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          * Map of (lowercase message key => index) for all software defined messages
  57          *
  58          * @var array
  59          */
  60         protected $overridable;
  61
  62         /**
  63          * @var bool[] Map of (language code => boolean)
  64          */
  65         protected $cacheVolatile = [];
  66
  67         /**
  68          * Should mean that database cannot be used, but check
  69          * @var bool $mDisable
  70          */
  71         protected $mDisable;
  72
  73         /**
  74          * Lifetime for cache, used by object caching.
  75          * Set on construction, see __construct().
  76          */
  77         protected $mExpiry;
  78
  79         /**
  80          * Message cache has its own parser which it uses to transform messages
  81          * @var ParserOptions
  82          */
  83         protected $mParserOptions;
  84         /** @var Parser */
  85         protected $mParser;
  86
  87         /**
  88          * @var bool $mInParser
  89          */
  90         protected $mInParser = false;
  91
  92         /** @var WANObjectCache */
  93         protected $wanCache;
  94         /** @var BagOStuff */
  95         protected $clusterCache;
  96         /** @var BagOStuff */
  97         protected $srvCache;
  98         /** @var Language */
  99         protected $contLang;
 100
 101         /**
 102          * Singleton instance
 103          *
 104          * @var MessageCache $instance
 105          */
 106         private static $instance;
 107
 108         /**
 109          * Get the signleton instance of this class
 110          *
 111          * @since 1.18
 112          * @return MessageCache
 113          */
 114         public static function singleton() {
 115                 if ( self::$instance === null ) {
 116                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry, $wgUseLocalMessageCache;
 117                         $services = MediaWikiServices::getInstance();
 118                         self::$instance = new self(
 119                                 $services->getMainWANObjectCache(),
 120                                 wfGetMessageCacheStorage(),
 121                                 $wgUseLocalMessageCache
 122                                         ? $services->getLocalServerObjectCache()
 123                                         : new EmptyBagOStuff(),
 124                                 $wgUseDatabaseMessages,
 125                                 $wgMsgCacheExpiry,
 126                                 $services->getContentLanguage()
 127                         );
 128                 }
 129
 130                 return self::$instance;
 131         }
 132
 133         /**
 134          * Destroy the singleton instance
 135          *
 136          * @since 1.18
 137          */
 138         public static function destroyInstance() {
 139                 self::$instance = null;
 140         }
 141
 142         /**
 143          * Normalize message key input
 144          *
 145          * @param string $key Input message key to be normalized
 146          * @return string Normalized message key
 147          */
 148         public static function normalizeKey( $key ) {
 149                 $lckey = strtr( $key, ' ', '_' );
 150                 if ( ord( $lckey ) < 128 ) {
 151                         $lckey[0] = strtolower( $lckey[0] );
 152                 } else {
 153                         $lckey = MediaWikiServices::getInstance()->getContentLanguage()->lcfirst( $lckey );
 154                 }
 155
 156                 return $lckey;
 157         }
 158
 159         /**
 160          * @param WANObjectCache $wanCache
 161          * @param BagOStuff $clusterCache
 162          * @param BagOStuff $serverCache
 163          * @param bool $useDB Whether to look for message overrides (e.g. MediaWiki: pages)
 164          * @param int $expiry Lifetime for cache. @see $mExpiry.
 165          * @param Language|null $contLang Content language of site
 166          */
 167         public function __construct(
 168                 WANObjectCache $wanCache,
 169                 BagOStuff $clusterCache,
 170                 BagOStuff $serverCache,
 171                 $useDB,
 172                 $expiry,
 173                 Language $contLang = null
 174         ) {
 175                 $this->wanCache = $wanCache;
 176                 $this->clusterCache = $clusterCache;
 177                 $this->srvCache = $serverCache;
 178
 179                 $this->cache = new MapCacheLRU( 5 ); // limit size for sanity
 180
 181                 $this->mDisable = !$useDB;
 182                 $this->mExpiry = $expiry;
 183                 $this->contLang = $contLang ?? MediaWikiServices::getInstance()->getContentLanguage();
 184         }
 185
 186         /**
 187          * ParserOptions is lazy initialised.
 188          *
 189          * @return ParserOptions
 190          */
 191         function getParserOptions() {
 192                 global $wgUser;
 193
 194                 if ( !$this->mParserOptions ) {
 195                         if ( !$wgUser->isSafeToLoad() ) {
 196                                 // $wgUser isn't unstubbable yet, so don't try to get a
 197                                 // ParserOptions for it. And don't cache this ParserOptions
 198                                 // either.
 199                                 $po = ParserOptions::newFromAnon();
 200                                 $po->setAllowUnsafeRawHtml( false );
 201                                 $po->setTidy( true );
 202                                 return $po;
 203                         }
 204
 205                         $this->mParserOptions = new ParserOptions;
 206                         // Messages may take parameters that could come
 207                         // from malicious sources. As a precaution, disable
 208                         // the <html> parser tag when parsing messages.
 209                         $this->mParserOptions->setAllowUnsafeRawHtml( false );
 210                         // For the same reason, tidy the output!
 211                         $this->mParserOptions->setTidy( true );
 212                 }
 213
 214                 return $this->mParserOptions;
 215         }
 216
 217         /**
 218          * Try to load the cache from APC.
 219          *
 220          * @param string $code Optional language code, see documenation of load().
 221          * @return array|bool The cache array, or false if not in cache.
 222          */
 223         protected function getLocalCache( $code ) {
 224                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 225
 226                 return $this->srvCache->get( $cacheKey );
 227         }
 228
 229         /**
 230          * Save the cache to APC.
 231          *
 232          * @param string $code
 233          * @param array $cache The cache array
 234          */
 235         protected function saveToLocalCache( $code, $cache ) {
 236                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 237                 $this->srvCache->set( $cacheKey, $cache );
 238         }
 239
 240         /**
 241          * Loads messages from caches or from database in this order:
 242          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 243          * (2) memcached
 244          * (3) from the database.
 245          *
 246          * When successfully loading from (2) or (3), all higher level caches are
 247          * updated for the newest version.
 248          *
 249          * Nothing is loaded if member variable mDisable is true, either manually
 250          * set by calling code or if message loading fails (is this possible?).
 251          *
 252          * Returns true if cache is already populated or it was successfully populated,
 253          * or false if populating empty cache fails. Also returns true if MessageCache
 254          * is disabled.
 255          *
 256          * @param string $code Language to which load messages
 257          * @param int|null $mode Use MessageCache::FOR_UPDATE to skip process cache [optional]
 258          * @throws InvalidArgumentException
 259          * @return bool
 260          */
 261         protected function load( $code, $mode = null ) {
 262                 if ( !is_string( $code ) ) {
 263                         throw new InvalidArgumentException( "Missing language code" );
 264                 }
 265
 266                 # Don't do double loading...
 267                 if ( $this->cache->has( $code ) && $mode != self::FOR_UPDATE ) {
 268                         return true;
 269                 }
 270
 271                 $this->overridable = array_flip( Language::getMessageKeysFor( $code ) );
 272
 273                 // T208897 array_flip can fail and return null
 274                 if ( is_null( $this->overridable ) ) {
 275                         LoggerFactory::getInstance( 'MessageCache' )->error(
 276                                 __METHOD__ . ': $this->overridable is null',
 277                                 [
 278                                         'message_keys' => Language::getMessageKeysFor( $code ),
 279                                         'code' => $code
 280                                 ]
 281                         );
 282                 }
 283
 284                 # 8 lines of code just to say (once) that message cache is disabled
 285                 if ( $this->mDisable ) {
 286                         static $shownDisabled = false;
 287                         if ( !$shownDisabled ) {
 288                                 wfDebug( __METHOD__ . ": disabled\n" );
 289                                 $shownDisabled = true;
 290                         }
 291
 292                         return true;
 293                 }
 294
 295                 # Loading code starts
 296                 $success = false; # Keep track of success
 297                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 298                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 299
 300                 # Hash of the contents is stored in memcache, to detect if data-center cache
 301                 # or local cache goes out of date (e.g. due to replace() on some other server)
 302                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 303                 $this->cacheVolatile[$code] = $hashVolatile;
 304
 305                 # Try the local cache and check against the cluster hash key...
 306                 $cache = $this->getLocalCache( $code );
 307                 if ( !$cache ) {
 308                         $where[] = 'local cache is empty';
 309                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 310                         $where[] = 'local cache has the wrong hash';
 311                         $staleCache = $cache;
 312                 } elseif ( $this->isCacheExpired( $cache ) ) {
 313                         $where[] = 'local cache is expired';
 314                         $staleCache = $cache;
 315                 } elseif ( $hashVolatile ) {
 316                         $where[] = 'local cache validation key is expired/volatile';
 317                         $staleCache = $cache;
 318                 } else {
 319                         $where[] = 'got from local cache';
 320                         $this->cache->set( $code, $cache );
 321                         $success = true;
 322                 }
 323
 324                 if ( !$success ) {
 325                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 326                         # Try the global cache. If it is empty, try to acquire a lock. If
 327                         # the lock can't be acquired, wait for the other thread to finish
 328                         # and then try the global cache a second time.
 329                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 330                                 if ( $hashVolatile && $staleCache ) {
 331                                         # Do not bother fetching the whole cache blob to avoid I/O.
 332                                         # Instead, just try to get the non-blocking $statusKey lock
 333                                         # below, and use the local stale value if it was not acquired.
 334                                         $where[] = 'global cache is presumed expired';
 335                                 } else {
 336                                         $cache = $this->clusterCache->get( $cacheKey );
 337                                         if ( !$cache ) {
 338                                                 $where[] = 'global cache is empty';
 339                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 340                                                 $where[] = 'global cache is expired';
 341                                                 $staleCache = $cache;
 342                                         } elseif ( $hashVolatile ) {
 343                                                 # DB results are replica DB lag prone until the holdoff TTL passes.
 344                                                 # By then, updates should be reflected in loadFromDBWithLock().
 345                                                 # One thread renerates the cache while others use old values.
 346                                                 $where[] = 'global cache is expired/volatile';
 347                                                 $staleCache = $cache;
 348                                         } else {
 349                                                 $where[] = 'got from global cache';
 350                                                 $this->cache->set( $code, $cache );
 351                                                 $this->saveToCaches( $cache, 'local-only', $code );
 352                                                 $success = true;
 353                                         }
 354                                 }
 355
 356                                 if ( $success ) {
 357                                         # Done, no need to retry
 358                                         break;
 359                                 }
 360
 361                                 # We need to call loadFromDB. Limit the concurrency to one process.
 362                                 # This prevents the site from going down when the cache expires.
 363                                 # Note that the DB slam protection lock here is non-blocking.
 364                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 365                                 if ( $loadStatus === true ) {
 366                                         $success = true;
 367                                         break;
 368                                 } elseif ( $staleCache ) {
 369                                         # Use the stale cache while some other thread constructs the new one
 370                                         $where[] = 'using stale cache';
 371                                         $this->cache->set( $code, $staleCache );
 372                                         $success = true;
 373                                         break;
 374                                 } elseif ( $failedAttempts > 0 ) {
 375                                         # Already blocked once, so avoid another lock/unlock cycle.
 376                                         # This case will typically be hit if memcached is down, or if
 377                                         # loadFromDB() takes longer than LOCK_WAIT.
 378                                         $where[] = "could not acquire status key.";
 379                                         break;
 380                                 } elseif ( $loadStatus === 'cantacquire' ) {
 381                                         # Wait for the other thread to finish, then retry. Normally,
 382                                         # the memcached get() will then yeild the other thread's result.
 383                                         $where[] = 'waited for other thread to complete';
 384                                         $this->getReentrantScopedLock( $cacheKey );
 385                                 } else {
 386                                         # Disable cache; $loadStatus is 'disabled'
 387                                         break;
 388                                 }
 389                         }
 390                 }
 391
 392                 if ( !$success ) {
 393                         $where[] = 'loading FAILED - cache is disabled';
 394                         $this->mDisable = true;
 395                         $this->cache->set( $code, [] );
 396                         wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
 397                         # This used to throw an exception, but that led to nasty side effects like
 398                         # the whole wiki being instantly down if the memcached server died
 399                 }
 400
 401                 if ( !$this->cache->has( $code ) ) { // sanity
 402                         throw new LogicException( "Process cache for '$code' should be set by now." );
 403                 }
 404
 405                 $info = implode( ', ', $where );
 406                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 407
 408                 return $success;
 409         }
 410
 411         /**
 412          * @param string $code
 413          * @param array &$where List of wfDebug() comments
 414          * @param int|null $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 415          * @return bool|string True on success or one of ("cantacquire", "disabled")
 416          */
 417         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 418                 # If cache updates on all levels fail, give up on message overrides.
 419                 # This is to avoid easy site outages; see $saveSuccess comments below.
 420                 $statusKey = $this->clusterCache->makeKey( 'messages', $code, 'status' );
 421                 $status = $this->clusterCache->get( $statusKey );
 422                 if ( $status === 'error' ) {
 423                         $where[] = "could not load; method is still globally disabled";
 424                         return 'disabled';
 425                 }
 426
 427                 # Now let's regenerate
 428                 $where[] = 'loading from database';
 429
 430                 # Lock the cache to prevent conflicting writes.
 431                 # This lock is non-blocking so stale cache can quickly be used.
 432                 # Note that load() will call a blocking getReentrantScopedLock()
 433                 # after this if it really need to wait for any current thread.
 434                 $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 435                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 436                 if ( !$scopedLock ) {
 437                         $where[] = 'could not acquire main lock';
 438                         return 'cantacquire';
 439                 }
 440
 441                 $cache = $this->loadFromDB( $code, $mode );
 442                 $this->cache->set( $code, $cache );
 443                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 444
 445                 if ( !$saveSuccess ) {
 446                         /**
 447                          * Cache save has failed.
 448                          *
 449                          * There are two main scenarios where this could be a problem:
 450                          * - The cache is more than the maximum size (typically 1MB compressed).
 451                          * - Memcached has no space remaining in the relevant slab class. This is
 452                          *   unlikely with recent versions of memcached.
 453                          *
 454                          * Either way, if there is a local cache, nothing bad will happen. If there
 455                          * is no local cache, disabling the message cache for all requests avoids
 456                          * incurring a loadFromDB() overhead on every request, and thus saves the
 457                          * wiki from complete downtime under moderate traffic conditions.
 458                          */
 459                         if ( $this->srvCache instanceof EmptyBagOStuff ) {
 460                                 $this->clusterCache->set( $statusKey, 'error', 60 * 5 );
 461                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 462                         } else {
 463                                 $where[] = "could not save global cache";
 464                         }
 465                 }
 466
 467                 return true;
 468         }
 469
 470         /**
 471          * Loads cacheable messages from the database. Messages bigger than
 472          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 473          * on-demand from the database later.
 474          *
 475          * @param string $code Language code
 476          * @param int|null $mode Use MessageCache::FOR_UPDATE to skip process cache
 477          * @return array Loaded messages for storing in caches
 478          */
 479         protected function loadFromDB( $code, $mode = null ) {
 480                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 481
 482                 // (T164666) The query here performs really poorly on WMF's
 483                 // contributions replicas. We don't have a way to say "any group except
 484                 // contributions", so for the moment let's specify 'api'.
 485                 // @todo: Get rid of this hack.
 486                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA, 'api' );
 487
 488                 $cache = [];
 489
 490                 $mostused = []; // list of "<cased message key>/<code>"
 491                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 492                         if ( !$this->cache->has( $wgLanguageCode ) ) {
 493                                 $this->load( $wgLanguageCode );
 494                         }
 495                         $mostused = array_keys( $this->cache->get( $wgLanguageCode ) );
 496                         foreach ( $mostused as $key => $value ) {
 497                                 $mostused[$key] = "$value/$code";
 498                         }
 499                 }
 500
 501                 // Get the list of software-defined messages in core/extensions
 502                 $overridable = array_flip( Language::getMessageKeysFor( $wgLanguageCode ) );
 503
 504                 // Common conditions
 505                 $conds = [
 506                         'page_is_redirect' => 0,
 507                         'page_namespace' => NS_MEDIAWIKI,
 508                 ];
 509                 if ( count( $mostused ) ) {
 510                         $conds['page_title'] = $mostused;
 511                 } elseif ( $code !== $wgLanguageCode ) {
 512                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 513                 } else {
 514                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 515                         # other than language code.
 516                         $conds[] = 'page_title NOT' .
 517                                 $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 518                 }
 519
 520                 // Set the stubs for oversized software-defined messages in the main cache map
 521                 $res = $dbr->select(
 522                         'page',
 523                         [ 'page_title', 'page_latest' ],
 524                         array_merge( $conds, [ 'page_len > ' . intval( $wgMaxMsgCacheEntrySize ) ] ),
 525                         __METHOD__ . "($code)-big"
 526                 );
 527                 foreach ( $res as $row ) {
 528                         $name = $this->contLang->lcfirst( $row->page_title );
 529                         // Include entries/stubs for all keys in $mostused in adaptive mode
 530                         if ( $wgAdaptiveMessageCache || $this->isMainCacheable( $name, $overridable ) ) {
 531                                 $cache[$row->page_title] = '!TOO BIG';
 532                         }
 533                         // At least include revision ID so page changes are reflected in the hash
 534                         $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 535                 }
 536
 537                 // Set the text for small software-defined messages in the main cache map
 538                 $res = $dbr->select(
 539                         [ 'page', 'revision', 'text' ],
 540                         [ 'page_title', 'page_latest', 'old_id', 'old_text', 'old_flags' ],
 541                         array_merge( $conds, [ 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize ) ] ),
 542                         __METHOD__ . "($code)-small",
 543                         [],
 544                         [
 545                                 'revision' => [ 'JOIN', 'page_latest=rev_id' ],
 546                                 'text' => [ 'JOIN', 'rev_text_id=old_id' ],
 547                         ]
 548                 );
 549                 foreach ( $res as $row ) {
 550                         $name = $this->contLang->lcfirst( $row->page_title );
 551                         // Include entries/stubs for all keys in $mostused in adaptive mode
 552                         if ( $wgAdaptiveMessageCache || $this->isMainCacheable( $name, $overridable ) ) {
 553                                 $text = Revision::getRevisionText( $row );
 554                                 if ( $text === false ) {
 555                                         // Failed to fetch data; possible ES errors?
 556                                         // Store a marker to fetch on-demand as a workaround...
 557                                         // TODO Use a differnt marker
 558                                         $entry = '!TOO BIG';
 559                                         wfDebugLog(
 560                                                 'MessageCache',
 561                                                 __METHOD__
 562                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 563                                         );
 564                                 } else {
 565                                         $entry = ' ' . $text;
 566                                 }
 567                                 $cache[$row->page_title] = $entry;
 568                         } else {
 569                                 // T193271: cache object gets too big and slow to generate.
 570                                 // At least include revision ID so page changes are reflected in the hash.
 571                                 $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 572                         }
 573                 }
 574
 575                 $cache['VERSION'] = MSG_CACHE_VERSION;
 576                 ksort( $cache );
 577
 578                 # Hash for validating local cache (APC). No need to take into account
 579                 # messages larger than $wgMaxMsgCacheEntrySize, since those are only
 580                 # stored and fetched from memcache.
 581                 $cache['HASH'] = md5( serialize( $cache ) );
 582                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 583                 unset( $cache['EXCESSIVE'] ); // only needed for hash
 584
 585                 return $cache;
 586         }
 587
 588         /**
 589          * @param string $name Message name with lowercase first letter
 590          * @param array $overridable Map of (key => unused) for software-defined messages
 591          * @return bool
 592          */
 593         private function isMainCacheable( $name, array $overridable ) {
 594                 // Include common conversion table pages. This also avoids problems with
 595                 // Installer::parse() bailing out due to disallowed DB queries (T207979).
 596                 return ( isset( $overridable[$name] ) || strpos( $name, 'conversiontable/' ) === 0 );
 597         }
 598
 599         /**
 600          * Updates cache as necessary when message page is changed
 601          *
 602          * @param string $title Message cache key with initial uppercase letter
 603          * @param string|bool $text New contents of the page (false if deleted)
 604          */
 605         public function replace( $title, $text ) {
 606                 global $wgLanguageCode;
 607
 608                 if ( $this->mDisable ) {
 609                         return;
 610                 }
 611
 612                 list( $msg, $code ) = $this->figureMessage( $title );
 613                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 614                         // Content language overrides do not use the /<code> suffix
 615                         return;
 616                 }
 617
 618                 // (a) Update the process cache with the new message text
 619                 if ( $text === false ) {
 620                         // Page deleted
 621                         $this->cache->setField( $code, $title, '!NONEXISTENT' );
 622                 } else {
 623                         // Ignore $wgMaxMsgCacheEntrySize so the process cache is up to date
 624                         $this->cache->setField( $code, $title, ' ' . $text );
 625                 }
 626
 627                 // (b) Update the shared caches in a deferred update with a fresh DB snapshot
 628                 DeferredUpdates::addUpdate(
 629                         new MessageCacheUpdate( $code, $title, $msg ),
 630                         DeferredUpdates::PRESEND
 631                 );
 632         }
 633
 634         /**
 635          * @param string $code
 636          * @param array[] $replacements List of (title, message key) pairs
 637          * @throws MWException
 638          */
 639         public function refreshAndReplaceInternal( $code, array $replacements ) {
 640                 global $wgMaxMsgCacheEntrySize;
 641
 642                 // Allow one caller at a time to avoid race conditions
 643                 $scopedLock = $this->getReentrantScopedLock(
 644                         $this->clusterCache->makeKey( 'messages', $code )
 645                 );
 646                 if ( !$scopedLock ) {
 647                         foreach ( $replacements as list( $title ) ) {
 648                                 LoggerFactory::getInstance( 'MessageCache' )->error(
 649                                         __METHOD__ . ': could not acquire lock to update {title} ({code})',
 650                                         [ 'title' => $title, 'code' => $code ] );
 651                         }
 652
 653                         return;
 654                 }
 655
 656                 // Load the existing cache to update it in the local DC cache.
 657                 // The other DCs will see a hash mismatch.
 658                 if ( $this->load( $code, self::FOR_UPDATE ) ) {
 659                         $cache = $this->cache->get( $code );
 660                 } else {
 661                         // Err? Fall back to loading from the database.
 662                         $cache = $this->loadFromDB( $code, self::FOR_UPDATE );
 663                 }
 664                 // Check if individual cache keys should exist and update cache accordingly
 665                 $newTextByTitle = []; // map of (title => content)
 666                 $newBigTitles = []; // map of (title => latest revision ID), like EXCESSIVE in loadFromDB()
 667                 foreach ( $replacements as list( $title ) ) {
 668                         $page = WikiPage::factory( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 669                         $page->loadPageData( $page::READ_LATEST );
 670                         $text = $this->getMessageTextFromContent( $page->getContent() );
 671                         // Remember the text for the blob store update later on
 672                         $newTextByTitle[$title] = $text;
 673                         // Note that if $text is false, then $cache should have a !NONEXISTANT entry
 674                         if ( !is_string( $text ) ) {
 675                                 $cache[$title] = '!NONEXISTENT';
 676                         } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 677                                 $cache[$title] = '!TOO BIG';
 678                                 $newBigTitles[$title] = $page->getLatest();
 679                         } else {
 680                                 $cache[$title] = ' ' . $text;
 681                         }
 682                 }
 683                 // Update HASH for the new key. Incorporates various administrative keys,
 684                 // including the old HASH (and thereby the EXCESSIVE value from loadFromDB()
 685                 // and previous replace() calls), but that doesn't really matter since we
 686                 // only ever compare it for equality with a copy saved by saveToCaches().
 687                 $cache['HASH'] = md5( serialize( $cache + [ 'EXCESSIVE' => $newBigTitles ] ) );
 688                 // Update the too-big WAN cache entries now that we have the new HASH
 689                 foreach ( $newBigTitles as $title => $id ) {
 690                         // Match logic of loadCachedMessagePageEntry()
 691                         $this->wanCache->set(
 692                                 $this->bigMessageCacheKey( $cache['HASH'], $title ),
 693                                 ' ' . $newTextByTitle[$title],
 694                                 $this->mExpiry
 695                         );
 696                 }
 697                 // Mark this cache as definitely being "latest" (non-volatile) so
 698                 // load() calls do not try to refresh the cache with replica DB data
 699                 $cache['LATEST'] = time();
 700                 // Update the process cache
 701                 $this->cache->set( $code, $cache );
 702                 // Pre-emptively update the local datacenter cache so things like edit filter and
 703                 // blacklist changes are reflected immediately; these often use MediaWiki: pages.
 704                 // The datacenter handling replace() calls should be the same one handling edits
 705                 // as they require HTTP POST.
 706                 $this->saveToCaches( $cache, 'all', $code );
 707                 // Release the lock now that the cache is saved
 708                 ScopedCallback::consume( $scopedLock );
 709
 710                 // Relay the purge. Touching this check key expires cache contents
 711                 // and local cache (APC) validation hash across all datacenters.
 712                 $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
 713
 714                 // Purge the messages in the message blob store and fire any hook handlers
 715                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 716                 $blobStore = $resourceloader->getMessageBlobStore();
 717                 foreach ( $replacements as list( $title, $msg ) ) {
 718                         $blobStore->updateMessage( $this->contLang->lcfirst( $msg ) );
 719                         Hooks::run( 'MessageCacheReplace', [ $title, $newTextByTitle[$title] ] );
 720                 }
 721         }
 722
 723         /**
 724          * Is the given cache array expired due to time passing or a version change?
 725          *
 726          * @param array $cache
 727          * @return bool
 728          */
 729         protected function isCacheExpired( $cache ) {
 730                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 731                         return true;
 732                 }
 733                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 734                         return true;
 735                 }
 736                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 737                         return true;
 738                 }
 739
 740                 return false;
 741         }
 742
 743         /**
 744          * Shortcut to update caches.
 745          *
 746          * @param array $cache Cached messages with a version.
 747          * @param string $dest Either "local-only" to save to local caches only
 748          *   or "all" to save to all caches.
 749          * @param string|bool $code Language code (default: false)
 750          * @return bool
 751          */
 752         protected function saveToCaches( array $cache, $dest, $code = false ) {
 753                 if ( $dest === 'all' ) {
 754                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 755                         $success = $this->clusterCache->set( $cacheKey, $cache );
 756                         $this->setValidationHash( $code, $cache );
 757                 } else {
 758                         $success = true;
 759                 }
 760
 761                 $this->saveToLocalCache( $code, $cache );
 762
 763                 return $success;
 764         }
 765
 766         /**
 767          * Get the md5 used to validate the local APC cache
 768          *
 769          * @param string $code
 770          * @return array (hash or false, bool expiry/volatility status)
 771          */
 772         protected function getValidationHash( $code ) {
 773                 $curTTL = null;
 774                 $value = $this->wanCache->get(
 775                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 776                         $curTTL,
 777                         [ $this->getCheckKey( $code ) ]
 778                 );
 779
 780                 if ( $value ) {
 781                         $hash = $value['hash'];
 782                         if ( ( time() - $value['latest'] ) < WANObjectCache::TTL_MINUTE ) {
 783                                 // Cache was recently updated via replace() and should be up-to-date.
 784                                 // That method is only called in the primary datacenter and uses FOR_UPDATE.
 785                                 // Also, it is unlikely that the current datacenter is *now* secondary one.
 786                                 $expired = false;
 787                         } else {
 788                                 // See if the "check" key was bumped after the hash was generated
 789                                 $expired = ( $curTTL < 0 );
 790                         }
 791                 } else {
 792                         // No hash found at all; cache must regenerate to be safe
 793                         $hash = false;
 794                         $expired = true;
 795                 }
 796
 797                 return [ $hash, $expired ];
 798         }
 799
 800         /**
 801          * Set the md5 used to validate the local disk cache
 802          *
 803          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 804          * be treated as "volatile" by getValidationHash() for the next few seconds.
 805          * This is triggered when $cache is generated using FOR_UPDATE mode.
 806          *
 807          * @param string $code
 808          * @param array $cache Cached messages with a version
 809          */
 810         protected function setValidationHash( $code, array $cache ) {
 811                 $this->wanCache->set(
 812                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 813                         [
 814                                 'hash' => $cache['HASH'],
 815                                 'latest' => $cache['LATEST'] ?? 0
 816                         ],
 817                         WANObjectCache::TTL_INDEFINITE
 818                 );
 819         }
 820
 821         /**
 822          * @param string $key A language message cache key that stores blobs
 823          * @param int $timeout Wait timeout in seconds
 824          * @return null|ScopedCallback
 825          */
 826         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 827                 return $this->clusterCache->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 828         }
 829
 830         /**
 831          * Get a message from either the content language or the user language.
 832          *
 833          * First, assemble a list of languages to attempt getting the message from. This
 834          * chain begins with the requested language and its fallbacks and then continues with
 835          * the content language and its fallbacks. For each language in the chain, the following
 836          * process will occur (in this order):
 837          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 838          *     Note: for the content language, there is no /lang subpage.
 839          *  2. Fetch from the static CDB cache.
 840          *  3. If available, check the database for fallback language overrides.
 841          *
 842          * This process provides a number of guarantees. When changing this code, make sure all
 843          * of these guarantees are preserved.
 844          *  * If the requested language is *not* the content language, then the CDB cache for that
 845          *    specific language will take precedence over the root database page ([[MW:msg]]).
 846          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 847          *    the message is available *anywhere* in the language for which it is a fallback.
 848          *
 849          * @param string $key The message key
 850          * @param bool $useDB If true, look for the message in the DB, false
 851          *   to use only the compiled l10n cache.
 852          * @param bool|string|object $langcode Code of the language to get the message for.
 853          *   - If string and a valid code, will create a standard language object
 854          *   - If string but not a valid code, will create a basic language object
 855          *   - If boolean and false, create object from the current users language
 856          *   - If boolean and true, create object from the wikis content language
 857          *   - If language object, use it as given
 858          *
 859          * @throws MWException When given an invalid key
 860          * @return string|bool False if the message doesn't exist, otherwise the
 861          *   message (which can be empty)
 862          */
 863         function get( $key, $useDB = true, $langcode = true ) {
 864                 if ( is_int( $key ) ) {
 865                         // Fix numerical strings that somehow become ints
 866                         // on their way here
 867                         $key = (string)$key;
 868                 } elseif ( !is_string( $key ) ) {
 869                         throw new MWException( 'Non-string key given' );
 870                 } elseif ( $key === '' ) {
 871                         // Shortcut: the empty key is always missing
 872                         return false;
 873                 }
 874
 875                 // Normalise title-case input (with some inlining)
 876                 $lckey = self::normalizeKey( $key );
 877
 878                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 879
 880                 // Loop through each language in the fallback list until we find something useful
 881                 $message = $this->getMessageFromFallbackChain(
 882                         wfGetLangObj( $langcode ),
 883                         $lckey,
 884                         !$this->mDisable && $useDB
 885                 );
 886
 887                 // If we still have no message, maybe the key was in fact a full key so try that
 888                 if ( $message === false ) {
 889                         $parts = explode( '/', $lckey );
 890                         // We may get calls for things that are http-urls from sidebar
 891                         // Let's not load nonexistent languages for those
 892                         // They usually have more than one slash.
 893                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 894                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 895                                 if ( $message === null ) {
 896                                         $message = false;
 897                                 }
 898                         }
 899                 }
 900
 901                 // Post-processing if the message exists
 902                 if ( $message !== false ) {
 903                         // Fix whitespace
 904                         $message = str_replace(
 905                                 [
 906                                         # Fix for trailing whitespace, removed by textarea
 907                                         '&#32;',
 908                                         # Fix for NBSP, converted to space by firefox
 909                                         '&nbsp;',
 910                                         '&#160;',
 911                                         '&shy;'
 912                                 ],
 913                                 [
 914                                         ' ',
 915                                         "\u{00A0}",
 916                                         "\u{00A0}",
 917                                         "\u{00AD}"
 918                                 ],
 919                                 $message
 920                         );
 921                 }
 922
 923                 return $message;
 924         }
 925
 926         /**
 927          * Given a language, try and fetch messages from that language.
 928          *
 929          * Will also consider fallbacks of that language, the site language, and fallbacks for
 930          * the site language.
 931          *
 932          * @see MessageCache::get
 933          * @param Language|StubObject $lang Preferred language
 934          * @param string $lckey Lowercase key for the message (as for localisation cache)
 935          * @param bool $useDB Whether to include messages from the wiki database
 936          * @return string|bool The message, or false if not found
 937          */
 938         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 939                 $alreadyTried = [];
 940
 941                 // First try the requested language.
 942                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 943                 if ( $message !== false ) {
 944                         return $message;
 945                 }
 946
 947                 // Now try checking the site language.
 948                 $message = $this->getMessageForLang( $this->contLang, $lckey, $useDB, $alreadyTried );
 949                 return $message;
 950         }
 951
 952         /**
 953          * Given a language, try and fetch messages from that language and its fallbacks.
 954          *
 955          * @see MessageCache::get
 956          * @param Language|StubObject $lang Preferred language
 957          * @param string $lckey Lowercase key for the message (as for localisation cache)
 958          * @param bool $useDB Whether to include messages from the wiki database
 959          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 960          * @return string|bool The message, or false if not found
 961          */
 962         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 963                 $langcode = $lang->getCode();
 964
 965                 // Try checking the database for the requested language
 966                 if ( $useDB ) {
 967                         $uckey = $this->contLang->ucfirst( $lckey );
 968
 969                         if ( !isset( $alreadyTried[$langcode] ) ) {
 970                                 $message = $this->getMsgFromNamespace(
 971                                         $this->getMessagePageName( $langcode, $uckey ),
 972                                         $langcode
 973                                 );
 974                                 if ( $message !== false ) {
 975                                         return $message;
 976                                 }
 977                                 $alreadyTried[$langcode] = true;
 978                         }
 979                 } else {
 980                         $uckey = null;
 981                 }
 982
 983                 // Check the CDB cache
 984                 $message = $lang->getMessage( $lckey );
 985                 if ( $message !== null ) {
 986                         return $message;
 987                 }
 988
 989                 // Try checking the database for all of the fallback languages
 990                 if ( $useDB ) {
 991                         $fallbackChain = Language::getFallbacksFor( $langcode );
 992
 993                         foreach ( $fallbackChain as $code ) {
 994                                 if ( isset( $alreadyTried[$code] ) ) {
 995                                         continue;
 996                                 }
 997
 998                                 $message = $this->getMsgFromNamespace(
 999                                         $this->getMessagePageName( $code, $uckey ), $code );
1000
1001                                 if ( $message !== false ) {
1002                                         return $message;
1003                                 }
1004                                 $alreadyTried[$code] = true;
1005                         }
1006                 }
1007
1008                 return false;
1009         }
1010
1011         /**
1012          * Get the message page name for a given language
1013          *
1014          * @param string $langcode
1015          * @param string $uckey Uppercase key for the message
1016          * @return string The page name
1017          */
1018         private function getMessagePageName( $langcode, $uckey ) {
1019                 global $wgLanguageCode;
1020
1021                 if ( $langcode === $wgLanguageCode ) {
1022                         // Messages created in the content language will not have the /lang extension
1023                         return $uckey;
1024                 } else {
1025                         return "$uckey/$langcode";
1026                 }
1027         }
1028
1029         /**
1030          * Get a message from the MediaWiki namespace, with caching. The key must
1031          * first be converted to two-part lang/msg form if necessary.
1032          *
1033          * Unlike self::get(), this function doesn't resolve fallback chains, and
1034          * some callers require this behavior. LanguageConverter::parseCachedTable()
1035          * and self::get() are some examples in core.
1036          *
1037          * @param string $title Message cache key with initial uppercase letter
1038          * @param string $code Code denoting the language to try
1039          * @return string|bool The message, or false if it does not exist or on error
1040          */
1041         public function getMsgFromNamespace( $title, $code ) {
1042                 // Load all MediaWiki page definitions into cache. Note that individual keys
1043                 // already loaded into cache during this request remain in the cache, which
1044                 // includes the value of hook-defined messages.
1045                 $this->load( $code );
1046
1047                 $entry = $this->cache->getField( $code, $title );
1048
1049                 if ( $entry !== null ) {
1050                         // Message page exists as an override of a software messages
1051                         if ( substr( $entry, 0, 1 ) === ' ' ) {
1052                                 // The message exists and is not '!TOO BIG'
1053                                 return (string)substr( $entry, 1 );
1054                         } elseif ( $entry === '!NONEXISTENT' ) {
1055                                 // The text might be '-' or missing due to some data loss
1056                                 return false;
1057                         }
1058                         // Load the message page, utilizing the individual message cache.
1059                         // If the page does not exist, there will be no hook handler fallbacks.
1060                         $entry = $this->loadCachedMessagePageEntry(
1061                                 $title,
1062                                 $code,
1063                                 $this->cache->getField( $code, 'HASH' )
1064                         );
1065                 } else {
1066                         // Message page either does not exist or does not override a software message
1067                         $name = $this->contLang->lcfirst( $title );
1068                         if ( !$this->isMainCacheable( $name, $this->overridable ) ) {
1069                                 // Message page does not override any software-defined message. A custom
1070                                 // message might be defined to have content or settings specific to the wiki.
1071                                 // Load the message page, utilizing the individual message cache as needed.
1072                                 $entry = $this->loadCachedMessagePageEntry(
1073                                         $title,
1074                                         $code,
1075                                         $this->cache->getField( $code, 'HASH' )
1076                                 );
1077                         }
1078                         if ( $entry === null || substr( $entry, 0, 1 ) !== ' ' ) {
1079                                 // Message does not have a MediaWiki page definition; try hook handlers
1080                                 $message = false;
1081                                 Hooks::run( 'MessagesPreLoad', [ $title, &$message, $code ] );
1082                                 if ( $message !== false ) {
1083                                         $this->cache->setField( $code, $title, ' ' . $message );
1084                                 } else {
1085                                         $this->cache->setField( $code, $title, '!NONEXISTENT' );
1086                                 }
1087
1088                                 return $message;
1089                         }
1090                 }
1091
1092                 if ( $entry !== false && substr( $entry, 0, 1 ) === ' ' ) {
1093                         if ( $this->cacheVolatile[$code] ) {
1094                                 // Make sure that individual keys respect the WAN cache holdoff period too
1095                                 LoggerFactory::getInstance( 'MessageCache' )->debug(
1096                                         __METHOD__ . ': loading volatile key \'{titleKey}\'',
1097                                         [ 'titleKey' => $title, 'code' => $code ] );
1098                         } else {
1099                                 $this->cache->setField( $code, $title, $entry );
1100                         }
1101                         // The message exists, so make sure a string is returned
1102                         return (string)substr( $entry, 1 );
1103                 }
1104
1105                 $this->cache->setField( $code, $title, '!NONEXISTENT' );
1106
1107                 return false;
1108         }
1109
1110         /**
1111          * @param string $dbKey
1112          * @param string $code
1113          * @param string $hash
1114          * @return string Either " <MESSAGE>" or "!NONEXISTANT"
1115          */
1116         private function loadCachedMessagePageEntry( $dbKey, $code, $hash ) {
1117                 $fname = __METHOD__;
1118                 return $this->srvCache->getWithSetCallback(
1119                         $this->srvCache->makeKey( 'messages-big', $hash, $dbKey ),
1120                         IExpiringStore::TTL_MINUTE,
1121                         function () use ( $code, $dbKey, $hash, $fname ) {
1122                                 return $this->wanCache->getWithSetCallback(
1123                                         $this->bigMessageCacheKey( $hash, $dbKey ),
1124                                         $this->mExpiry,
1125                                         function ( $oldValue, &$ttl, &$setOpts ) use ( $dbKey, $code, $fname ) {
1126                                                 // Try loading the message from the database
1127                                                 $dbr = wfGetDB( DB_REPLICA );
1128                                                 $setOpts += Database::getCacheSetOptions( $dbr );
1129                                                 // Use newKnownCurrent() to avoid querying revision/user tables
1130                                                 $title = Title::makeTitle( NS_MEDIAWIKI, $dbKey );
1131                                                 $revision = Revision::newKnownCurrent( $dbr, $title );
1132                                                 if ( !$revision ) {
1133                                                         // The wiki doesn't have a local override page. Cache absence with normal TTL.
1134                                                         // When overrides are created, self::replace() takes care of the cache.
1135                                                         return '!NONEXISTENT';
1136                                                 }
1137                                                 $content = $revision->getContent();
1138                                                 if ( $content ) {
1139                                                         $message = $this->getMessageTextFromContent( $content );
1140                                                 } else {
1141                                                         LoggerFactory::getInstance( 'MessageCache' )->warning(
1142                                                                 $fname . ': failed to load page text for \'{titleKey}\'',
1143                                                                 [ 'titleKey' => $dbKey, 'code' => $code ]
1144                                                         );
1145                                                         $message = null;
1146                                                 }
1147
1148                                                 if ( !is_string( $message ) ) {
1149                                                         // Revision failed to load Content, or Content is incompatible with wikitext.
1150                                                         // Possibly a temporary loading failure.
1151                                                         $ttl = 5;
1152
1153                                                         return '!NONEXISTENT';
1154                                                 }
1155
1156                                                 return ' ' . $message;
1157                                         }
1158                                 );
1159                         }
1160                 );
1161         }
1162
1163         /**
1164          * @param string $message
1165          * @param bool $interface
1166          * @param Language|null $language
1167          * @param Title|null $title
1168          * @return string
1169          */
1170         public function transform( $message, $interface = false, $language = null, $title = null ) {
1171                 // Avoid creating parser if nothing to transform
1172                 if ( strpos( $message, '{{' ) === false ) {
1173                         return $message;
1174                 }
1175
1176                 if ( $this->mInParser ) {
1177                         return $message;
1178                 }
1179
1180                 $parser = $this->getParser();
1181                 if ( $parser ) {
1182                         $popts = $this->getParserOptions();
1183                         $popts->setInterfaceMessage( $interface );
1184                         $popts->setTargetLanguage( $language );
1185
1186                         $userlang = $popts->setUserLang( $language );
1187                         $this->mInParser = true;
1188                         $message = $parser->transformMsg( $message, $popts, $title );
1189                         $this->mInParser = false;
1190                         $popts->setUserLang( $userlang );
1191                 }
1192
1193                 return $message;
1194         }
1195
1196         /**
1197          * @return Parser
1198          */
1199         public function getParser() {
1200                 global $wgParser, $wgParserConf;
1201
1202                 if ( !$this->mParser && isset( $wgParser ) ) {
1203                         # Do some initialisation so that we don't have to do it twice
1204                         $wgParser->firstCallInit();
1205                         # Clone it and store it
1206                         $class = $wgParserConf['class'];
1207                         if ( $class == ParserDiffTest::class ) {
1208                                 # Uncloneable
1209                                 $this->mParser = new $class( $wgParserConf );
1210                         } else {
1211                                 $this->mParser = clone $wgParser;
1212                         }
1213                 }
1214
1215                 return $this->mParser;
1216         }
1217
1218         /**
1219          * @param string $text
1220          * @param Title|null $title
1221          * @param bool $linestart Whether or not this is at the start of a line
1222          * @param bool $interface Whether this is an interface message
1223          * @param Language|string|null $language Language code
1224          * @return ParserOutput|string
1225          */
1226         public function parse( $text, $title = null, $linestart = true,
1227                 $interface = false, $language = null
1228         ) {
1229                 global $wgTitle;
1230
1231                 if ( $this->mInParser ) {
1232                         return htmlspecialchars( $text );
1233                 }
1234
1235                 $parser = $this->getParser();
1236                 $popts = $this->getParserOptions();
1237                 $popts->setInterfaceMessage( $interface );
1238
1239                 if ( is_string( $language ) ) {
1240                         $language = Language::factory( $language );
1241                 }
1242                 $popts->setTargetLanguage( $language );
1243
1244                 if ( !$title || !$title instanceof Title ) {
1245                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1246                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1247                         $title = $wgTitle;
1248                 }
1249                 // Sometimes $wgTitle isn't set either...
1250                 if ( !$title ) {
1251                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1252                         # Create a ghost title in such case
1253                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1254                 }
1255
1256                 $this->mInParser = true;
1257                 $res = $parser->parse( $text, $title, $popts, $linestart );
1258                 $this->mInParser = false;
1259
1260                 return $res;
1261         }
1262
1263         public function disable() {
1264                 $this->mDisable = true;
1265         }
1266
1267         public function enable() {
1268                 $this->mDisable = false;
1269         }
1270
1271         /**
1272          * Whether DB/cache usage is disabled for determining messages
1273          *
1274          * If so, this typically indicates either:
1275          *   - a) load() failed to find a cached copy nor query the DB
1276          *   - b) we are in a special context or error mode that cannot use the DB
1277          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1278          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1279          *
1280          * @return bool
1281          * @since 1.27
1282          */
1283         public function isDisabled() {
1284                 return $this->mDisable;
1285         }
1286
1287         /**
1288          * Clear all stored messages in global and local cache
1289          *
1290          * Mainly used after a mass rebuild
1291          */
1292         public function clear() {
1293                 $langs = Language::fetchLanguageNames( null, 'mw' );
1294                 foreach ( array_keys( $langs ) as $code ) {
1295                         $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
1296                 }
1297                 $this->cache->clear();
1298         }
1299
1300         /**
1301          * @param string $key
1302          * @return array
1303          */
1304         public function figureMessage( $key ) {
1305                 global $wgLanguageCode;
1306
1307                 $pieces = explode( '/', $key );
1308                 if ( count( $pieces ) < 2 ) {
1309                         return [ $key, $wgLanguageCode ];
1310                 }
1311
1312                 $lang = array_pop( $pieces );
1313                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1314                         return [ $key, $wgLanguageCode ];
1315                 }
1316
1317                 $message = implode( '/', $pieces );
1318
1319                 return [ $message, $lang ];
1320         }
1321
1322         /**
1323          * Get all message keys stored in the message cache for a given language.
1324          * If $code is the content language code, this will return all message keys
1325          * for which MediaWiki:msgkey exists. If $code is another language code, this
1326          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1327          * @param string $code Language code
1328          * @return array Array of message keys (strings)
1329          */
1330         public function getAllMessageKeys( $code ) {
1331                 $this->load( $code );
1332                 if ( !$this->cache->has( $code ) ) {
1333                         // Apparently load() failed
1334                         return null;
1335                 }
1336                 // Remove administrative keys
1337                 $cache = $this->cache->get( $code );
1338                 unset( $cache['VERSION'] );
1339                 unset( $cache['EXPIRY'] );
1340                 unset( $cache['EXCESSIVE'] );
1341                 // Remove any !NONEXISTENT keys
1342                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1343
1344                 // Keys may appear with a capital first letter. lcfirst them.
1345                 return array_map( [ $this->contLang, 'lcfirst' ], array_keys( $cache ) );
1346         }
1347
1348         /**
1349          * Purge message caches when a MediaWiki: page is created, updated, or deleted
1350          *
1351          * @param Title $title Message page title
1352          * @param Content|null $content New content for edit/create, null on deletion
1353          * @since 1.29
1354          */
1355         public function updateMessageOverride( Title $title, Content $content = null ) {
1356                 $msgText = $this->getMessageTextFromContent( $content );
1357                 if ( $msgText === null ) {
1358                         $msgText = false; // treat as not existing
1359                 }
1360
1361                 $this->replace( $title->getDBkey(), $msgText );
1362
1363                 if ( $this->contLang->hasVariants() ) {
1364                         $this->contLang->updateConversionTable( $title );
1365                 }
1366         }
1367
1368         /**
1369          * @param string $code Language code
1370          * @return string WAN cache key usable as a "check key" against language page edits
1371          */
1372         public function getCheckKey( $code ) {
1373                 return $this->wanCache->makeKey( 'messages', $code );
1374         }
1375
1376         /**
1377          * @param Content|null $content Content or null if the message page does not exist
1378          * @return string|bool|null Returns false if $content is null and null on error
1379          */
1380         private function getMessageTextFromContent( Content $content = null ) {
1381                 // @TODO: could skip pseudo-messages like js/css here, based on content model
1382                 if ( $content ) {
1383                         // Message page exists...
1384                         // XXX: Is this the right way to turn a Content object into a message?
1385                         // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1386                         //       CssContent. MessageContent is *not* used for storing messages, it's
1387                         //       only used for wrapping them when needed.
1388                         $msgText = $content->getWikitextForTransclusion();
1389                         if ( $msgText === false || $msgText === null ) {
1390                                 // This might be due to some kind of misconfiguration...
1391                                 $msgText = null;
1392                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1393                                         __METHOD__ . ": message content doesn't provide wikitext "
1394                                         . "(content model: " . $content->getModel() . ")" );
1395                         }
1396                 } else {
1397                         // Message page does not exist...
1398                         $msgText = false;
1399                 }
1400
1401                 return $msgText;
1402         }
1403
1404         /**
1405          * @param string $hash Hash for this version of the entire key/value overrides map
1406          * @param string $title Message cache key with initial uppercase letter
1407          * @return string
1408          */
1409         private function bigMessageCacheKey( $hash, $title ) {
1410                 return $this->wanCache->makeKey( 'messages-big', $hash, $title );
1411         }
1412 }