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" or "!ERROR")
  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 documentation 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 regenerates 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 yield 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                         // Include entries/stubs for all keys in $mostused in adaptive mode
 529                         if ( $wgAdaptiveMessageCache || $this->isMainCacheable( $row->page_title, $overridable ) ) {
 530                                 $cache[$row->page_title] = '!TOO BIG';
 531                         }
 532                         // At least include revision ID so page changes are reflected in the hash
 533                         $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 534                 }
 535
 536                 // Set the text for small software-defined messages in the main cache map
 537                 $revisionStore = MediaWikiServices::getInstance()->getRevisionStore();
 538                 $revQuery = $revisionStore->getQueryInfo( [ 'page', 'user' ] );
 539                 $res = $dbr->select(
 540                         $revQuery['tables'],
 541                         $revQuery['fields'],
 542                         array_merge( $conds, [
 543                                 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize ),
 544                                 'page_latest = rev_id' // get the latest revision only
 545                         ] ),
 546                         __METHOD__ . "($code)-small",
 547                         [],
 548                         $revQuery['joins']
 549                 );
 550                 foreach ( $res as $row ) {
 551                         // Include entries/stubs for all keys in $mostused in adaptive mode
 552                         if ( $wgAdaptiveMessageCache || $this->isMainCacheable( $row->page_title, $overridable ) ) {
 553                                 try {
 554                                         $rev = $revisionStore->newRevisionFromRow( $row );
 555                                         $content = $rev->getContent( MediaWiki\Revision\SlotRecord::MAIN );
 556                                         $text = $this->getMessageTextFromContent( $content );
 557                                 } catch ( Exception $ex ) {
 558                                         $text = false;
 559                                 }
 560
 561                                 if ( !is_string( $text ) ) {
 562                                         $entry = '!ERROR';
 563                                         wfDebugLog(
 564                                                 'MessageCache',
 565                                                 __METHOD__
 566                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 567                                         );
 568                                 } else {
 569                                         $entry = ' ' . $text;
 570                                 }
 571                                 $cache[$row->page_title] = $entry;
 572                         } else {
 573                                 // T193271: cache object gets too big and slow to generate.
 574                                 // At least include revision ID so page changes are reflected in the hash.
 575                                 $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 576                         }
 577                 }
 578
 579                 $cache['VERSION'] = MSG_CACHE_VERSION;
 580                 ksort( $cache );
 581
 582                 # Hash for validating local cache (APC). No need to take into account
 583                 # messages larger than $wgMaxMsgCacheEntrySize, since those are only
 584                 # stored and fetched from memcache.
 585                 $cache['HASH'] = md5( serialize( $cache ) );
 586                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 587                 unset( $cache['EXCESSIVE'] ); // only needed for hash
 588
 589                 return $cache;
 590         }
 591
 592         /**
 593          * @param string $name Message name (possibly with /code suffix)
 594          * @param array $overridable Map of (key => unused) for software-defined messages
 595          * @return bool
 596          */
 597         private function isMainCacheable( $name, array $overridable ) {
 598                 // Convert first letter to lowercase, and strip /code suffix
 599                 $name = $this->contLang->lcfirst( $name );
 600                 $msg = preg_replace( '/\/[a-z0-9-]{2,}$/', '', $name );
 601                 // Include common conversion table pages. This also avoids problems with
 602                 // Installer::parse() bailing out due to disallowed DB queries (T207979).
 603                 return ( isset( $overridable[$msg] ) || strpos( $name, 'conversiontable/' ) === 0 );
 604         }
 605
 606         /**
 607          * Updates cache as necessary when message page is changed
 608          *
 609          * @param string $title Message cache key with initial uppercase letter
 610          * @param string|bool $text New contents of the page (false if deleted)
 611          */
 612         public function replace( $title, $text ) {
 613                 global $wgLanguageCode;
 614
 615                 if ( $this->mDisable ) {
 616                         return;
 617                 }
 618
 619                 list( $msg, $code ) = $this->figureMessage( $title );
 620                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 621                         // Content language overrides do not use the /<code> suffix
 622                         return;
 623                 }
 624
 625                 // (a) Update the process cache with the new message text
 626                 if ( $text === false ) {
 627                         // Page deleted
 628                         $this->cache->setField( $code, $title, '!NONEXISTENT' );
 629                 } else {
 630                         // Ignore $wgMaxMsgCacheEntrySize so the process cache is up to date
 631                         $this->cache->setField( $code, $title, ' ' . $text );
 632                 }
 633
 634                 // (b) Update the shared caches in a deferred update with a fresh DB snapshot
 635                 DeferredUpdates::addUpdate(
 636                         new MessageCacheUpdate( $code, $title, $msg ),
 637                         DeferredUpdates::PRESEND
 638                 );
 639         }
 640
 641         /**
 642          * @param string $code
 643          * @param array[] $replacements List of (title, message key) pairs
 644          * @throws MWException
 645          */
 646         public function refreshAndReplaceInternal( $code, array $replacements ) {
 647                 global $wgMaxMsgCacheEntrySize;
 648
 649                 // Allow one caller at a time to avoid race conditions
 650                 $scopedLock = $this->getReentrantScopedLock(
 651                         $this->clusterCache->makeKey( 'messages', $code )
 652                 );
 653                 if ( !$scopedLock ) {
 654                         foreach ( $replacements as list( $title ) ) {
 655                                 LoggerFactory::getInstance( 'MessageCache' )->error(
 656                                         __METHOD__ . ': could not acquire lock to update {title} ({code})',
 657                                         [ 'title' => $title, 'code' => $code ] );
 658                         }
 659
 660                         return;
 661                 }
 662
 663                 // Load the existing cache to update it in the local DC cache.
 664                 // The other DCs will see a hash mismatch.
 665                 if ( $this->load( $code, self::FOR_UPDATE ) ) {
 666                         $cache = $this->cache->get( $code );
 667                 } else {
 668                         // Err? Fall back to loading from the database.
 669                         $cache = $this->loadFromDB( $code, self::FOR_UPDATE );
 670                 }
 671                 // Check if individual cache keys should exist and update cache accordingly
 672                 $newTextByTitle = []; // map of (title => content)
 673                 $newBigTitles = []; // map of (title => latest revision ID), like EXCESSIVE in loadFromDB()
 674                 foreach ( $replacements as list( $title ) ) {
 675                         $page = WikiPage::factory( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 676                         $page->loadPageData( $page::READ_LATEST );
 677                         $text = $this->getMessageTextFromContent( $page->getContent() );
 678                         // Remember the text for the blob store update later on
 679                         $newTextByTitle[$title] = $text;
 680                         // Note that if $text is false, then $cache should have a !NONEXISTANT entry
 681                         if ( !is_string( $text ) ) {
 682                                 $cache[$title] = '!NONEXISTENT';
 683                         } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 684                                 $cache[$title] = '!TOO BIG';
 685                                 $newBigTitles[$title] = $page->getLatest();
 686                         } else {
 687                                 $cache[$title] = ' ' . $text;
 688                         }
 689                 }
 690                 // Update HASH for the new key. Incorporates various administrative keys,
 691                 // including the old HASH (and thereby the EXCESSIVE value from loadFromDB()
 692                 // and previous replace() calls), but that doesn't really matter since we
 693                 // only ever compare it for equality with a copy saved by saveToCaches().
 694                 $cache['HASH'] = md5( serialize( $cache + [ 'EXCESSIVE' => $newBigTitles ] ) );
 695                 // Update the too-big WAN cache entries now that we have the new HASH
 696                 foreach ( $newBigTitles as $title => $id ) {
 697                         // Match logic of loadCachedMessagePageEntry()
 698                         $this->wanCache->set(
 699                                 $this->bigMessageCacheKey( $cache['HASH'], $title ),
 700                                 ' ' . $newTextByTitle[$title],
 701                                 $this->mExpiry
 702                         );
 703                 }
 704                 // Mark this cache as definitely being "latest" (non-volatile) so
 705                 // load() calls do not try to refresh the cache with replica DB data
 706                 $cache['LATEST'] = time();
 707                 // Update the process cache
 708                 $this->cache->set( $code, $cache );
 709                 // Pre-emptively update the local datacenter cache so things like edit filter and
 710                 // blacklist changes are reflected immediately; these often use MediaWiki: pages.
 711                 // The datacenter handling replace() calls should be the same one handling edits
 712                 // as they require HTTP POST.
 713                 $this->saveToCaches( $cache, 'all', $code );
 714                 // Release the lock now that the cache is saved
 715                 ScopedCallback::consume( $scopedLock );
 716
 717                 // Relay the purge. Touching this check key expires cache contents
 718                 // and local cache (APC) validation hash across all datacenters.
 719                 $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
 720
 721                 // Purge the messages in the message blob store and fire any hook handlers
 722                 $blobStore = MediaWikiServices::getInstance()->getResourceLoader()->getMessageBlobStore();
 723                 foreach ( $replacements as list( $title, $msg ) ) {
 724                         $blobStore->updateMessage( $this->contLang->lcfirst( $msg ) );
 725                         Hooks::run( 'MessageCacheReplace', [ $title, $newTextByTitle[$title] ] );
 726                 }
 727         }
 728
 729         /**
 730          * Is the given cache array expired due to time passing or a version change?
 731          *
 732          * @param array $cache
 733          * @return bool
 734          */
 735         protected function isCacheExpired( $cache ) {
 736                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 737                         return true;
 738                 }
 739                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 740                         return true;
 741                 }
 742                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 743                         return true;
 744                 }
 745
 746                 return false;
 747         }
 748
 749         /**
 750          * Shortcut to update caches.
 751          *
 752          * @param array $cache Cached messages with a version.
 753          * @param string $dest Either "local-only" to save to local caches only
 754          *   or "all" to save to all caches.
 755          * @param string|bool $code Language code (default: false)
 756          * @return bool
 757          */
 758         protected function saveToCaches( array $cache, $dest, $code = false ) {
 759                 if ( $dest === 'all' ) {
 760                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 761                         $success = $this->clusterCache->set( $cacheKey, $cache );
 762                         $this->setValidationHash( $code, $cache );
 763                 } else {
 764                         $success = true;
 765                 }
 766
 767                 $this->saveToLocalCache( $code, $cache );
 768
 769                 return $success;
 770         }
 771
 772         /**
 773          * Get the md5 used to validate the local APC cache
 774          *
 775          * @param string $code
 776          * @return array (hash or false, bool expiry/volatility status)
 777          */
 778         protected function getValidationHash( $code ) {
 779                 $curTTL = null;
 780                 $value = $this->wanCache->get(
 781                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 782                         $curTTL,
 783                         [ $this->getCheckKey( $code ) ]
 784                 );
 785
 786                 if ( $value ) {
 787                         $hash = $value['hash'];
 788                         if ( ( time() - $value['latest'] ) < WANObjectCache::TTL_MINUTE ) {
 789                                 // Cache was recently updated via replace() and should be up-to-date.
 790                                 // That method is only called in the primary datacenter and uses FOR_UPDATE.
 791                                 // Also, it is unlikely that the current datacenter is *now* secondary one.
 792                                 $expired = false;
 793                         } else {
 794                                 // See if the "check" key was bumped after the hash was generated
 795                                 $expired = ( $curTTL < 0 );
 796                         }
 797                 } else {
 798                         // No hash found at all; cache must regenerate to be safe
 799                         $hash = false;
 800                         $expired = true;
 801                 }
 802
 803                 return [ $hash, $expired ];
 804         }
 805
 806         /**
 807          * Set the md5 used to validate the local disk cache
 808          *
 809          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 810          * be treated as "volatile" by getValidationHash() for the next few seconds.
 811          * This is triggered when $cache is generated using FOR_UPDATE mode.
 812          *
 813          * @param string $code
 814          * @param array $cache Cached messages with a version
 815          */
 816         protected function setValidationHash( $code, array $cache ) {
 817                 $this->wanCache->set(
 818                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 819                         [
 820                                 'hash' => $cache['HASH'],
 821                                 'latest' => $cache['LATEST'] ?? 0
 822                         ],
 823                         WANObjectCache::TTL_INDEFINITE
 824                 );
 825         }
 826
 827         /**
 828          * @param string $key A language message cache key that stores blobs
 829          * @param int $timeout Wait timeout in seconds
 830          * @return null|ScopedCallback
 831          */
 832         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 833                 return $this->clusterCache->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 834         }
 835
 836         /**
 837          * Get a message from either the content language or the user language.
 838          *
 839          * First, assemble a list of languages to attempt getting the message from. This
 840          * chain begins with the requested language and its fallbacks and then continues with
 841          * the content language and its fallbacks. For each language in the chain, the following
 842          * process will occur (in this order):
 843          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 844          *     Note: for the content language, there is no /lang subpage.
 845          *  2. Fetch from the static CDB cache.
 846          *  3. If available, check the database for fallback language overrides.
 847          *
 848          * This process provides a number of guarantees. When changing this code, make sure all
 849          * of these guarantees are preserved.
 850          *  * If the requested language is *not* the content language, then the CDB cache for that
 851          *    specific language will take precedence over the root database page ([[MW:msg]]).
 852          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 853          *    the message is available *anywhere* in the language for which it is a fallback.
 854          *
 855          * @param string $key The message key
 856          * @param bool $useDB If true, look for the message in the DB, false
 857          *   to use only the compiled l10n cache.
 858          * @param bool|string|object $langcode Code of the language to get the message for.
 859          *   - If string and a valid code, will create a standard language object
 860          *   - If string but not a valid code, will create a basic language object
 861          *   - If boolean and false, create object from the current users language
 862          *   - If boolean and true, create object from the wikis content language
 863          *   - If language object, use it as given
 864          *
 865          * @throws MWException When given an invalid key
 866          * @return string|bool False if the message doesn't exist, otherwise the
 867          *   message (which can be empty)
 868          */
 869         function get( $key, $useDB = true, $langcode = true ) {
 870                 if ( is_int( $key ) ) {
 871                         // Fix numerical strings that somehow become ints
 872                         // on their way here
 873                         $key = (string)$key;
 874                 } elseif ( !is_string( $key ) ) {
 875                         throw new MWException( 'Non-string key given' );
 876                 } elseif ( $key === '' ) {
 877                         // Shortcut: the empty key is always missing
 878                         return false;
 879                 }
 880
 881                 // Normalise title-case input (with some inlining)
 882                 $lckey = self::normalizeKey( $key );
 883
 884                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 885
 886                 // Loop through each language in the fallback list until we find something useful
 887                 $message = $this->getMessageFromFallbackChain(
 888                         wfGetLangObj( $langcode ),
 889                         $lckey,
 890                         !$this->mDisable && $useDB
 891                 );
 892
 893                 // If we still have no message, maybe the key was in fact a full key so try that
 894                 if ( $message === false ) {
 895                         $parts = explode( '/', $lckey );
 896                         // We may get calls for things that are http-urls from sidebar
 897                         // Let's not load nonexistent languages for those
 898                         // They usually have more than one slash.
 899                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 900                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 901                                 if ( $message === null ) {
 902                                         $message = false;
 903                                 }
 904                         }
 905                 }
 906
 907                 // Post-processing if the message exists
 908                 if ( $message !== false ) {
 909                         // Fix whitespace
 910                         $message = str_replace(
 911                                 [
 912                                         # Fix for trailing whitespace, removed by textarea
 913                                         '&#32;',
 914                                         # Fix for NBSP, converted to space by firefox
 915                                         '&nbsp;',
 916                                         '&#160;',
 917                                         '&shy;'
 918                                 ],
 919                                 [
 920                                         ' ',
 921                                         "\u{00A0}",
 922                                         "\u{00A0}",
 923                                         "\u{00AD}"
 924                                 ],
 925                                 $message
 926                         );
 927                 }
 928
 929                 return $message;
 930         }
 931
 932         /**
 933          * Given a language, try and fetch messages from that language.
 934          *
 935          * Will also consider fallbacks of that language, the site language, and fallbacks for
 936          * the site language.
 937          *
 938          * @see MessageCache::get
 939          * @param Language|StubObject $lang Preferred language
 940          * @param string $lckey Lowercase key for the message (as for localisation cache)
 941          * @param bool $useDB Whether to include messages from the wiki database
 942          * @return string|bool The message, or false if not found
 943          */
 944         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 945                 $alreadyTried = [];
 946
 947                 // First try the requested language.
 948                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 949                 if ( $message !== false ) {
 950                         return $message;
 951                 }
 952
 953                 // Now try checking the site language.
 954                 $message = $this->getMessageForLang( $this->contLang, $lckey, $useDB, $alreadyTried );
 955                 return $message;
 956         }
 957
 958         /**
 959          * Given a language, try and fetch messages from that language and its fallbacks.
 960          *
 961          * @see MessageCache::get
 962          * @param Language|StubObject $lang Preferred language
 963          * @param string $lckey Lowercase key for the message (as for localisation cache)
 964          * @param bool $useDB Whether to include messages from the wiki database
 965          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 966          * @return string|bool The message, or false if not found
 967          */
 968         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 969                 $langcode = $lang->getCode();
 970
 971                 // Try checking the database for the requested language
 972                 if ( $useDB ) {
 973                         $uckey = $this->contLang->ucfirst( $lckey );
 974
 975                         if ( !isset( $alreadyTried[$langcode] ) ) {
 976                                 $message = $this->getMsgFromNamespace(
 977                                         $this->getMessagePageName( $langcode, $uckey ),
 978                                         $langcode
 979                                 );
 980                                 if ( $message !== false ) {
 981                                         return $message;
 982                                 }
 983                                 $alreadyTried[$langcode] = true;
 984                         }
 985                 } else {
 986                         $uckey = null;
 987                 }
 988
 989                 // Check the CDB cache
 990                 $message = $lang->getMessage( $lckey );
 991                 if ( $message !== null ) {
 992                         return $message;
 993                 }
 994
 995                 // Try checking the database for all of the fallback languages
 996                 if ( $useDB ) {
 997                         $fallbackChain = Language::getFallbacksFor( $langcode );
 998
 999                         foreach ( $fallbackChain as $code ) {
1000                                 if ( isset( $alreadyTried[$code] ) ) {
1001                                         continue;
1002                                 }
1003
1004                                 $message = $this->getMsgFromNamespace(
1005                                         $this->getMessagePageName( $code, $uckey ), $code );
1006
1007                                 if ( $message !== false ) {
1008                                         return $message;
1009                                 }
1010                                 $alreadyTried[$code] = true;
1011                         }
1012                 }
1013
1014                 return false;
1015         }
1016
1017         /**
1018          * Get the message page name for a given language
1019          *
1020          * @param string $langcode
1021          * @param string $uckey Uppercase key for the message
1022          * @return string The page name
1023          */
1024         private function getMessagePageName( $langcode, $uckey ) {
1025                 global $wgLanguageCode;
1026
1027                 if ( $langcode === $wgLanguageCode ) {
1028                         // Messages created in the content language will not have the /lang extension
1029                         return $uckey;
1030                 } else {
1031                         return "$uckey/$langcode";
1032                 }
1033         }
1034
1035         /**
1036          * Get a message from the MediaWiki namespace, with caching. The key must
1037          * first be converted to two-part lang/msg form if necessary.
1038          *
1039          * Unlike self::get(), this function doesn't resolve fallback chains, and
1040          * some callers require this behavior. LanguageConverter::parseCachedTable()
1041          * and self::get() are some examples in core.
1042          *
1043          * @param string $title Message cache key with initial uppercase letter
1044          * @param string $code Code denoting the language to try
1045          * @return string|bool The message, or false if it does not exist or on error
1046          */
1047         public function getMsgFromNamespace( $title, $code ) {
1048                 // Load all MediaWiki page definitions into cache. Note that individual keys
1049                 // already loaded into cache during this request remain in the cache, which
1050                 // includes the value of hook-defined messages.
1051                 $this->load( $code );
1052
1053                 $entry = $this->cache->getField( $code, $title );
1054
1055                 if ( $entry !== null ) {
1056                         // Message page exists as an override of a software messages
1057                         if ( substr( $entry, 0, 1 ) === ' ' ) {
1058                                 // The message exists and is not '!TOO BIG' or '!ERROR'
1059                                 return (string)substr( $entry, 1 );
1060                         } elseif ( $entry === '!NONEXISTENT' ) {
1061                                 // The text might be '-' or missing due to some data loss
1062                                 return false;
1063                         }
1064                         // Load the message page, utilizing the individual message cache.
1065                         // If the page does not exist, there will be no hook handler fallbacks.
1066                         $entry = $this->loadCachedMessagePageEntry(
1067                                 $title,
1068                                 $code,
1069                                 $this->cache->getField( $code, 'HASH' )
1070                         );
1071                 } else {
1072                         // Message page either does not exist or does not override a software message
1073                         if ( !$this->isMainCacheable( $title, $this->overridable ) ) {
1074                                 // Message page does not override any software-defined message. A custom
1075                                 // message might be defined to have content or settings specific to the wiki.
1076                                 // Load the message page, utilizing the individual message cache as needed.
1077                                 $entry = $this->loadCachedMessagePageEntry(
1078                                         $title,
1079                                         $code,
1080                                         $this->cache->getField( $code, 'HASH' )
1081                                 );
1082                         }
1083                         if ( $entry === null || substr( $entry, 0, 1 ) !== ' ' ) {
1084                                 // Message does not have a MediaWiki page definition; try hook handlers
1085                                 $message = false;
1086                                 Hooks::run( 'MessagesPreLoad', [ $title, &$message, $code ] );
1087                                 if ( $message !== false ) {
1088                                         $this->cache->setField( $code, $title, ' ' . $message );
1089                                 } else {
1090                                         $this->cache->setField( $code, $title, '!NONEXISTENT' );
1091                                 }
1092
1093                                 return $message;
1094                         }
1095                 }
1096
1097                 if ( $entry !== false && substr( $entry, 0, 1 ) === ' ' ) {
1098                         if ( $this->cacheVolatile[$code] ) {
1099                                 // Make sure that individual keys respect the WAN cache holdoff period too
1100                                 LoggerFactory::getInstance( 'MessageCache' )->debug(
1101                                         __METHOD__ . ': loading volatile key \'{titleKey}\'',
1102                                         [ 'titleKey' => $title, 'code' => $code ] );
1103                         } else {
1104                                 $this->cache->setField( $code, $title, $entry );
1105                         }
1106                         // The message exists, so make sure a string is returned
1107                         return (string)substr( $entry, 1 );
1108                 }
1109
1110                 $this->cache->setField( $code, $title, '!NONEXISTENT' );
1111
1112                 return false;
1113         }
1114
1115         /**
1116          * @param string $dbKey
1117          * @param string $code
1118          * @param string $hash
1119          * @return string Either " <MESSAGE>" or "!NONEXISTANT"
1120          */
1121         private function loadCachedMessagePageEntry( $dbKey, $code, $hash ) {
1122                 $fname = __METHOD__;
1123                 return $this->srvCache->getWithSetCallback(
1124                         $this->srvCache->makeKey( 'messages-big', $hash, $dbKey ),
1125                         IExpiringStore::TTL_MINUTE,
1126                         function () use ( $code, $dbKey, $hash, $fname ) {
1127                                 return $this->wanCache->getWithSetCallback(
1128                                         $this->bigMessageCacheKey( $hash, $dbKey ),
1129                                         $this->mExpiry,
1130                                         function ( $oldValue, &$ttl, &$setOpts ) use ( $dbKey, $code, $fname ) {
1131                                                 // Try loading the message from the database
1132                                                 $dbr = wfGetDB( DB_REPLICA );
1133                                                 $setOpts += Database::getCacheSetOptions( $dbr );
1134                                                 // Use newKnownCurrent() to avoid querying revision/user tables
1135                                                 $title = Title::makeTitle( NS_MEDIAWIKI, $dbKey );
1136                                                 $revision = Revision::newKnownCurrent( $dbr, $title );
1137                                                 if ( !$revision ) {
1138                                                         // The wiki doesn't have a local override page. Cache absence with normal TTL.
1139                                                         // When overrides are created, self::replace() takes care of the cache.
1140                                                         return '!NONEXISTENT';
1141                                                 }
1142                                                 $content = $revision->getContent();
1143                                                 if ( $content ) {
1144                                                         $message = $this->getMessageTextFromContent( $content );
1145                                                 } else {
1146                                                         LoggerFactory::getInstance( 'MessageCache' )->warning(
1147                                                                 $fname . ': failed to load page text for \'{titleKey}\'',
1148                                                                 [ 'titleKey' => $dbKey, 'code' => $code ]
1149                                                         );
1150                                                         $message = null;
1151                                                 }
1152
1153                                                 if ( !is_string( $message ) ) {
1154                                                         // Revision failed to load Content, or Content is incompatible with wikitext.
1155                                                         // Possibly a temporary loading failure.
1156                                                         $ttl = 5;
1157
1158                                                         return '!NONEXISTENT';
1159                                                 }
1160
1161                                                 return ' ' . $message;
1162                                         }
1163                                 );
1164                         }
1165                 );
1166         }
1167
1168         /**
1169          * @param string $message
1170          * @param bool $interface
1171          * @param Language|null $language
1172          * @param Title|null $title
1173          * @return string
1174          */
1175         public function transform( $message, $interface = false, $language = null, $title = null ) {
1176                 // Avoid creating parser if nothing to transform
1177                 if ( strpos( $message, '{{' ) === false ) {
1178                         return $message;
1179                 }
1180
1181                 if ( $this->mInParser ) {
1182                         return $message;
1183                 }
1184
1185                 $parser = $this->getParser();
1186                 if ( $parser ) {
1187                         $popts = $this->getParserOptions();
1188                         $popts->setInterfaceMessage( $interface );
1189                         $popts->setTargetLanguage( $language );
1190
1191                         $userlang = $popts->setUserLang( $language );
1192                         $this->mInParser = true;
1193                         $message = $parser->transformMsg( $message, $popts, $title );
1194                         $this->mInParser = false;
1195                         $popts->setUserLang( $userlang );
1196                 }
1197
1198                 return $message;
1199         }
1200
1201         /**
1202          * @return Parser
1203          */
1204         public function getParser() {
1205                 global $wgParserConf;
1206                 if ( !$this->mParser ) {
1207                         $parser = MediaWikiServices::getInstance()->getParser();
1208                         # Do some initialisation so that we don't have to do it twice
1209                         $parser->firstCallInit();
1210                         # Clone it and store it
1211                         $class = $wgParserConf['class'];
1212                         if ( $class == ParserDiffTest::class ) {
1213                                 # Uncloneable
1214                                 $this->mParser = new $class( $wgParserConf );
1215                         } else {
1216                                 $this->mParser = clone $parser;
1217                         }
1218                 }
1219
1220                 return $this->mParser;
1221         }
1222
1223         /**
1224          * @param string $text
1225          * @param Title|null $title
1226          * @param bool $linestart Whether or not this is at the start of a line
1227          * @param bool $interface Whether this is an interface message
1228          * @param Language|string|null $language Language code
1229          * @return ParserOutput|string
1230          */
1231         public function parse( $text, $title = null, $linestart = true,
1232                 $interface = false, $language = null
1233         ) {
1234                 global $wgTitle;
1235
1236                 if ( $this->mInParser ) {
1237                         return htmlspecialchars( $text );
1238                 }
1239
1240                 $parser = $this->getParser();
1241                 $popts = $this->getParserOptions();
1242                 $popts->setInterfaceMessage( $interface );
1243
1244                 if ( is_string( $language ) ) {
1245                         $language = Language::factory( $language );
1246                 }
1247                 $popts->setTargetLanguage( $language );
1248
1249                 if ( !$title || !$title instanceof Title ) {
1250                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1251                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1252                         $title = $wgTitle;
1253                 }
1254                 // Sometimes $wgTitle isn't set either...
1255                 if ( !$title ) {
1256                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1257                         # Create a ghost title in such case
1258                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1259                 }
1260
1261                 $this->mInParser = true;
1262                 $res = $parser->parse( $text, $title, $popts, $linestart );
1263                 $this->mInParser = false;
1264
1265                 return $res;
1266         }
1267
1268         public function disable() {
1269                 $this->mDisable = true;
1270         }
1271
1272         public function enable() {
1273                 $this->mDisable = false;
1274         }
1275
1276         /**
1277          * Whether DB/cache usage is disabled for determining messages
1278          *
1279          * If so, this typically indicates either:
1280          *   - a) load() failed to find a cached copy nor query the DB
1281          *   - b) we are in a special context or error mode that cannot use the DB
1282          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1283          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1284          *
1285          * @return bool
1286          * @since 1.27
1287          */
1288         public function isDisabled() {
1289                 return $this->mDisable;
1290         }
1291
1292         /**
1293          * Clear all stored messages in global and local cache
1294          *
1295          * Mainly used after a mass rebuild
1296          */
1297         public function clear() {
1298                 $langs = Language::fetchLanguageNames( null, 'mw' );
1299                 foreach ( array_keys( $langs ) as $code ) {
1300                         $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
1301                 }
1302                 $this->cache->clear();
1303         }
1304
1305         /**
1306          * @param string $key
1307          * @return array
1308          */
1309         public function figureMessage( $key ) {
1310                 global $wgLanguageCode;
1311
1312                 $pieces = explode( '/', $key );
1313                 if ( count( $pieces ) < 2 ) {
1314                         return [ $key, $wgLanguageCode ];
1315                 }
1316
1317                 $lang = array_pop( $pieces );
1318                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1319                         return [ $key, $wgLanguageCode ];
1320                 }
1321
1322                 $message = implode( '/', $pieces );
1323
1324                 return [ $message, $lang ];
1325         }
1326
1327         /**
1328          * Get all message keys stored in the message cache for a given language.
1329          * If $code is the content language code, this will return all message keys
1330          * for which MediaWiki:msgkey exists. If $code is another language code, this
1331          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1332          * @param string $code Language code
1333          * @return array Array of message keys (strings)
1334          */
1335         public function getAllMessageKeys( $code ) {
1336                 $this->load( $code );
1337                 if ( !$this->cache->has( $code ) ) {
1338                         // Apparently load() failed
1339                         return null;
1340                 }
1341                 // Remove administrative keys
1342                 $cache = $this->cache->get( $code );
1343                 unset( $cache['VERSION'] );
1344                 unset( $cache['EXPIRY'] );
1345                 unset( $cache['EXCESSIVE'] );
1346                 // Remove any !NONEXISTENT keys
1347                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1348
1349                 // Keys may appear with a capital first letter. lcfirst them.
1350                 return array_map( [ $this->contLang, 'lcfirst' ], array_keys( $cache ) );
1351         }
1352
1353         /**
1354          * Purge message caches when a MediaWiki: page is created, updated, or deleted
1355          *
1356          * @param Title $title Message page title
1357          * @param Content|null $content New content for edit/create, null on deletion
1358          * @since 1.29
1359          */
1360         public function updateMessageOverride( Title $title, Content $content = null ) {
1361                 $msgText = $this->getMessageTextFromContent( $content );
1362                 if ( $msgText === null ) {
1363                         $msgText = false; // treat as not existing
1364                 }
1365
1366                 $this->replace( $title->getDBkey(), $msgText );
1367
1368                 if ( $this->contLang->hasVariants() ) {
1369                         $this->contLang->updateConversionTable( $title );
1370                 }
1371         }
1372
1373         /**
1374          * @param string $code Language code
1375          * @return string WAN cache key usable as a "check key" against language page edits
1376          */
1377         public function getCheckKey( $code ) {
1378                 return $this->wanCache->makeKey( 'messages', $code );
1379         }
1380
1381         /**
1382          * @param Content|null $content Content or null if the message page does not exist
1383          * @return string|bool|null Returns false if $content is null and null on error
1384          */
1385         private function getMessageTextFromContent( Content $content = null ) {
1386                 // @TODO: could skip pseudo-messages like js/css here, based on content model
1387                 if ( $content ) {
1388                         // Message page exists...
1389                         // XXX: Is this the right way to turn a Content object into a message?
1390                         // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1391                         //       CssContent. MessageContent is *not* used for storing messages, it's
1392                         //       only used for wrapping them when needed.
1393                         $msgText = $content->getWikitextForTransclusion();
1394                         if ( $msgText === false || $msgText === null ) {
1395                                 // This might be due to some kind of misconfiguration...
1396                                 $msgText = null;
1397                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1398                                         __METHOD__ . ": message content doesn't provide wikitext "
1399                                         . "(content model: " . $content->getModel() . ")" );
1400                         }
1401                 } else {
1402                         // Message page does not exist...
1403                         $msgText = false;
1404                 }
1405
1406                 return $msgText;
1407         }
1408
1409         /**
1410          * @param string $hash Hash for this version of the entire key/value overrides map
1411          * @param string $title Message cache key with initial uppercase letter
1412          * @return string
1413          */
1414         private function bigMessageCacheKey( $hash, $title ) {
1415                 return $this->wanCache->makeKey( 'messages-big', $hash, $title );
1416         }
1417 }