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, $wgUseLocalMessageCache;
 110                         self::$instance = new self(
 111                                 MediaWikiServices::getInstance()->getMainWANObjectCache(),
 112                                 wfGetMessageCacheStorage(),
 113                                 $wgUseLocalMessageCache
 114                                         ? MediaWikiServices::getInstance()->getLocalServerObjectCache()
 115                                         : new EmptyBagOStuff(),
 116                                 $wgUseDatabaseMessages,
 117                                 $wgMsgCacheExpiry,
 118                                 MediaWikiServices::getInstance()->getContentLanguage()
 119                         );
 120                 }
 121
 122                 return self::$instance;
 123         }
 124
 125         /**
 126          * Destroy the singleton instance
 127          *
 128          * @since 1.18
 129          */
 130         public static function destroyInstance() {
 131                 self::$instance = null;
 132         }
 133
 134         /**
 135          * Normalize message key input
 136          *
 137          * @param string $key Input message key to be normalized
 138          * @return string Normalized message key
 139          */
 140         public static function normalizeKey( $key ) {
 141                 $lckey = strtr( $key, ' ', '_' );
 142                 if ( ord( $lckey ) < 128 ) {
 143                         $lckey[0] = strtolower( $lckey[0] );
 144                 } else {
 145                         $lckey = MediaWikiServices::getInstance()->getContentLanguage()->lcfirst( $lckey );
 146                 }
 147
 148                 return $lckey;
 149         }
 150
 151         /**
 152          * @param WANObjectCache $wanCache
 153          * @param BagOStuff $clusterCache
 154          * @param BagOStuff $serverCache
 155          * @param bool $useDB Whether to look for message overrides (e.g. MediaWiki: pages)
 156          * @param int $expiry Lifetime for cache. @see $mExpiry.
 157          * @param Language|null $contLang Content language of site
 158          */
 159         public function __construct(
 160                 WANObjectCache $wanCache,
 161                 BagOStuff $clusterCache,
 162                 BagOStuff $serverCache,
 163                 $useDB,
 164                 $expiry,
 165                 Language $contLang = null
 166         ) {
 167                 $this->wanCache = $wanCache;
 168                 $this->clusterCache = $clusterCache;
 169                 $this->srvCache = $serverCache;
 170
 171                 $this->cache = new MapCacheLRU( 5 ); // limit size for sanity
 172
 173                 $this->mDisable = !$useDB;
 174                 $this->mExpiry = $expiry;
 175                 $this->contLang = $contLang ?? MediaWikiServices::getInstance()->getContentLanguage();
 176         }
 177
 178         /**
 179          * ParserOptions is lazy initialised.
 180          *
 181          * @return ParserOptions
 182          */
 183         function getParserOptions() {
 184                 global $wgUser;
 185
 186                 if ( !$this->mParserOptions ) {
 187                         if ( !$wgUser->isSafeToLoad() ) {
 188                                 // $wgUser isn't unstubbable yet, so don't try to get a
 189                                 // ParserOptions for it. And don't cache this ParserOptions
 190                                 // either.
 191                                 $po = ParserOptions::newFromAnon();
 192                                 $po->setAllowUnsafeRawHtml( false );
 193                                 return $po;
 194                         }
 195
 196                         $this->mParserOptions = new ParserOptions;
 197                         // Messages may take parameters that could come
 198                         // from malicious sources. As a precaution, disable
 199                         // the <html> parser tag when parsing messages.
 200                         $this->mParserOptions->setAllowUnsafeRawHtml( false );
 201                 }
 202
 203                 return $this->mParserOptions;
 204         }
 205
 206         /**
 207          * Try to load the cache from APC.
 208          *
 209          * @param string $code Optional language code, see documenation of load().
 210          * @return array|bool The cache array, or false if not in cache.
 211          */
 212         protected function getLocalCache( $code ) {
 213                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 214
 215                 return $this->srvCache->get( $cacheKey );
 216         }
 217
 218         /**
 219          * Save the cache to APC.
 220          *
 221          * @param string $code
 222          * @param array $cache The cache array
 223          */
 224         protected function saveToLocalCache( $code, $cache ) {
 225                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 226                 $this->srvCache->set( $cacheKey, $cache );
 227         }
 228
 229         /**
 230          * Loads messages from caches or from database in this order:
 231          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 232          * (2) memcached
 233          * (3) from the database.
 234          *
 235          * When successfully loading from (2) or (3), all higher level caches are
 236          * updated for the newest version.
 237          *
 238          * Nothing is loaded if member variable mDisable is true, either manually
 239          * set by calling code or if message loading fails (is this possible?).
 240          *
 241          * Returns true if cache is already populated or it was successfully populated,
 242          * or false if populating empty cache fails. Also returns true if MessageCache
 243          * is disabled.
 244          *
 245          * @param string $code Language to which load messages
 246          * @param int|null $mode Use MessageCache::FOR_UPDATE to skip process cache [optional]
 247          * @throws InvalidArgumentException
 248          * @return bool
 249          */
 250         protected function load( $code, $mode = null ) {
 251                 if ( !is_string( $code ) ) {
 252                         throw new InvalidArgumentException( "Missing language code" );
 253                 }
 254
 255                 # Don't do double loading...
 256                 if ( $this->cache->has( $code ) && $mode != self::FOR_UPDATE ) {
 257                         return true;
 258                 }
 259
 260                 # 8 lines of code just to say (once) that message cache is disabled
 261                 if ( $this->mDisable ) {
 262                         static $shownDisabled = false;
 263                         if ( !$shownDisabled ) {
 264                                 wfDebug( __METHOD__ . ": disabled\n" );
 265                                 $shownDisabled = true;
 266                         }
 267
 268                         return true;
 269                 }
 270
 271                 # Loading code starts
 272                 $success = false; # Keep track of success
 273                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 274                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 275
 276                 # Hash of the contents is stored in memcache, to detect if data-center cache
 277                 # or local cache goes out of date (e.g. due to replace() on some other server)
 278                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 279                 $this->cacheVolatile[$code] = $hashVolatile;
 280
 281                 # Try the local cache and check against the cluster hash key...
 282                 $cache = $this->getLocalCache( $code );
 283                 if ( !$cache ) {
 284                         $where[] = 'local cache is empty';
 285                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 286                         $where[] = 'local cache has the wrong hash';
 287                         $staleCache = $cache;
 288                 } elseif ( $this->isCacheExpired( $cache ) ) {
 289                         $where[] = 'local cache is expired';
 290                         $staleCache = $cache;
 291                 } elseif ( $hashVolatile ) {
 292                         $where[] = 'local cache validation key is expired/volatile';
 293                         $staleCache = $cache;
 294                 } else {
 295                         $where[] = 'got from local cache';
 296                         $this->cache->set( $code, $cache );
 297                         $success = true;
 298                 }
 299
 300                 if ( !$success ) {
 301                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 302                         # Try the global cache. If it is empty, try to acquire a lock. If
 303                         # the lock can't be acquired, wait for the other thread to finish
 304                         # and then try the global cache a second time.
 305                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 306                                 if ( $hashVolatile && $staleCache ) {
 307                                         # Do not bother fetching the whole cache blob to avoid I/O.
 308                                         # Instead, just try to get the non-blocking $statusKey lock
 309                                         # below, and use the local stale value if it was not acquired.
 310                                         $where[] = 'global cache is presumed expired';
 311                                 } else {
 312                                         $cache = $this->clusterCache->get( $cacheKey );
 313                                         if ( !$cache ) {
 314                                                 $where[] = 'global cache is empty';
 315                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 316                                                 $where[] = 'global cache is expired';
 317                                                 $staleCache = $cache;
 318                                         } elseif ( $hashVolatile ) {
 319                                                 # DB results are replica DB lag prone until the holdoff TTL passes.
 320                                                 # By then, updates should be reflected in loadFromDBWithLock().
 321                                                 # One thread renerates the cache while others use old values.
 322                                                 $where[] = 'global cache is expired/volatile';
 323                                                 $staleCache = $cache;
 324                                         } else {
 325                                                 $where[] = 'got from global cache';
 326                                                 $this->cache->set( $code, $cache );
 327                                                 $this->saveToCaches( $cache, 'local-only', $code );
 328                                                 $success = true;
 329                                         }
 330                                 }
 331
 332                                 if ( $success ) {
 333                                         # Done, no need to retry
 334                                         break;
 335                                 }
 336
 337                                 # We need to call loadFromDB. Limit the concurrency to one process.
 338                                 # This prevents the site from going down when the cache expires.
 339                                 # Note that the DB slam protection lock here is non-blocking.
 340                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 341                                 if ( $loadStatus === true ) {
 342                                         $success = true;
 343                                         break;
 344                                 } elseif ( $staleCache ) {
 345                                         # Use the stale cache while some other thread constructs the new one
 346                                         $where[] = 'using stale cache';
 347                                         $this->cache->set( $code, $staleCache );
 348                                         $success = true;
 349                                         break;
 350                                 } elseif ( $failedAttempts > 0 ) {
 351                                         # Already blocked once, so avoid another lock/unlock cycle.
 352                                         # This case will typically be hit if memcached is down, or if
 353                                         # loadFromDB() takes longer than LOCK_WAIT.
 354                                         $where[] = "could not acquire status key.";
 355                                         break;
 356                                 } elseif ( $loadStatus === 'cantacquire' ) {
 357                                         # Wait for the other thread to finish, then retry. Normally,
 358                                         # the memcached get() will then yeild the other thread's result.
 359                                         $where[] = 'waited for other thread to complete';
 360                                         $this->getReentrantScopedLock( $cacheKey );
 361                                 } else {
 362                                         # Disable cache; $loadStatus is 'disabled'
 363                                         break;
 364                                 }
 365                         }
 366                 }
 367
 368                 if ( !$success ) {
 369                         $where[] = 'loading FAILED - cache is disabled';
 370                         $this->mDisable = true;
 371                         $this->cache->set( $code, [] );
 372                         wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
 373                         # This used to throw an exception, but that led to nasty side effects like
 374                         # the whole wiki being instantly down if the memcached server died
 375                 }
 376
 377                 if ( !$this->cache->has( $code ) ) { // sanity
 378                         throw new LogicException( "Process cache for '$code' should be set by now." );
 379                 }
 380
 381                 $info = implode( ', ', $where );
 382                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 383
 384                 return $success;
 385         }
 386
 387         /**
 388          * @param string $code
 389          * @param array &$where List of wfDebug() comments
 390          * @param int|null $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 391          * @return bool|string True on success or one of ("cantacquire", "disabled")
 392          */
 393         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 394                 # If cache updates on all levels fail, give up on message overrides.
 395                 # This is to avoid easy site outages; see $saveSuccess comments below.
 396                 $statusKey = $this->clusterCache->makeKey( 'messages', $code, 'status' );
 397                 $status = $this->clusterCache->get( $statusKey );
 398                 if ( $status === 'error' ) {
 399                         $where[] = "could not load; method is still globally disabled";
 400                         return 'disabled';
 401                 }
 402
 403                 # Now let's regenerate
 404                 $where[] = 'loading from database';
 405
 406                 # Lock the cache to prevent conflicting writes.
 407                 # This lock is non-blocking so stale cache can quickly be used.
 408                 # Note that load() will call a blocking getReentrantScopedLock()
 409                 # after this if it really need to wait for any current thread.
 410                 $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 411                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 412                 if ( !$scopedLock ) {
 413                         $where[] = 'could not acquire main lock';
 414                         return 'cantacquire';
 415                 }
 416
 417                 $cache = $this->loadFromDB( $code, $mode );
 418                 $this->cache->set( $code, $cache );
 419                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 420
 421                 if ( !$saveSuccess ) {
 422                         /**
 423                          * Cache save has failed.
 424                          *
 425                          * There are two main scenarios where this could be a problem:
 426                          * - The cache is more than the maximum size (typically 1MB compressed).
 427                          * - Memcached has no space remaining in the relevant slab class. This is
 428                          *   unlikely with recent versions of memcached.
 429                          *
 430                          * Either way, if there is a local cache, nothing bad will happen. If there
 431                          * is no local cache, disabling the message cache for all requests avoids
 432                          * incurring a loadFromDB() overhead on every request, and thus saves the
 433                          * wiki from complete downtime under moderate traffic conditions.
 434                          */
 435                         if ( $this->srvCache instanceof EmptyBagOStuff ) {
 436                                 $this->clusterCache->set( $statusKey, 'error', 60 * 5 );
 437                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 438                         } else {
 439                                 $where[] = "could not save global cache";
 440                         }
 441                 }
 442
 443                 return true;
 444         }
 445
 446         /**
 447          * Loads cacheable messages from the database. Messages bigger than
 448          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 449          * on-demand from the database later.
 450          *
 451          * @param string $code Language code
 452          * @param int|null $mode Use MessageCache::FOR_UPDATE to skip process cache
 453          * @return array Loaded messages for storing in caches
 454          */
 455         protected function loadFromDB( $code, $mode = null ) {
 456                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 457
 458                 // (T164666) The query here performs really poorly on WMF's
 459                 // contributions replicas. We don't have a way to say "any group except
 460                 // contributions", so for the moment let's specify 'api'.
 461                 // @todo: Get rid of this hack.
 462                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA, 'api' );
 463
 464                 $cache = [];
 465
 466                 # Common conditions
 467                 $conds = [
 468                         'page_is_redirect' => 0,
 469                         'page_namespace' => NS_MEDIAWIKI,
 470                 ];
 471
 472                 $mostused = [];
 473                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 474                         if ( !$this->cache->has( $wgLanguageCode ) ) {
 475                                 $this->load( $wgLanguageCode );
 476                         }
 477                         $mostused = array_keys( $this->cache->get( $wgLanguageCode ) );
 478                         foreach ( $mostused as $key => $value ) {
 479                                 $mostused[$key] = "$value/$code";
 480                         }
 481                 }
 482
 483                 if ( count( $mostused ) ) {
 484                         $conds['page_title'] = $mostused;
 485                 } elseif ( $code !== $wgLanguageCode ) {
 486                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 487                 } else {
 488                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 489                         # other than language code.
 490                         $conds[] = 'page_title NOT' .
 491                                 $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 492                 }
 493
 494                 # Conditions to fetch oversized pages to ignore them
 495                 $bigConds = $conds;
 496                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 497
 498                 # Load titles for all oversized pages in the MediaWiki namespace
 499                 $res = $dbr->select(
 500                         'page',
 501                         [ 'page_title', 'page_latest' ],
 502                         $bigConds,
 503                         __METHOD__ . "($code)-big"
 504                 );
 505                 foreach ( $res as $row ) {
 506                         $cache[$row->page_title] = '!TOO BIG';
 507                         // At least include revision ID so page changes are reflected in the hash
 508                         $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 509                 }
 510
 511                 # Conditions to load the remaining pages with their contents
 512                 $smallConds = $conds;
 513                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 514
 515                 $res = $dbr->select(
 516                         [ 'page', 'revision', 'text' ],
 517                         [ 'page_title', 'old_id', 'old_text', 'old_flags' ],
 518                         $smallConds,
 519                         __METHOD__ . "($code)-small",
 520                         [],
 521                         [
 522                                 'revision' => [ 'JOIN', 'page_latest=rev_id' ],
 523                                 'text' => [ 'JOIN', 'rev_text_id=old_id' ],
 524                         ]
 525                 );
 526
 527                 foreach ( $res as $row ) {
 528                         $text = Revision::getRevisionText( $row );
 529                         if ( $text === false ) {
 530                                 // Failed to fetch data; possible ES errors?
 531                                 // Store a marker to fetch on-demand as a workaround...
 532                                 // TODO Use a differnt marker
 533                                 $entry = '!TOO BIG';
 534                                 wfDebugLog(
 535                                         'MessageCache',
 536                                         __METHOD__
 537                                         . ": failed to load message page text for {$row->page_title} ($code)"
 538                                 );
 539                         } else {
 540                                 $entry = ' ' . $text;
 541                         }
 542                         $cache[$row->page_title] = $entry;
 543                 }
 544
 545                 $cache['VERSION'] = MSG_CACHE_VERSION;
 546                 ksort( $cache );
 547
 548                 # Hash for validating local cache (APC). No need to take into account
 549                 # messages larger than $wgMaxMsgCacheEntrySize, since those are only
 550                 # stored and fetched from memcache.
 551                 $cache['HASH'] = md5( serialize( $cache ) );
 552                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 553
 554                 return $cache;
 555         }
 556
 557         /**
 558          * Updates cache as necessary when message page is changed
 559          *
 560          * @param string $title Message cache key with initial uppercase letter
 561          * @param string|bool $text New contents of the page (false if deleted)
 562          */
 563         public function replace( $title, $text ) {
 564                 global $wgLanguageCode;
 565
 566                 if ( $this->mDisable ) {
 567                         return;
 568                 }
 569
 570                 list( $msg, $code ) = $this->figureMessage( $title );
 571                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 572                         // Content language overrides do not use the /<code> suffix
 573                         return;
 574                 }
 575
 576                 // (a) Update the process cache with the new message text
 577                 if ( $text === false ) {
 578                         // Page deleted
 579                         $this->cache->setField( $code, $title, '!NONEXISTENT' );
 580                 } else {
 581                         // Ignore $wgMaxMsgCacheEntrySize so the process cache is up to date
 582                         $this->cache->setField( $code, $title, ' ' . $text );
 583                 }
 584
 585                 // (b) Update the shared caches in a deferred update with a fresh DB snapshot
 586                 DeferredUpdates::addCallableUpdate(
 587                         function () use ( $title, $msg, $code ) {
 588                                 global $wgMaxMsgCacheEntrySize;
 589                                 // Allow one caller at a time to avoid race conditions
 590                                 $scopedLock = $this->getReentrantScopedLock(
 591                                         $this->clusterCache->makeKey( 'messages', $code )
 592                                 );
 593                                 if ( !$scopedLock ) {
 594                                         LoggerFactory::getInstance( 'MessageCache' )->error(
 595                                                 __METHOD__ . ': could not acquire lock to update {title} ({code})',
 596                                                 [ 'title' => $title, 'code' => $code ] );
 597                                         return;
 598                                 }
 599                                 // Reload messages from the database and pre-populate dc-local caches
 600                                 // as optimisation. Use the master DB to avoid race conditions.
 601                                 $cache = $this->loadFromDB( $code, self::FOR_UPDATE );
 602                                 // Check if an individual cache key should exist and update cache accordingly
 603                                 $page = WikiPage::factory( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 604                                 $page->loadPageData( $page::READ_LATEST );
 605                                 $text = $this->getMessageTextFromContent( $page->getContent() );
 606                                 if ( is_string( $text ) && strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 607                                         // Match logic of loadCachedMessagePageEntry()
 608                                         $this->wanCache->set(
 609                                                 $this->bigMessageCacheKey( $cache['HASH'], $title ),
 610                                                 ' ' . $text,
 611                                                 $this->mExpiry
 612                                         );
 613                                 }
 614                                 // Mark this cache as definitely being "latest" (non-volatile) so
 615                                 // load() calls do not try to refresh the cache with replica DB data
 616                                 $cache['LATEST'] = time();
 617                                 // Update the process cache
 618                                 $this->cache->set( $code, $cache );
 619                                 // Pre-emptively update the local datacenter cache so things like edit filter and
 620                                 // blacklist changes are reflected immediately; these often use MediaWiki: pages.
 621                                 // The datacenter handling replace() calls should be the same one handling edits
 622                                 // as they require HTTP POST.
 623                                 $this->saveToCaches( $cache, 'all', $code );
 624                                 // Release the lock now that the cache is saved
 625                                 ScopedCallback::consume( $scopedLock );
 626
 627                                 // Relay the purge. Touching this check key expires cache contents
 628                                 // and local cache (APC) validation hash across all datacenters.
 629                                 $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
 630
 631                                 // Purge the message in the message blob store
 632                                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 633                                 $blobStore = $resourceloader->getMessageBlobStore();
 634                                 $blobStore->updateMessage( $this->contLang->lcfirst( $msg ) );
 635
 636                                 Hooks::run( 'MessageCacheReplace', [ $title, $text ] );
 637                         },
 638                         DeferredUpdates::PRESEND
 639                 );
 640         }
 641
 642         /**
 643          * Is the given cache array expired due to time passing or a version change?
 644          *
 645          * @param array $cache
 646          * @return bool
 647          */
 648         protected function isCacheExpired( $cache ) {
 649                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 650                         return true;
 651                 }
 652                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 653                         return true;
 654                 }
 655                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 656                         return true;
 657                 }
 658
 659                 return false;
 660         }
 661
 662         /**
 663          * Shortcut to update caches.
 664          *
 665          * @param array $cache Cached messages with a version.
 666          * @param string $dest Either "local-only" to save to local caches only
 667          *   or "all" to save to all caches.
 668          * @param string|bool $code Language code (default: false)
 669          * @return bool
 670          */
 671         protected function saveToCaches( array $cache, $dest, $code = false ) {
 672                 if ( $dest === 'all' ) {
 673                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 674                         $success = $this->clusterCache->set( $cacheKey, $cache );
 675                         $this->setValidationHash( $code, $cache );
 676                 } else {
 677                         $success = true;
 678                 }
 679
 680                 $this->saveToLocalCache( $code, $cache );
 681
 682                 return $success;
 683         }
 684
 685         /**
 686          * Get the md5 used to validate the local APC cache
 687          *
 688          * @param string $code
 689          * @return array (hash or false, bool expiry/volatility status)
 690          */
 691         protected function getValidationHash( $code ) {
 692                 $curTTL = null;
 693                 $value = $this->wanCache->get(
 694                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 695                         $curTTL,
 696                         [ $this->getCheckKey( $code ) ]
 697                 );
 698
 699                 if ( $value ) {
 700                         $hash = $value['hash'];
 701                         if ( ( time() - $value['latest'] ) < WANObjectCache::TTL_MINUTE ) {
 702                                 // Cache was recently updated via replace() and should be up-to-date.
 703                                 // That method is only called in the primary datacenter and uses FOR_UPDATE.
 704                                 // Also, it is unlikely that the current datacenter is *now* secondary one.
 705                                 $expired = false;
 706                         } else {
 707                                 // See if the "check" key was bumped after the hash was generated
 708                                 $expired = ( $curTTL < 0 );
 709                         }
 710                 } else {
 711                         // No hash found at all; cache must regenerate to be safe
 712                         $hash = false;
 713                         $expired = true;
 714                 }
 715
 716                 return [ $hash, $expired ];
 717         }
 718
 719         /**
 720          * Set the md5 used to validate the local disk cache
 721          *
 722          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 723          * be treated as "volatile" by getValidationHash() for the next few seconds.
 724          * This is triggered when $cache is generated using FOR_UPDATE mode.
 725          *
 726          * @param string $code
 727          * @param array $cache Cached messages with a version
 728          */
 729         protected function setValidationHash( $code, array $cache ) {
 730                 $this->wanCache->set(
 731                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 732                         [
 733                                 'hash' => $cache['HASH'],
 734                                 'latest' => $cache['LATEST'] ?? 0
 735                         ],
 736                         WANObjectCache::TTL_INDEFINITE
 737                 );
 738         }
 739
 740         /**
 741          * @param string $key A language message cache key that stores blobs
 742          * @param int $timeout Wait timeout in seconds
 743          * @return null|ScopedCallback
 744          */
 745         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 746                 return $this->clusterCache->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 747         }
 748
 749         /**
 750          * Get a message from either the content language or the user language.
 751          *
 752          * First, assemble a list of languages to attempt getting the message from. This
 753          * chain begins with the requested language and its fallbacks and then continues with
 754          * the content language and its fallbacks. For each language in the chain, the following
 755          * process will occur (in this order):
 756          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 757          *     Note: for the content language, there is no /lang subpage.
 758          *  2. Fetch from the static CDB cache.
 759          *  3. If available, check the database for fallback language overrides.
 760          *
 761          * This process provides a number of guarantees. When changing this code, make sure all
 762          * of these guarantees are preserved.
 763          *  * If the requested language is *not* the content language, then the CDB cache for that
 764          *    specific language will take precedence over the root database page ([[MW:msg]]).
 765          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 766          *    the message is available *anywhere* in the language for which it is a fallback.
 767          *
 768          * @param string $key The message key
 769          * @param bool $useDB If true, look for the message in the DB, false
 770          *   to use only the compiled l10n cache.
 771          * @param bool|string|object $langcode Code of the language to get the message for.
 772          *   - If string and a valid code, will create a standard language object
 773          *   - If string but not a valid code, will create a basic language object
 774          *   - If boolean and false, create object from the current users language
 775          *   - If boolean and true, create object from the wikis content language
 776          *   - If language object, use it as given
 777          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 778          *
 779          * @throws MWException When given an invalid key
 780          * @return string|bool False if the message doesn't exist, otherwise the
 781          *   message (which can be empty)
 782          */
 783         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 784                 if ( is_int( $key ) ) {
 785                         // Fix numerical strings that somehow become ints
 786                         // on their way here
 787                         $key = (string)$key;
 788                 } elseif ( !is_string( $key ) ) {
 789                         throw new MWException( 'Non-string key given' );
 790                 } elseif ( $key === '' ) {
 791                         // Shortcut: the empty key is always missing
 792                         return false;
 793                 }
 794
 795                 // For full keys, get the language code from the key
 796                 $pos = strrpos( $key, '/' );
 797                 if ( $isFullKey && $pos !== false ) {
 798                         $langcode = substr( $key, $pos + 1 );
 799                         $key = substr( $key, 0, $pos );
 800                 }
 801
 802                 // Normalise title-case input (with some inlining)
 803                 $lckey = self::normalizeKey( $key );
 804
 805                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 806
 807                 // Loop through each language in the fallback list until we find something useful
 808                 $lang = wfGetLangObj( $langcode );
 809                 $message = $this->getMessageFromFallbackChain(
 810                         $lang,
 811                         $lckey,
 812                         !$this->mDisable && $useDB
 813                 );
 814
 815                 // If we still have no message, maybe the key was in fact a full key so try that
 816                 if ( $message === false ) {
 817                         $parts = explode( '/', $lckey );
 818                         // We may get calls for things that are http-urls from sidebar
 819                         // Let's not load nonexistent languages for those
 820                         // They usually have more than one slash.
 821                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 822                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 823                                 if ( $message === null ) {
 824                                         $message = false;
 825                                 }
 826                         }
 827                 }
 828
 829                 // Post-processing if the message exists
 830                 if ( $message !== false ) {
 831                         // Fix whitespace
 832                         $message = str_replace(
 833                                 [
 834                                         # Fix for trailing whitespace, removed by textarea
 835                                         '&#32;',
 836                                         # Fix for NBSP, converted to space by firefox
 837                                         '&nbsp;',
 838                                         '&#160;',
 839                                         '&shy;'
 840                                 ],
 841                                 [
 842                                         ' ',
 843                                         "\u{00A0}",
 844                                         "\u{00A0}",
 845                                         "\u{00AD}"
 846                                 ],
 847                                 $message
 848                         );
 849                 }
 850
 851                 return $message;
 852         }
 853
 854         /**
 855          * Given a language, try and fetch messages from that language.
 856          *
 857          * Will also consider fallbacks of that language, the site language, and fallbacks for
 858          * the site language.
 859          *
 860          * @see MessageCache::get
 861          * @param Language|StubObject $lang Preferred language
 862          * @param string $lckey Lowercase key for the message (as for localisation cache)
 863          * @param bool $useDB Whether to include messages from the wiki database
 864          * @return string|bool The message, or false if not found
 865          */
 866         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 867                 $alreadyTried = [];
 868
 869                 // First try the requested language.
 870                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 871                 if ( $message !== false ) {
 872                         return $message;
 873                 }
 874
 875                 // Now try checking the site language.
 876                 $message = $this->getMessageForLang( $this->contLang, $lckey, $useDB, $alreadyTried );
 877                 return $message;
 878         }
 879
 880         /**
 881          * Given a language, try and fetch messages from that language and its fallbacks.
 882          *
 883          * @see MessageCache::get
 884          * @param Language|StubObject $lang Preferred language
 885          * @param string $lckey Lowercase key for the message (as for localisation cache)
 886          * @param bool $useDB Whether to include messages from the wiki database
 887          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 888          * @return string|bool The message, or false if not found
 889          */
 890         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 891                 $langcode = $lang->getCode();
 892
 893                 // Try checking the database for the requested language
 894                 if ( $useDB ) {
 895                         $uckey = $this->contLang->ucfirst( $lckey );
 896
 897                         if ( !isset( $alreadyTried[$langcode] ) ) {
 898                                 $message = $this->getMsgFromNamespace(
 899                                         $this->getMessagePageName( $langcode, $uckey ),
 900                                         $langcode
 901                                 );
 902
 903                                 if ( $message !== false ) {
 904                                         return $message;
 905                                 }
 906                                 $alreadyTried[$langcode] = true;
 907                         }
 908                 } else {
 909                         $uckey = null;
 910                 }
 911
 912                 // Check the CDB cache
 913                 $message = $lang->getMessage( $lckey );
 914                 if ( $message !== null ) {
 915                         return $message;
 916                 }
 917
 918                 // Try checking the database for all of the fallback languages
 919                 if ( $useDB ) {
 920                         $fallbackChain = Language::getFallbacksFor( $langcode );
 921
 922                         foreach ( $fallbackChain as $code ) {
 923                                 if ( isset( $alreadyTried[$code] ) ) {
 924                                         continue;
 925                                 }
 926
 927                                 $message = $this->getMsgFromNamespace(
 928                                         $this->getMessagePageName( $code, $uckey ), $code );
 929
 930                                 if ( $message !== false ) {
 931                                         return $message;
 932                                 }
 933                                 $alreadyTried[$code] = true;
 934                         }
 935                 }
 936
 937                 return false;
 938         }
 939
 940         /**
 941          * Get the message page name for a given language
 942          *
 943          * @param string $langcode
 944          * @param string $uckey Uppercase key for the message
 945          * @return string The page name
 946          */
 947         private function getMessagePageName( $langcode, $uckey ) {
 948                 global $wgLanguageCode;
 949
 950                 if ( $langcode === $wgLanguageCode ) {
 951                         // Messages created in the content language will not have the /lang extension
 952                         return $uckey;
 953                 } else {
 954                         return "$uckey/$langcode";
 955                 }
 956         }
 957
 958         /**
 959          * Get a message from the MediaWiki namespace, with caching. The key must
 960          * first be converted to two-part lang/msg form if necessary.
 961          *
 962          * Unlike self::get(), this function doesn't resolve fallback chains, and
 963          * some callers require this behavior. LanguageConverter::parseCachedTable()
 964          * and self::get() are some examples in core.
 965          *
 966          * @param string $title Message cache key with initial uppercase letter
 967          * @param string $code Code denoting the language to try
 968          * @return string|bool The message, or false if it does not exist or on error
 969          */
 970         public function getMsgFromNamespace( $title, $code ) {
 971                 // Load all MediaWiki page definitions into cache. Note that individual keys
 972                 // already loaded into cache during this request remain in the cache, which
 973                 // includes the value of hook-defined messages.
 974                 $this->load( $code );
 975
 976                 $entry = $this->cache->getField( $code, $title );
 977                 if ( $entry !== null ) {
 978                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 979                                 // The message exists and is not '!TOO BIG'
 980                                 return (string)substr( $entry, 1 );
 981                         } elseif ( $entry === '!NONEXISTENT' ) {
 982                                 return false;
 983                         }
 984                         // Fall through and try invididual message cache below
 985                 } else {
 986                         // Message does not have a MediaWiki page definition
 987                         $message = false;
 988                         Hooks::run( 'MessagesPreLoad', [ $title, &$message, $code ] );
 989                         if ( $message !== false ) {
 990                                 $this->cache->setField( $code, $title, ' ' . $message );
 991                         } else {
 992                                 $this->cache->setField( $code, $title, '!NONEXISTENT' );
 993                         }
 994
 995                         return $message;
 996                 }
 997
 998                 if ( $this->cacheVolatile[$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' => $title, 'code' => $code ] );
1004                 } else {
1005                         // Try the individual message cache
1006                         $entry = $this->loadCachedMessagePageEntry(
1007                                 $title,
1008                                 $code,
1009                                 $this->cache->getField( $code, 'HASH' )
1010                         );
1011                 }
1012
1013                 if ( $entry !== false && substr( $entry, 0, 1 ) === ' ' ) {
1014                         $this->cache->setField( $code, $title, $entry );
1015                         // The message exists, so make sure a string is returned
1016                         return (string)substr( $entry, 1 );
1017                 }
1018
1019                 $this->cache->setField( $code, $title, '!NONEXISTENT' );
1020
1021                 return false;
1022         }
1023
1024         /**
1025          * @param string $dbKey
1026          * @param string $code
1027          * @param string $hash
1028          * @return string Either " <MESSAGE>" or "!NONEXISTANT"
1029          */
1030         private function loadCachedMessagePageEntry( $dbKey, $code, $hash ) {
1031                 return $this->srvCache->getWithSetCallback(
1032                         $this->srvCache->makeKey( 'messages-big', $hash, $dbKey ),
1033                         IExpiringStore::TTL_MINUTE,
1034                         function () use ( $code, $dbKey, $hash ) {
1035                                 return $this->wanCache->getWithSetCallback(
1036                                         $this->bigMessageCacheKey( $hash, $dbKey ),
1037                                         $this->mExpiry,
1038                                         function ( $oldValue, &$ttl, &$setOpts ) use ( $dbKey, $code ) {
1039                                                 // Try loading the message from the database
1040                                                 $dbr = wfGetDB( DB_REPLICA );
1041                                                 $setOpts += Database::getCacheSetOptions( $dbr );
1042                                                 // Use newKnownCurrent() to avoid querying revision/user tables
1043                                                 $title = Title::makeTitle( NS_MEDIAWIKI, $dbKey );
1044                                                 $revision = Revision::newKnownCurrent( $dbr, $title );
1045                                                 if ( !$revision ) {
1046                                                         // The wiki doesn't have a local override page. Cache absence with normal TTL.
1047                                                         // When overrides are created, self::replace() takes care of the cache.
1048                                                         return '!NONEXISTENT';
1049                                                 }
1050                                                 $content = $revision->getContent();
1051                                                 if ( $content ) {
1052                                                         $message = $this->getMessageTextFromContent( $content );
1053                                                 } else {
1054                                                         LoggerFactory::getInstance( 'MessageCache' )->warning(
1055                                                                 __METHOD__ . ': failed to load page text for \'{titleKey}\'',
1056                                                                 [ 'titleKey' => $dbKey, 'code' => $code ]
1057                                                         );
1058                                                         $message = null;
1059                                                 }
1060
1061                                                 if ( !is_string( $message ) ) {
1062                                                         // Revision failed to load Content, or Content is incompatible with wikitext.
1063                                                         // Possibly a temporary loading failure.
1064                                                         $ttl = 5;
1065
1066                                                         return '!NONEXISTENT';
1067                                                 }
1068
1069                                                 return ' ' . $message;
1070                                         }
1071                                 );
1072                         }
1073                 );
1074         }
1075
1076         /**
1077          * @param string $message
1078          * @param bool $interface
1079          * @param Language|null $language
1080          * @param Title|null $title
1081          * @return string
1082          */
1083         public function transform( $message, $interface = false, $language = null, $title = null ) {
1084                 // Avoid creating parser if nothing to transform
1085                 if ( strpos( $message, '{{' ) === false ) {
1086                         return $message;
1087                 }
1088
1089                 if ( $this->mInParser ) {
1090                         return $message;
1091                 }
1092
1093                 $parser = $this->getParser();
1094                 if ( $parser ) {
1095                         $popts = $this->getParserOptions();
1096                         $popts->setInterfaceMessage( $interface );
1097                         $popts->setTargetLanguage( $language );
1098
1099                         $userlang = $popts->setUserLang( $language );
1100                         $this->mInParser = true;
1101                         $message = $parser->transformMsg( $message, $popts, $title );
1102                         $this->mInParser = false;
1103                         $popts->setUserLang( $userlang );
1104                 }
1105
1106                 return $message;
1107         }
1108
1109         /**
1110          * @return Parser
1111          */
1112         public function getParser() {
1113                 global $wgParser, $wgParserConf;
1114
1115                 if ( !$this->mParser && isset( $wgParser ) ) {
1116                         # Do some initialisation so that we don't have to do it twice
1117                         $wgParser->firstCallInit();
1118                         # Clone it and store it
1119                         $class = $wgParserConf['class'];
1120                         if ( $class == ParserDiffTest::class ) {
1121                                 # Uncloneable
1122                                 $this->mParser = new $class( $wgParserConf );
1123                         } else {
1124                                 $this->mParser = clone $wgParser;
1125                         }
1126                 }
1127
1128                 return $this->mParser;
1129         }
1130
1131         /**
1132          * @param string $text
1133          * @param Title|null $title
1134          * @param bool $linestart Whether or not this is at the start of a line
1135          * @param bool $interface Whether this is an interface message
1136          * @param Language|string|null $language Language code
1137          * @return ParserOutput|string
1138          */
1139         public function parse( $text, $title = null, $linestart = true,
1140                 $interface = false, $language = null
1141         ) {
1142                 global $wgTitle;
1143
1144                 if ( $this->mInParser ) {
1145                         return htmlspecialchars( $text );
1146                 }
1147
1148                 $parser = $this->getParser();
1149                 $popts = $this->getParserOptions();
1150                 $popts->setInterfaceMessage( $interface );
1151
1152                 if ( is_string( $language ) ) {
1153                         $language = Language::factory( $language );
1154                 }
1155                 $popts->setTargetLanguage( $language );
1156
1157                 if ( !$title || !$title instanceof Title ) {
1158                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1159                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1160                         $title = $wgTitle;
1161                 }
1162                 // Sometimes $wgTitle isn't set either...
1163                 if ( !$title ) {
1164                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1165                         # Create a ghost title in such case
1166                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1167                 }
1168
1169                 $this->mInParser = true;
1170                 $res = $parser->parse( $text, $title, $popts, $linestart );
1171                 $this->mInParser = false;
1172
1173                 return $res;
1174         }
1175
1176         public function disable() {
1177                 $this->mDisable = true;
1178         }
1179
1180         public function enable() {
1181                 $this->mDisable = false;
1182         }
1183
1184         /**
1185          * Whether DB/cache usage is disabled for determining messages
1186          *
1187          * If so, this typically indicates either:
1188          *   - a) load() failed to find a cached copy nor query the DB
1189          *   - b) we are in a special context or error mode that cannot use the DB
1190          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1191          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1192          *
1193          * @return bool
1194          * @since 1.27
1195          */
1196         public function isDisabled() {
1197                 return $this->mDisable;
1198         }
1199
1200         /**
1201          * Clear all stored messages in global and local cache
1202          *
1203          * Mainly used after a mass rebuild
1204          */
1205         public function clear() {
1206                 $langs = Language::fetchLanguageNames( null, 'mw' );
1207                 foreach ( array_keys( $langs ) as $code ) {
1208                         $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
1209                 }
1210                 $this->cache->clear();
1211         }
1212
1213         /**
1214          * @param string $key
1215          * @return array
1216          */
1217         public function figureMessage( $key ) {
1218                 global $wgLanguageCode;
1219
1220                 $pieces = explode( '/', $key );
1221                 if ( count( $pieces ) < 2 ) {
1222                         return [ $key, $wgLanguageCode ];
1223                 }
1224
1225                 $lang = array_pop( $pieces );
1226                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1227                         return [ $key, $wgLanguageCode ];
1228                 }
1229
1230                 $message = implode( '/', $pieces );
1231
1232                 return [ $message, $lang ];
1233         }
1234
1235         /**
1236          * Get all message keys stored in the message cache for a given language.
1237          * If $code is the content language code, this will return all message keys
1238          * for which MediaWiki:msgkey exists. If $code is another language code, this
1239          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1240          * @param string $code Language code
1241          * @return array Array of message keys (strings)
1242          */
1243         public function getAllMessageKeys( $code ) {
1244                 $this->load( $code );
1245                 if ( !$this->cache->has( $code ) ) {
1246                         // Apparently load() failed
1247                         return null;
1248                 }
1249                 // Remove administrative keys
1250                 $cache = $this->cache->get( $code );
1251                 unset( $cache['VERSION'] );
1252                 unset( $cache['EXPIRY'] );
1253                 unset( $cache['EXCESSIVE'] );
1254                 // Remove any !NONEXISTENT keys
1255                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1256
1257                 // Keys may appear with a capital first letter. lcfirst them.
1258                 return array_map( [ $this->contLang, 'lcfirst' ], array_keys( $cache ) );
1259         }
1260
1261         /**
1262          * Purge message caches when a MediaWiki: page is created, updated, or deleted
1263          *
1264          * @param Title $title Message page title
1265          * @param Content|null $content New content for edit/create, null on deletion
1266          * @since 1.29
1267          */
1268         public function updateMessageOverride( Title $title, Content $content = null ) {
1269                 $msgText = $this->getMessageTextFromContent( $content );
1270                 if ( $msgText === null ) {
1271                         $msgText = false; // treat as not existing
1272                 }
1273
1274                 $this->replace( $title->getDBkey(), $msgText );
1275
1276                 if ( $this->contLang->hasVariants() ) {
1277                         $this->contLang->updateConversionTable( $title );
1278                 }
1279         }
1280
1281         /**
1282          * @param string $code Language code
1283          * @return string WAN cache key usable as a "check key" against language page edits
1284          */
1285         public function getCheckKey( $code ) {
1286                 return $this->wanCache->makeKey( 'messages', $code );
1287         }
1288
1289         /**
1290          * @param Content|null $content Content or null if the message page does not exist
1291          * @return string|bool|null Returns false if $content is null and null on error
1292          */
1293         private function getMessageTextFromContent( Content $content = null ) {
1294                 // @TODO: could skip pseudo-messages like js/css here, based on content model
1295                 if ( $content ) {
1296                         // Message page exists...
1297                         // XXX: Is this the right way to turn a Content object into a message?
1298                         // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1299                         //       CssContent. MessageContent is *not* used for storing messages, it's
1300                         //       only used for wrapping them when needed.
1301                         $msgText = $content->getWikitextForTransclusion();
1302                         if ( $msgText === false || $msgText === null ) {
1303                                 // This might be due to some kind of misconfiguration...
1304                                 $msgText = null;
1305                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1306                                         __METHOD__ . ": message content doesn't provide wikitext "
1307                                         . "(content model: " . $content->getModel() . ")" );
1308                         }
1309                 } else {
1310                         // Message page does not exist...
1311                         $msgText = false;
1312                 }
1313
1314                 return $msgText;
1315         }
1316
1317         /**
1318          * @param string $hash Hash for this version of the entire key/value overrides map
1319          * @param string $title Message cache key with initial uppercase letter
1320          * @return string
1321          */
1322         private function bigMessageCacheKey( $hash, $title ) {
1323                 return $this->wanCache->makeKey( 'messages-big', $hash, $title );
1324         }
1325 }