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 cache of loaded messages that are defined in MediaWiki namespace
  50          *
  51          * @var MapCacheLRU Map of (language code => key => " <MESSAGE>" or "!TOO BIG")
  52          */
  53         protected $cache;
  54
  55         /**
  56          * @var bool[] Map of (language code => boolean)
  57          */
  58         protected $cacheVolatile = [];
  59
  60         /**
  61          * Should mean that database cannot be used, but check
  62          * @var bool $mDisable
  63          */
  64         protected $mDisable;
  65
  66         /**
  67          * Lifetime for cache, used by object caching.
  68          * Set on construction, see __construct().
  69          */
  70         protected $mExpiry;
  71
  72         /**
  73          * Message cache has its own parser which it uses to transform messages
  74          * @var ParserOptions
  75          */
  76         protected $mParserOptions;
  77         /** @var Parser */
  78         protected $mParser;
  79
  80         /**
  81          * @var bool $mInParser
  82          */
  83         protected $mInParser = false;
  84
  85         /** @var WANObjectCache */
  86         protected $wanCache;
  87         /** @var BagOStuff */
  88         protected $clusterCache;
  89         /** @var BagOStuff */
  90         protected $srvCache;
  91         /** @var Language */
  92         protected $contLang;
  93
  94         /**
  95          * Singleton instance
  96          *
  97          * @var MessageCache $instance
  98          */
  99         private static $instance;
 100
 101         /**
 102          * Get the signleton instance of this class
 103          *
 104          * @since 1.18
 105          * @return MessageCache
 106          */
 107         public static function singleton() {
 108                 if ( self::$instance === null ) {
 109                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry, $wgUseLocalMessageCache;
 110                         $services = MediaWikiServices::getInstance();
 111                         self::$instance = new self(
 112                                 $services->getMainWANObjectCache(),
 113                                 wfGetMessageCacheStorage(),
 114                                 $wgUseLocalMessageCache
 115                                         ? $services->getLocalServerObjectCache()
 116                                         : new EmptyBagOStuff(),
 117                                 $wgUseDatabaseMessages,
 118                                 $wgMsgCacheExpiry,
 119                                 $services->getContentLanguage()
 120                         );
 121                 }
 122
 123                 return self::$instance;
 124         }
 125
 126         /**
 127          * Destroy the singleton instance
 128          *
 129          * @since 1.18
 130          */
 131         public static function destroyInstance() {
 132                 self::$instance = null;
 133         }
 134
 135         /**
 136          * Normalize message key input
 137          *
 138          * @param string $key Input message key to be normalized
 139          * @return string Normalized message key
 140          */
 141         public static function normalizeKey( $key ) {
 142                 $lckey = strtr( $key, ' ', '_' );
 143                 if ( ord( $lckey ) < 128 ) {
 144                         $lckey[0] = strtolower( $lckey[0] );
 145                 } else {
 146                         $lckey = MediaWikiServices::getInstance()->getContentLanguage()->lcfirst( $lckey );
 147                 }
 148
 149                 return $lckey;
 150         }
 151
 152         /**
 153          * @param WANObjectCache $wanCache
 154          * @param BagOStuff $clusterCache
 155          * @param BagOStuff $serverCache
 156          * @param bool $useDB Whether to look for message overrides (e.g. MediaWiki: pages)
 157          * @param int $expiry Lifetime for cache. @see $mExpiry.
 158          * @param Language|null $contLang Content language of site
 159          */
 160         public function __construct(
 161                 WANObjectCache $wanCache,
 162                 BagOStuff $clusterCache,
 163                 BagOStuff $serverCache,
 164                 $useDB,
 165                 $expiry,
 166                 Language $contLang = null
 167         ) {
 168                 $this->wanCache = $wanCache;
 169                 $this->clusterCache = $clusterCache;
 170                 $this->srvCache = $serverCache;
 171
 172                 $this->cache = new MapCacheLRU( 5 ); // limit size for sanity
 173
 174                 $this->mDisable = !$useDB;
 175                 $this->mExpiry = $expiry;
 176                 $this->contLang = $contLang ?? MediaWikiServices::getInstance()->getContentLanguage();
 177         }
 178
 179         /**
 180          * ParserOptions is lazy initialised.
 181          *
 182          * @return ParserOptions
 183          */
 184         function getParserOptions() {
 185                 global $wgUser;
 186
 187                 if ( !$this->mParserOptions ) {
 188                         if ( !$wgUser->isSafeToLoad() ) {
 189                                 // $wgUser isn't unstubbable yet, so don't try to get a
 190                                 // ParserOptions for it. And don't cache this ParserOptions
 191                                 // either.
 192                                 $po = ParserOptions::newFromAnon();
 193                                 $po->setAllowUnsafeRawHtml( false );
 194                                 return $po;
 195                         }
 196
 197                         $this->mParserOptions = new ParserOptions;
 198                         // Messages may take parameters that could come
 199                         // from malicious sources. As a precaution, disable
 200                         // the <html> parser tag when parsing messages.
 201                         $this->mParserOptions->setAllowUnsafeRawHtml( false );
 202                 }
 203
 204                 return $this->mParserOptions;
 205         }
 206
 207         /**
 208          * Try to load the cache from APC.
 209          *
 210          * @param string $code Optional language code, see documenation of load().
 211          * @return array|bool The cache array, or false if not in cache.
 212          */
 213         protected function getLocalCache( $code ) {
 214                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 215
 216                 return $this->srvCache->get( $cacheKey );
 217         }
 218
 219         /**
 220          * Save the cache to APC.
 221          *
 222          * @param string $code
 223          * @param array $cache The cache array
 224          */
 225         protected function saveToLocalCache( $code, $cache ) {
 226                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 227                 $this->srvCache->set( $cacheKey, $cache );
 228         }
 229
 230         /**
 231          * Loads messages from caches or from database in this order:
 232          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 233          * (2) memcached
 234          * (3) from the database.
 235          *
 236          * When successfully loading from (2) or (3), all higher level caches are
 237          * updated for the newest version.
 238          *
 239          * Nothing is loaded if member variable mDisable is true, either manually
 240          * set by calling code or if message loading fails (is this possible?).
 241          *
 242          * Returns true if cache is already populated or it was successfully populated,
 243          * or false if populating empty cache fails. Also returns true if MessageCache
 244          * is disabled.
 245          *
 246          * @param string $code Language to which load messages
 247          * @param int|null $mode Use MessageCache::FOR_UPDATE to skip process cache [optional]
 248          * @throws InvalidArgumentException
 249          * @return bool
 250          */
 251         protected function load( $code, $mode = null ) {
 252                 if ( !is_string( $code ) ) {
 253                         throw new InvalidArgumentException( "Missing language code" );
 254                 }
 255
 256                 # Don't do double loading...
 257                 if ( $this->cache->has( $code ) && $mode != self::FOR_UPDATE ) {
 258                         return true;
 259                 }
 260
 261                 # 8 lines of code just to say (once) that message cache is disabled
 262                 if ( $this->mDisable ) {
 263                         static $shownDisabled = false;
 264                         if ( !$shownDisabled ) {
 265                                 wfDebug( __METHOD__ . ": disabled\n" );
 266                                 $shownDisabled = true;
 267                         }
 268
 269                         return true;
 270                 }
 271
 272                 # Loading code starts
 273                 $success = false; # Keep track of success
 274                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 275                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 276
 277                 # Hash of the contents is stored in memcache, to detect if data-center cache
 278                 # or local cache goes out of date (e.g. due to replace() on some other server)
 279                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 280                 $this->cacheVolatile[$code] = $hashVolatile;
 281
 282                 # Try the local cache and check against the cluster hash key...
 283                 $cache = $this->getLocalCache( $code );
 284                 if ( !$cache ) {
 285                         $where[] = 'local cache is empty';
 286                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 287                         $where[] = 'local cache has the wrong hash';
 288                         $staleCache = $cache;
 289                 } elseif ( $this->isCacheExpired( $cache ) ) {
 290                         $where[] = 'local cache is expired';
 291                         $staleCache = $cache;
 292                 } elseif ( $hashVolatile ) {
 293                         $where[] = 'local cache validation key is expired/volatile';
 294                         $staleCache = $cache;
 295                 } else {
 296                         $where[] = 'got from local cache';
 297                         $this->cache->set( $code, $cache );
 298                         $success = true;
 299                 }
 300
 301                 if ( !$success ) {
 302                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 303                         # Try the global cache. If it is empty, try to acquire a lock. If
 304                         # the lock can't be acquired, wait for the other thread to finish
 305                         # and then try the global cache a second time.
 306                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 307                                 if ( $hashVolatile && $staleCache ) {
 308                                         # Do not bother fetching the whole cache blob to avoid I/O.
 309                                         # Instead, just try to get the non-blocking $statusKey lock
 310                                         # below, and use the local stale value if it was not acquired.
 311                                         $where[] = 'global cache is presumed expired';
 312                                 } else {
 313                                         $cache = $this->clusterCache->get( $cacheKey );
 314                                         if ( !$cache ) {
 315                                                 $where[] = 'global cache is empty';
 316                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 317                                                 $where[] = 'global cache is expired';
 318                                                 $staleCache = $cache;
 319                                         } elseif ( $hashVolatile ) {
 320                                                 # DB results are replica DB lag prone until the holdoff TTL passes.
 321                                                 # By then, updates should be reflected in loadFromDBWithLock().
 322                                                 # One thread renerates the cache while others use old values.
 323                                                 $where[] = 'global cache is expired/volatile';
 324                                                 $staleCache = $cache;
 325                                         } else {
 326                                                 $where[] = 'got from global cache';
 327                                                 $this->cache->set( $code, $cache );
 328                                                 $this->saveToCaches( $cache, 'local-only', $code );
 329                                                 $success = true;
 330                                         }
 331                                 }
 332
 333                                 if ( $success ) {
 334                                         # Done, no need to retry
 335                                         break;
 336                                 }
 337
 338                                 # We need to call loadFromDB. Limit the concurrency to one process.
 339                                 # This prevents the site from going down when the cache expires.
 340                                 # Note that the DB slam protection lock here is non-blocking.
 341                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 342                                 if ( $loadStatus === true ) {
 343                                         $success = true;
 344                                         break;
 345                                 } elseif ( $staleCache ) {
 346                                         # Use the stale cache while some other thread constructs the new one
 347                                         $where[] = 'using stale cache';
 348                                         $this->cache->set( $code, $staleCache );
 349                                         $success = true;
 350                                         break;
 351                                 } elseif ( $failedAttempts > 0 ) {
 352                                         # Already blocked once, so avoid another lock/unlock cycle.
 353                                         # This case will typically be hit if memcached is down, or if
 354                                         # loadFromDB() takes longer than LOCK_WAIT.
 355                                         $where[] = "could not acquire status key.";
 356                                         break;
 357                                 } elseif ( $loadStatus === 'cantacquire' ) {
 358                                         # Wait for the other thread to finish, then retry. Normally,
 359                                         # the memcached get() will then yeild the other thread's result.
 360                                         $where[] = 'waited for other thread to complete';
 361                                         $this->getReentrantScopedLock( $cacheKey );
 362                                 } else {
 363                                         # Disable cache; $loadStatus is 'disabled'
 364                                         break;
 365                                 }
 366                         }
 367                 }
 368
 369                 if ( !$success ) {
 370                         $where[] = 'loading FAILED - cache is disabled';
 371                         $this->mDisable = true;
 372                         $this->cache->set( $code, [] );
 373                         wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
 374                         # This used to throw an exception, but that led to nasty side effects like
 375                         # the whole wiki being instantly down if the memcached server died
 376                 }
 377
 378                 if ( !$this->cache->has( $code ) ) { // sanity
 379                         throw new LogicException( "Process cache for '$code' should be set by now." );
 380                 }
 381
 382                 $info = implode( ', ', $where );
 383                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 384
 385                 return $success;
 386         }
 387
 388         /**
 389          * @param string $code
 390          * @param array &$where List of wfDebug() comments
 391          * @param int|null $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 392          * @return bool|string True on success or one of ("cantacquire", "disabled")
 393          */
 394         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 395                 # If cache updates on all levels fail, give up on message overrides.
 396                 # This is to avoid easy site outages; see $saveSuccess comments below.
 397                 $statusKey = $this->clusterCache->makeKey( 'messages', $code, 'status' );
 398                 $status = $this->clusterCache->get( $statusKey );
 399                 if ( $status === 'error' ) {
 400                         $where[] = "could not load; method is still globally disabled";
 401                         return 'disabled';
 402                 }
 403
 404                 # Now let's regenerate
 405                 $where[] = 'loading from database';
 406
 407                 # Lock the cache to prevent conflicting writes.
 408                 # This lock is non-blocking so stale cache can quickly be used.
 409                 # Note that load() will call a blocking getReentrantScopedLock()
 410                 # after this if it really need to wait for any current thread.
 411                 $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 412                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 413                 if ( !$scopedLock ) {
 414                         $where[] = 'could not acquire main lock';
 415                         return 'cantacquire';
 416                 }
 417
 418                 $cache = $this->loadFromDB( $code, $mode );
 419                 $this->cache->set( $code, $cache );
 420                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 421
 422                 if ( !$saveSuccess ) {
 423                         /**
 424                          * Cache save has failed.
 425                          *
 426                          * There are two main scenarios where this could be a problem:
 427                          * - The cache is more than the maximum size (typically 1MB compressed).
 428                          * - Memcached has no space remaining in the relevant slab class. This is
 429                          *   unlikely with recent versions of memcached.
 430                          *
 431                          * Either way, if there is a local cache, nothing bad will happen. If there
 432                          * is no local cache, disabling the message cache for all requests avoids
 433                          * incurring a loadFromDB() overhead on every request, and thus saves the
 434                          * wiki from complete downtime under moderate traffic conditions.
 435                          */
 436                         if ( $this->srvCache instanceof EmptyBagOStuff ) {
 437                                 $this->clusterCache->set( $statusKey, 'error', 60 * 5 );
 438                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 439                         } else {
 440                                 $where[] = "could not save global cache";
 441                         }
 442                 }
 443
 444                 return true;
 445         }
 446
 447         /**
 448          * Loads cacheable messages from the database. Messages bigger than
 449          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 450          * on-demand from the database later.
 451          *
 452          * @param string $code Language code
 453          * @param int|null $mode Use MessageCache::FOR_UPDATE to skip process cache
 454          * @return array Loaded messages for storing in caches
 455          */
 456         protected function loadFromDB( $code, $mode = null ) {
 457                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 458
 459                 // (T164666) The query here performs really poorly on WMF's
 460                 // contributions replicas. We don't have a way to say "any group except
 461                 // contributions", so for the moment let's specify 'api'.
 462                 // @todo: Get rid of this hack.
 463                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA, 'api' );
 464
 465                 $cache = [];
 466
 467                 # Common conditions
 468                 $conds = [
 469                         'page_is_redirect' => 0,
 470                         'page_namespace' => NS_MEDIAWIKI,
 471                 ];
 472
 473                 $mostused = [];
 474                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 475                         if ( !$this->cache->has( $wgLanguageCode ) ) {
 476                                 $this->load( $wgLanguageCode );
 477                         }
 478                         $mostused = array_keys( $this->cache->get( $wgLanguageCode ) );
 479                         foreach ( $mostused as $key => $value ) {
 480                                 $mostused[$key] = "$value/$code";
 481                         }
 482                 }
 483
 484                 if ( count( $mostused ) ) {
 485                         $conds['page_title'] = $mostused;
 486                 } elseif ( $code !== $wgLanguageCode ) {
 487                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 488                 } else {
 489                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 490                         # other than language code.
 491                         $conds[] = 'page_title NOT' .
 492                                 $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 493                 }
 494
 495                 # Conditions to fetch oversized pages to ignore them
 496                 $bigConds = $conds;
 497                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 498
 499                 # Load titles for all oversized pages in the MediaWiki namespace
 500                 $res = $dbr->select(
 501                         'page',
 502                         [ 'page_title', 'page_latest' ],
 503                         $bigConds,
 504                         __METHOD__ . "($code)-big"
 505                 );
 506                 foreach ( $res as $row ) {
 507                         $cache[$row->page_title] = '!TOO BIG';
 508                         // At least include revision ID so page changes are reflected in the hash
 509                         $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 510                 }
 511
 512                 # Conditions to load the remaining pages with their contents
 513                 $smallConds = $conds;
 514                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 515
 516                 $res = $dbr->select(
 517                         [ 'page', 'revision', 'text' ],
 518                         [ 'page_title', 'old_id', 'old_text', 'old_flags' ],
 519                         $smallConds,
 520                         __METHOD__ . "($code)-small",
 521                         [],
 522                         [
 523                                 'revision' => [ 'JOIN', 'page_latest=rev_id' ],
 524                                 'text' => [ 'JOIN', 'rev_text_id=old_id' ],
 525                         ]
 526                 );
 527
 528                 foreach ( $res as $row ) {
 529                         $text = Revision::getRevisionText( $row );
 530                         if ( $text === false ) {
 531                                 // Failed to fetch data; possible ES errors?
 532                                 // Store a marker to fetch on-demand as a workaround...
 533                                 // TODO Use a differnt marker
 534                                 $entry = '!TOO BIG';
 535                                 wfDebugLog(
 536                                         'MessageCache',
 537                                         __METHOD__
 538                                         . ": failed to load message page text for {$row->page_title} ($code)"
 539                                 );
 540                         } else {
 541                                 $entry = ' ' . $text;
 542                         }
 543                         $cache[$row->page_title] = $entry;
 544                 }
 545
 546                 $cache['VERSION'] = MSG_CACHE_VERSION;
 547                 ksort( $cache );
 548
 549                 # Hash for validating local cache (APC). No need to take into account
 550                 # messages larger than $wgMaxMsgCacheEntrySize, since those are only
 551                 # stored and fetched from memcache.
 552                 $cache['HASH'] = md5( serialize( $cache ) );
 553                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 554                 unset( $cache['EXCESSIVE'] ); // only needed for hash
 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->cache->setField( $code, $title, '!NONEXISTENT' );
 582                 } else {
 583                         // Ignore $wgMaxMsgCacheEntrySize so the process cache is up to date
 584                         $this->cache->setField( $code, $title, ' ' . $text );
 585                 }
 586
 587                 // (b) Update the shared caches in a deferred update with a fresh DB snapshot
 588                 DeferredUpdates::addUpdate(
 589                         new MessageCacheUpdate( $code, $title, $msg ),
 590                         DeferredUpdates::PRESEND
 591                 );
 592         }
 593
 594         /**
 595          * @param string $code
 596          * @param array[] $replacements List of (title, message key) pairs
 597          * @throws MWException
 598          */
 599         public function refreshAndReplaceInternal( $code, array $replacements ) {
 600                 global $wgMaxMsgCacheEntrySize;
 601
 602                 // Allow one caller at a time to avoid race conditions
 603                 $scopedLock = $this->getReentrantScopedLock(
 604                         $this->clusterCache->makeKey( 'messages', $code )
 605                 );
 606                 if ( !$scopedLock ) {
 607                         foreach ( $replacements as list( $title ) ) {
 608                                 LoggerFactory::getInstance( 'MessageCache' )->error(
 609                                         __METHOD__ . ': could not acquire lock to update {title} ({code})',
 610                                         [ 'title' => $title, 'code' => $code ] );
 611                         }
 612
 613                         return;
 614                 }
 615
 616                 // Reload messages from the database and pre-populate dc-local caches
 617                 // as optimisation. Use the master DB to avoid race conditions.
 618                 $cache = $this->loadFromDB( $code, self::FOR_UPDATE );
 619                 // Check if individual cache keys should exist and update cache accordingly
 620                 $newTextByTitle = []; // map of (title => content)
 621                 foreach ( $replacements as list( $title ) ) {
 622                         $page = WikiPage::factory( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 623                         $page->loadPageData( $page::READ_LATEST );
 624                         $text = $this->getMessageTextFromContent( $page->getContent() );
 625                         // Remember the text for the blob store update later on
 626                         $newTextByTitle[$title] = $text;
 627                         // Note that if $text is false, then $cache should have a !NONEXISTANT entry
 628                         if ( is_string( $text ) && strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 629                                 // Match logic of loadCachedMessagePageEntry()
 630                                 $this->wanCache->set(
 631                                         $this->bigMessageCacheKey( $cache['HASH'], $title ),
 632                                         ' ' . $text,
 633                                         $this->mExpiry
 634                                 );
 635                         }
 636                 }
 637                 // Mark this cache as definitely being "latest" (non-volatile) so
 638                 // load() calls do not try to refresh the cache with replica DB data
 639                 $cache['LATEST'] = time();
 640                 // Update the process cache
 641                 $this->cache->set( $code, $cache );
 642                 // Pre-emptively update the local datacenter cache so things like edit filter and
 643                 // blacklist changes are reflected immediately; these often use MediaWiki: pages.
 644                 // The datacenter handling replace() calls should be the same one handling edits
 645                 // as they require HTTP POST.
 646                 $this->saveToCaches( $cache, 'all', $code );
 647                 // Release the lock now that the cache is saved
 648                 ScopedCallback::consume( $scopedLock );
 649
 650                 // Relay the purge. Touching this check key expires cache contents
 651                 // and local cache (APC) validation hash across all datacenters.
 652                 $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
 653
 654                 // Purge the messages in the message blob store and fire any hook handlers
 655                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 656                 $blobStore = $resourceloader->getMessageBlobStore();
 657                 foreach ( $replacements as list( $title, $msg ) ) {
 658                         $blobStore->updateMessage( $this->contLang->lcfirst( $msg ) );
 659                         Hooks::run( 'MessageCacheReplace', [ $title, $newTextByTitle[$title] ] );
 660                 }
 661         }
 662
 663         /**
 664          * Is the given cache array expired due to time passing or a version change?
 665          *
 666          * @param array $cache
 667          * @return bool
 668          */
 669         protected function isCacheExpired( $cache ) {
 670                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 671                         return true;
 672                 }
 673                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 674                         return true;
 675                 }
 676                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 677                         return true;
 678                 }
 679
 680                 return false;
 681         }
 682
 683         /**
 684          * Shortcut to update caches.
 685          *
 686          * @param array $cache Cached messages with a version.
 687          * @param string $dest Either "local-only" to save to local caches only
 688          *   or "all" to save to all caches.
 689          * @param string|bool $code Language code (default: false)
 690          * @return bool
 691          */
 692         protected function saveToCaches( array $cache, $dest, $code = false ) {
 693                 if ( $dest === 'all' ) {
 694                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 695                         $success = $this->clusterCache->set( $cacheKey, $cache );
 696                         $this->setValidationHash( $code, $cache );
 697                 } else {
 698                         $success = true;
 699                 }
 700
 701                 $this->saveToLocalCache( $code, $cache );
 702
 703                 return $success;
 704         }
 705
 706         /**
 707          * Get the md5 used to validate the local APC cache
 708          *
 709          * @param string $code
 710          * @return array (hash or false, bool expiry/volatility status)
 711          */
 712         protected function getValidationHash( $code ) {
 713                 $curTTL = null;
 714                 $value = $this->wanCache->get(
 715                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 716                         $curTTL,
 717                         [ $this->getCheckKey( $code ) ]
 718                 );
 719
 720                 if ( $value ) {
 721                         $hash = $value['hash'];
 722                         if ( ( time() - $value['latest'] ) < WANObjectCache::TTL_MINUTE ) {
 723                                 // Cache was recently updated via replace() and should be up-to-date.
 724                                 // That method is only called in the primary datacenter and uses FOR_UPDATE.
 725                                 // Also, it is unlikely that the current datacenter is *now* secondary one.
 726                                 $expired = false;
 727                         } else {
 728                                 // See if the "check" key was bumped after the hash was generated
 729                                 $expired = ( $curTTL < 0 );
 730                         }
 731                 } else {
 732                         // No hash found at all; cache must regenerate to be safe
 733                         $hash = false;
 734                         $expired = true;
 735                 }
 736
 737                 return [ $hash, $expired ];
 738         }
 739
 740         /**
 741          * Set the md5 used to validate the local disk cache
 742          *
 743          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 744          * be treated as "volatile" by getValidationHash() for the next few seconds.
 745          * This is triggered when $cache is generated using FOR_UPDATE mode.
 746          *
 747          * @param string $code
 748          * @param array $cache Cached messages with a version
 749          */
 750         protected function setValidationHash( $code, array $cache ) {
 751                 $this->wanCache->set(
 752                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 753                         [
 754                                 'hash' => $cache['HASH'],
 755                                 'latest' => $cache['LATEST'] ?? 0
 756                         ],
 757                         WANObjectCache::TTL_INDEFINITE
 758                 );
 759         }
 760
 761         /**
 762          * @param string $key A language message cache key that stores blobs
 763          * @param int $timeout Wait timeout in seconds
 764          * @return null|ScopedCallback
 765          */
 766         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 767                 return $this->clusterCache->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 768         }
 769
 770         /**
 771          * Get a message from either the content language or the user language.
 772          *
 773          * First, assemble a list of languages to attempt getting the message from. This
 774          * chain begins with the requested language and its fallbacks and then continues with
 775          * the content language and its fallbacks. For each language in the chain, the following
 776          * process will occur (in this order):
 777          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 778          *     Note: for the content language, there is no /lang subpage.
 779          *  2. Fetch from the static CDB cache.
 780          *  3. If available, check the database for fallback language overrides.
 781          *
 782          * This process provides a number of guarantees. When changing this code, make sure all
 783          * of these guarantees are preserved.
 784          *  * If the requested language is *not* the content language, then the CDB cache for that
 785          *    specific language will take precedence over the root database page ([[MW:msg]]).
 786          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 787          *    the message is available *anywhere* in the language for which it is a fallback.
 788          *
 789          * @param string $key The message key
 790          * @param bool $useDB If true, look for the message in the DB, false
 791          *   to use only the compiled l10n cache.
 792          * @param bool|string|object $langcode Code of the language to get the message for.
 793          *   - If string and a valid code, will create a standard language object
 794          *   - If string but not a valid code, will create a basic language object
 795          *   - If boolean and false, create object from the current users language
 796          *   - If boolean and true, create object from the wikis content language
 797          *   - If language object, use it as given
 798          *
 799          * @throws MWException When given an invalid key
 800          * @return string|bool False if the message doesn't exist, otherwise the
 801          *   message (which can be empty)
 802          */
 803         function get( $key, $useDB = true, $langcode = true ) {
 804                 if ( is_int( $key ) ) {
 805                         // Fix numerical strings that somehow become ints
 806                         // on their way here
 807                         $key = (string)$key;
 808                 } elseif ( !is_string( $key ) ) {
 809                         throw new MWException( 'Non-string key given' );
 810                 } elseif ( $key === '' ) {
 811                         // Shortcut: the empty key is always missing
 812                         return false;
 813                 }
 814
 815                 // Normalise title-case input (with some inlining)
 816                 $lckey = self::normalizeKey( $key );
 817
 818                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 819
 820                 // Loop through each language in the fallback list until we find something useful
 821                 $lang = wfGetLangObj( $langcode );
 822                 $message = $this->getMessageFromFallbackChain(
 823                         $lang,
 824                         $lckey,
 825                         !$this->mDisable && $useDB
 826                 );
 827
 828                 // If we still have no message, maybe the key was in fact a full key so try that
 829                 if ( $message === false ) {
 830                         $parts = explode( '/', $lckey );
 831                         // We may get calls for things that are http-urls from sidebar
 832                         // Let's not load nonexistent languages for those
 833                         // They usually have more than one slash.
 834                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 835                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 836                                 if ( $message === null ) {
 837                                         $message = false;
 838                                 }
 839                         }
 840                 }
 841
 842                 // Post-processing if the message exists
 843                 if ( $message !== false ) {
 844                         // Fix whitespace
 845                         $message = str_replace(
 846                                 [
 847                                         # Fix for trailing whitespace, removed by textarea
 848                                         '&#32;',
 849                                         # Fix for NBSP, converted to space by firefox
 850                                         '&nbsp;',
 851                                         '&#160;',
 852                                         '&shy;'
 853                                 ],
 854                                 [
 855                                         ' ',
 856                                         "\u{00A0}",
 857                                         "\u{00A0}",
 858                                         "\u{00AD}"
 859                                 ],
 860                                 $message
 861                         );
 862                 }
 863
 864                 return $message;
 865         }
 866
 867         /**
 868          * Given a language, try and fetch messages from that language.
 869          *
 870          * Will also consider fallbacks of that language, the site language, and fallbacks for
 871          * the site language.
 872          *
 873          * @see MessageCache::get
 874          * @param Language|StubObject $lang Preferred language
 875          * @param string $lckey Lowercase key for the message (as for localisation cache)
 876          * @param bool $useDB Whether to include messages from the wiki database
 877          * @return string|bool The message, or false if not found
 878          */
 879         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 880                 $alreadyTried = [];
 881
 882                 // First try the requested language.
 883                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 884                 if ( $message !== false ) {
 885                         return $message;
 886                 }
 887
 888                 // Now try checking the site language.
 889                 $message = $this->getMessageForLang( $this->contLang, $lckey, $useDB, $alreadyTried );
 890                 return $message;
 891         }
 892
 893         /**
 894          * Given a language, try and fetch messages from that language and its fallbacks.
 895          *
 896          * @see MessageCache::get
 897          * @param Language|StubObject $lang Preferred language
 898          * @param string $lckey Lowercase key for the message (as for localisation cache)
 899          * @param bool $useDB Whether to include messages from the wiki database
 900          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 901          * @return string|bool The message, or false if not found
 902          */
 903         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 904                 $langcode = $lang->getCode();
 905
 906                 // Try checking the database for the requested language
 907                 if ( $useDB ) {
 908                         $uckey = $this->contLang->ucfirst( $lckey );
 909
 910                         if ( !isset( $alreadyTried[$langcode] ) ) {
 911                                 $message = $this->getMsgFromNamespace(
 912                                         $this->getMessagePageName( $langcode, $uckey ),
 913                                         $langcode
 914                                 );
 915
 916                                 if ( $message !== false ) {
 917                                         return $message;
 918                                 }
 919                                 $alreadyTried[$langcode] = true;
 920                         }
 921                 } else {
 922                         $uckey = null;
 923                 }
 924
 925                 // Check the CDB cache
 926                 $message = $lang->getMessage( $lckey );
 927                 if ( $message !== null ) {
 928                         return $message;
 929                 }
 930
 931                 // Try checking the database for all of the fallback languages
 932                 if ( $useDB ) {
 933                         $fallbackChain = Language::getFallbacksFor( $langcode );
 934
 935                         foreach ( $fallbackChain as $code ) {
 936                                 if ( isset( $alreadyTried[$code] ) ) {
 937                                         continue;
 938                                 }
 939
 940                                 $message = $this->getMsgFromNamespace(
 941                                         $this->getMessagePageName( $code, $uckey ), $code );
 942
 943                                 if ( $message !== false ) {
 944                                         return $message;
 945                                 }
 946                                 $alreadyTried[$code] = true;
 947                         }
 948                 }
 949
 950                 return false;
 951         }
 952
 953         /**
 954          * Get the message page name for a given language
 955          *
 956          * @param string $langcode
 957          * @param string $uckey Uppercase key for the message
 958          * @return string The page name
 959          */
 960         private function getMessagePageName( $langcode, $uckey ) {
 961                 global $wgLanguageCode;
 962
 963                 if ( $langcode === $wgLanguageCode ) {
 964                         // Messages created in the content language will not have the /lang extension
 965                         return $uckey;
 966                 } else {
 967                         return "$uckey/$langcode";
 968                 }
 969         }
 970
 971         /**
 972          * Get a message from the MediaWiki namespace, with caching. The key must
 973          * first be converted to two-part lang/msg form if necessary.
 974          *
 975          * Unlike self::get(), this function doesn't resolve fallback chains, and
 976          * some callers require this behavior. LanguageConverter::parseCachedTable()
 977          * and self::get() are some examples in core.
 978          *
 979          * @param string $title Message cache key with initial uppercase letter
 980          * @param string $code Code denoting the language to try
 981          * @return string|bool The message, or false if it does not exist or on error
 982          */
 983         public function getMsgFromNamespace( $title, $code ) {
 984                 // Load all MediaWiki page definitions into cache. Note that individual keys
 985                 // already loaded into cache during this request remain in the cache, which
 986                 // includes the value of hook-defined messages.
 987                 $this->load( $code );
 988
 989                 $entry = $this->cache->getField( $code, $title );
 990                 if ( $entry !== null ) {
 991                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 992                                 // The message exists and is not '!TOO BIG'
 993                                 return (string)substr( $entry, 1 );
 994                         } elseif ( $entry === '!NONEXISTENT' ) {
 995                                 return false;
 996                         }
 997                         // Fall through and try invididual message cache below
 998                 } else {
 999                         // Message does not have a MediaWiki page definition
1000                         $message = false;
1001                         Hooks::run( 'MessagesPreLoad', [ $title, &$message, $code ] );
1002                         if ( $message !== false ) {
1003                                 $this->cache->setField( $code, $title, ' ' . $message );
1004                         } else {
1005                                 $this->cache->setField( $code, $title, '!NONEXISTENT' );
1006                         }
1007
1008                         return $message;
1009                 }
1010
1011                 if ( $this->cacheVolatile[$code] ) {
1012                         $entry = false;
1013                         // Make sure that individual keys respect the WAN cache holdoff period too
1014                         LoggerFactory::getInstance( 'MessageCache' )->debug(
1015                                 __METHOD__ . ': loading volatile key \'{titleKey}\'',
1016                                 [ 'titleKey' => $title, 'code' => $code ] );
1017                 } else {
1018                         // Try the individual message cache
1019                         $entry = $this->loadCachedMessagePageEntry(
1020                                 $title,
1021                                 $code,
1022                                 $this->cache->getField( $code, 'HASH' )
1023                         );
1024                 }
1025
1026                 if ( $entry !== false && substr( $entry, 0, 1 ) === ' ' ) {
1027                         $this->cache->setField( $code, $title, $entry );
1028                         // The message exists, so make sure a string is returned
1029                         return (string)substr( $entry, 1 );
1030                 }
1031
1032                 $this->cache->setField( $code, $title, '!NONEXISTENT' );
1033
1034                 return false;
1035         }
1036
1037         /**
1038          * @param string $dbKey
1039          * @param string $code
1040          * @param string $hash
1041          * @return string Either " <MESSAGE>" or "!NONEXISTANT"
1042          */
1043         private function loadCachedMessagePageEntry( $dbKey, $code, $hash ) {
1044                 $fname = __METHOD__;
1045                 return $this->srvCache->getWithSetCallback(
1046                         $this->srvCache->makeKey( 'messages-big', $hash, $dbKey ),
1047                         IExpiringStore::TTL_MINUTE,
1048                         function () use ( $code, $dbKey, $hash, $fname ) {
1049                                 return $this->wanCache->getWithSetCallback(
1050                                         $this->bigMessageCacheKey( $hash, $dbKey ),
1051                                         $this->mExpiry,
1052                                         function ( $oldValue, &$ttl, &$setOpts ) use ( $dbKey, $code, $fname ) {
1053                                                 // Try loading the message from the database
1054                                                 $dbr = wfGetDB( DB_REPLICA );
1055                                                 $setOpts += Database::getCacheSetOptions( $dbr );
1056                                                 // Use newKnownCurrent() to avoid querying revision/user tables
1057                                                 $title = Title::makeTitle( NS_MEDIAWIKI, $dbKey );
1058                                                 $revision = Revision::newKnownCurrent( $dbr, $title );
1059                                                 if ( !$revision ) {
1060                                                         // The wiki doesn't have a local override page. Cache absence with normal TTL.
1061                                                         // When overrides are created, self::replace() takes care of the cache.
1062                                                         return '!NONEXISTENT';
1063                                                 }
1064                                                 $content = $revision->getContent();
1065                                                 if ( $content ) {
1066                                                         $message = $this->getMessageTextFromContent( $content );
1067                                                 } else {
1068                                                         LoggerFactory::getInstance( 'MessageCache' )->warning(
1069                                                                 $fname . ': failed to load page text for \'{titleKey}\'',
1070                                                                 [ 'titleKey' => $dbKey, 'code' => $code ]
1071                                                         );
1072                                                         $message = null;
1073                                                 }
1074
1075                                                 if ( !is_string( $message ) ) {
1076                                                         // Revision failed to load Content, or Content is incompatible with wikitext.
1077                                                         // Possibly a temporary loading failure.
1078                                                         $ttl = 5;
1079
1080                                                         return '!NONEXISTENT';
1081                                                 }
1082
1083                                                 return ' ' . $message;
1084                                         }
1085                                 );
1086                         }
1087                 );
1088         }
1089
1090         /**
1091          * @param string $message
1092          * @param bool $interface
1093          * @param Language|null $language
1094          * @param Title|null $title
1095          * @return string
1096          */
1097         public function transform( $message, $interface = false, $language = null, $title = null ) {
1098                 // Avoid creating parser if nothing to transform
1099                 if ( strpos( $message, '{{' ) === false ) {
1100                         return $message;
1101                 }
1102
1103                 if ( $this->mInParser ) {
1104                         return $message;
1105                 }
1106
1107                 $parser = $this->getParser();
1108                 if ( $parser ) {
1109                         $popts = $this->getParserOptions();
1110                         $popts->setInterfaceMessage( $interface );
1111                         $popts->setTargetLanguage( $language );
1112
1113                         $userlang = $popts->setUserLang( $language );
1114                         $this->mInParser = true;
1115                         $message = $parser->transformMsg( $message, $popts, $title );
1116                         $this->mInParser = false;
1117                         $popts->setUserLang( $userlang );
1118                 }
1119
1120                 return $message;
1121         }
1122
1123         /**
1124          * @return Parser
1125          */
1126         public function getParser() {
1127                 global $wgParser, $wgParserConf;
1128
1129                 if ( !$this->mParser && isset( $wgParser ) ) {
1130                         # Do some initialisation so that we don't have to do it twice
1131                         $wgParser->firstCallInit();
1132                         # Clone it and store it
1133                         $class = $wgParserConf['class'];
1134                         if ( $class == ParserDiffTest::class ) {
1135                                 # Uncloneable
1136                                 $this->mParser = new $class( $wgParserConf );
1137                         } else {
1138                                 $this->mParser = clone $wgParser;
1139                         }
1140                 }
1141
1142                 return $this->mParser;
1143         }
1144
1145         /**
1146          * @param string $text
1147          * @param Title|null $title
1148          * @param bool $linestart Whether or not this is at the start of a line
1149          * @param bool $interface Whether this is an interface message
1150          * @param Language|string|null $language Language code
1151          * @return ParserOutput|string
1152          */
1153         public function parse( $text, $title = null, $linestart = true,
1154                 $interface = false, $language = null
1155         ) {
1156                 global $wgTitle;
1157
1158                 if ( $this->mInParser ) {
1159                         return htmlspecialchars( $text );
1160                 }
1161
1162                 $parser = $this->getParser();
1163                 $popts = $this->getParserOptions();
1164                 $popts->setInterfaceMessage( $interface );
1165
1166                 if ( is_string( $language ) ) {
1167                         $language = Language::factory( $language );
1168                 }
1169                 $popts->setTargetLanguage( $language );
1170
1171                 if ( !$title || !$title instanceof Title ) {
1172                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1173                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1174                         $title = $wgTitle;
1175                 }
1176                 // Sometimes $wgTitle isn't set either...
1177                 if ( !$title ) {
1178                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1179                         # Create a ghost title in such case
1180                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1181                 }
1182
1183                 $this->mInParser = true;
1184                 $res = $parser->parse( $text, $title, $popts, $linestart );
1185                 $this->mInParser = false;
1186
1187                 return $res;
1188         }
1189
1190         public function disable() {
1191                 $this->mDisable = true;
1192         }
1193
1194         public function enable() {
1195                 $this->mDisable = false;
1196         }
1197
1198         /**
1199          * Whether DB/cache usage is disabled for determining messages
1200          *
1201          * If so, this typically indicates either:
1202          *   - a) load() failed to find a cached copy nor query the DB
1203          *   - b) we are in a special context or error mode that cannot use the DB
1204          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1205          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1206          *
1207          * @return bool
1208          * @since 1.27
1209          */
1210         public function isDisabled() {
1211                 return $this->mDisable;
1212         }
1213
1214         /**
1215          * Clear all stored messages in global and local cache
1216          *
1217          * Mainly used after a mass rebuild
1218          */
1219         public function clear() {
1220                 $langs = Language::fetchLanguageNames( null, 'mw' );
1221                 foreach ( array_keys( $langs ) as $code ) {
1222                         $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
1223                 }
1224                 $this->cache->clear();
1225         }
1226
1227         /**
1228          * @param string $key
1229          * @return array
1230          */
1231         public function figureMessage( $key ) {
1232                 global $wgLanguageCode;
1233
1234                 $pieces = explode( '/', $key );
1235                 if ( count( $pieces ) < 2 ) {
1236                         return [ $key, $wgLanguageCode ];
1237                 }
1238
1239                 $lang = array_pop( $pieces );
1240                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1241                         return [ $key, $wgLanguageCode ];
1242                 }
1243
1244                 $message = implode( '/', $pieces );
1245
1246                 return [ $message, $lang ];
1247         }
1248
1249         /**
1250          * Get all message keys stored in the message cache for a given language.
1251          * If $code is the content language code, this will return all message keys
1252          * for which MediaWiki:msgkey exists. If $code is another language code, this
1253          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1254          * @param string $code Language code
1255          * @return array Array of message keys (strings)
1256          */
1257         public function getAllMessageKeys( $code ) {
1258                 $this->load( $code );
1259                 if ( !$this->cache->has( $code ) ) {
1260                         // Apparently load() failed
1261                         return null;
1262                 }
1263                 // Remove administrative keys
1264                 $cache = $this->cache->get( $code );
1265                 unset( $cache['VERSION'] );
1266                 unset( $cache['EXPIRY'] );
1267                 unset( $cache['EXCESSIVE'] );
1268                 // Remove any !NONEXISTENT keys
1269                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1270
1271                 // Keys may appear with a capital first letter. lcfirst them.
1272                 return array_map( [ $this->contLang, 'lcfirst' ], array_keys( $cache ) );
1273         }
1274
1275         /**
1276          * Purge message caches when a MediaWiki: page is created, updated, or deleted
1277          *
1278          * @param Title $title Message page title
1279          * @param Content|null $content New content for edit/create, null on deletion
1280          * @since 1.29
1281          */
1282         public function updateMessageOverride( Title $title, Content $content = null ) {
1283                 $msgText = $this->getMessageTextFromContent( $content );
1284                 if ( $msgText === null ) {
1285                         $msgText = false; // treat as not existing
1286                 }
1287
1288                 $this->replace( $title->getDBkey(), $msgText );
1289
1290                 if ( $this->contLang->hasVariants() ) {
1291                         $this->contLang->updateConversionTable( $title );
1292                 }
1293         }
1294
1295         /**
1296          * @param string $code Language code
1297          * @return string WAN cache key usable as a "check key" against language page edits
1298          */
1299         public function getCheckKey( $code ) {
1300                 return $this->wanCache->makeKey( 'messages', $code );
1301         }
1302
1303         /**
1304          * @param Content|null $content Content or null if the message page does not exist
1305          * @return string|bool|null Returns false if $content is null and null on error
1306          */
1307         private function getMessageTextFromContent( Content $content = null ) {
1308                 // @TODO: could skip pseudo-messages like js/css here, based on content model
1309                 if ( $content ) {
1310                         // Message page exists...
1311                         // XXX: Is this the right way to turn a Content object into a message?
1312                         // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1313                         //       CssContent. MessageContent is *not* used for storing messages, it's
1314                         //       only used for wrapping them when needed.
1315                         $msgText = $content->getWikitextForTransclusion();
1316                         if ( $msgText === false || $msgText === null ) {
1317                                 // This might be due to some kind of misconfiguration...
1318                                 $msgText = null;
1319                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1320                                         __METHOD__ . ": message content doesn't provide wikitext "
1321                                         . "(content model: " . $content->getModel() . ")" );
1322                         }
1323                 } else {
1324                         // Message page does not exist...
1325                         $msgText = false;
1326                 }
1327
1328                 return $msgText;
1329         }
1330
1331         /**
1332          * @param string $hash Hash for this version of the entire key/value overrides map
1333          * @param string $title Message cache key with initial uppercase letter
1334          * @return string
1335          */
1336         private function bigMessageCacheKey( $hash, $title ) {
1337                 return $this->wanCache->makeKey( 'messages-big', $hash, $title );
1338         }
1339 }