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  * Message cache
  36  * Performs various MediaWiki namespace-related functions
  37  * @ingroup Cache
  38  */
  39 class MessageCache {
  40         const FOR_UPDATE = 1; // force message reload
  41
  42         /** How long to wait for memcached locks */
  43         const WAIT_SEC = 15;
  44         /** How long memcached locks last */
  45         const LOCK_TTL = 30;
  46
  47         /**
  48          * Process local cache of loaded messages that are defined in
  49          * MediaWiki namespace. First array level is a language code,
  50          * second level is message key and the values are either message
  51          * content prefixed with space, or !NONEXISTENT for negative
  52          * caching.
  53          * @var array $mCache
  54          */
  55         protected $mCache;
  56
  57         /**
  58          * @var bool[] Map of (language code => boolean)
  59          */
  60         protected $mCacheVolatile = [];
  61
  62         /**
  63          * Should mean that database cannot be used, but check
  64          * @var bool $mDisable
  65          */
  66         protected $mDisable;
  67
  68         /**
  69          * Lifetime for cache, used by object caching.
  70          * Set on construction, see __construct().
  71          */
  72         protected $mExpiry;
  73
  74         /**
  75          * Message cache has its own parser which it uses to transform messages
  76          * @var ParserOptions
  77          */
  78         protected $mParserOptions;
  79         /** @var Parser */
  80         protected $mParser;
  81
  82         /**
  83          * Variable for tracking which variables are already loaded
  84          * @var array $mLoadedLanguages
  85          */
  86         protected $mLoadedLanguages = [];
  87
  88         /**
  89          * @var bool $mInParser
  90          */
  91         protected $mInParser = false;
  92
  93         /** @var WANObjectCache */
  94         protected $wanCache;
  95         /** @var BagOStuff */
  96         protected $clusterCache;
  97         /** @var BagOStuff */
  98         protected $srvCache;
  99
 100         /**
 101          * Singleton instance
 102          *
 103          * @var MessageCache $instance
 104          */
 105         private static $instance;
 106
 107         /**
 108          * Get the signleton instance of this class
 109          *
 110          * @since 1.18
 111          * @return MessageCache
 112          */
 113         public static function singleton() {
 114                 if ( self::$instance === null ) {
 115                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry, $wgUseLocalMessageCache;
 116                         self::$instance = new self(
 117                                 MediaWikiServices::getInstance()->getMainWANObjectCache(),
 118                                 wfGetMessageCacheStorage(),
 119                                 $wgUseLocalMessageCache
 120                                         ? MediaWikiServices::getInstance()->getLocalServerObjectCache()
 121                                         : new EmptyBagOStuff(),
 122                                 $wgUseDatabaseMessages,
 123                                 $wgMsgCacheExpiry
 124                         );
 125                 }
 126
 127                 return self::$instance;
 128         }
 129
 130         /**
 131          * Destroy the singleton instance
 132          *
 133          * @since 1.18
 134          */
 135         public static function destroyInstance() {
 136                 self::$instance = null;
 137         }
 138
 139         /**
 140          * Normalize message key input
 141          *
 142          * @param string $key Input message key to be normalized
 143          * @return string Normalized message key
 144          */
 145         public static function normalizeKey( $key ) {
 146                 global $wgContLang;
 147
 148                 $lckey = strtr( $key, ' ', '_' );
 149                 if ( ord( $lckey ) < 128 ) {
 150                         $lckey[0] = strtolower( $lckey[0] );
 151                 } else {
 152                         $lckey = $wgContLang->lcfirst( $lckey );
 153                 }
 154
 155                 return $lckey;
 156         }
 157
 158         /**
 159          * @param WANObjectCache $wanCache
 160          * @param BagOStuff $clusterCache
 161          * @param BagOStuff $serverCache
 162          * @param bool $useDB Whether to look for message overrides (e.g. MediaWiki: pages)
 163          * @param int $expiry Lifetime for cache. @see $mExpiry.
 164          */
 165         public function __construct(
 166                 WANObjectCache $wanCache,
 167                 BagOStuff $clusterCache,
 168                 BagOStuff $serverCache,
 169                 $useDB,
 170                 $expiry
 171         ) {
 172                 $this->wanCache = $wanCache;
 173                 $this->clusterCache = $clusterCache;
 174                 $this->srvCache = $serverCache;
 175
 176                 $this->mDisable = !$useDB;
 177                 $this->mExpiry = $expiry;
 178         }
 179
 180         /**
 181          * ParserOptions is lazy initialised.
 182          *
 183          * @return ParserOptions
 184          */
 185         function getParserOptions() {
 186                 global $wgUser;
 187
 188                 if ( !$this->mParserOptions ) {
 189                         if ( !$wgUser->isSafeToLoad() ) {
 190                                 // $wgUser isn't unstubbable yet, so don't try to get a
 191                                 // ParserOptions for it. And don't cache this ParserOptions
 192                                 // either.
 193                                 $po = ParserOptions::newFromAnon();
 194                                 $po->setEditSection( false );
 195                                 $po->setAllowUnsafeRawHtml( false );
 196                                 return $po;
 197                         }
 198
 199                         $this->mParserOptions = new ParserOptions;
 200                         $this->mParserOptions->setEditSection( false );
 201                         // Messages may take parameters that could come
 202                         // from malicious sources. As a precaution, disable
 203                         // the <html> parser tag when parsing messages.
 204                         $this->mParserOptions->setAllowUnsafeRawHtml( false );
 205                 }
 206
 207                 return $this->mParserOptions;
 208         }
 209
 210         /**
 211          * Try to load the cache from APC.
 212          *
 213          * @param string $code Optional language code, see documenation of load().
 214          * @return array|bool The cache array, or false if not in cache.
 215          */
 216         protected function getLocalCache( $code ) {
 217                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 218
 219                 return $this->srvCache->get( $cacheKey );
 220         }
 221
 222         /**
 223          * Save the cache to APC.
 224          *
 225          * @param string $code
 226          * @param array $cache The cache array
 227          */
 228         protected function saveToLocalCache( $code, $cache ) {
 229                 $cacheKey = $this->srvCache->makeKey( __CLASS__, $code );
 230                 $this->srvCache->set( $cacheKey, $cache );
 231         }
 232
 233         /**
 234          * Loads messages from caches or from database in this order:
 235          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 236          * (2) memcached
 237          * (3) from the database.
 238          *
 239          * When succesfully loading from (2) or (3), all higher level caches are
 240          * updated for the newest version.
 241          *
 242          * Nothing is loaded if member variable mDisable is true, either manually
 243          * set by calling code or if message loading fails (is this possible?).
 244          *
 245          * Returns true if cache is already populated or it was succesfully populated,
 246          * or false if populating empty cache fails. Also returns true if MessageCache
 247          * is disabled.
 248          *
 249          * @param string $code Language to which load messages
 250          * @param int $mode Use MessageCache::FOR_UPDATE to skip process cache [optional]
 251          * @throws MWException
 252          * @return bool
 253          */
 254         protected function load( $code, $mode = null ) {
 255                 if ( !is_string( $code ) ) {
 256                         throw new InvalidArgumentException( "Missing language code" );
 257                 }
 258
 259                 # Don't do double loading...
 260                 if ( isset( $this->mLoadedLanguages[$code] ) && $mode != self::FOR_UPDATE ) {
 261                         return true;
 262                 }
 263
 264                 # 8 lines of code just to say (once) that message cache is disabled
 265                 if ( $this->mDisable ) {
 266                         static $shownDisabled = false;
 267                         if ( !$shownDisabled ) {
 268                                 wfDebug( __METHOD__ . ": disabled\n" );
 269                                 $shownDisabled = true;
 270                         }
 271
 272                         return true;
 273                 }
 274
 275                 # Loading code starts
 276                 $success = false; # Keep track of success
 277                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 278                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 279
 280                 # Hash of the contents is stored in memcache, to detect if data-center cache
 281                 # or local cache goes out of date (e.g. due to replace() on some other server)
 282                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 283                 $this->mCacheVolatile[$code] = $hashVolatile;
 284
 285                 # Try the local cache and check against the cluster hash key...
 286                 $cache = $this->getLocalCache( $code );
 287                 if ( !$cache ) {
 288                         $where[] = 'local cache is empty';
 289                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 290                         $where[] = 'local cache has the wrong hash';
 291                         $staleCache = $cache;
 292                 } elseif ( $this->isCacheExpired( $cache ) ) {
 293                         $where[] = 'local cache is expired';
 294                         $staleCache = $cache;
 295                 } elseif ( $hashVolatile ) {
 296                         $where[] = 'local cache validation key is expired/volatile';
 297                         $staleCache = $cache;
 298                 } else {
 299                         $where[] = 'got from local cache';
 300                         $success = true;
 301                         $this->mCache[$code] = $cache;
 302                 }
 303
 304                 if ( !$success ) {
 305                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code ); # Key in memc for messages
 306                         # Try the global cache. If it is empty, try to acquire a lock. If
 307                         # the lock can't be acquired, wait for the other thread to finish
 308                         # and then try the global cache a second time.
 309                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 310                                 if ( $hashVolatile && $staleCache ) {
 311                                         # Do not bother fetching the whole cache blob to avoid I/O.
 312                                         # Instead, just try to get the non-blocking $statusKey lock
 313                                         # below, and use the local stale value if it was not acquired.
 314                                         $where[] = 'global cache is presumed expired';
 315                                 } else {
 316                                         $cache = $this->clusterCache->get( $cacheKey );
 317                                         if ( !$cache ) {
 318                                                 $where[] = 'global cache is empty';
 319                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 320                                                 $where[] = 'global cache is expired';
 321                                                 $staleCache = $cache;
 322                                         } elseif ( $hashVolatile ) {
 323                                                 # DB results are replica DB lag prone until the holdoff TTL passes.
 324                                                 # By then, updates should be reflected in loadFromDBWithLock().
 325                                                 # One thread renerates the cache while others use old values.
 326                                                 $where[] = 'global cache is expired/volatile';
 327                                                 $staleCache = $cache;
 328                                         } else {
 329                                                 $where[] = 'got from global cache';
 330                                                 $this->mCache[$code] = $cache;
 331                                                 $this->saveToCaches( $cache, 'local-only', $code );
 332                                                 $success = true;
 333                                         }
 334                                 }
 335
 336                                 if ( $success ) {
 337                                         # Done, no need to retry
 338                                         break;
 339                                 }
 340
 341                                 # We need to call loadFromDB. Limit the concurrency to one process.
 342                                 # This prevents the site from going down when the cache expires.
 343                                 # Note that the DB slam protection lock here is non-blocking.
 344                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 345                                 if ( $loadStatus === true ) {
 346                                         $success = true;
 347                                         break;
 348                                 } elseif ( $staleCache ) {
 349                                         # Use the stale cache while some other thread constructs the new one
 350                                         $where[] = 'using stale cache';
 351                                         $this->mCache[$code] = $staleCache;
 352                                         $success = true;
 353                                         break;
 354                                 } elseif ( $failedAttempts > 0 ) {
 355                                         # Already blocked once, so avoid another lock/unlock cycle.
 356                                         # This case will typically be hit if memcached is down, or if
 357                                         # loadFromDB() takes longer than LOCK_WAIT.
 358                                         $where[] = "could not acquire status key.";
 359                                         break;
 360                                 } elseif ( $loadStatus === 'cantacquire' ) {
 361                                         # Wait for the other thread to finish, then retry. Normally,
 362                                         # the memcached get() will then yeild the other thread's result.
 363                                         $where[] = 'waited for other thread to complete';
 364                                         $this->getReentrantScopedLock( $cacheKey );
 365                                 } else {
 366                                         # Disable cache; $loadStatus is 'disabled'
 367                                         break;
 368                                 }
 369                         }
 370                 }
 371
 372                 if ( !$success ) {
 373                         $where[] = 'loading FAILED - cache is disabled';
 374                         $this->mDisable = true;
 375                         $this->mCache = false;
 376                         wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
 377                         # This used to throw an exception, but that led to nasty side effects like
 378                         # the whole wiki being instantly down if the memcached server died
 379                 } else {
 380                         # All good, just record the success
 381                         $this->mLoadedLanguages[$code] = true;
 382                 }
 383
 384                 $info = implode( ', ', $where );
 385                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 386
 387                 return $success;
 388         }
 389
 390         /**
 391          * @param string $code
 392          * @param array &$where List of wfDebug() comments
 393          * @param int $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 394          * @return bool|string True on success or one of ("cantacquire", "disabled")
 395          */
 396         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 397                 # If cache updates on all levels fail, give up on message overrides.
 398                 # This is to avoid easy site outages; see $saveSuccess comments below.
 399                 $statusKey = $this->clusterCache->makeKey( 'messages', $code, 'status' );
 400                 $status = $this->clusterCache->get( $statusKey );
 401                 if ( $status === 'error' ) {
 402                         $where[] = "could not load; method is still globally disabled";
 403                         return 'disabled';
 404                 }
 405
 406                 # Now let's regenerate
 407                 $where[] = 'loading from database';
 408
 409                 # Lock the cache to prevent conflicting writes.
 410                 # This lock is non-blocking so stale cache can quickly be used.
 411                 # Note that load() will call a blocking getReentrantScopedLock()
 412                 # after this if it really need to wait for any current thread.
 413                 $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 414                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 415                 if ( !$scopedLock ) {
 416                         $where[] = 'could not acquire main lock';
 417                         return 'cantacquire';
 418                 }
 419
 420                 $cache = $this->loadFromDB( $code, $mode );
 421                 $this->mCache[$code] = $cache;
 422                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 423
 424                 if ( !$saveSuccess ) {
 425                         /**
 426                          * Cache save has failed.
 427                          *
 428                          * There are two main scenarios where this could be a problem:
 429                          * - The cache is more than the maximum size (typically 1MB compressed).
 430                          * - Memcached has no space remaining in the relevant slab class. This is
 431                          *   unlikely with recent versions of memcached.
 432                          *
 433                          * Either way, if there is a local cache, nothing bad will happen. If there
 434                          * is no local cache, disabling the message cache for all requests avoids
 435                          * incurring a loadFromDB() overhead on every request, and thus saves the
 436                          * wiki from complete downtime under moderate traffic conditions.
 437                          */
 438                         if ( $this->srvCache instanceof EmptyBagOStuff ) {
 439                                 $this->clusterCache->set( $statusKey, 'error', 60 * 5 );
 440                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 441                         } else {
 442                                 $where[] = "could not save global cache";
 443                         }
 444                 }
 445
 446                 return true;
 447         }
 448
 449         /**
 450          * Loads cacheable messages from the database. Messages bigger than
 451          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 452          * on-demand from the database later.
 453          *
 454          * @param string $code Language code
 455          * @param int $mode Use MessageCache::FOR_UPDATE to skip process cache
 456          * @return array Loaded messages for storing in caches
 457          */
 458         protected function loadFromDB( $code, $mode = null ) {
 459                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 460
 461                 // (T164666) The query here performs really poorly on WMF's
 462                 // contributions replicas. We don't have a way to say "any group except
 463                 // contributions", so for the moment let's specify 'api'.
 464                 // @todo: Get rid of this hack.
 465                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA, 'api' );
 466
 467                 $cache = [];
 468
 469                 # Common conditions
 470                 $conds = [
 471                         'page_is_redirect' => 0,
 472                         'page_namespace' => NS_MEDIAWIKI,
 473                 ];
 474
 475                 $mostused = [];
 476                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 477                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 478                                 $this->load( $wgLanguageCode );
 479                         }
 480                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 481                         foreach ( $mostused as $key => $value ) {
 482                                 $mostused[$key] = "$value/$code";
 483                         }
 484                 }
 485
 486                 if ( count( $mostused ) ) {
 487                         $conds['page_title'] = $mostused;
 488                 } elseif ( $code !== $wgLanguageCode ) {
 489                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 490                 } else {
 491                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 492                         # other than language code.
 493                         $conds[] = 'page_title NOT' .
 494                                 $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 495                 }
 496
 497                 # Conditions to fetch oversized pages to ignore them
 498                 $bigConds = $conds;
 499                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 500
 501                 # Load titles for all oversized pages in the MediaWiki namespace
 502                 $res = $dbr->select(
 503                         'page',
 504                         [ 'page_title', 'page_latest' ],
 505                         $bigConds,
 506                         __METHOD__ . "($code)-big"
 507                 );
 508                 foreach ( $res as $row ) {
 509                         $cache[$row->page_title] = '!TOO BIG';
 510                         // At least include revision ID so page changes are reflected in the hash
 511                         $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 512                 }
 513
 514                 # Conditions to load the remaining pages with their contents
 515                 $smallConds = $conds;
 516                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 517
 518                 $res = $dbr->select(
 519                         [ 'page', 'revision', 'text' ],
 520                         [ 'page_title', 'old_id', 'old_text', 'old_flags' ],
 521                         $smallConds,
 522                         __METHOD__ . "($code)-small",
 523                         [],
 524                         [
 525                                 'revision' => [ 'JOIN', 'page_latest=rev_id' ],
 526                                 'text' => [ 'JOIN', 'rev_text_id=old_id' ],
 527                         ]
 528                 );
 529
 530                 foreach ( $res as $row ) {
 531                         $text = Revision::getRevisionText( $row );
 532                         if ( $text === false ) {
 533                                 // Failed to fetch data; possible ES errors?
 534                                 // Store a marker to fetch on-demand as a workaround...
 535                                 // TODO Use a differnt marker
 536                                 $entry = '!TOO BIG';
 537                                 wfDebugLog(
 538                                         'MessageCache',
 539                                         __METHOD__
 540                                         . ": failed to load message page text for {$row->page_title} ($code)"
 541                                 );
 542                         } else {
 543                                 $entry = ' ' . $text;
 544                         }
 545                         $cache[$row->page_title] = $entry;
 546                 }
 547
 548                 $cache['VERSION'] = MSG_CACHE_VERSION;
 549                 ksort( $cache );
 550
 551                 # Hash for validating local cache (APC). No need to take into account
 552                 # messages larger than $wgMaxMsgCacheEntrySize, since those are only
 553                 # stored and fetched from memcache.
 554                 $cache['HASH'] = md5( serialize( $cache ) );
 555                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 556
 557                 return $cache;
 558         }
 559
 560         /**
 561          * Updates cache as necessary when message page is changed
 562          *
 563          * @param string $title Message cache key with initial uppercase letter
 564          * @param string|bool $text New contents of the page (false if deleted)
 565          */
 566         public function replace( $title, $text ) {
 567                 global $wgLanguageCode;
 568
 569                 if ( $this->mDisable ) {
 570                         return;
 571                 }
 572
 573                 list( $msg, $code ) = $this->figureMessage( $title );
 574                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 575                         // Content language overrides do not use the /<code> suffix
 576                         return;
 577                 }
 578
 579                 // (a) Update the process cache with the new message text
 580                 if ( $text === false ) {
 581                         // Page deleted
 582                         $this->mCache[$code][$title] = '!NONEXISTENT';
 583                 } else {
 584                         // Ignore $wgMaxMsgCacheEntrySize so the process cache is up to date
 585                         $this->mCache[$code][$title] = ' ' . $text;
 586                 }
 587
 588                 // (b) Update the shared caches in a deferred update with a fresh DB snapshot
 589                 DeferredUpdates::addCallableUpdate(
 590                         function () use ( $title, $msg, $code ) {
 591                                 global $wgContLang, $wgMaxMsgCacheEntrySize;
 592                                 // Allow one caller at a time to avoid race conditions
 593                                 $scopedLock = $this->getReentrantScopedLock(
 594                                         $this->clusterCache->makeKey( 'messages', $code )
 595                                 );
 596                                 if ( !$scopedLock ) {
 597                                         LoggerFactory::getInstance( 'MessageCache' )->error(
 598                                                 __METHOD__ . ': could not acquire lock to update {title} ({code})',
 599                                                 [ 'title' => $title, 'code' => $code ] );
 600                                         return;
 601                                 }
 602                                 // Load the messages from the master DB to avoid race conditions
 603                                 $cache = $this->loadFromDB( $code, self::FOR_UPDATE );
 604                                 $this->mCache[$code] = $cache;
 605                                 // Load the process cache values and set the per-title cache keys
 606                                 $page = WikiPage::factory( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 607                                 $page->loadPageData( $page::READ_LATEST );
 608                                 $text = $this->getMessageTextFromContent( $page->getContent() );
 609                                 // Check if an individual cache key should exist and update cache accordingly
 610                                 if ( is_string( $text ) && strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 611                                         $titleKey = $this->bigMessageCacheKey( $this->mCache[$code]['HASH'], $title );
 612                                         $this->wanCache->set( $titleKey, ' ' . $text, $this->mExpiry );
 613                                 }
 614                                 // Mark this cache as definitely being "latest" (non-volatile) so
 615                                 // load() calls do try to refresh the cache with replica DB data
 616                                 $this->mCache[$code]['LATEST'] = time();
 617                                 // Pre-emptively update the local datacenter cache so things like edit filter and
 618                                 // blacklist changes are reflect immediately, as these often use MediaWiki: pages.
 619                                 // The datacenter handling replace() calls should be the same one handling edits
 620                                 // as they require HTTP POST.
 621                                 $this->saveToCaches( $this->mCache[$code], 'all', $code );
 622                                 // Release the lock now that the cache is saved
 623                                 ScopedCallback::consume( $scopedLock );
 624
 625                                 // Relay the purge. Touching this check key expires cache contents
 626                                 // and local cache (APC) validation hash across all datacenters.
 627                                 $this->wanCache->touchCheckKey( $this->wanCache->makeKey( 'messages', $code ) );
 628                                 // Also delete cached sidebar... just in case it is affected
 629                                 // @TODO: shouldn't this be $code === $wgLanguageCode?
 630                                 if ( $code === 'en' ) {
 631                                         // Purge all language sidebars, e.g. on ?action=purge to the sidebar messages
 632                                         $codes = array_keys( Language::fetchLanguageNames() );
 633                                 } else {
 634                                         // Purge only the sidebar for this language
 635                                         $codes = [ $code ];
 636                                 }
 637                                 foreach ( $codes as $code ) {
 638                                         $this->wanCache->delete( $this->wanCache->makeKey( 'sidebar', $code ) );
 639                                 }
 640
 641                                 // Purge the message in the message blob store
 642                                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 643                                 $blobStore = $resourceloader->getMessageBlobStore();
 644                                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 645
 646                                 Hooks::run( 'MessageCacheReplace', [ $title, $text ] );
 647                         },
 648                         DeferredUpdates::PRESEND
 649                 );
 650         }
 651
 652         /**
 653          * Is the given cache array expired due to time passing or a version change?
 654          *
 655          * @param array $cache
 656          * @return bool
 657          */
 658         protected function isCacheExpired( $cache ) {
 659                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 660                         return true;
 661                 }
 662                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 663                         return true;
 664                 }
 665                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 666                         return true;
 667                 }
 668
 669                 return false;
 670         }
 671
 672         /**
 673          * Shortcut to update caches.
 674          *
 675          * @param array $cache Cached messages with a version.
 676          * @param string $dest Either "local-only" to save to local caches only
 677          *   or "all" to save to all caches.
 678          * @param string|bool $code Language code (default: false)
 679          * @return bool
 680          */
 681         protected function saveToCaches( array $cache, $dest, $code = false ) {
 682                 if ( $dest === 'all' ) {
 683                         $cacheKey = $this->clusterCache->makeKey( 'messages', $code );
 684                         $success = $this->clusterCache->set( $cacheKey, $cache );
 685                         $this->setValidationHash( $code, $cache );
 686                 } else {
 687                         $success = true;
 688                 }
 689
 690                 $this->saveToLocalCache( $code, $cache );
 691
 692                 return $success;
 693         }
 694
 695         /**
 696          * Get the md5 used to validate the local APC cache
 697          *
 698          * @param string $code
 699          * @return array (hash or false, bool expiry/volatility status)
 700          */
 701         protected function getValidationHash( $code ) {
 702                 $curTTL = null;
 703                 $value = $this->wanCache->get(
 704                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 705                         $curTTL,
 706                         [ $this->wanCache->makeKey( 'messages', $code ) ]
 707                 );
 708
 709                 if ( $value ) {
 710                         $hash = $value['hash'];
 711                         if ( ( time() - $value['latest'] ) < WANObjectCache::TTL_MINUTE ) {
 712                                 // Cache was recently updated via replace() and should be up-to-date.
 713                                 // That method is only called in the primary datacenter and uses FOR_UPDATE.
 714                                 // Also, it is unlikely that the current datacenter is *now* secondary one.
 715                                 $expired = false;
 716                         } else {
 717                                 // See if the "check" key was bumped after the hash was generated
 718                                 $expired = ( $curTTL < 0 );
 719                         }
 720                 } else {
 721                         // No hash found at all; cache must regenerate to be safe
 722                         $hash = false;
 723                         $expired = true;
 724                 }
 725
 726                 return [ $hash, $expired ];
 727         }
 728
 729         /**
 730          * Set the md5 used to validate the local disk cache
 731          *
 732          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 733          * be treated as "volatile" by getValidationHash() for the next few seconds.
 734          * This is triggered when $cache is generated using FOR_UPDATE mode.
 735          *
 736          * @param string $code
 737          * @param array $cache Cached messages with a version
 738          */
 739         protected function setValidationHash( $code, array $cache ) {
 740                 $this->wanCache->set(
 741                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 742                         [
 743                                 'hash' => $cache['HASH'],
 744                                 'latest' => isset( $cache['LATEST'] ) ? $cache['LATEST'] : 0
 745                         ],
 746                         WANObjectCache::TTL_INDEFINITE
 747                 );
 748         }
 749
 750         /**
 751          * @param string $key A language message cache key that stores blobs
 752          * @param int $timeout Wait timeout in seconds
 753          * @return null|ScopedCallback
 754          */
 755         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 756                 return $this->clusterCache->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 757         }
 758
 759         /**
 760          * Get a message from either the content language or the user language.
 761          *
 762          * First, assemble a list of languages to attempt getting the message from. This
 763          * chain begins with the requested language and its fallbacks and then continues with
 764          * the content language and its fallbacks. For each language in the chain, the following
 765          * process will occur (in this order):
 766          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 767          *     Note: for the content language, there is no /lang subpage.
 768          *  2. Fetch from the static CDB cache.
 769          *  3. If available, check the database for fallback language overrides.
 770          *
 771          * This process provides a number of guarantees. When changing this code, make sure all
 772          * of these guarantees are preserved.
 773          *  * If the requested language is *not* the content language, then the CDB cache for that
 774          *    specific language will take precedence over the root database page ([[MW:msg]]).
 775          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 776          *    the message is available *anywhere* in the language for which it is a fallback.
 777          *
 778          * @param string $key The message key
 779          * @param bool $useDB If true, look for the message in the DB, false
 780          *   to use only the compiled l10n cache.
 781          * @param bool|string|object $langcode Code of the language to get the message for.
 782          *   - If string and a valid code, will create a standard language object
 783          *   - If string but not a valid code, will create a basic language object
 784          *   - If boolean and false, create object from the current users language
 785          *   - If boolean and true, create object from the wikis content language
 786          *   - If language object, use it as given
 787          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 788          *
 789          * @throws MWException When given an invalid key
 790          * @return string|bool False if the message doesn't exist, otherwise the
 791          *   message (which can be empty)
 792          */
 793         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 794                 if ( is_int( $key ) ) {
 795                         // Fix numerical strings that somehow become ints
 796                         // on their way here
 797                         $key = (string)$key;
 798                 } elseif ( !is_string( $key ) ) {
 799                         throw new MWException( 'Non-string key given' );
 800                 } elseif ( $key === '' ) {
 801                         // Shortcut: the empty key is always missing
 802                         return false;
 803                 }
 804
 805                 // For full keys, get the language code from the key
 806                 $pos = strrpos( $key, '/' );
 807                 if ( $isFullKey && $pos !== false ) {
 808                         $langcode = substr( $key, $pos + 1 );
 809                         $key = substr( $key, 0, $pos );
 810                 }
 811
 812                 // Normalise title-case input (with some inlining)
 813                 $lckey = self::normalizeKey( $key );
 814
 815                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 816
 817                 // Loop through each language in the fallback list until we find something useful
 818                 $lang = wfGetLangObj( $langcode );
 819                 $message = $this->getMessageFromFallbackChain(
 820                         $lang,
 821                         $lckey,
 822                         !$this->mDisable && $useDB
 823                 );
 824
 825                 // If we still have no message, maybe the key was in fact a full key so try that
 826                 if ( $message === false ) {
 827                         $parts = explode( '/', $lckey );
 828                         // We may get calls for things that are http-urls from sidebar
 829                         // Let's not load nonexistent languages for those
 830                         // They usually have more than one slash.
 831                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 832                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 833                                 if ( $message === null ) {
 834                                         $message = false;
 835                                 }
 836                         }
 837                 }
 838
 839                 // Post-processing if the message exists
 840                 if ( $message !== false ) {
 841                         // Fix whitespace
 842                         $message = str_replace(
 843                                 [
 844                                         # Fix for trailing whitespace, removed by textarea
 845                                         '&#32;',
 846                                         # Fix for NBSP, converted to space by firefox
 847                                         '&nbsp;',
 848                                         '&#160;',
 849                                         '&shy;'
 850                                 ],
 851                                 [
 852                                         ' ',
 853                                         "\xc2\xa0",
 854                                         "\xc2\xa0",
 855                                         "\xc2\xad"
 856                                 ],
 857                                 $message
 858                         );
 859                 }
 860
 861                 return $message;
 862         }
 863
 864         /**
 865          * Given a language, try and fetch messages from that language.
 866          *
 867          * Will also consider fallbacks of that language, the site language, and fallbacks for
 868          * the site language.
 869          *
 870          * @see MessageCache::get
 871          * @param Language|StubObject $lang Preferred language
 872          * @param string $lckey Lowercase key for the message (as for localisation cache)
 873          * @param bool $useDB Whether to include messages from the wiki database
 874          * @return string|bool The message, or false if not found
 875          */
 876         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 877                 global $wgContLang;
 878
 879                 $alreadyTried = [];
 880
 881                 // First try the requested language.
 882                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 883                 if ( $message !== false ) {
 884                         return $message;
 885                 }
 886
 887                 // Now try checking the site language.
 888                 $message = $this->getMessageForLang( $wgContLang, $lckey, $useDB, $alreadyTried );
 889                 return $message;
 890         }
 891
 892         /**
 893          * Given a language, try and fetch messages from that language and its fallbacks.
 894          *
 895          * @see MessageCache::get
 896          * @param Language|StubObject $lang Preferred language
 897          * @param string $lckey Lowercase key for the message (as for localisation cache)
 898          * @param bool $useDB Whether to include messages from the wiki database
 899          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 900          * @return string|bool The message, or false if not found
 901          */
 902         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 903                 global $wgContLang;
 904
 905                 $langcode = $lang->getCode();
 906
 907                 // Try checking the database for the requested language
 908                 if ( $useDB ) {
 909                         $uckey = $wgContLang->ucfirst( $lckey );
 910
 911                         if ( !isset( $alreadyTried[ $langcode ] ) ) {
 912                                 $message = $this->getMsgFromNamespace(
 913                                         $this->getMessagePageName( $langcode, $uckey ),
 914                                         $langcode
 915                                 );
 916
 917                                 if ( $message !== false ) {
 918                                         return $message;
 919                                 }
 920                                 $alreadyTried[ $langcode ] = true;
 921                         }
 922                 } else {
 923                         $uckey = null;
 924                 }
 925
 926                 // Check the CDB cache
 927                 $message = $lang->getMessage( $lckey );
 928                 if ( $message !== null ) {
 929                         return $message;
 930                 }
 931
 932                 // Try checking the database for all of the fallback languages
 933                 if ( $useDB ) {
 934                         $fallbackChain = Language::getFallbacksFor( $langcode );
 935
 936                         foreach ( $fallbackChain as $code ) {
 937                                 if ( isset( $alreadyTried[ $code ] ) ) {
 938                                         continue;
 939                                 }
 940
 941                                 $message = $this->getMsgFromNamespace(
 942                                         $this->getMessagePageName( $code, $uckey ), $code );
 943
 944                                 if ( $message !== false ) {
 945                                         return $message;
 946                                 }
 947                                 $alreadyTried[ $code ] = true;
 948                         }
 949                 }
 950
 951                 return false;
 952         }
 953
 954         /**
 955          * Get the message page name for a given language
 956          *
 957          * @param string $langcode
 958          * @param string $uckey Uppercase key for the message
 959          * @return string The page name
 960          */
 961         private function getMessagePageName( $langcode, $uckey ) {
 962                 global $wgLanguageCode;
 963
 964                 if ( $langcode === $wgLanguageCode ) {
 965                         // Messages created in the content language will not have the /lang extension
 966                         return $uckey;
 967                 } else {
 968                         return "$uckey/$langcode";
 969                 }
 970         }
 971
 972         /**
 973          * Get a message from the MediaWiki namespace, with caching. The key must
 974          * first be converted to two-part lang/msg form if necessary.
 975          *
 976          * Unlike self::get(), this function doesn't resolve fallback chains, and
 977          * some callers require this behavior. LanguageConverter::parseCachedTable()
 978          * and self::get() are some examples in core.
 979          *
 980          * @param string $title Message cache key with initial uppercase letter
 981          * @param string $code Code denoting the language to try
 982          * @return string|bool The message, or false if it does not exist or on error
 983          */
 984         public function getMsgFromNamespace( $title, $code ) {
 985                 $this->load( $code );
 986
 987                 if ( isset( $this->mCache[$code][$title] ) ) {
 988                         $entry = $this->mCache[$code][$title];
 989                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 990                                 // The message exists, so make sure a string is returned.
 991                                 return (string)substr( $entry, 1 );
 992                         } elseif ( $entry === '!NONEXISTENT' ) {
 993                                 return false;
 994                         } elseif ( $entry === '!TOO BIG' ) {
 995                                 // Fall through and try invididual message cache below
 996                         }
 997                 } else {
 998                         // XXX: This is not cached in process cache, should it?
 999                         $message = false;
1000                         Hooks::run( 'MessagesPreLoad', [ $title, &$message, $code ] );
1001                         if ( $message !== false ) {
1002                                 return $message;
1003                         }
1004
1005                         return false;
1006                 }
1007
1008                 // Individual message cache key
1009                 $titleKey = $this->bigMessageCacheKey( $this->mCache[$code]['HASH'], $title );
1010
1011                 if ( $this->mCacheVolatile[$code] ) {
1012                         $entry = false;
1013                         // Make sure that individual keys respect the WAN cache holdoff period too
1014                         LoggerFactory::getInstance( 'MessageCache' )->debug(
1015                                 __METHOD__ . ': loading volatile key \'{titleKey}\'',
1016                                 [ 'titleKey' => $titleKey, 'code' => $code ] );
1017                 } else {
1018                         // Try the individual message cache
1019                         $entry = $this->wanCache->get( $titleKey );
1020                 }
1021
1022                 if ( $entry !== false ) {
1023                         if ( substr( $entry, 0, 1 ) === ' ' ) {
1024                                 $this->mCache[$code][$title] = $entry;
1025                                 // The message exists, so make sure a string is returned
1026                                 return (string)substr( $entry, 1 );
1027                         } elseif ( $entry === '!NONEXISTENT' ) {
1028                                 $this->mCache[$code][$title] = '!NONEXISTENT';
1029
1030                                 return false;
1031                         } else {
1032                                 // Corrupt/obsolete entry, delete it
1033                                 $this->wanCache->delete( $titleKey );
1034                         }
1035                 }
1036
1037                 // Try loading the message from the database
1038                 $dbr = wfGetDB( DB_REPLICA );
1039                 $cacheOpts = Database::getCacheSetOptions( $dbr );
1040                 // Use newKnownCurrent() to avoid querying revision/user tables
1041                 $titleObj = Title::makeTitle( NS_MEDIAWIKI, $title );
1042                 if ( $titleObj->getLatestRevID() ) {
1043                         $revision = Revision::newKnownCurrent(
1044                                 $dbr,
1045                                 $titleObj
1046                         );
1047                 } else {
1048                         $revision = false;
1049                 }
1050
1051                 if ( $revision ) {
1052                         $content = $revision->getContent();
1053                         if ( $content ) {
1054                                 $message = $this->getMessageTextFromContent( $content );
1055                                 if ( is_string( $message ) ) {
1056                                         $this->mCache[$code][$title] = ' ' . $message;
1057                                         $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry, $cacheOpts );
1058                                 }
1059                         } else {
1060                                 // A possibly temporary loading failure
1061                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1062                                         __METHOD__ . ': failed to load message page text for \'{titleKey}\'',
1063                                         [ 'titleKey' => $titleKey, 'code' => $code ] );
1064                                 $message = null; // no negative caching
1065                         }
1066                 } else {
1067                         $message = false; // negative caching
1068                 }
1069
1070                 if ( $message === false ) {
1071                         // Negative caching in case a "too big" message is no longer available (deleted)
1072                         $this->mCache[$code][$title] = '!NONEXISTENT';
1073                         $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry, $cacheOpts );
1074                 }
1075
1076                 return $message;
1077         }
1078
1079         /**
1080          * @param string $message
1081          * @param bool $interface
1082          * @param string $language Language code
1083          * @param Title $title
1084          * @return string
1085          */
1086         function transform( $message, $interface = false, $language = null, $title = null ) {
1087                 // Avoid creating parser if nothing to transform
1088                 if ( strpos( $message, '{{' ) === false ) {
1089                         return $message;
1090                 }
1091
1092                 if ( $this->mInParser ) {
1093                         return $message;
1094                 }
1095
1096                 $parser = $this->getParser();
1097                 if ( $parser ) {
1098                         $popts = $this->getParserOptions();
1099                         $popts->setInterfaceMessage( $interface );
1100                         $popts->setTargetLanguage( $language );
1101
1102                         $userlang = $popts->setUserLang( $language );
1103                         $this->mInParser = true;
1104                         $message = $parser->transformMsg( $message, $popts, $title );
1105                         $this->mInParser = false;
1106                         $popts->setUserLang( $userlang );
1107                 }
1108
1109                 return $message;
1110         }
1111
1112         /**
1113          * @return Parser
1114          */
1115         function getParser() {
1116                 global $wgParser, $wgParserConf;
1117
1118                 if ( !$this->mParser && isset( $wgParser ) ) {
1119                         # Do some initialisation so that we don't have to do it twice
1120                         $wgParser->firstCallInit();
1121                         # Clone it and store it
1122                         $class = $wgParserConf['class'];
1123                         if ( $class == ParserDiffTest::class ) {
1124                                 # Uncloneable
1125                                 $this->mParser = new $class( $wgParserConf );
1126                         } else {
1127                                 $this->mParser = clone $wgParser;
1128                         }
1129                 }
1130
1131                 return $this->mParser;
1132         }
1133
1134         /**
1135          * @param string $text
1136          * @param Title $title
1137          * @param bool $linestart Whether or not this is at the start of a line
1138          * @param bool $interface Whether this is an interface message
1139          * @param Language|string $language Language code
1140          * @return ParserOutput|string
1141          */
1142         public function parse( $text, $title = null, $linestart = true,
1143                 $interface = false, $language = null
1144         ) {
1145                 global $wgTitle;
1146
1147                 if ( $this->mInParser ) {
1148                         return htmlspecialchars( $text );
1149                 }
1150
1151                 $parser = $this->getParser();
1152                 $popts = $this->getParserOptions();
1153                 $popts->setInterfaceMessage( $interface );
1154
1155                 if ( is_string( $language ) ) {
1156                         $language = Language::factory( $language );
1157                 }
1158                 $popts->setTargetLanguage( $language );
1159
1160                 if ( !$title || !$title instanceof Title ) {
1161                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1162                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1163                         $title = $wgTitle;
1164                 }
1165                 // Sometimes $wgTitle isn't set either...
1166                 if ( !$title ) {
1167                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1168                         # Create a ghost title in such case
1169                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1170                 }
1171
1172                 $this->mInParser = true;
1173                 $res = $parser->parse( $text, $title, $popts, $linestart );
1174                 $this->mInParser = false;
1175
1176                 return $res;
1177         }
1178
1179         function disable() {
1180                 $this->mDisable = true;
1181         }
1182
1183         function enable() {
1184                 $this->mDisable = false;
1185         }
1186
1187         /**
1188          * Whether DB/cache usage is disabled for determining messages
1189          *
1190          * If so, this typically indicates either:
1191          *   - a) load() failed to find a cached copy nor query the DB
1192          *   - b) we are in a special context or error mode that cannot use the DB
1193          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1194          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1195          *
1196          * @return bool
1197          * @since 1.27
1198          */
1199         public function isDisabled() {
1200                 return $this->mDisable;
1201         }
1202
1203         /**
1204          * Clear all stored messages. Mainly used after a mass rebuild.
1205          */
1206         function clear() {
1207                 $langs = Language::fetchLanguageNames( null, 'mw' );
1208                 foreach ( array_keys( $langs ) as $code ) {
1209                         # Global and local caches
1210                         $this->wanCache->touchCheckKey( $this->wanCache->makeKey( 'messages', $code ) );
1211                 }
1212
1213                 $this->mLoadedLanguages = [];
1214         }
1215
1216         /**
1217          * @param string $key
1218          * @return array
1219          */
1220         public function figureMessage( $key ) {
1221                 global $wgLanguageCode;
1222
1223                 $pieces = explode( '/', $key );
1224                 if ( count( $pieces ) < 2 ) {
1225                         return [ $key, $wgLanguageCode ];
1226                 }
1227
1228                 $lang = array_pop( $pieces );
1229                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1230                         return [ $key, $wgLanguageCode ];
1231                 }
1232
1233                 $message = implode( '/', $pieces );
1234
1235                 return [ $message, $lang ];
1236         }
1237
1238         /**
1239          * Get all message keys stored in the message cache for a given language.
1240          * If $code is the content language code, this will return all message keys
1241          * for which MediaWiki:msgkey exists. If $code is another language code, this
1242          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1243          * @param string $code Language code
1244          * @return array Array of message keys (strings)
1245          */
1246         public function getAllMessageKeys( $code ) {
1247                 global $wgContLang;
1248
1249                 $this->load( $code );
1250                 if ( !isset( $this->mCache[$code] ) ) {
1251                         // Apparently load() failed
1252                         return null;
1253                 }
1254                 // Remove administrative keys
1255                 $cache = $this->mCache[$code];
1256                 unset( $cache['VERSION'] );
1257                 unset( $cache['EXPIRY'] );
1258                 unset( $cache['EXCESSIVE'] );
1259                 // Remove any !NONEXISTENT keys
1260                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1261
1262                 // Keys may appear with a capital first letter. lcfirst them.
1263                 return array_map( [ $wgContLang, 'lcfirst' ], array_keys( $cache ) );
1264         }
1265
1266         /**
1267          * Purge message caches when a MediaWiki: page is created, updated, or deleted
1268          *
1269          * @param Title $title Message page title
1270          * @param Content|null $content New content for edit/create, null on deletion
1271          * @since 1.29
1272          */
1273         public function updateMessageOverride( Title $title, Content $content = null ) {
1274                 global $wgContLang;
1275
1276                 $msgText = $this->getMessageTextFromContent( $content );
1277                 if ( $msgText === null ) {
1278                         $msgText = false; // treat as not existing
1279                 }
1280
1281                 $this->replace( $title->getDBkey(), $msgText );
1282
1283                 if ( $wgContLang->hasVariants() ) {
1284                         $wgContLang->updateConversionTable( $title );
1285                 }
1286         }
1287
1288         /**
1289          * @param Content|null $content Content or null if the message page does not exist
1290          * @return string|bool|null Returns false if $content is null and null on error
1291          */
1292         private function getMessageTextFromContent( Content $content = null ) {
1293                 // @TODO: could skip pseudo-messages like js/css here, based on content model
1294                 if ( $content ) {
1295                         // Message page exists...
1296                         // XXX: Is this the right way to turn a Content object into a message?
1297                         // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1298                         //       CssContent. MessageContent is *not* used for storing messages, it's
1299                         //       only used for wrapping them when needed.
1300                         $msgText = $content->getWikitextForTransclusion();
1301                         if ( $msgText === false || $msgText === null ) {
1302                                 // This might be due to some kind of misconfiguration...
1303                                 $msgText = null;
1304                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1305                                         __METHOD__ . ": message content doesn't provide wikitext "
1306                                         . "(content model: " . $content->getModel() . ")" );
1307                         }
1308                 } else {
1309                         // Message page does not exist...
1310                         $msgText = false;
1311                 }
1312
1313                 return $msgText;
1314         }
1315
1316         /**
1317          * @param string $hash Hash for this version of the entire key/value overrides map
1318          * @param string $title Message cache key with initial uppercase letter
1319          * @return string
1320          */
1321         private function bigMessageCacheKey( $hash, $title ) {
1322                 return $this->wanCache->makeKey( 'messages-big', $hash, $title );
1323         }
1324 }