includes/cache/MessageCache.php

   1 <?php
   2 /**
   3  * Localisation messages cache.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Cache
  22  */
  23 use MediaWiki\MediaWikiServices;
  24 use Wikimedia\ScopedCallback;
  25 use MediaWiki\Logger\LoggerFactory;
  26 use Wikimedia\Rdbms\Database;
  27
  28 /**
  29  * MediaWiki message cache structure version.
  30  * Bump this whenever the message cache format has changed.
  31  */
  32 define( 'MSG_CACHE_VERSION', 2 );
  33
  34 /**
  35  * Cache of messages that are defined by MediaWiki namespace pages or by hooks
  36  *
  37  * Performs various MediaWiki namespace-related functions
  38  * @ingroup Cache
  39  */
  40 class MessageCache {
  41         const FOR_UPDATE = 1; // force message reload
  42
  43         /** How long to wait for memcached locks */
  44         const WAIT_SEC = 15;
  45         /** How long memcached locks last */
  46         const LOCK_TTL = 30;
  47
  48         /**
  49          * Process cache of loaded messages that are defined in MediaWiki namespace
  50          *
  51          * @var MapCacheLRU Map of (language code => key => " <MESSAGE>" or "!TOO BIG")
  52          */
  53         protected $cache;
  54
  55         /**
  56          * @var bool[] Map of (language code => boolean)
  57          */
  58         protected $cacheVolatile = [];
  59
  60         /**
  61          * Should mean that database cannot be used, but check
  62          * @var bool $mDisable
  63          */
  64         protected $mDisable;
  65
  66         /**
  67          * Lifetime for cache, used by object caching.
  68          * Set on construction, see __construct().
  69          */
  70         protected $mExpiry;
  71
  72         /**
  73          * Message cache has its own parser which it uses to transform messages
  74          * @var ParserOptions
  75          */
  76         protected $mParserOptions;
  77         /** @var Parser */
  78         protected $mParser;
  79
  80         /**
  81          * @var bool $mInParser
  82          */
  83         protected $mInParser = false;
  84
  85         /** @var WANObjectCache */
  86         protected $wanCache;
  87         /** @var BagOStuff */
  88         protected $clusterCache;
  89         /** @var BagOStuff */
  90         protected $srvCache;
  91         /** @var Language */
  92         protected $contLang;
  93
  94         /**
  95          * Singleton instance
  96          *
  97          * @var MessageCache $instance
  98          */
  99         private static $instance;
 100
 101         /**
 102          * Get the signleton instance of this class
 103          *
 104          * @since 1.18
 105          * @return MessageCache
 106          */
 107         public static function singleton() {
 108                 if ( self::$instance === null ) {
 109                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry, $wgUseLocalMessageCache;
 110                         $services = MediaWikiServices::getInstance();
 111                         self::$instance = new self(
 112                                 $services->getMainWANObjectCache(),
 113                                 wfGetMessageCacheStorage(),
 114                                 $wgUseLocalMessageCache
 115                                         ? $services->getLocalServerObjectCache()
 116                                         : new EmptyBagOStuff(),
 117                                 $wgUseDatabaseMessages,
 118                                 $wgMsgCacheExpiry,
 119                                 $services->getContentLanguage()
 120                         );
 121                 }
 122
 123                 return self::$instance;
 124         }
 125
 126         /**
 127          * Destroy the singleton instance
 128          *
 129          * @since 1.18
 130          */
 131         public static function destroyInstance() {
 132                 self::$instance = null;
 133         }
 134
 135         /**
 136          * Normalize message key input
 137          *
 138          * @param string $key Input message key to be normalized
 139          * @return string Normalized message key
 140          */
 141         public static function normalizeKey( $key ) {
 142                 $lckey = strtr( $key, ' ', '_' );
 143                 if ( ord( $lckey ) < 128 ) {
 144                         $lckey[0] = strtolower( $lckey[0] );
 145                 } else {
 146                         $lckey = MediaWikiServices::getInstance()->getContentLanguage()->lcfirst( $lckey );
 147                 }
 148
 149                 return $lckey;
 150         }
 151
 152         /**
 153          * @param WANObjectCache $wanCache
 154          * @param BagOStuff $clusterCache
 155          * @param BagOStuff $serverCache
 156          * @param bool $useDB Whether to look for message overrides (e.g. MediaWiki: pages)
 157          * @param int $expiry Lifetime for cache. @see $mExpiry.
 158          * @param Language|null $contLang Content language of site
 159          */
 160         public function __construct(
 161                 WANObjectCache $wanCache,
 162                 BagOStuff $clusterCache,
 163                 BagOStuff $serverCache,
 164                 $useDB,
 165                 $expiry,
 166                 Language $contLang = null
 167         ) {
 168                 $this->wanCache = $wanCache;
 169                 $this->clusterCache = $clusterCache;
 170                 $this->srvCache = $serverCache;
 171
 172                 $this->cache = new MapCacheLRU( 5 ); // limit size for sanity
 173
 174                 $this->mDisable = !$useDB;
 175                 $this->mExpiry = $expiry;
 176                 $this->contLang = $contLang ?? MediaWikiServices::getInstance()->getContentLanguage();
 177         }
 178
 179         /**
 180          * ParserOptions is lazy initialised.
 181          *
 182          * @return ParserOptions
 183          */
 184         function getParserOptions() {
 185                 global $wgUser;
 186
 187                 if ( !$this->mParserOptions ) {
 188                         if ( !$wgUser->isSafeToLoad() ) {
 189                                 // $wgUser isn't unstubbable yet, so don't try to get a
 190                                 // ParserOptions for it. And don't cache this ParserOptions
 191                                 // either.
 192                                 $po = ParserOptions::newFromAnon();
 193                                 $po->setAllowUnsafeRawHtml( false );
 194                                 return $po;
 195                         }
 196
 197                         $this->mParserOptions = new ParserOptions;
 198                         // Messages may take parameters that could come
 199                         // from malicious sources. As a precaution, disable
 200                         // the <html> parser tag when parsing messages.
 201                         $this->mParserOptions->setAllowUnsafeRawHtml( false );
 202                 }
 203
 204                 return $this->mParserOptions;
 205         }
 206
 207         /**
 208          * Try to load the cache from APC.
 209          *
 210          * @param string $code Optional language code, see documenation of load().
 211          * @return array|bool The cache array, or false if not in cache.
 212          */
 213         protected function getLocalCache( $code ) {
 214                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 215
 216                 return $this->srvCache->get( $cacheKey );
 217         }
 218
 219         /**
 220          * Save the cache to APC.
 221          *
 222          * @param string $code
 223          * @param array $cache The cache array
 224          */
 225         protected function saveToLocalCache( $code, $cache ) {
 226                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 227                 $this->srvCache->set( $cacheKey, $cache );
 228         }
 229
 230         /**
 231          * Loads messages from caches or from database in this order:
 232          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 233          * (2) memcached
 234          * (3) from the database.
 235          *
 236          * When successfully loading from (2) or (3), all higher level caches are
 237          * updated for the newest version.
 238          *
 239          * Nothing is loaded if member variable mDisable is true, either manually
 240          * set by calling code or if message loading fails (is this possible?).
 241          *
 242          * Returns true if cache is already populated or it was successfully populated,
 243          * or false if populating empty cache fails. Also returns true if MessageCache
 244          * is disabled.
 245          *
 246          * @param string $code Language to which load messages
 247          * @param int|null $mode Use MessageCache::FOR_UPDATE to skip process cache [optional]
 248          * @throws InvalidArgumentException
 249          * @return bool
 250          */
 251         protected function load( $code, $mode = null ) {
 252                 if ( !is_string( $code ) ) {
 253                         throw new InvalidArgumentException( "Missing language code" );
 254                 }
 255
 256                 # Don't do double loading...
 257                 if ( $this->cache->has( $code ) && $mode != self::FOR_UPDATE ) {
 258                         return true;
 259                 }
 260
 261                 # 8 lines of code just to say (once) that message cache is disabled
 262                 if ( $this->mDisable ) {
 263                         static $shownDisabled = false;
 264                         if ( !$shownDisabled ) {
 265                                 wfDebug( __METHOD__ . ": disabled\n" );
 266                                 $shownDisabled = true;
 267                         }
 268
 269                         return true;
 270                 }
 271
 272                 # Loading code starts
 273                 $success = false; # Keep track of success
 274                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 275                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 276
 277                 # Hash of the contents is stored in memcache, to detect if data-center cache
 278                 # or local cache goes out of date (e.g. due to replace() on some other server)
 279                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 280                 $this->cacheVolatile[$code] = $hashVolatile;
 281
 282                 # Try the local cache and check against the cluster hash key...
 283                 $cache = $this->getLocalCache( $code );
 284                 if ( !$cache ) {
 285                         $where[] = 'local cache is empty';
 286                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 287                         $where[] = 'local cache has the wrong hash';
 288                         $staleCache = $cache;
 289                 } elseif ( $this->isCacheExpired( $cache ) ) {
 290                         $where[] = 'local cache is expired';
 291                         $staleCache = $cache;
 292                 } elseif ( $hashVolatile ) {
 293                         $where[] = 'local cache validation key is expired/volatile';
 294                         $staleCache = $cache;
 295                 } else {
 296                         $where[] = 'got from local cache';
 297                         $this->cache->set( $code, $cache );
 298                         $success = true;
 299                 }
 300
 301                 if ( !$success ) {
 302                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 303                         # Try the global cache. If it is empty, try to acquire a lock. If
 304                         # the lock can't be acquired, wait for the other thread to finish
 305                         # and then try the global cache a second time.
 306                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 307                                 if ( $hashVolatile && $staleCache ) {
 308                                         # Do not bother fetching the whole cache blob to avoid I/O.
 309                                         # Instead, just try to get the non-blocking $statusKey lock
 310                                         # below, and use the local stale value if it was not acquired.
 311                                         $where[] = 'global cache is presumed expired';
 312                                 } else {
 313                                         $cache = $this->clusterCache->get( $cacheKey );
 314                                         if ( !$cache ) {
 315                                                 $where[] = 'global cache is empty';
 316                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 317                                                 $where[] = 'global cache is expired';
 318                                                 $staleCache = $cache;
 319                                         } elseif ( $hashVolatile ) {
 320                                                 # DB results are replica DB lag prone until the holdoff TTL passes.
 321                                                 # By then, updates should be reflected in loadFromDBWithLock().
 322                                                 # One thread renerates the cache while others use old values.
 323                                                 $where[] = 'global cache is expired/volatile';
 324                                                 $staleCache = $cache;
 325                                         } else {
 326                                                 $where[] = 'got from global cache';
 327                                                 $this->cache->set( $code, $cache );
 328                                                 $this->saveToCaches( $cache, 'local-only', $code );
 329                                                 $success = true;
 330                                         }
 331                                 }
 332
 333                                 if ( $success ) {
 334                                         # Done, no need to retry
 335                                         break;
 336                                 }
 337
 338                                 # We need to call loadFromDB. Limit the concurrency to one process.
 339                                 # This prevents the site from going down when the cache expires.
 340                                 # Note that the DB slam protection lock here is non-blocking.
 341                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 342                                 if ( $loadStatus === true ) {
 343                                         $success = true;
 344                                         break;
 345                                 } elseif ( $staleCache ) {
 346                                         # Use the stale cache while some other thread constructs the new one
 347                                         $where[] = 'using stale cache';
 348                                         $this->cache->set( $code, $staleCache );
 349                                         $success = true;
 350                                         break;
 351                                 } elseif ( $failedAttempts > 0 ) {
 352                                         # Already blocked once, so avoid another lock/unlock cycle.
 353                                         # This case will typically be hit if memcached is down, or if
 354                                         # loadFromDB() takes longer than LOCK_WAIT.
 355                                         $where[] = "could not acquire status key.";
 356                                         break;
 357                                 } elseif ( $loadStatus === 'cantacquire' ) {
 358                                         # Wait for the other thread to finish, then retry. Normally,
 359                                         # the memcached get() will then yeild the other thread's result.
 360                                         $where[] = 'waited for other thread to complete';
 361                                         $this->getReentrantScopedLock( $cacheKey );
 362                                 } else {
 363                                         # Disable cache; $loadStatus is 'disabled'
 364                                         break;
 365                                 }
 366                         }
 367                 }
 368
 369                 if ( !$success ) {
 370                         $where[] = 'loading FAILED - cache is disabled';
 371                         $this->mDisable = true;
 372                         $this->cache->set( $code, [] );
 373                         wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
 374                         # This used to throw an exception, but that led to nasty side effects like
 375                         # the whole wiki being instantly down if the memcached server died
 376                 }
 377
 378                 if ( !$this->cache->has( $code ) ) { // sanity
 379                         throw new LogicException( "Process cache for '$code' should be set by now." );
 380                 }
 381
 382                 $info = implode( ', ', $where );
 383                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 384
 385                 return $success;
 386         }
 387
 388         /**
 389          * @param string $code
 390          * @param array &$where List of wfDebug() comments
 391          * @param int|null $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 392          * @return bool|string True on success or one of ("cantacquire", "disabled")
 393          */
 394         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 395                 # If cache updates on all levels fail, give up on message overrides.
 396                 # This is to avoid easy site outages; see $saveSuccess comments below.
 397                 $statusKey = $this->clusterCache->makeKey( 'messages', $code, 'status' );
 398                 $status = $this->clusterCache->get( $statusKey );
 399                 if ( $status === 'error' ) {
 400                         $where[] = "could not load; method is still globally disabled";
 401                         return 'disabled';
 402                 }
 403
 404                 # Now let's regenerate
 405                 $where[] = 'loading from database';
 406
 407                 # Lock the cache to prevent conflicting writes.
 408                 # This lock is non-blocking so stale cache can quickly be used.
 409                 # Note that load() will call a blocking getReentrantScopedLock()
 410                 # after this if it really need to wait for any current thread.
 411                 $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 412                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 413                 if ( !$scopedLock ) {
 414                         $where[] = 'could not acquire main lock';
 415                         return 'cantacquire';
 416                 }
 417
 418                 $cache = $this->loadFromDB( $code, $mode );
 419                 $this->cache->set( $code, $cache );
 420                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 421
 422                 if ( !$saveSuccess ) {
 423                         /**
 424                          * Cache save has failed.
 425                          *
 426                          * There are two main scenarios where this could be a problem:
 427                          * - The cache is more than the maximum size (typically 1MB compressed).
 428                          * - Memcached has no space remaining in the relevant slab class. This is
 429                          *   unlikely with recent versions of memcached.
 430                          *
 431                          * Either way, if there is a local cache, nothing bad will happen. If there
 432                          * is no local cache, disabling the message cache for all requests avoids
 433                          * incurring a loadFromDB() overhead on every request, and thus saves the
 434                          * wiki from complete downtime under moderate traffic conditions.
 435                          */
 436                         if ( $this->srvCache instanceof EmptyBagOStuff ) {
 437                                 $this->clusterCache->set( $statusKey, 'error', 60 * 5 );
 438                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 439                         } else {
 440                                 $where[] = "could not save global cache";
 441                         }
 442                 }
 443
 444                 return true;
 445         }
 446
 447         /**
 448          * Loads cacheable messages from the database. Messages bigger than
 449          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 450          * on-demand from the database later.
 451          *
 452          * @param string $code Language code
 453          * @param int|null $mode Use MessageCache::FOR_UPDATE to skip process cache
 454          * @return array Loaded messages for storing in caches
 455          */
 456         protected function loadFromDB( $code, $mode = null ) {
 457                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 458
 459                 // (T164666) The query here performs really poorly on WMF's
 460                 // contributions replicas. We don't have a way to say "any group except
 461                 // contributions", so for the moment let's specify 'api'.
 462                 // @todo: Get rid of this hack.
 463                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA, 'api' );
 464
 465                 $cache = [];
 466
 467                 # Common conditions
 468                 $conds = [
 469                         'page_is_redirect' => 0,
 470                         'page_namespace' => NS_MEDIAWIKI,
 471                 ];
 472
 473                 $mostused = [];
 474                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 475                         if ( !$this->cache->has( $wgLanguageCode ) ) {
 476                                 $this->load( $wgLanguageCode );
 477                         }
 478                         $mostused = array_keys( $this->cache->get( $wgLanguageCode ) );
 479                         foreach ( $mostused as $key => $value ) {
 480                                 $mostused[$key] = "$value/$code";
 481                         }
 482                 }
 483
 484                 if ( count( $mostused ) ) {
 485                         $conds['page_title'] = $mostused;
 486                 } elseif ( $code !== $wgLanguageCode ) {
 487                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 488                 } else {
 489                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 490                         # other than language code.
 491                         $conds[] = 'page_title NOT' .
 492                                 $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 493                 }
 494
 495                 # Conditions to fetch oversized pages to ignore them
 496                 $bigConds = $conds;
 497                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 498
 499                 # Load titles for all oversized pages in the MediaWiki namespace
 500                 $res = $dbr->select(
 501                         'page',
 502                         [ 'page_title', 'page_latest' ],
 503                         $bigConds,
 504                         __METHOD__ . "($code)-big"
 505                 );
 506                 foreach ( $res as $row ) {
 507                         $cache[$row->page_title] = '!TOO BIG';
 508                         // At least include revision ID so page changes are reflected in the hash
 509                         $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 510                 }
 511
 512                 # Conditions to load the remaining pages with their contents
 513                 $smallConds = $conds;
 514                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 515
 516                 $res = $dbr->select(
 517                         [ 'page', 'revision', 'text' ],
 518                         [ 'page_title', 'old_id', 'old_text', 'old_flags' ],
 519                         $smallConds,
 520                         __METHOD__ . "($code)-small",
 521                         [],
 522                         [
 523                                 'revision' => [ 'JOIN', 'page_latest=rev_id' ],
 524                                 'text' => [ 'JOIN', 'rev_text_id=old_id' ],
 525                         ]
 526                 );
 527
 528                 foreach ( $res as $row ) {
 529                         $text = Revision::getRevisionText( $row );
 530                         if ( $text === false ) {
 531                                 // Failed to fetch data; possible ES errors?
 532                                 // Store a marker to fetch on-demand as a workaround...
 533                                 // TODO Use a differnt marker
 534                                 $entry = '!TOO BIG';
 535                                 wfDebugLog(
 536                                         'MessageCache',
 537                                         __METHOD__
 538                                         . ": failed to load message page text for {$row->page_title} ($code)"
 539                                 );
 540                         } else {
 541                                 $entry = ' ' . $text;
 542                         }
 543                         $cache[$row->page_title] = $entry;
 544                 }
 545
 546                 $cache['VERSION'] = MSG_CACHE_VERSION;
 547                 ksort( $cache );
 548
 549                 # Hash for validating local cache (APC). No need to take into account
 550                 # messages larger than $wgMaxMsgCacheEntrySize, since those are only
 551                 # stored and fetched from memcache.
 552                 $cache['HASH'] = md5( serialize( $cache ) );
 553                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 554
 555                 return $cache;
 556         }
 557
 558         /**
 559          * Updates cache as necessary when message page is changed
 560          *
 561          * @param string $title Message cache key with initial uppercase letter
 562          * @param string|bool $text New contents of the page (false if deleted)
 563          */
 564         public function replace( $title, $text ) {
 565                 global $wgLanguageCode;
 566
 567                 if ( $this->mDisable ) {
 568                         return;
 569                 }
 570
 571                 list( $msg, $code ) = $this->figureMessage( $title );
 572                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 573                         // Content language overrides do not use the /<code> suffix
 574                         return;
 575                 }
 576
 577                 // (a) Update the process cache with the new message text
 578                 if ( $text === false ) {
 579                         // Page deleted
 580                         $this->cache->setField( $code, $title, '!NONEXISTENT' );
 581                 } else {
 582                         // Ignore $wgMaxMsgCacheEntrySize so the process cache is up to date
 583                         $this->cache->setField( $code, $title, ' ' . $text );
 584                 }
 585
 586                 // (b) Update the shared caches in a deferred update with a fresh DB snapshot
 587                 DeferredUpdates::addCallableUpdate(
 588                         function () use ( $title, $msg, $code ) {
 589                                 global $wgMaxMsgCacheEntrySize;
 590                                 // Allow one caller at a time to avoid race conditions
 591                                 $scopedLock = $this->getReentrantScopedLock(
 592                                         $this->clusterCache->makeKey( 'messages', $code )
 593                                 );
 594                                 if ( !$scopedLock ) {
 595                                         LoggerFactory::getInstance( 'MessageCache' )->error(
 596                                                 __METHOD__ . ': could not acquire lock to update {title} ({code})',
 597                                                 [ 'title' => $title, 'code' => $code ] );
 598                                         return;
 599                                 }
 600                                 // Reload messages from the database and pre-populate dc-local caches
 601                                 // as optimisation. Use the master DB to avoid race conditions.
 602                                 $cache = $this->loadFromDB( $code, self::FOR_UPDATE );
 603                                 // Check if an individual cache key should exist and update cache accordingly
 604                                 $page = WikiPage::factory( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 605                                 $page->loadPageData( $page::READ_LATEST );
 606                                 $text = $this->getMessageTextFromContent( $page->getContent() );
 607                                 if ( is_string( $text ) && strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 608                                         // Match logic of loadCachedMessagePageEntry()
 609                                         $this->wanCache->set(
 610                                                 $this->bigMessageCacheKey( $cache['HASH'], $title ),
 611                                                 ' ' . $text,
 612                                                 $this->mExpiry
 613                                         );
 614                                 }
 615                                 // Mark this cache as definitely being "latest" (non-volatile) so
 616                                 // load() calls do not try to refresh the cache with replica DB data
 617                                 $cache['LATEST'] = time();
 618                                 // Update the process cache
 619                                 $this->cache->set( $code, $cache );
 620                                 // Pre-emptively update the local datacenter cache so things like edit filter and
 621                                 // blacklist changes are reflected immediately; these often use MediaWiki: pages.
 622                                 // The datacenter handling replace() calls should be the same one handling edits
 623                                 // as they require HTTP POST.
 624                                 $this->saveToCaches( $cache, 'all', $code );
 625                                 // Release the lock now that the cache is saved
 626                                 ScopedCallback::consume( $scopedLock );
 627
 628                                 // Relay the purge. Touching this check key expires cache contents
 629                                 // and local cache (APC) validation hash across all datacenters.
 630                                 $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
 631
 632                                 // Purge the message in the message blob store
 633                                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 634                                 $blobStore = $resourceloader->getMessageBlobStore();
 635                                 $blobStore->updateMessage( $this->contLang->lcfirst( $msg ) );
 636
 637                                 Hooks::run( 'MessageCacheReplace', [ $title, $text ] );
 638                         },
 639                         DeferredUpdates::PRESEND
 640                 );
 641         }
 642
 643         /**
 644          * Is the given cache array expired due to time passing or a version change?
 645          *
 646          * @param array $cache
 647          * @return bool
 648          */
 649         protected function isCacheExpired( $cache ) {
 650                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 651                         return true;
 652                 }
 653                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 654                         return true;
 655                 }
 656                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 657                         return true;
 658                 }
 659
 660                 return false;
 661         }
 662
 663         /**
 664          * Shortcut to update caches.
 665          *
 666          * @param array $cache Cached messages with a version.
 667          * @param string $dest Either "local-only" to save to local caches only
 668          *   or "all" to save to all caches.
 669          * @param string|bool $code Language code (default: false)
 670          * @return bool
 671          */
 672         protected function saveToCaches( array $cache, $dest, $code = false ) {
 673                 if ( $dest === 'all' ) {
 674                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 675                         $success = $this->clusterCache->set( $cacheKey, $cache );
 676                         $this->setValidationHash( $code, $cache );
 677                 } else {
 678                         $success = true;
 679                 }
 680
 681                 $this->saveToLocalCache( $code, $cache );
 682
 683                 return $success;
 684         }
 685
 686         /**
 687          * Get the md5 used to validate the local APC cache
 688          *
 689          * @param string $code
 690          * @return array (hash or false, bool expiry/volatility status)
 691          */
 692         protected function getValidationHash( $code ) {
 693                 $curTTL = null;
 694                 $value = $this->wanCache->get(
 695                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 696                         $curTTL,
 697                         [ $this->getCheckKey( $code ) ]
 698                 );
 699
 700                 if ( $value ) {
 701                         $hash = $value['hash'];
 702                         if ( ( time() - $value['latest'] ) < WANObjectCache::TTL_MINUTE ) {
 703                                 // Cache was recently updated via replace() and should be up-to-date.
 704                                 // That method is only called in the primary datacenter and uses FOR_UPDATE.
 705                                 // Also, it is unlikely that the current datacenter is *now* secondary one.
 706                                 $expired = false;
 707                         } else {
 708                                 // See if the "check" key was bumped after the hash was generated
 709                                 $expired = ( $curTTL < 0 );
 710                         }
 711                 } else {
 712                         // No hash found at all; cache must regenerate to be safe
 713                         $hash = false;
 714                         $expired = true;
 715                 }
 716
 717                 return [ $hash, $expired ];
 718         }
 719
 720         /**
 721          * Set the md5 used to validate the local disk cache
 722          *
 723          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 724          * be treated as "volatile" by getValidationHash() for the next few seconds.
 725          * This is triggered when $cache is generated using FOR_UPDATE mode.
 726          *
 727          * @param string $code
 728          * @param array $cache Cached messages with a version
 729          */
 730         protected function setValidationHash( $code, array $cache ) {
 731                 $this->wanCache->set(
 732                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 733                         [
 734                                 'hash' => $cache['HASH'],
 735                                 'latest' => $cache['LATEST'] ?? 0
 736                         ],
 737                         WANObjectCache::TTL_INDEFINITE
 738                 );
 739         }
 740
 741         /**
 742          * @param string $key A language message cache key that stores blobs
 743          * @param int $timeout Wait timeout in seconds
 744          * @return null|ScopedCallback
 745          */
 746         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 747                 return $this->clusterCache->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 748         }
 749
 750         /**
 751          * Get a message from either the content language or the user language.
 752          *
 753          * First, assemble a list of languages to attempt getting the message from. This
 754          * chain begins with the requested language and its fallbacks and then continues with
 755          * the content language and its fallbacks. For each language in the chain, the following
 756          * process will occur (in this order):
 757          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 758          *     Note: for the content language, there is no /lang subpage.
 759          *  2. Fetch from the static CDB cache.
 760          *  3. If available, check the database for fallback language overrides.
 761          *
 762          * This process provides a number of guarantees. When changing this code, make sure all
 763          * of these guarantees are preserved.
 764          *  * If the requested language is *not* the content language, then the CDB cache for that
 765          *    specific language will take precedence over the root database page ([[MW:msg]]).
 766          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 767          *    the message is available *anywhere* in the language for which it is a fallback.
 768          *
 769          * @param string $key The message key
 770          * @param bool $useDB If true, look for the message in the DB, false
 771          *   to use only the compiled l10n cache.
 772          * @param bool|string|object $langcode Code of the language to get the message for.
 773          *   - If string and a valid code, will create a standard language object
 774          *   - If string but not a valid code, will create a basic language object
 775          *   - If boolean and false, create object from the current users language
 776          *   - If boolean and true, create object from the wikis content language
 777          *   - If language object, use it as given
 778          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 779          *
 780          * @throws MWException When given an invalid key
 781          * @return string|bool False if the message doesn't exist, otherwise the
 782          *   message (which can be empty)
 783          */
 784         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 785                 if ( is_int( $key ) ) {
 786                         // Fix numerical strings that somehow become ints
 787                         // on their way here
 788                         $key = (string)$key;
 789                 } elseif ( !is_string( $key ) ) {
 790                         throw new MWException( 'Non-string key given' );
 791                 } elseif ( $key === '' ) {
 792                         // Shortcut: the empty key is always missing
 793                         return false;
 794                 }
 795
 796                 // For full keys, get the language code from the key
 797                 $pos = strrpos( $key, '/' );
 798                 if ( $isFullKey && $pos !== false ) {
 799                         $langcode = substr( $key, $pos + 1 );
 800                         $key = substr( $key, 0, $pos );
 801                 }
 802
 803                 // Normalise title-case input (with some inlining)
 804                 $lckey = self::normalizeKey( $key );
 805
 806                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 807
 808                 // Loop through each language in the fallback list until we find something useful
 809                 $lang = wfGetLangObj( $langcode );
 810                 $message = $this->getMessageFromFallbackChain(
 811                         $lang,
 812                         $lckey,
 813                         !$this->mDisable && $useDB
 814                 );
 815
 816                 // If we still have no message, maybe the key was in fact a full key so try that
 817                 if ( $message === false ) {
 818                         $parts = explode( '/', $lckey );
 819                         // We may get calls for things that are http-urls from sidebar
 820                         // Let's not load nonexistent languages for those
 821                         // They usually have more than one slash.
 822                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 823                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 824                                 if ( $message === null ) {
 825                                         $message = false;
 826                                 }
 827                         }
 828                 }
 829
 830                 // Post-processing if the message exists
 831                 if ( $message !== false ) {
 832                         // Fix whitespace
 833                         $message = str_replace(
 834                                 [
 835                                         # Fix for trailing whitespace, removed by textarea
 836                                         '&#32;',
 837                                         # Fix for NBSP, converted to space by firefox
 838                                         '&nbsp;',
 839                                         '&#160;',
 840                                         '&shy;'
 841                                 ],
 842                                 [
 843                                         ' ',
 844                                         "\u{00A0}",
 845                                         "\u{00A0}",
 846                                         "\u{00AD}"
 847                                 ],
 848                                 $message
 849                         );
 850                 }
 851
 852                 return $message;
 853         }
 854
 855         /**
 856          * Given a language, try and fetch messages from that language.
 857          *
 858          * Will also consider fallbacks of that language, the site language, and fallbacks for
 859          * the site language.
 860          *
 861          * @see MessageCache::get
 862          * @param Language|StubObject $lang Preferred language
 863          * @param string $lckey Lowercase key for the message (as for localisation cache)
 864          * @param bool $useDB Whether to include messages from the wiki database
 865          * @return string|bool The message, or false if not found
 866          */
 867         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 868                 $alreadyTried = [];
 869
 870                 // First try the requested language.
 871                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 872                 if ( $message !== false ) {
 873                         return $message;
 874                 }
 875
 876                 // Now try checking the site language.
 877                 $message = $this->getMessageForLang( $this->contLang, $lckey, $useDB, $alreadyTried );
 878                 return $message;
 879         }
 880
 881         /**
 882          * Given a language, try and fetch messages from that language and its fallbacks.
 883          *
 884          * @see MessageCache::get
 885          * @param Language|StubObject $lang Preferred language
 886          * @param string $lckey Lowercase key for the message (as for localisation cache)
 887          * @param bool $useDB Whether to include messages from the wiki database
 888          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 889          * @return string|bool The message, or false if not found
 890          */
 891         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 892                 $langcode = $lang->getCode();
 893
 894                 // Try checking the database for the requested language
 895                 if ( $useDB ) {
 896                         $uckey = $this->contLang->ucfirst( $lckey );
 897
 898                         if ( !isset( $alreadyTried[$langcode] ) ) {
 899                                 $message = $this->getMsgFromNamespace(
 900                                         $this->getMessagePageName( $langcode, $uckey ),
 901                                         $langcode
 902                                 );
 903
 904                                 if ( $message !== false ) {
 905                                         return $message;
 906                                 }
 907                                 $alreadyTried[$langcode] = true;
 908                         }
 909                 } else {
 910                         $uckey = null;
 911                 }
 912
 913                 // Check the CDB cache
 914                 $message = $lang->getMessage( $lckey );
 915                 if ( $message !== null ) {
 916                         return $message;
 917                 }
 918
 919                 // Try checking the database for all of the fallback languages
 920                 if ( $useDB ) {
 921                         $fallbackChain = Language::getFallbacksFor( $langcode );
 922
 923                         foreach ( $fallbackChain as $code ) {
 924                                 if ( isset( $alreadyTried[$code] ) ) {
 925                                         continue;
 926                                 }
 927
 928                                 $message = $this->getMsgFromNamespace(
 929                                         $this->getMessagePageName( $code, $uckey ), $code );
 930
 931                                 if ( $message !== false ) {
 932                                         return $message;
 933                                 }
 934                                 $alreadyTried[$code] = true;
 935                         }
 936                 }
 937
 938                 return false;
 939         }
 940
 941         /**
 942          * Get the message page name for a given language
 943          *
 944          * @param string $langcode
 945          * @param string $uckey Uppercase key for the message
 946          * @return string The page name
 947          */
 948         private function getMessagePageName( $langcode, $uckey ) {
 949                 global $wgLanguageCode;
 950
 951                 if ( $langcode === $wgLanguageCode ) {
 952                         // Messages created in the content language will not have the /lang extension
 953                         return $uckey;
 954                 } else {
 955                         return "$uckey/$langcode";
 956                 }
 957         }
 958
 959         /**
 960          * Get a message from the MediaWiki namespace, with caching. The key must
 961          * first be converted to two-part lang/msg form if necessary.
 962          *
 963          * Unlike self::get(), this function doesn't resolve fallback chains, and
 964          * some callers require this behavior. LanguageConverter::parseCachedTable()
 965          * and self::get() are some examples in core.
 966          *
 967          * @param string $title Message cache key with initial uppercase letter
 968          * @param string $code Code denoting the language to try
 969          * @return string|bool The message, or false if it does not exist or on error
 970          */
 971         public function getMsgFromNamespace( $title, $code ) {
 972                 // Load all MediaWiki page definitions into cache. Note that individual keys
 973                 // already loaded into cache during this request remain in the cache, which
 974                 // includes the value of hook-defined messages.
 975                 $this->load( $code );
 976
 977                 $entry = $this->cache->getField( $code, $title );
 978                 if ( $entry !== null ) {
 979                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 980                                 // The message exists and is not '!TOO BIG'
 981                                 return (string)substr( $entry, 1 );
 982                         } elseif ( $entry === '!NONEXISTENT' ) {
 983                                 return false;
 984                         }
 985                         // Fall through and try invididual message cache below
 986                 } else {
 987                         // Message does not have a MediaWiki page definition
 988                         $message = false;
 989                         Hooks::run( 'MessagesPreLoad', [ $title, &$message, $code ] );
 990                         if ( $message !== false ) {
 991                                 $this->cache->setField( $code, $title, ' ' . $message );
 992                         } else {
 993                                 $this->cache->setField( $code, $title, '!NONEXISTENT' );
 994                         }
 995
 996                         return $message;
 997                 }
 998
 999                 if ( $this->cacheVolatile[$code] ) {
1000                         $entry = false;
1001                         // Make sure that individual keys respect the WAN cache holdoff period too
1002                         LoggerFactory::getInstance( 'MessageCache' )->debug(
1003                                 __METHOD__ . ': loading volatile key \'{titleKey}\'',
1004                                 [ 'titleKey' => $title, 'code' => $code ] );
1005                 } else {
1006                         // Try the individual message cache
1007                         $entry = $this->loadCachedMessagePageEntry(
1008                                 $title,
1009                                 $code,
1010                                 $this->cache->getField( $code, 'HASH' )
1011                         );
1012                 }
1013
1014                 if ( $entry !== false && substr( $entry, 0, 1 ) === ' ' ) {
1015                         $this->cache->setField( $code, $title, $entry );
1016                         // The message exists, so make sure a string is returned
1017                         return (string)substr( $entry, 1 );
1018                 }
1019
1020                 $this->cache->setField( $code, $title, '!NONEXISTENT' );
1021
1022                 return false;
1023         }
1024
1025         /**
1026          * @param string $dbKey
1027          * @param string $code
1028          * @param string $hash
1029          * @return string Either " <MESSAGE>" or "!NONEXISTANT"
1030          */
1031         private function loadCachedMessagePageEntry( $dbKey, $code, $hash ) {
1032                 return $this->srvCache->getWithSetCallback(
1033                         $this->srvCache->makeKey( 'messages-big', $hash, $dbKey ),
1034                         IExpiringStore::TTL_MINUTE,
1035                         function () use ( $code, $dbKey, $hash ) {
1036                                 return $this->wanCache->getWithSetCallback(
1037                                         $this->bigMessageCacheKey( $hash, $dbKey ),
1038                                         $this->mExpiry,
1039                                         function ( $oldValue, &$ttl, &$setOpts ) use ( $dbKey, $code ) {
1040                                                 // Try loading the message from the database
1041                                                 $dbr = wfGetDB( DB_REPLICA );
1042                                                 $setOpts += Database::getCacheSetOptions( $dbr );
1043                                                 // Use newKnownCurrent() to avoid querying revision/user tables
1044                                                 $title = Title::makeTitle( NS_MEDIAWIKI, $dbKey );
1045                                                 $revision = Revision::newKnownCurrent( $dbr, $title );
1046                                                 if ( !$revision ) {
1047                                                         // The wiki doesn't have a local override page. Cache absence with normal TTL.
1048                                                         // When overrides are created, self::replace() takes care of the cache.
1049                                                         return '!NONEXISTENT';
1050                                                 }
1051                                                 $content = $revision->getContent();
1052                                                 if ( $content ) {
1053                                                         $message = $this->getMessageTextFromContent( $content );
1054                                                 } else {
1055                                                         LoggerFactory::getInstance( 'MessageCache' )->warning(
1056                                                                 __METHOD__ . ': failed to load page text for \'{titleKey}\'',
1057                                                                 [ 'titleKey' => $dbKey, 'code' => $code ]
1058                                                         );
1059                                                         $message = null;
1060                                                 }
1061
1062                                                 if ( !is_string( $message ) ) {
1063                                                         // Revision failed to load Content, or Content is incompatible with wikitext.
1064                                                         // Possibly a temporary loading failure.
1065                                                         $ttl = 5;
1066
1067                                                         return '!NONEXISTENT';
1068                                                 }
1069
1070                                                 return ' ' . $message;
1071                                         }
1072                                 );
1073                         }
1074                 );
1075         }
1076
1077         /**
1078          * @param string $message
1079          * @param bool $interface
1080          * @param Language|null $language
1081          * @param Title|null $title
1082          * @return string
1083          */
1084         public function transform( $message, $interface = false, $language = null, $title = null ) {
1085                 // Avoid creating parser if nothing to transform
1086                 if ( strpos( $message, '{{' ) === false ) {
1087                         return $message;
1088                 }
1089
1090                 if ( $this->mInParser ) {
1091                         return $message;
1092                 }
1093
1094                 $parser = $this->getParser();
1095                 if ( $parser ) {
1096                         $popts = $this->getParserOptions();
1097                         $popts->setInterfaceMessage( $interface );
1098                         $popts->setTargetLanguage( $language );
1099
1100                         $userlang = $popts->setUserLang( $language );
1101                         $this->mInParser = true;
1102                         $message = $parser->transformMsg( $message, $popts, $title );
1103                         $this->mInParser = false;
1104                         $popts->setUserLang( $userlang );
1105                 }
1106
1107                 return $message;
1108         }
1109
1110         /**
1111          * @return Parser
1112          */
1113         public function getParser() {
1114                 global $wgParser, $wgParserConf;
1115
1116                 if ( !$this->mParser && isset( $wgParser ) ) {
1117                         # Do some initialisation so that we don't have to do it twice
1118                         $wgParser->firstCallInit();
1119                         # Clone it and store it
1120                         $class = $wgParserConf['class'];
1121                         if ( $class == ParserDiffTest::class ) {
1122                                 # Uncloneable
1123                                 $this->mParser = new $class( $wgParserConf );
1124                         } else {
1125                                 $this->mParser = clone $wgParser;
1126                         }
1127                 }
1128
1129                 return $this->mParser;
1130         }
1131
1132         /**
1133          * @param string $text
1134          * @param Title|null $title
1135          * @param bool $linestart Whether or not this is at the start of a line
1136          * @param bool $interface Whether this is an interface message
1137          * @param Language|string|null $language Language code
1138          * @return ParserOutput|string
1139          */
1140         public function parse( $text, $title = null, $linestart = true,
1141                 $interface = false, $language = null
1142         ) {
1143                 global $wgTitle;
1144
1145                 if ( $this->mInParser ) {
1146                         return htmlspecialchars( $text );
1147                 }
1148
1149                 $parser = $this->getParser();
1150                 $popts = $this->getParserOptions();
1151                 $popts->setInterfaceMessage( $interface );
1152
1153                 if ( is_string( $language ) ) {
1154                         $language = Language::factory( $language );
1155                 }
1156                 $popts->setTargetLanguage( $language );
1157
1158                 if ( !$title || !$title instanceof Title ) {
1159                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1160                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1161                         $title = $wgTitle;
1162                 }
1163                 // Sometimes $wgTitle isn't set either...
1164                 if ( !$title ) {
1165                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1166                         # Create a ghost title in such case
1167                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1168                 }
1169
1170                 $this->mInParser = true;
1171                 $res = $parser->parse( $text, $title, $popts, $linestart );
1172                 $this->mInParser = false;
1173
1174                 return $res;
1175         }
1176
1177         public function disable() {
1178                 $this->mDisable = true;
1179         }
1180
1181         public function enable() {
1182                 $this->mDisable = false;
1183         }
1184
1185         /**
1186          * Whether DB/cache usage is disabled for determining messages
1187          *
1188          * If so, this typically indicates either:
1189          *   - a) load() failed to find a cached copy nor query the DB
1190          *   - b) we are in a special context or error mode that cannot use the DB
1191          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1192          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1193          *
1194          * @return bool
1195          * @since 1.27
1196          */
1197         public function isDisabled() {
1198                 return $this->mDisable;
1199         }
1200
1201         /**
1202          * Clear all stored messages in global and local cache
1203          *
1204          * Mainly used after a mass rebuild
1205          */
1206         public function clear() {
1207                 $langs = Language::fetchLanguageNames( null, 'mw' );
1208                 foreach ( array_keys( $langs ) as $code ) {
1209                         $this->wanCache->touchCheckKey( $this->getCheckKey( $code ) );
1210                 }
1211                 $this->cache->clear();
1212         }
1213
1214         /**
1215          * @param string $key
1216          * @return array
1217          */
1218         public function figureMessage( $key ) {
1219                 global $wgLanguageCode;
1220
1221                 $pieces = explode( '/', $key );
1222                 if ( count( $pieces ) < 2 ) {
1223                         return [ $key, $wgLanguageCode ];
1224                 }
1225
1226                 $lang = array_pop( $pieces );
1227                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1228                         return [ $key, $wgLanguageCode ];
1229                 }
1230
1231                 $message = implode( '/', $pieces );
1232
1233                 return [ $message, $lang ];
1234         }
1235
1236         /**
1237          * Get all message keys stored in the message cache for a given language.
1238          * If $code is the content language code, this will return all message keys
1239          * for which MediaWiki:msgkey exists. If $code is another language code, this
1240          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1241          * @param string $code Language code
1242          * @return array Array of message keys (strings)
1243          */
1244         public function getAllMessageKeys( $code ) {
1245                 $this->load( $code );
1246                 if ( !$this->cache->has( $code ) ) {
1247                         // Apparently load() failed
1248                         return null;
1249                 }
1250                 // Remove administrative keys
1251                 $cache = $this->cache->get( $code );
1252                 unset( $cache['VERSION'] );
1253                 unset( $cache['EXPIRY'] );
1254                 unset( $cache['EXCESSIVE'] );
1255                 // Remove any !NONEXISTENT keys
1256                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1257
1258                 // Keys may appear with a capital first letter. lcfirst them.
1259                 return array_map( [ $this->contLang, 'lcfirst' ], array_keys( $cache ) );
1260         }
1261
1262         /**
1263          * Purge message caches when a MediaWiki: page is created, updated, or deleted
1264          *
1265          * @param Title $title Message page title
1266          * @param Content|null $content New content for edit/create, null on deletion
1267          * @since 1.29
1268          */
1269         public function updateMessageOverride( Title $title, Content $content = null ) {
1270                 $msgText = $this->getMessageTextFromContent( $content );
1271                 if ( $msgText === null ) {
1272                         $msgText = false; // treat as not existing
1273                 }
1274
1275                 $this->replace( $title->getDBkey(), $msgText );
1276
1277                 if ( $this->contLang->hasVariants() ) {
1278                         $this->contLang->updateConversionTable( $title );
1279                 }
1280         }
1281
1282         /**
1283          * @param string $code Language code
1284          * @return string WAN cache key usable as a "check key" against language page edits
1285          */
1286         public function getCheckKey( $code ) {
1287                 return $this->wanCache->makeKey( 'messages', $code );
1288         }
1289
1290         /**
1291          * @param Content|null $content Content or null if the message page does not exist
1292          * @return string|bool|null Returns false if $content is null and null on error
1293          */
1294         private function getMessageTextFromContent( Content $content = null ) {
1295                 // @TODO: could skip pseudo-messages like js/css here, based on content model
1296                 if ( $content ) {
1297                         // Message page exists...
1298                         // XXX: Is this the right way to turn a Content object into a message?
1299                         // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1300                         //       CssContent. MessageContent is *not* used for storing messages, it's
1301                         //       only used for wrapping them when needed.
1302                         $msgText = $content->getWikitextForTransclusion();
1303                         if ( $msgText === false || $msgText === null ) {
1304                                 // This might be due to some kind of misconfiguration...
1305                                 $msgText = null;
1306                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1307                                         __METHOD__ . ": message content doesn't provide wikitext "
1308                                         . "(content model: " . $content->getModel() . ")" );
1309                         }
1310                 } else {
1311                         // Message page does not exist...
1312                         $msgText = false;
1313                 }
1314
1315                 return $msgText;
1316         }
1317
1318         /**
1319          * @param string $hash Hash for this version of the entire key/value overrides map
1320          * @param string $title Message cache key with initial uppercase letter
1321          * @return string
1322          */
1323         private function bigMessageCacheKey( $hash, $title ) {
1324                 return $this->wanCache->makeKey( 'messages-big', $hash, $title );
1325         }
1326 }