The page name
 947          */
 948         private function getMessagePageName( $langcode, $uckey ) {
 949                 global $wgLanguageCode;
 950
 951                 if ( $langcode === $wgLanguageCode ) {
 952                         // Messages created in the content language will not have the /lang extension
 953                         return $uckey;
 954                 } else {
 955                         return "$uckey/$langcode";
 956                 }
 957         }
 958
 959         /**
 960          * Get a message from the MediaWiki namespace, with caching. The key must
 961          * first be converted to two-part lang/msg form if necessary.
 962          *
 963          * Unlike self::get(), this function doesn't resolve fallback chains, and
 964          * some callers require this behavior. LanguageConverter::parseCachedTable()
 965          * and self::get() are some examples in core.
 966          *
 967          * @param string $title Message cache key with initial uppercase letter
 968          * @param string $code Code denoting the language to try
 969          * @return string|bool The message, or false if it does not exist or on error
 970          */
 971         public function getMsgFromNamespace( $title, $code ) {
 972                 $this->load( $code );
 973
 974                 if ( isset( $this->mCache[$code][$title] ) ) {
 975                         $entry = $this->mCache[$code][$title];
 976                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 977                                 // The message exists and is not '!TOO BIG'
 978                                 return (string)substr( $entry, 1 );
 979                         } elseif ( $entry === '!NONEXISTENT' ) {
 980                                 return false;
 981                         }
 982                         // Fall through and try invididual message cache below
 983                 } else {
 984                         $message = false;
 985                         Hooks::run( 'MessagesPreLoad', [ $title, &$message, $code ] );
 986                         if ( $message !== false ) {
 987                                 $this->mCache[$code][$title] = ' ' . $message;
 988                         } else {
 989                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 990                         }
 991
 992                         return $message;
 993                 }
 994
 995                 // Individual message cache key
 996                 $titleKey = $this->bigMessageCacheKey( $this->mCache[$code]['HASH'], $title );
 997
 998                 if ( $this->mCacheVolatile[$code] ) {
 999                         $entry = false;
1000                         // Make sure that individual keys respect the WAN cache holdoff period too
1001                         LoggerFactory::getInstance( 'MessageCache' )->debug(
1002                                 __METHOD__ . ': loading volatile key \'{titleKey}\'',
1003                                 [ 'titleKey' => $titleKey, 'code' => $code ] );
1004                 } else {
1005                         // Try the individual message cache
1006                         $entry = $this->wanCache->get( $titleKey );
1007                 }
1008
1009                 if ( $entry !== false ) {
1010                         if ( substr( $entry, 0, 1 ) === ' ' ) {
1011                                 $this->mCache[$code][$title] = $entry;
1012                                 // The message exists, so make sure a string is returned
1013                                 return (string)substr( $entry, 1 );
1014                         } elseif ( $entry === '!NONEXISTENT' ) {
1015                                 $this->mCache[$code][$title] = '!NONEXISTENT';
1016
1017                                 return false;
1018                         } else {
1019                                 // Corrupt/obsolete entry, delete it
1020                                 $this->wanCache->delete( $titleKey );
1021                         }
1022                 }
1023
1024                 // Try loading the message from the database
1025                 $dbr = wfGetDB( DB_REPLICA );
1026                 $cacheOpts = Database::getCacheSetOptions( $dbr );
1027                 // Use newKnownCurrent() to avoid querying revision/user tables
1028                 $titleObj = Title::makeTitle( NS_MEDIAWIKI, $title );
1029                 if ( $titleObj->getLatestRevID() ) {
1030                         $revision = Revision::newKnownCurrent(
1031                                 $dbr,
1032                                 $titleObj
1033                         );
1034                 } else {
1035                         $revision = false;
1036                 }
1037
1038                 if ( $revision ) {
1039                         $content = $revision->getContent();
1040                         if ( $content ) {
1041                                 $message = $this->getMessageTextFromContent( $content );
1042                                 if ( is_string( $message ) ) {
1043                                         $this->mCache[$code][$title] = ' ' . $message;
1044                                         $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry, $cacheOpts );
1045                                 }
1046                         } else {
1047                                 // A possibly temporary loading failure
1048                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1049                                         __METHOD__ . ': failed to load message page text for \'{titleKey}\'',
1050                                         [ 'titleKey' => $titleKey, 'code' => $code ] );
1051                                 $message = null; // no negative caching
1052                         }
1053                 } else {
1054                         $message = false; // negative caching
1055                 }
1056
1057                 if ( $message === false ) {
1058                         // Negative caching in case a "too big" message is no longer available (deleted)
1059                         $this->mCache[$code][$title] = '!NONEXISTENT';
1060                         $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry, $cacheOpts );
1061                 }
1062
1063                 return $message;
1064         }
1065
1066         /**
1067          * @param string $message
1068          * @param bool $interface
1069          * @param Language $language
1070          * @param Title $title
1071          * @return string
1072          */
1073         public function transform( $message, $interface = false, $language = null, $title = null ) {
1074                 // Avoid creating parser if nothing to transform
1075                 if ( strpos( $message, '{{' ) === false ) {
1076                         return $message;
1077                 }
1078
1079                 if ( $this->mInParser ) {
1080                         return $message;
1081                 }
1082
1083                 $parser = $this->getParser();
1084                 if ( $parser ) {
1085                         $popts = $this->getParserOptions();
1086                         $popts->setInterfaceMessage( $interface );
1087                         $popts->setTargetLanguage( $language );
1088
1089                         $userlang = $popts->setUserLang( $language );
1090                         $this->mInParser = true;
1091                         $message = $parser->transformMsg( $message, $popts, $title );
1092                         $this->mInParser = false;
1093                         $popts->setUserLang( $userlang );
1094                 }
1095
1096                 return $message;
1097         }
1098
1099         /**
1100          * @return Parser
1101          */
1102         public function getParser() {
1103                 global $wgParser, $wgParserConf;
1104
1105                 if ( !$this->mParser && isset( $wgParser ) ) {
1106                         # Do some initialisation so that we don't have to do it twice
1107                         $wgParser->firstCallInit();
1108                         # Clone it and store it
1109                         $class = $wgParserConf['class'];
1110                         if ( $class == ParserDiffTest::class ) {
1111                                 # Uncloneable
1112                                 $this->mParser = new $class( $wgParserConf );
1113                         } else {
1114                                 $this->mParser = clone $wgParser;
1115                         }
1116                 }
1117
1118                 return $this->mParser;
1119         }
1120
1121         /**
1122          * @param string $text
1123          * @param Title $title
1124          * @param bool $linestart Whether or not this is at the start of a line
1125          * @param bool $interface Whether this is an interface message
1126          * @param Language|string $language Language code
1127          * @return ParserOutput|string
1128          */
1129         public function parse( $text, $title = null, $linestart = true,
1130                 $interface = false, $language = null
1131         ) {
1132                 global $wgTitle;
1133
1134                 if ( $this->mInParser ) {
1135                         return htmlspecialchars( $text );
1136                 }
1137
1138                 $parser = $this->getParser();
1139                 $popts = $this->getParserOptions();
1140                 $popts->setInterfaceMessage( $interface );
1141
1142                 if ( is_string( $language ) ) {
1143                         $language = Language::factory( $language );
1144                 }
1145                 $popts->setTargetLanguage( $language );
1146
1147                 if ( !$title || !$title instanceof Title ) {
1148                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1149                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1150                         $title = $wgTitle;
1151                 }
1152                 // Sometimes $wgTitle isn't set either...
1153                 if ( !$title ) {
1154                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1155                         # Create a ghost title in such case
1156                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1157                 }
1158
1159                 $this->mInParser = true;
1160                 $res = $parser->parse( $text, $title, $popts, $linestart );
1161                 $this->mInParser = false;
1162
1163                 return $res;
1164         }
1165
1166         public function disable() {
1167                 $this->mDisable = true;
1168         }
1169
1170         public function enable() {
1171                 $this->mDisable = false;
1172         }
1173
1174         /**
1175          * Whether DB/cache usage is disabled for determining messages
1176          *
1177          * If so, this typically indicates either:
1178          *   - a) load() failed to find a cached copy nor query the DB
1179          *   - b) we are in a special context or error mode that cannot use the DB
1180          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1181          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1182          *
1183          * @return bool
1184          * @since 1.27
1185          */
1186         public function isDisabled() {
1187                 return $this->mDisable;
1188         }
1189
1190         /**
1191          * Clear all stored messages in global and local cache
1192          *
1193          * Mainly used after a mass rebuild
1194          */
1195         function clear() {
1196                 $langs = Language::fetchLanguageNames( null, 'mw' );
1197                 foreach ( array_keys( $langs ) as $code ) {
1198                         $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
1199                 }
1200
1201                 $this->mLoadedLanguages = [];
1202         }
1203
1204         /**
1205          * @param string $key
1206          * @return array
1207          */
1208         public function figureMessage( $key ) {
1209                 global $wgLanguageCode;
1210
1211                 $pieces = explode( '/', $key );
1212                 if ( count( $pieces ) < 2 ) {
1213                         return [ $key, $wgLanguageCode ];
1214                 }
1215
1216                 $lang = array_pop( $pieces );
1217                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1218                         return [ $key, $wgLanguageCode ];
1219                 }
1220
1221                 $message = implode( '/', $pieces );
1222
1223                 return [ $message, $lang ];
1224         }
1225
1226         /**
1227          * Get all message keys stored in the message cache for a given language.
1228          * If $code is the content language code, this will return all message keys
1229          * for which MediaWiki:msgkey exists. If $code is another language code, this
1230          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1231          * @param string $code Language code
1232          * @return array Array of message keys (strings)
1233          */
1234         public function getAllMessageKeys( $code ) {
1235                 global $wgContLang;
1236
1237                 $this->load( $code );
1238                 if ( !isset( $this->mCache[$code] ) ) {
1239                         // Apparently load() failed
1240                         return null;
1241                 }
1242                 // Remove administrative keys
1243                 $cache = $this->mCache[$code];
1244                 unset( $cache['VERSION'] );
1245                 unset( $cache['EXPIRY'] );
1246                 unset( $cache['EXCESSIVE'] );
1247                 // Remove any !NONEXISTENT keys
1248                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1249
1250                 // Keys may appear with a capital first letter. lcfirst them.
1251                 return array_map( [ $wgContLang, 'lcfirst' ], array_keys( $cache ) );
1252         }
1253
1254         /**
1255          * Purge message caches when a MediaWiki: page is created, updated, or deleted
1256          *
1257          * @param Title $title Message page title
1258          * @param Content|null $content New content for edit/create, null on deletion
1259          * @since 1.29
1260          */
1261         public function updateMessageOverride( Title $title, Content $content = null ) {
1262                 global $wgContLang;
1263
1264                 $msgText = $this->getMessageTextFromContent( $content );
1265                 if ( $msgText === null ) {
1266                         $msgText = false; // treat as not existing
1267                 }
1268
1269                 $this->replace( $title->getDBkey(), $msgText );
1270
1271                 if ( $wgContLang->hasVariants() ) {
1272                         $wgContLang->updateConversionTable( $title );
1273                 }
1274         }
1275
1276         /**
1277          * @param string $code Language code
1278          * @return string WAN cache key usable as a "check key" against language page edits
1279          */
1280         public function getCheckKey( $code ) {
1281                 return $this->wanCache->makeKey( 'messages', $code );
1282         }
1283
1284         /**
1285          * @param Content|null $content Content or null if the message page does not exist
1286          * @return string|bool|null Returns false if $content is null and null on error
1287          */
1288         private function getMessageTextFromContent( Content $content = null ) {
1289                 // @TODO: could skip pseudo-messages like js/css here, based on content model
1290                 if ( $content ) {
1291                         // Message page exists...
1292                         // XXX: Is this the right way to turn a Content object into a message?
1293                         // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1294                         //       CssContent. MessageContent is *not* used for storing messages, it's
1295                         //       only used for wrapping them when needed.
1296                         $msgText = $content->getWikitextForTransclusion();
1297                         if ( $msgText === false || $msgText === null ) {
1298                                 // This might be due to some kind of misconfiguration...
1299                                 $msgText = null;
1300                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1301                                         __METHOD__ . ": message content doesn't provide wikitext "
1302                                         . "(content model: " . $content->getModel() . ")" );
1303                         }
1304                 } else {
1305                         // Message page does not exist...
1306                         $msgText = false;
1307                 }
1308
1309                 return $msgText;
1310         }
1311
1312         /**
1313          * @param string $hash Hash for this version of the entire key/value overrides map
1314          * @param string $title Message cache key with initial uppercase letter
1315          * @return string
1316          */
1317         private function bigMessageCacheKey( $hash, $title ) {
1318                 return $this->wanCache->makeKey( 'messages-big', $hash, $title );
1319         }
1320 }