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
  25 /**
  26  * MediaWiki message cache structure version.
  27  * Bump this whenever the message cache format has changed.
  28  */
  29 define( 'MSG_CACHE_VERSION', 2 );
  30
  31 /**
  32  * Message cache
  33  * Performs various MediaWiki namespace-related functions
  34  * @ingroup Cache
  35  */
  36 class MessageCache {
  37         const FOR_UPDATE = 1; // force message reload
  38
  39         /** How long to wait for memcached locks */
  40         const WAIT_SEC = 15;
  41         /** How long memcached locks last */
  42         const LOCK_TTL = 30;
  43
  44         /**
  45          * Process local cache of loaded messages that are defined in
  46          * MediaWiki namespace. First array level is a language code,
  47          * second level is message key and the values are either message
  48          * content prefixed with space, or !NONEXISTENT for negative
  49          * caching.
  50          * @var array $mCache
  51          */
  52         protected $mCache;
  53
  54         /**
  55          * Should mean that database cannot be used, but check
  56          * @var bool $mDisable
  57          */
  58         protected $mDisable;
  59
  60         /**
  61          * Lifetime for cache, used by object caching.
  62          * Set on construction, see __construct().
  63          */
  64         protected $mExpiry;
  65
  66         /**
  67          * Message cache has its own parser which it uses to transform
  68          * messages.
  69          */
  70         protected $mParserOptions, $mParser;
  71
  72         /**
  73          * Variable for tracking which variables are already loaded
  74          * @var array $mLoadedLanguages
  75          */
  76         protected $mLoadedLanguages = [];
  77
  78         /**
  79          * @var bool $mInParser
  80          */
  81         protected $mInParser = false;
  82
  83         /** @var BagOStuff */
  84         protected $mMemc;
  85         /** @var WANObjectCache */
  86         protected $wanCache;
  87
  88         /**
  89          * Singleton instance
  90          *
  91          * @var MessageCache $instance
  92          */
  93         private static $instance;
  94
  95         /**
  96          * Get the signleton instance of this class
  97          *
  98          * @since 1.18
  99          * @return MessageCache
 100          */
 101         public static function singleton() {
 102                 if ( self::$instance === null ) {
 103                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
 104                         self::$instance = new self(
 105                                 wfGetMessageCacheStorage(),
 106                                 $wgUseDatabaseMessages,
 107                                 $wgMsgCacheExpiry
 108                         );
 109                 }
 110
 111                 return self::$instance;
 112         }
 113
 114         /**
 115          * Destroy the singleton instance
 116          *
 117          * @since 1.18
 118          */
 119         public static function destroyInstance() {
 120                 self::$instance = null;
 121         }
 122
 123         /**
 124          * Normalize message key input
 125          *
 126          * @param string $key Input message key to be normalized
 127          * @return string Normalized message key
 128          */
 129         public static function normalizeKey( $key ) {
 130                 global $wgContLang;
 131                 $lckey = strtr( $key, ' ', '_' );
 132                 if ( ord( $lckey ) < 128 ) {
 133                         $lckey[0] = strtolower( $lckey[0] );
 134                 } else {
 135                         $lckey = $wgContLang->lcfirst( $lckey );
 136                 }
 137
 138                 return $lckey;
 139         }
 140
 141         /**
 142          * @param BagOStuff $memCached A cache instance. If none, fall back to CACHE_NONE.
 143          * @param bool $useDB
 144          * @param int $expiry Lifetime for cache. @see $mExpiry.
 145          */
 146         function __construct( $memCached, $useDB, $expiry ) {
 147                 global $wgUseLocalMessageCache;
 148
 149                 if ( !$memCached ) {
 150                         $memCached = wfGetCache( CACHE_NONE );
 151                 }
 152
 153                 $this->mMemc = $memCached;
 154                 $this->mDisable = !$useDB;
 155                 $this->mExpiry = $expiry;
 156
 157                 if ( $wgUseLocalMessageCache ) {
 158                         $this->localCache = MediaWikiServices::getInstance()->getLocalServerObjectCache();
 159                 } else {
 160                         $this->localCache = new EmptyBagOStuff();
 161                 }
 162
 163                 $this->wanCache = ObjectCache::getMainWANInstance();
 164         }
 165
 166         /**
 167          * ParserOptions is lazy initialised.
 168          *
 169          * @return ParserOptions
 170          */
 171         function getParserOptions() {
 172                 global $wgUser;
 173
 174                 if ( !$this->mParserOptions ) {
 175                         if ( !$wgUser->isSafeToLoad() ) {
 176                                 // $wgUser isn't unstubbable yet, so don't try to get a
 177                                 // ParserOptions for it. And don't cache this ParserOptions
 178                                 // either.
 179                                 $po = ParserOptions::newFromAnon();
 180                                 $po->setEditSection( false );
 181                                 return $po;
 182                         }
 183
 184                         $this->mParserOptions = new ParserOptions;
 185                         $this->mParserOptions->setEditSection( false );
 186                 }
 187
 188                 return $this->mParserOptions;
 189         }
 190
 191         /**
 192          * Try to load the cache from APC.
 193          *
 194          * @param string $code Optional language code, see documenation of load().
 195          * @return array|bool The cache array, or false if not in cache.
 196          */
 197         protected function getLocalCache( $code ) {
 198                 $cacheKey = wfMemcKey( __CLASS__, $code );
 199
 200                 return $this->localCache->get( $cacheKey );
 201         }
 202
 203         /**
 204          * Save the cache to APC.
 205          *
 206          * @param string $code
 207          * @param array $cache The cache array
 208          */
 209         protected function saveToLocalCache( $code, $cache ) {
 210                 $cacheKey = wfMemcKey( __CLASS__, $code );
 211                 $this->localCache->set( $cacheKey, $cache );
 212         }
 213
 214         /**
 215          * Loads messages from caches or from database in this order:
 216          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 217          * (2) memcached
 218          * (3) from the database.
 219          *
 220          * When succesfully loading from (2) or (3), all higher level caches are
 221          * updated for the newest version.
 222          *
 223          * Nothing is loaded if member variable mDisable is true, either manually
 224          * set by calling code or if message loading fails (is this possible?).
 225          *
 226          * Returns true if cache is already populated or it was succesfully populated,
 227          * or false if populating empty cache fails. Also returns true if MessageCache
 228          * is disabled.
 229          *
 230          * @param bool|string $code Language to which load messages
 231          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 232          * @throws MWException
 233          * @return bool
 234          */
 235         function load( $code = false, $mode = null ) {
 236                 if ( !is_string( $code ) ) {
 237                         # This isn't really nice, so at least make a note about it and try to
 238                         # fall back
 239                         wfDebug( __METHOD__ . " called without providing a language code\n" );
 240                         $code = 'en';
 241                 }
 242
 243                 # Don't do double loading...
 244                 if ( isset( $this->mLoadedLanguages[$code] ) && $mode != self::FOR_UPDATE ) {
 245                         return true;
 246                 }
 247
 248                 # 8 lines of code just to say (once) that message cache is disabled
 249                 if ( $this->mDisable ) {
 250                         static $shownDisabled = false;
 251                         if ( !$shownDisabled ) {
 252                                 wfDebug( __METHOD__ . ": disabled\n" );
 253                                 $shownDisabled = true;
 254                         }
 255
 256                         return true;
 257                 }
 258
 259                 # Loading code starts
 260                 $success = false; # Keep track of success
 261                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 262                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 263
 264                 # Hash of the contents is stored in memcache, to detect if data-center cache
 265                 # or local cache goes out of date (e.g. due to replace() on some other server)
 266                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 267
 268                 # Try the local cache and check against the cluster hash key...
 269                 $cache = $this->getLocalCache( $code );
 270                 if ( !$cache ) {
 271                         $where[] = 'local cache is empty';
 272                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 273                         $where[] = 'local cache has the wrong hash';
 274                         $staleCache = $cache;
 275                 } elseif ( $this->isCacheExpired( $cache ) ) {
 276                         $where[] = 'local cache is expired';
 277                         $staleCache = $cache;
 278                 } elseif ( $hashVolatile ) {
 279                         $where[] = 'local cache validation key is expired/volatile';
 280                         $staleCache = $cache;
 281                 } else {
 282                         $where[] = 'got from local cache';
 283                         $success = true;
 284                         $this->mCache[$code] = $cache;
 285                 }
 286
 287                 if ( !$success ) {
 288                         $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 289                         # Try the global cache. If it is empty, try to acquire a lock. If
 290                         # the lock can't be acquired, wait for the other thread to finish
 291                         # and then try the global cache a second time.
 292                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 293                                 if ( $hashVolatile && $staleCache ) {
 294                                         # Do not bother fetching the whole cache blob to avoid I/O.
 295                                         # Instead, just try to get the non-blocking $statusKey lock
 296                                         # below, and use the local stale value if it was not acquired.
 297                                         $where[] = 'global cache is presumed expired';
 298                                 } else {
 299                                         $cache = $this->mMemc->get( $cacheKey );
 300                                         if ( !$cache ) {
 301                                                 $where[] = 'global cache is empty';
 302                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 303                                                 $where[] = 'global cache is expired';
 304                                                 $staleCache = $cache;
 305                                         } elseif ( $hashVolatile ) {
 306                                                 # DB results are replica DB lag prone until the holdoff TTL passes.
 307                                                 # By then, updates should be reflected in loadFromDBWithLock().
 308                                                 # One thread renerates the cache while others use old values.
 309                                                 $where[] = 'global cache is expired/volatile';
 310                                                 $staleCache = $cache;
 311                                         } else {
 312                                                 $where[] = 'got from global cache';
 313                                                 $this->mCache[$code] = $cache;
 314                                                 $this->saveToCaches( $cache, 'local-only', $code );
 315                                                 $success = true;
 316                                         }
 317                                 }
 318
 319                                 if ( $success ) {
 320                                         # Done, no need to retry
 321                                         break;
 322                                 }
 323
 324                                 # We need to call loadFromDB. Limit the concurrency to one process.
 325                                 # This prevents the site from going down when the cache expires.
 326                                 # Note that the DB slam protection lock here is non-blocking.
 327                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 328                                 if ( $loadStatus === true ) {
 329                                         $success = true;
 330                                         break;
 331                                 } elseif ( $staleCache ) {
 332                                         # Use the stale cache while some other thread constructs the new one
 333                                         $where[] = 'using stale cache';
 334                                         $this->mCache[$code] = $staleCache;
 335                                         $success = true;
 336                                         break;
 337                                 } elseif ( $failedAttempts > 0 ) {
 338                                         # Already blocked once, so avoid another lock/unlock cycle.
 339                                         # This case will typically be hit if memcached is down, or if
 340                                         # loadFromDB() takes longer than LOCK_WAIT.
 341                                         $where[] = "could not acquire status key.";
 342                                         break;
 343                                 } elseif ( $loadStatus === 'cantacquire' ) {
 344                                         # Wait for the other thread to finish, then retry. Normally,
 345                                         # the memcached get() will then yeild the other thread's result.
 346                                         $where[] = 'waited for other thread to complete';
 347                                         $this->getReentrantScopedLock( $cacheKey );
 348                                 } else {
 349                                         # Disable cache; $loadStatus is 'disabled'
 350                                         break;
 351                                 }
 352                         }
 353                 }
 354
 355                 if ( !$success ) {
 356                         $where[] = 'loading FAILED - cache is disabled';
 357                         $this->mDisable = true;
 358                         $this->mCache = false;
 359                         wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
 360                         # This used to throw an exception, but that led to nasty side effects like
 361                         # the whole wiki being instantly down if the memcached server died
 362                 } else {
 363                         # All good, just record the success
 364                         $this->mLoadedLanguages[$code] = true;
 365                 }
 366
 367                 $info = implode( ', ', $where );
 368                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 369
 370                 return $success;
 371         }
 372
 373         /**
 374          * @param string $code
 375          * @param array $where List of wfDebug() comments
 376          * @param integer $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 377          * @return bool|string True on success or one of ("cantacquire", "disabled")
 378          */
 379         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 380                 global $wgUseLocalMessageCache;
 381
 382                 # If cache updates on all levels fail, give up on message overrides.
 383                 # This is to avoid easy site outages; see $saveSuccess comments below.
 384                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 385                 $status = $this->mMemc->get( $statusKey );
 386                 if ( $status === 'error' ) {
 387                         $where[] = "could not load; method is still globally disabled";
 388                         return 'disabled';
 389                 }
 390
 391                 # Now let's regenerate
 392                 $where[] = 'loading from database';
 393
 394                 # Lock the cache to prevent conflicting writes.
 395                 # This lock is non-blocking so stale cache can quickly be used.
 396                 # Note that load() will call a blocking getReentrantScopedLock()
 397                 # after this if it really need to wait for any current thread.
 398                 $cacheKey = wfMemcKey( 'messages', $code );
 399                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 400                 if ( !$scopedLock ) {
 401                         $where[] = 'could not acquire main lock';
 402                         return 'cantacquire';
 403                 }
 404
 405                 $cache = $this->loadFromDB( $code, $mode );
 406                 $this->mCache[$code] = $cache;
 407                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 408
 409                 if ( !$saveSuccess ) {
 410                         /**
 411                          * Cache save has failed.
 412                          *
 413                          * There are two main scenarios where this could be a problem:
 414                          * - The cache is more than the maximum size (typically 1MB compressed).
 415                          * - Memcached has no space remaining in the relevant slab class. This is
 416                          *   unlikely with recent versions of memcached.
 417                          *
 418                          * Either way, if there is a local cache, nothing bad will happen. If there
 419                          * is no local cache, disabling the message cache for all requests avoids
 420                          * incurring a loadFromDB() overhead on every request, and thus saves the
 421                          * wiki from complete downtime under moderate traffic conditions.
 422                          */
 423                         if ( !$wgUseLocalMessageCache ) {
 424                                 $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 425                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 426                         } else {
 427                                 $where[] = "could not save global cache";
 428                         }
 429                 }
 430
 431                 return true;
 432         }
 433
 434         /**
 435          * Loads cacheable messages from the database. Messages bigger than
 436          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 437          * on-demand from the database later.
 438          *
 439          * @param string $code Language code
 440          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 441          * @return array Loaded messages for storing in caches
 442          */
 443         function loadFromDB( $code, $mode = null ) {
 444                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 445
 446                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA );
 447
 448                 $cache = [];
 449
 450                 # Common conditions
 451                 $conds = [
 452                         'page_is_redirect' => 0,
 453                         'page_namespace' => NS_MEDIAWIKI,
 454                 ];
 455
 456                 $mostused = [];
 457                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 458                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 459                                 $this->load( $wgLanguageCode );
 460                         }
 461                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 462                         foreach ( $mostused as $key => $value ) {
 463                                 $mostused[$key] = "$value/$code";
 464                         }
 465                 }
 466
 467                 if ( count( $mostused ) ) {
 468                         $conds['page_title'] = $mostused;
 469                 } elseif ( $code !== $wgLanguageCode ) {
 470                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 471                 } else {
 472                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 473                         # other than language code.
 474                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 475                 }
 476
 477                 # Conditions to fetch oversized pages to ignore them
 478                 $bigConds = $conds;
 479                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 480
 481                 # Load titles for all oversized pages in the MediaWiki namespace
 482                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 483                 foreach ( $res as $row ) {
 484                         $cache[$row->page_title] = '!TOO BIG';
 485                 }
 486
 487                 # Conditions to load the remaining pages with their contents
 488                 $smallConds = $conds;
 489                 $smallConds[] = 'page_latest=rev_id';
 490                 $smallConds[] = 'rev_text_id=old_id';
 491                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 492
 493                 $res = $dbr->select(
 494                         [ 'page', 'revision', 'text' ],
 495                         [ 'page_title', 'old_text', 'old_flags' ],
 496                         $smallConds,
 497                         __METHOD__ . "($code)-small"
 498                 );
 499
 500                 foreach ( $res as $row ) {
 501                         $text = Revision::getRevisionText( $row );
 502                         if ( $text === false ) {
 503                                 // Failed to fetch data; possible ES errors?
 504                                 // Store a marker to fetch on-demand as a workaround...
 505                                 $entry = '!TOO BIG';
 506                                 wfDebugLog(
 507                                         'MessageCache',
 508                                         __METHOD__
 509                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 510                                 );
 511                         } else {
 512                                 $entry = ' ' . $text;
 513                         }
 514                         $cache[$row->page_title] = $entry;
 515                 }
 516
 517                 $cache['VERSION'] = MSG_CACHE_VERSION;
 518                 ksort( $cache );
 519                 $cache['HASH'] = md5( serialize( $cache ) );
 520                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 521
 522                 return $cache;
 523         }
 524
 525         /**
 526          * Updates cache as necessary when message page is changed
 527          *
 528          * @param string|bool $title Name of the page changed (false if deleted)
 529          * @param mixed $text New contents of the page.
 530          */
 531         public function replace( $title, $text ) {
 532                 global $wgMaxMsgCacheEntrySize, $wgContLang, $wgLanguageCode;
 533
 534                 if ( $this->mDisable ) {
 535                         return;
 536                 }
 537
 538                 list( $msg, $code ) = $this->figureMessage( $title );
 539                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 540                         // Content language overrides do not use the /<code> suffix
 541                         return;
 542                 }
 543
 544                 // Note that if the cache is volatile, load() may trigger a DB fetch.
 545                 // In that case we reenter/reuse the existing cache key lock to avoid
 546                 // a self-deadlock. This is safe as no reads happen *directly* in this
 547                 // method between getReentrantScopedLock() and load() below. There is
 548                 // no risk of data "changing under our feet" for replace().
 549                 $cacheKey = wfMemcKey( 'messages', $code );
 550                 $scopedLock = $this->getReentrantScopedLock( $cacheKey );
 551                 $this->load( $code, self::FOR_UPDATE );
 552
 553                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 554                 if ( $text === false ) {
 555                         // Article was deleted
 556                         $this->mCache[$code][$title] = '!NONEXISTENT';
 557                         $this->wanCache->delete( $titleKey );
 558                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 559                         // Check for size
 560                         $this->mCache[$code][$title] = '!TOO BIG';
 561                         $this->wanCache->set( $titleKey, ' ' . $text, $this->mExpiry );
 562                 } else {
 563                         $this->mCache[$code][$title] = ' ' . $text;
 564                         $this->wanCache->delete( $titleKey );
 565                 }
 566
 567                 // Mark this cache as definitely "latest" (non-volatile) so
 568                 // load() calls do try to refresh the cache with replica DB data
 569                 $this->mCache[$code]['LATEST'] = time();
 570
 571                 // Update caches if the lock was acquired
 572                 if ( $scopedLock ) {
 573                         $this->saveToCaches( $this->mCache[$code], 'all', $code );
 574                 }
 575
 576                 ScopedCallback::consume( $scopedLock );
 577                 // Relay the purge to APC and other DCs
 578                 $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
 579
 580                 // Also delete cached sidebar... just in case it is affected
 581                 $codes = [ $code ];
 582                 if ( $code === 'en' ) {
 583                         // Delete all sidebars, like for example on action=purge on the
 584                         // sidebar messages
 585                         $codes = array_keys( Language::fetchLanguageNames() );
 586                 }
 587
 588                 foreach ( $codes as $code ) {
 589                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 590                         $this->wanCache->delete( $sidebarKey );
 591                 }
 592
 593                 // Update the message in the message blob store
 594                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 595                 $blobStore = $resourceloader->getMessageBlobStore();
 596                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 597
 598                 Hooks::run( 'MessageCacheReplace', [ $title, $text ] );
 599         }
 600
 601         /**
 602          * Is the given cache array expired due to time passing or a version change?
 603          *
 604          * @param array $cache
 605          * @return bool
 606          */
 607         protected function isCacheExpired( $cache ) {
 608                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 609                         return true;
 610                 }
 611                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 612                         return true;
 613                 }
 614                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 615                         return true;
 616                 }
 617
 618                 return false;
 619         }
 620
 621         /**
 622          * Shortcut to update caches.
 623          *
 624          * @param array $cache Cached messages with a version.
 625          * @param string $dest Either "local-only" to save to local caches only
 626          *   or "all" to save to all caches.
 627          * @param string|bool $code Language code (default: false)
 628          * @return bool
 629          */
 630         protected function saveToCaches( array $cache, $dest, $code = false ) {
 631                 if ( $dest === 'all' ) {
 632                         $cacheKey = wfMemcKey( 'messages', $code );
 633                         $success = $this->mMemc->set( $cacheKey, $cache );
 634                 } else {
 635                         $success = true;
 636                 }
 637
 638                 $this->setValidationHash( $code, $cache );
 639                 $this->saveToLocalCache( $code, $cache );
 640
 641                 return $success;
 642         }
 643
 644         /**
 645          * Get the md5 used to validate the local APC cache
 646          *
 647          * @param string $code
 648          * @return array (hash or false, bool expiry/volatility status)
 649          */
 650         protected function getValidationHash( $code ) {
 651                 $curTTL = null;
 652                 $value = $this->wanCache->get(
 653                         wfMemcKey( 'messages', $code, 'hash', 'v1' ),
 654                         $curTTL,
 655                         [ wfMemcKey( 'messages', $code ) ]
 656                 );
 657
 658                 if ( !$value ) {
 659                         // No hash found at all; cache must regenerate to be safe
 660                         $hash = false;
 661                         $expired = true;
 662                 } else {
 663                         $hash = $value['hash'];
 664                         if ( ( time() - $value['latest'] ) < WANObjectCache::HOLDOFF_TTL ) {
 665                                 // Cache was recently updated via replace() and should be up-to-date
 666                                 $expired = false;
 667                         } else {
 668                                 // See if the "check" key was bumped after the hash was generated
 669                                 $expired = ( $curTTL < 0 );
 670                         }
 671                 }
 672
 673                 return [ $hash, $expired ];
 674         }
 675
 676         /**
 677          * Set the md5 used to validate the local disk cache
 678          *
 679          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 680          * be treated as "volatile" by getValidationHash() for the next few seconds
 681          *
 682          * @param string $code
 683          * @param array $cache Cached messages with a version
 684          */
 685         protected function setValidationHash( $code, array $cache ) {
 686                 $this->wanCache->set(
 687                         wfMemcKey( 'messages', $code, 'hash', 'v1' ),
 688                         [
 689                                 'hash' => $cache['HASH'],
 690                                 'latest' => isset( $cache['LATEST'] ) ? $cache['LATEST'] : 0
 691                         ],
 692                         WANObjectCache::TTL_INDEFINITE
 693                 );
 694         }
 695
 696         /**
 697          * @param string $key A language message cache key that stores blobs
 698          * @param integer $timeout Wait timeout in seconds
 699          * @return null|ScopedCallback
 700          */
 701         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 702                 return $this->mMemc->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 703         }
 704
 705         /**
 706          * Get a message from either the content language or the user language.
 707          *
 708          * First, assemble a list of languages to attempt getting the message from. This
 709          * chain begins with the requested language and its fallbacks and then continues with
 710          * the content language and its fallbacks. For each language in the chain, the following
 711          * process will occur (in this order):
 712          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 713          *     Note: for the content language, there is no /lang subpage.
 714          *  2. Fetch from the static CDB cache.
 715          *  3. If available, check the database for fallback language overrides.
 716          *
 717          * This process provides a number of guarantees. When changing this code, make sure all
 718          * of these guarantees are preserved.
 719          *  * If the requested language is *not* the content language, then the CDB cache for that
 720          *    specific language will take precedence over the root database page ([[MW:msg]]).
 721          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 722          *    the message is available *anywhere* in the language for which it is a fallback.
 723          *
 724          * @param string $key The message key
 725          * @param bool $useDB If true, look for the message in the DB, false
 726          *   to use only the compiled l10n cache.
 727          * @param bool|string|object $langcode Code of the language to get the message for.
 728          *   - If string and a valid code, will create a standard language object
 729          *   - If string but not a valid code, will create a basic language object
 730          *   - If boolean and false, create object from the current users language
 731          *   - If boolean and true, create object from the wikis content language
 732          *   - If language object, use it as given
 733          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 734          *
 735          * @throws MWException When given an invalid key
 736          * @return string|bool False if the message doesn't exist, otherwise the
 737          *   message (which can be empty)
 738          */
 739         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 740                 if ( is_int( $key ) ) {
 741                         // Fix numerical strings that somehow become ints
 742                         // on their way here
 743                         $key = (string)$key;
 744                 } elseif ( !is_string( $key ) ) {
 745                         throw new MWException( 'Non-string key given' );
 746                 } elseif ( $key === '' ) {
 747                         // Shortcut: the empty key is always missing
 748                         return false;
 749                 }
 750
 751                 // For full keys, get the language code from the key
 752                 $pos = strrpos( $key, '/' );
 753                 if ( $isFullKey && $pos !== false ) {
 754                         $langcode = substr( $key, $pos + 1 );
 755                         $key = substr( $key, 0, $pos );
 756                 }
 757
 758                 // Normalise title-case input (with some inlining)
 759                 $lckey = MessageCache::normalizeKey( $key );
 760
 761                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 762
 763                 // Loop through each language in the fallback list until we find something useful
 764                 $lang = wfGetLangObj( $langcode );
 765                 $message = $this->getMessageFromFallbackChain(
 766                         $lang,
 767                         $lckey,
 768                         !$this->mDisable && $useDB
 769                 );
 770
 771                 // If we still have no message, maybe the key was in fact a full key so try that
 772                 if ( $message === false ) {
 773                         $parts = explode( '/', $lckey );
 774                         // We may get calls for things that are http-urls from sidebar
 775                         // Let's not load nonexistent languages for those
 776                         // They usually have more than one slash.
 777                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 778                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 779                                 if ( $message === null ) {
 780                                         $message = false;
 781                                 }
 782                         }
 783                 }
 784
 785                 // Post-processing if the message exists
 786                 if ( $message !== false ) {
 787                         // Fix whitespace
 788                         $message = str_replace(
 789                                 [
 790                                         # Fix for trailing whitespace, removed by textarea
 791                                         '&#32;',
 792                                         # Fix for NBSP, converted to space by firefox
 793                                         '&nbsp;',
 794                                         '&#160;',
 795                                         '&shy;'
 796                                 ],
 797                                 [
 798                                         ' ',
 799                                         "\xc2\xa0",
 800                                         "\xc2\xa0",
 801                                         "\xc2\xad"
 802                                 ],
 803                                 $message
 804                         );
 805                 }
 806
 807                 return $message;
 808         }
 809
 810         /**
 811          * Given a language, try and fetch messages from that language.
 812          *
 813          * Will also consider fallbacks of that language, the site language, and fallbacks for
 814          * the site language.
 815          *
 816          * @see MessageCache::get
 817          * @param Language|StubObject $lang Preferred language
 818          * @param string $lckey Lowercase key for the message (as for localisation cache)
 819          * @param bool $useDB Whether to include messages from the wiki database
 820          * @return string|bool The message, or false if not found
 821          */
 822         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 823                 global $wgContLang;
 824
 825                 $alreadyTried = [];
 826
 827                  // First try the requested language.
 828                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 829                 if ( $message !== false ) {
 830                         return $message;
 831                 }
 832
 833                 // Now try checking the site language.
 834                 $message = $this->getMessageForLang( $wgContLang, $lckey, $useDB, $alreadyTried );
 835                 return $message;
 836         }
 837
 838         /**
 839          * Given a language, try and fetch messages from that language and its fallbacks.
 840          *
 841          * @see MessageCache::get
 842          * @param Language|StubObject $lang Preferred language
 843          * @param string $lckey Lowercase key for the message (as for localisation cache)
 844          * @param bool $useDB Whether to include messages from the wiki database
 845          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 846          * @return string|bool The message, or false if not found
 847          */
 848         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 849                 global $wgContLang;
 850                 $langcode = $lang->getCode();
 851
 852                 // Try checking the database for the requested language
 853                 if ( $useDB ) {
 854                         $uckey = $wgContLang->ucfirst( $lckey );
 855
 856                         if ( !isset( $alreadyTried[ $langcode ] ) ) {
 857                                 $message = $this->getMsgFromNamespace(
 858                                         $this->getMessagePageName( $langcode, $uckey ),
 859                                         $langcode
 860                                 );
 861
 862                                 if ( $message !== false ) {
 863                                         return $message;
 864                                 }
 865                                 $alreadyTried[ $langcode ] = true;
 866                         }
 867                 }
 868
 869                 // Check the CDB cache
 870                 $message = $lang->getMessage( $lckey );
 871                 if ( $message !== null ) {
 872                         return $message;
 873                 }
 874
 875                 // Try checking the database for all of the fallback languages
 876                 if ( $useDB ) {
 877                         $fallbackChain = Language::getFallbacksFor( $langcode );
 878
 879                         foreach ( $fallbackChain as $code ) {
 880                                 if ( isset( $alreadyTried[ $code ] ) ) {
 881                                         continue;
 882                                 }
 883
 884                                 $message = $this->getMsgFromNamespace( $this->getMessagePageName( $code, $uckey ), $code );
 885
 886                                 if ( $message !== false ) {
 887                                         return $message;
 888                                 }
 889                                 $alreadyTried[ $code ] = true;
 890                         }
 891                 }
 892
 893                 return false;
 894         }
 895
 896         /**
 897          * Get the message page name for a given language
 898          *
 899          * @param string $langcode
 900          * @param string $uckey Uppercase key for the message
 901          * @return string The page name
 902          */
 903         private function getMessagePageName( $langcode, $uckey ) {
 904                 global $wgLanguageCode;
 905                 if ( $langcode === $wgLanguageCode ) {
 906                         // Messages created in the content language will not have the /lang extension
 907                         return $uckey;
 908                 } else {
 909                         return "$uckey/$langcode";
 910                 }
 911         }
 912
 913         /**
 914          * Get a message from the MediaWiki namespace, with caching. The key must
 915          * first be converted to two-part lang/msg form if necessary.
 916          *
 917          * Unlike self::get(), this function doesn't resolve fallback chains, and
 918          * some callers require this behavior. LanguageConverter::parseCachedTable()
 919          * and self::get() are some examples in core.
 920          *
 921          * @param string $title Message cache key with initial uppercase letter.
 922          * @param string $code Code denoting the language to try.
 923          * @return string|bool The message, or false if it does not exist or on error
 924          */
 925         public function getMsgFromNamespace( $title, $code ) {
 926                 $this->load( $code );
 927                 if ( isset( $this->mCache[$code][$title] ) ) {
 928                         $entry = $this->mCache[$code][$title];
 929                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 930                                 // The message exists, so make sure a string
 931                                 // is returned.
 932                                 return (string)substr( $entry, 1 );
 933                         } elseif ( $entry === '!NONEXISTENT' ) {
 934                                 return false;
 935                         } elseif ( $entry === '!TOO BIG' ) {
 936                                 // Fall through and try invididual message cache below
 937                         }
 938                 } else {
 939                         // XXX: This is not cached in process cache, should it?
 940                         $message = false;
 941                         Hooks::run( 'MessagesPreLoad', [ $title, &$message ] );
 942                         if ( $message !== false ) {
 943                                 return $message;
 944                         }
 945
 946                         return false;
 947                 }
 948
 949                 # Try the individual message cache
 950                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 951                 $entry = $this->wanCache->get( $titleKey );
 952                 if ( $entry ) {
 953                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 954                                 $this->mCache[$code][$title] = $entry;
 955
 956                                 // The message exists, so make sure a string
 957                                 // is returned.
 958                                 return (string)substr( $entry, 1 );
 959                         } elseif ( $entry === '!NONEXISTENT' ) {
 960                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 961
 962                                 return false;
 963                         } else {
 964                                 # Corrupt/obsolete entry, delete it
 965                                 $this->wanCache->delete( $titleKey );
 966                         }
 967                 }
 968
 969                 # Try loading it from the database
 970                 $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 971                 if ( $revision ) {
 972                         $content = $revision->getContent();
 973                         if ( !$content ) {
 974                                 // A possibly temporary loading failure.
 975                                 wfDebugLog(
 976                                         'MessageCache',
 977                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
 978                                 );
 979                                 $message = null; // no negative caching
 980                         } else {
 981                                 // XXX: Is this the right way to turn a Content object into a message?
 982                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
 983                                 //       CssContent. MessageContent is *not* used for storing messages, it's
 984                                 //       only used for wrapping them when needed.
 985                                 $message = $content->getWikitextForTransclusion();
 986
 987                                 if ( $message === false || $message === null ) {
 988                                         wfDebugLog(
 989                                                 'MessageCache',
 990                                                 __METHOD__ . ": message content doesn't provide wikitext "
 991                                                         . "(content model: " . $content->getModel() . ")"
 992                                         );
 993
 994                                         $message = false; // negative caching
 995                                 } else {
 996                                         $this->mCache[$code][$title] = ' ' . $message;
 997                                         $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry );
 998                                 }
 999                         }
1000                 } else {
1001                         $message = false; // negative caching
1002                 }
1003
1004                 if ( $message === false ) { // negative caching
1005                         $this->mCache[$code][$title] = '!NONEXISTENT';
1006                         $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
1007                 }
1008
1009                 return $message;
1010         }
1011
1012         /**
1013          * @param string $message
1014          * @param bool $interface
1015          * @param string $language Language code
1016          * @param Title $title
1017          * @return string
1018          */
1019         function transform( $message, $interface = false, $language = null, $title = null ) {
1020                 // Avoid creating parser if nothing to transform
1021                 if ( strpos( $message, '{{' ) === false ) {
1022                         return $message;
1023                 }
1024
1025                 if ( $this->mInParser ) {
1026                         return $message;
1027                 }
1028
1029                 $parser = $this->getParser();
1030                 if ( $parser ) {
1031                         $popts = $this->getParserOptions();
1032                         $popts->setInterfaceMessage( $interface );
1033                         $popts->setTargetLanguage( $language );
1034
1035                         $userlang = $popts->setUserLang( $language );
1036                         $this->mInParser = true;
1037                         $message = $parser->transformMsg( $message, $popts, $title );
1038                         $this->mInParser = false;
1039                         $popts->setUserLang( $userlang );
1040                 }
1041
1042                 return $message;
1043         }
1044
1045         /**
1046          * @return Parser
1047          */
1048         function getParser() {
1049                 global $wgParser, $wgParserConf;
1050                 if ( !$this->mParser && isset( $wgParser ) ) {
1051                         # Do some initialisation so that we don't have to do it twice
1052                         $wgParser->firstCallInit();
1053                         # Clone it and store it
1054                         $class = $wgParserConf['class'];
1055                         if ( $class == 'ParserDiffTest' ) {
1056                                 # Uncloneable
1057                                 $this->mParser = new $class( $wgParserConf );
1058                         } else {
1059                                 $this->mParser = clone $wgParser;
1060                         }
1061                 }
1062
1063                 return $this->mParser;
1064         }
1065
1066         /**
1067          * @param string $text
1068          * @param Title $title
1069          * @param bool $linestart Whether or not this is at the start of a line
1070          * @param bool $interface Whether this is an interface message
1071          * @param Language|string $language Language code
1072          * @return ParserOutput|string
1073          */
1074         public function parse( $text, $title = null, $linestart = true,
1075                 $interface = false, $language = null
1076         ) {
1077                 if ( $this->mInParser ) {
1078                         return htmlspecialchars( $text );
1079                 }
1080
1081                 $parser = $this->getParser();
1082                 $popts = $this->getParserOptions();
1083                 $popts->setInterfaceMessage( $interface );
1084
1085                 if ( is_string( $language ) ) {
1086                         $language = Language::factory( $language );
1087                 }
1088                 $popts->setTargetLanguage( $language );
1089
1090                 if ( !$title || !$title instanceof Title ) {
1091                         global $wgTitle;
1092                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1093                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1094                         $title = $wgTitle;
1095                 }
1096                 // Sometimes $wgTitle isn't set either...
1097                 if ( !$title ) {
1098                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1099                         # Create a ghost title in such case
1100                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1101                 }
1102
1103                 $this->mInParser = true;
1104                 $res = $parser->parse( $text, $title, $popts, $linestart );
1105                 $this->mInParser = false;
1106
1107                 return $res;
1108         }
1109
1110         function disable() {
1111                 $this->mDisable = true;
1112         }
1113
1114         function enable() {
1115                 $this->mDisable = false;
1116         }
1117
1118         /**
1119          * Whether DB/cache usage is disabled for determining messages
1120          *
1121          * If so, this typically indicates either:
1122          *   - a) load() failed to find a cached copy nor query the DB
1123          *   - b) we are in a special context or error mode that cannot use the DB
1124          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1125          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1126          *
1127          * @return bool
1128          * @since 1.27
1129          */
1130         public function isDisabled() {
1131                 return $this->mDisable;
1132         }
1133
1134         /**
1135          * Clear all stored messages. Mainly used after a mass rebuild.
1136          */
1137         function clear() {
1138                 $langs = Language::fetchLanguageNames( null, 'mw' );
1139                 foreach ( array_keys( $langs ) as $code ) {
1140                         # Global and local caches
1141                         $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
1142                 }
1143
1144                 $this->mLoadedLanguages = [];
1145         }
1146
1147         /**
1148          * @param string $key
1149          * @return array
1150          */
1151         public function figureMessage( $key ) {
1152                 global $wgLanguageCode;
1153
1154                 $pieces = explode( '/', $key );
1155                 if ( count( $pieces ) < 2 ) {
1156                         return [ $key, $wgLanguageCode ];
1157                 }
1158
1159                 $lang = array_pop( $pieces );
1160                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1161                         return [ $key, $wgLanguageCode ];
1162                 }
1163
1164                 $message = implode( '/', $pieces );
1165
1166                 return [ $message, $lang ];
1167         }
1168
1169         /**
1170          * Get all message keys stored in the message cache for a given language.
1171          * If $code is the content language code, this will return all message keys
1172          * for which MediaWiki:msgkey exists. If $code is another language code, this
1173          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1174          * @param string $code Language code
1175          * @return array Array of message keys (strings)
1176          */
1177         public function getAllMessageKeys( $code ) {
1178                 global $wgContLang;
1179                 $this->load( $code );
1180                 if ( !isset( $this->mCache[$code] ) ) {
1181                         // Apparently load() failed
1182                         return null;
1183                 }
1184                 // Remove administrative keys
1185                 $cache = $this->mCache[$code];
1186                 unset( $cache['VERSION'] );
1187                 unset( $cache['EXPIRY'] );
1188                 // Remove any !NONEXISTENT keys
1189                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1190
1191                 // Keys may appear with a capital first letter. lcfirst them.
1192                 return array_map( [ $wgContLang, 'lcfirst' ], array_keys( $cache ) );
1193         }
1194 }