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
  27 /**
  28  * MediaWiki message cache structure version.
  29  * Bump this whenever the message cache format has changed.
  30  */
  31 define( 'MSG_CACHE_VERSION', 2 );
  32
  33 /**
  34  * Message cache
  35  * Performs various MediaWiki namespace-related functions
  36  * @ingroup Cache
  37  */
  38 class MessageCache {
  39         const FOR_UPDATE = 1; // force message reload
  40
  41         /** How long to wait for memcached locks */
  42         const WAIT_SEC = 15;
  43         /** How long memcached locks last */
  44         const LOCK_TTL = 30;
  45
  46         /**
  47          * Process local cache of loaded messages that are defined in
  48          * MediaWiki namespace. First array level is a language code,
  49          * second level is message key and the values are either message
  50          * content prefixed with space, or !NONEXISTENT for negative
  51          * caching.
  52          * @var array $mCache
  53          */
  54         protected $mCache;
  55
  56         /**
  57          * @var bool[] Map of (language code => boolean)
  58          */
  59         protected $mCacheVolatile = [];
  60
  61         /**
  62          * Should mean that database cannot be used, but check
  63          * @var bool $mDisable
  64          */
  65         protected $mDisable;
  66
  67         /**
  68          * Lifetime for cache, used by object caching.
  69          * Set on construction, see __construct().
  70          */
  71         protected $mExpiry;
  72
  73         /**
  74          * Message cache has its own parser which it uses to transform messages
  75          * @var ParserOptions
  76          */
  77         protected $mParserOptions;
  78         /** @var Parser */
  79         protected $mParser;
  80
  81         /**
  82          * Variable for tracking which variables are already loaded
  83          * @var array $mLoadedLanguages
  84          */
  85         protected $mLoadedLanguages = [];
  86
  87         /**
  88          * @var bool $mInParser
  89          */
  90         protected $mInParser = false;
  91
  92         /** @var BagOStuff */
  93         protected $mMemc;
  94         /** @var WANObjectCache */
  95         protected $wanCache;
  96
  97         /**
  98          * Singleton instance
  99          *
 100          * @var MessageCache $instance
 101          */
 102         private static $instance;
 103
 104         /**
 105          * Get the signleton instance of this class
 106          *
 107          * @since 1.18
 108          * @return MessageCache
 109          */
 110         public static function singleton() {
 111                 if ( self::$instance === null ) {
 112                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
 113                         self::$instance = new self(
 114                                 wfGetMessageCacheStorage(),
 115                                 $wgUseDatabaseMessages,
 116                                 $wgMsgCacheExpiry
 117                         );
 118                 }
 119
 120                 return self::$instance;
 121         }
 122
 123         /**
 124          * Destroy the singleton instance
 125          *
 126          * @since 1.18
 127          */
 128         public static function destroyInstance() {
 129                 self::$instance = null;
 130         }
 131
 132         /**
 133          * Normalize message key input
 134          *
 135          * @param string $key Input message key to be normalized
 136          * @return string Normalized message key
 137          */
 138         public static function normalizeKey( $key ) {
 139                 global $wgContLang;
 140
 141                 $lckey = strtr( $key, ' ', '_' );
 142                 if ( ord( $lckey ) < 128 ) {
 143                         $lckey[0] = strtolower( $lckey[0] );
 144                 } else {
 145                         $lckey = $wgContLang->lcfirst( $lckey );
 146                 }
 147
 148                 return $lckey;
 149         }
 150
 151         /**
 152          * @param BagOStuff $memCached A cache instance. If none, fall back to CACHE_NONE.
 153          * @param bool $useDB
 154          * @param int $expiry Lifetime for cache. @see $mExpiry.
 155          */
 156         function __construct( $memCached, $useDB, $expiry ) {
 157                 global $wgUseLocalMessageCache;
 158
 159                 if ( !$memCached ) {
 160                         $memCached = wfGetCache( CACHE_NONE );
 161                 }
 162
 163                 $this->mMemc = $memCached;
 164                 $this->mDisable = !$useDB;
 165                 $this->mExpiry = $expiry;
 166
 167                 if ( $wgUseLocalMessageCache ) {
 168                         $this->localCache = MediaWikiServices::getInstance()->getLocalServerObjectCache();
 169                 } else {
 170                         $this->localCache = new EmptyBagOStuff();
 171                 }
 172
 173                 $this->wanCache = ObjectCache::getMainWANInstance();
 174         }
 175
 176         /**
 177          * ParserOptions is lazy initialised.
 178          *
 179          * @return ParserOptions
 180          */
 181         function getParserOptions() {
 182                 global $wgUser;
 183
 184                 if ( !$this->mParserOptions ) {
 185                         if ( !$wgUser->isSafeToLoad() ) {
 186                                 // $wgUser isn't unstubbable yet, so don't try to get a
 187                                 // ParserOptions for it. And don't cache this ParserOptions
 188                                 // either.
 189                                 $po = ParserOptions::newFromAnon();
 190                                 $po->setEditSection( false );
 191                                 return $po;
 192                         }
 193
 194                         $this->mParserOptions = new ParserOptions;
 195                         $this->mParserOptions->setEditSection( false );
 196                 }
 197
 198                 return $this->mParserOptions;
 199         }
 200
 201         /**
 202          * Try to load the cache from APC.
 203          *
 204          * @param string $code Optional language code, see documenation of load().
 205          * @return array|bool The cache array, or false if not in cache.
 206          */
 207         protected function getLocalCache( $code ) {
 208                 $cacheKey = wfMemcKey( __CLASS__, $code );
 209
 210                 return $this->localCache->get( $cacheKey );
 211         }
 212
 213         /**
 214          * Save the cache to APC.
 215          *
 216          * @param string $code
 217          * @param array $cache The cache array
 218          */
 219         protected function saveToLocalCache( $code, $cache ) {
 220                 $cacheKey = wfMemcKey( __CLASS__, $code );
 221                 $this->localCache->set( $cacheKey, $cache );
 222         }
 223
 224         /**
 225          * Loads messages from caches or from database in this order:
 226          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 227          * (2) memcached
 228          * (3) from the database.
 229          *
 230          * When succesfully loading from (2) or (3), all higher level caches are
 231          * updated for the newest version.
 232          *
 233          * Nothing is loaded if member variable mDisable is true, either manually
 234          * set by calling code or if message loading fails (is this possible?).
 235          *
 236          * Returns true if cache is already populated or it was succesfully populated,
 237          * or false if populating empty cache fails. Also returns true if MessageCache
 238          * is disabled.
 239          *
 240          * @param string $code Language to which load messages
 241          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache [optional]
 242          * @throws MWException
 243          * @return bool
 244          */
 245         protected function load( $code, $mode = null ) {
 246                 if ( !is_string( $code ) ) {
 247                         throw new InvalidArgumentException( "Missing language code" );
 248                 }
 249
 250                 # Don't do double loading...
 251                 if ( isset( $this->mLoadedLanguages[$code] ) && $mode != self::FOR_UPDATE ) {
 252                         return true;
 253                 }
 254
 255                 # 8 lines of code just to say (once) that message cache is disabled
 256                 if ( $this->mDisable ) {
 257                         static $shownDisabled = false;
 258                         if ( !$shownDisabled ) {
 259                                 wfDebug( __METHOD__ . ": disabled\n" );
 260                                 $shownDisabled = true;
 261                         }
 262
 263                         return true;
 264                 }
 265
 266                 # Loading code starts
 267                 $success = false; # Keep track of success
 268                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 269                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 270
 271                 # Hash of the contents is stored in memcache, to detect if data-center cache
 272                 # or local cache goes out of date (e.g. due to replace() on some other server)
 273                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 274                 $this->mCacheVolatile[$code] = $hashVolatile;
 275
 276                 # Try the local cache and check against the cluster hash key...
 277                 $cache = $this->getLocalCache( $code );
 278                 if ( !$cache ) {
 279                         $where[] = 'local cache is empty';
 280                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 281                         $where[] = 'local cache has the wrong hash';
 282                         $staleCache = $cache;
 283                 } elseif ( $this->isCacheExpired( $cache ) ) {
 284                         $where[] = 'local cache is expired';
 285                         $staleCache = $cache;
 286                 } elseif ( $hashVolatile ) {
 287                         $where[] = 'local cache validation key is expired/volatile';
 288                         $staleCache = $cache;
 289                 } else {
 290                         $where[] = 'got from local cache';
 291                         $success = true;
 292                         $this->mCache[$code] = $cache;
 293                 }
 294
 295                 if ( !$success ) {
 296                         $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 297                         # Try the global cache. If it is empty, try to acquire a lock. If
 298                         # the lock can't be acquired, wait for the other thread to finish
 299                         # and then try the global cache a second time.
 300                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 301                                 if ( $hashVolatile && $staleCache ) {
 302                                         # Do not bother fetching the whole cache blob to avoid I/O.
 303                                         # Instead, just try to get the non-blocking $statusKey lock
 304                                         # below, and use the local stale value if it was not acquired.
 305                                         $where[] = 'global cache is presumed expired';
 306                                 } else {
 307                                         $cache = $this->mMemc->get( $cacheKey );
 308                                         if ( !$cache ) {
 309                                                 $where[] = 'global cache is empty';
 310                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 311                                                 $where[] = 'global cache is expired';
 312                                                 $staleCache = $cache;
 313                                         } elseif ( $hashVolatile ) {
 314                                                 # DB results are replica DB lag prone until the holdoff TTL passes.
 315                                                 # By then, updates should be reflected in loadFromDBWithLock().
 316                                                 # One thread renerates the cache while others use old values.
 317                                                 $where[] = 'global cache is expired/volatile';
 318                                                 $staleCache = $cache;
 319                                         } else {
 320                                                 $where[] = 'got from global cache';
 321                                                 $this->mCache[$code] = $cache;
 322                                                 $this->saveToCaches( $cache, 'local-only', $code );
 323                                                 $success = true;
 324                                         }
 325                                 }
 326
 327                                 if ( $success ) {
 328                                         # Done, no need to retry
 329                                         break;
 330                                 }
 331
 332                                 # We need to call loadFromDB. Limit the concurrency to one process.
 333                                 # This prevents the site from going down when the cache expires.
 334                                 # Note that the DB slam protection lock here is non-blocking.
 335                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 336                                 if ( $loadStatus === true ) {
 337                                         $success = true;
 338                                         break;
 339                                 } elseif ( $staleCache ) {
 340                                         # Use the stale cache while some other thread constructs the new one
 341                                         $where[] = 'using stale cache';
 342                                         $this->mCache[$code] = $staleCache;
 343                                         $success = true;
 344                                         break;
 345                                 } elseif ( $failedAttempts > 0 ) {
 346                                         # Already blocked once, so avoid another lock/unlock cycle.
 347                                         # This case will typically be hit if memcached is down, or if
 348                                         # loadFromDB() takes longer than LOCK_WAIT.
 349                                         $where[] = "could not acquire status key.";
 350                                         break;
 351                                 } elseif ( $loadStatus === 'cantacquire' ) {
 352                                         # Wait for the other thread to finish, then retry. Normally,
 353                                         # the memcached get() will then yeild the other thread's result.
 354                                         $where[] = 'waited for other thread to complete';
 355                                         $this->getReentrantScopedLock( $cacheKey );
 356                                 } else {
 357                                         # Disable cache; $loadStatus is 'disabled'
 358                                         break;
 359                                 }
 360                         }
 361                 }
 362
 363                 if ( !$success ) {
 364                         $where[] = 'loading FAILED - cache is disabled';
 365                         $this->mDisable = true;
 366                         $this->mCache = false;
 367                         wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
 368                         # This used to throw an exception, but that led to nasty side effects like
 369                         # the whole wiki being instantly down if the memcached server died
 370                 } else {
 371                         # All good, just record the success
 372                         $this->mLoadedLanguages[$code] = true;
 373                 }
 374
 375                 $info = implode( ', ', $where );
 376                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 377
 378                 return $success;
 379         }
 380
 381         /**
 382          * @param string $code
 383          * @param array $where List of wfDebug() comments
 384          * @param integer $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 385          * @return bool|string True on success or one of ("cantacquire", "disabled")
 386          */
 387         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 388                 global $wgUseLocalMessageCache;
 389
 390                 # If cache updates on all levels fail, give up on message overrides.
 391                 # This is to avoid easy site outages; see $saveSuccess comments below.
 392                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 393                 $status = $this->mMemc->get( $statusKey );
 394                 if ( $status === 'error' ) {
 395                         $where[] = "could not load; method is still globally disabled";
 396                         return 'disabled';
 397                 }
 398
 399                 # Now let's regenerate
 400                 $where[] = 'loading from database';
 401
 402                 # Lock the cache to prevent conflicting writes.
 403                 # This lock is non-blocking so stale cache can quickly be used.
 404                 # Note that load() will call a blocking getReentrantScopedLock()
 405                 # after this if it really need to wait for any current thread.
 406                 $cacheKey = wfMemcKey( 'messages', $code );
 407                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 408                 if ( !$scopedLock ) {
 409                         $where[] = 'could not acquire main lock';
 410                         return 'cantacquire';
 411                 }
 412
 413                 $cache = $this->loadFromDB( $code, $mode );
 414                 $this->mCache[$code] = $cache;
 415                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 416
 417                 if ( !$saveSuccess ) {
 418                         /**
 419                          * Cache save has failed.
 420                          *
 421                          * There are two main scenarios where this could be a problem:
 422                          * - The cache is more than the maximum size (typically 1MB compressed).
 423                          * - Memcached has no space remaining in the relevant slab class. This is
 424                          *   unlikely with recent versions of memcached.
 425                          *
 426                          * Either way, if there is a local cache, nothing bad will happen. If there
 427                          * is no local cache, disabling the message cache for all requests avoids
 428                          * incurring a loadFromDB() overhead on every request, and thus saves the
 429                          * wiki from complete downtime under moderate traffic conditions.
 430                          */
 431                         if ( !$wgUseLocalMessageCache ) {
 432                                 $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 433                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 434                         } else {
 435                                 $where[] = "could not save global cache";
 436                         }
 437                 }
 438
 439                 return true;
 440         }
 441
 442         /**
 443          * Loads cacheable messages from the database. Messages bigger than
 444          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 445          * on-demand from the database later.
 446          *
 447          * @param string $code Language code
 448          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 449          * @return array Loaded messages for storing in caches
 450          */
 451         function loadFromDB( $code, $mode = null ) {
 452                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 453
 454                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA );
 455
 456                 $cache = [];
 457
 458                 # Common conditions
 459                 $conds = [
 460                         'page_is_redirect' => 0,
 461                         'page_namespace' => NS_MEDIAWIKI,
 462                 ];
 463
 464                 $mostused = [];
 465                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 466                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 467                                 $this->load( $wgLanguageCode );
 468                         }
 469                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 470                         foreach ( $mostused as $key => $value ) {
 471                                 $mostused[$key] = "$value/$code";
 472                         }
 473                 }
 474
 475                 if ( count( $mostused ) ) {
 476                         $conds['page_title'] = $mostused;
 477                 } elseif ( $code !== $wgLanguageCode ) {
 478                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 479                 } else {
 480                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 481                         # other than language code.
 482                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 483                 }
 484
 485                 # Conditions to fetch oversized pages to ignore them
 486                 $bigConds = $conds;
 487                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 488
 489                 # Load titles for all oversized pages in the MediaWiki namespace
 490                 $res = $dbr->select(
 491                         'page',
 492                         [ 'page_title', 'page_latest' ],
 493                         $bigConds,
 494                         __METHOD__ . "($code)-big"
 495                 );
 496                 foreach ( $res as $row ) {
 497                         $cache[$row->page_title] = '!TOO BIG';
 498                         // At least include revision ID so page changes are reflected in the hash
 499                         $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 500                 }
 501
 502                 # Conditions to load the remaining pages with their contents
 503                 $smallConds = $conds;
 504                 $smallConds[] = 'page_latest=rev_id';
 505                 $smallConds[] = 'rev_text_id=old_id';
 506                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 507
 508                 $res = $dbr->select(
 509                         [ 'page', 'revision', 'text' ],
 510                         [ 'page_title', 'old_text', 'old_flags' ],
 511                         $smallConds,
 512                         __METHOD__ . "($code)-small"
 513                 );
 514
 515                 foreach ( $res as $row ) {
 516                         $text = Revision::getRevisionText( $row );
 517                         if ( $text === false ) {
 518                                 // Failed to fetch data; possible ES errors?
 519                                 // Store a marker to fetch on-demand as a workaround...
 520                                 $entry = '!TOO BIG';
 521                                 wfDebugLog(
 522                                         'MessageCache',
 523                                         __METHOD__
 524                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 525                                 );
 526                         } else {
 527                                 $entry = ' ' . $text;
 528                         }
 529                         $cache[$row->page_title] = $entry;
 530                 }
 531
 532                 $cache['VERSION'] = MSG_CACHE_VERSION;
 533                 ksort( $cache );
 534                 $cache['HASH'] = md5( serialize( $cache ) );
 535                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 536
 537                 return $cache;
 538         }
 539
 540         /**
 541          * Updates cache as necessary when message page is changed
 542          *
 543          * @param string|bool $title Name of the page changed (false if deleted)
 544          * @param string|bool $text New contents of the page (false if deleted)
 545          */
 546         public function replace( $title, $text ) {
 547                 global $wgMaxMsgCacheEntrySize, $wgContLang, $wgLanguageCode;
 548
 549                 if ( $this->mDisable ) {
 550                         return;
 551                 }
 552
 553                 list( $msg, $code ) = $this->figureMessage( $title );
 554                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 555                         // Content language overrides do not use the /<code> suffix
 556                         return;
 557                 }
 558
 559                 // Note that if the cache is volatile, load() may trigger a DB fetch.
 560                 // In that case we reenter/reuse the existing cache key lock to avoid
 561                 // a self-deadlock. This is safe as no reads happen *directly* in this
 562                 // method between getReentrantScopedLock() and load() below. There is
 563                 // no risk of data "changing under our feet" for replace().
 564                 $scopedLock = $this->getReentrantScopedLock( wfMemcKey( 'messages', $code ) );
 565                 // Load the messages from the master DB to avoid race conditions
 566                 $this->load( $code, self::FOR_UPDATE );
 567
 568                 // Load the new value into the process cache...
 569                 if ( $text === false ) {
 570                         $this->mCache[$code][$title] = '!NONEXISTENT';
 571                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 572                         $this->mCache[$code][$title] = '!TOO BIG';
 573                         // Pre-fill the individual key cache with the known latest message text
 574                         $key = $this->wanCache->makeKey( 'messages-big', $this->mCache[$code]['HASH'], $title );
 575                         $this->wanCache->set( $key, " $text", $this->mExpiry );
 576                 } else {
 577                         $this->mCache[$code][$title] = ' ' . $text;
 578                 }
 579                 // Mark this cache as definitely being "latest" (non-volatile) so
 580                 // load() calls do not try to refresh the cache with replica DB data
 581                 $this->mCache[$code]['LATEST'] = time();
 582
 583                 // Update caches if the lock was acquired
 584                 if ( $scopedLock ) {
 585                         $this->saveToCaches( $this->mCache[$code], 'all', $code );
 586                 } else {
 587                         LoggerFactory::getInstance( 'MessageCache' )->error(
 588                                 __METHOD__ . ': could not acquire lock to update {title} ({code})',
 589                                 [ 'title' => $title, 'code' => $code ] );
 590                 }
 591
 592                 ScopedCallback::consume( $scopedLock );
 593                 // Relay the purge to APC and other DCs
 594                 $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
 595
 596                 // Also delete cached sidebar... just in case it is affected
 597                 $codes = [ $code ];
 598                 if ( $code === 'en' ) {
 599                         // Delete all sidebars, like for example on action=purge on the
 600                         // sidebar messages
 601                         $codes = array_keys( Language::fetchLanguageNames() );
 602                 }
 603
 604                 foreach ( $codes as $code ) {
 605                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 606                         $this->wanCache->delete( $sidebarKey );
 607                 }
 608
 609                 // Update the message in the message blob store
 610                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 611                 $blobStore = $resourceloader->getMessageBlobStore();
 612                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 613
 614                 Hooks::run( 'MessageCacheReplace', [ $title, $text ] );
 615         }
 616
 617         /**
 618          * Is the given cache array expired due to time passing or a version change?
 619          *
 620          * @param array $cache
 621          * @return bool
 622          */
 623         protected function isCacheExpired( $cache ) {
 624                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 625                         return true;
 626                 }
 627                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 628                         return true;
 629                 }
 630                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 631                         return true;
 632                 }
 633
 634                 return false;
 635         }
 636
 637         /**
 638          * Shortcut to update caches.
 639          *
 640          * @param array $cache Cached messages with a version.
 641          * @param string $dest Either "local-only" to save to local caches only
 642          *   or "all" to save to all caches.
 643          * @param string|bool $code Language code (default: false)
 644          * @return bool
 645          */
 646         protected function saveToCaches( array $cache, $dest, $code = false ) {
 647                 if ( $dest === 'all' ) {
 648                         $cacheKey = wfMemcKey( 'messages', $code );
 649                         $success = $this->mMemc->set( $cacheKey, $cache );
 650                         $this->setValidationHash( $code, $cache );
 651                 } else {
 652                         $success = true;
 653                 }
 654
 655                 $this->saveToLocalCache( $code, $cache );
 656
 657                 return $success;
 658         }
 659
 660         /**
 661          * Get the md5 used to validate the local APC cache
 662          *
 663          * @param string $code
 664          * @return array (hash or false, bool expiry/volatility status)
 665          */
 666         protected function getValidationHash( $code ) {
 667                 $curTTL = null;
 668                 $value = $this->wanCache->get(
 669                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 670                         $curTTL,
 671                         [ wfMemcKey( 'messages', $code ) ]
 672                 );
 673
 674                 if ( $value ) {
 675                         $hash = $value['hash'];
 676                         if ( ( time() - $value['latest'] ) < WANObjectCache::TTL_MINUTE ) {
 677                                 // Cache was recently updated via replace() and should be up-to-date.
 678                                 // That method is only called in the primary datacenter and uses FOR_UPDATE.
 679                                 // Also, it is unlikely that the current datacenter is *now* secondary one.
 680                                 $expired = false;
 681                         } else {
 682                                 // See if the "check" key was bumped after the hash was generated
 683                                 $expired = ( $curTTL < 0 );
 684                         }
 685                 } else {
 686                         // No hash found at all; cache must regenerate to be safe
 687                         $hash = false;
 688                         $expired = true;
 689                 }
 690
 691                 return [ $hash, $expired ];
 692         }
 693
 694         /**
 695          * Set the md5 used to validate the local disk cache
 696          *
 697          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 698          * be treated as "volatile" by getValidationHash() for the next few seconds.
 699          * This is triggered when $cache is generated using FOR_UPDATE mode.
 700          *
 701          * @param string $code
 702          * @param array $cache Cached messages with a version
 703          */
 704         protected function setValidationHash( $code, array $cache ) {
 705                 $this->wanCache->set(
 706                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 707                         [
 708                                 'hash' => $cache['HASH'],
 709                                 'latest' => isset( $cache['LATEST'] ) ? $cache['LATEST'] : 0
 710                         ],
 711                         WANObjectCache::TTL_INDEFINITE
 712                 );
 713         }
 714
 715         /**
 716          * @param string $key A language message cache key that stores blobs
 717          * @param integer $timeout Wait timeout in seconds
 718          * @return null|ScopedCallback
 719          */
 720         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 721                 return $this->mMemc->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 722         }
 723
 724         /**
 725          * Get a message from either the content language or the user language.
 726          *
 727          * First, assemble a list of languages to attempt getting the message from. This
 728          * chain begins with the requested language and its fallbacks and then continues with
 729          * the content language and its fallbacks. For each language in the chain, the following
 730          * process will occur (in this order):
 731          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 732          *     Note: for the content language, there is no /lang subpage.
 733          *  2. Fetch from the static CDB cache.
 734          *  3. If available, check the database for fallback language overrides.
 735          *
 736          * This process provides a number of guarantees. When changing this code, make sure all
 737          * of these guarantees are preserved.
 738          *  * If the requested language is *not* the content language, then the CDB cache for that
 739          *    specific language will take precedence over the root database page ([[MW:msg]]).
 740          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 741          *    the message is available *anywhere* in the language for which it is a fallback.
 742          *
 743          * @param string $key The message key
 744          * @param bool $useDB If true, look for the message in the DB, false
 745          *   to use only the compiled l10n cache.
 746          * @param bool|string|object $langcode Code of the language to get the message for.
 747          *   - If string and a valid code, will create a standard language object
 748          *   - If string but not a valid code, will create a basic language object
 749          *   - If boolean and false, create object from the current users language
 750          *   - If boolean and true, create object from the wikis content language
 751          *   - If language object, use it as given
 752          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 753          *
 754          * @throws MWException When given an invalid key
 755          * @return string|bool False if the message doesn't exist, otherwise the
 756          *   message (which can be empty)
 757          */
 758         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 759                 if ( is_int( $key ) ) {
 760                         // Fix numerical strings that somehow become ints
 761                         // on their way here
 762                         $key = (string)$key;
 763                 } elseif ( !is_string( $key ) ) {
 764                         throw new MWException( 'Non-string key given' );
 765                 } elseif ( $key === '' ) {
 766                         // Shortcut: the empty key is always missing
 767                         return false;
 768                 }
 769
 770                 // For full keys, get the language code from the key
 771                 $pos = strrpos( $key, '/' );
 772                 if ( $isFullKey && $pos !== false ) {
 773                         $langcode = substr( $key, $pos + 1 );
 774                         $key = substr( $key, 0, $pos );
 775                 }
 776
 777                 // Normalise title-case input (with some inlining)
 778                 $lckey = MessageCache::normalizeKey( $key );
 779
 780                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 781
 782                 // Loop through each language in the fallback list until we find something useful
 783                 $lang = wfGetLangObj( $langcode );
 784                 $message = $this->getMessageFromFallbackChain(
 785                         $lang,
 786                         $lckey,
 787                         !$this->mDisable && $useDB
 788                 );
 789
 790                 // If we still have no message, maybe the key was in fact a full key so try that
 791                 if ( $message === false ) {
 792                         $parts = explode( '/', $lckey );
 793                         // We may get calls for things that are http-urls from sidebar
 794                         // Let's not load nonexistent languages for those
 795                         // They usually have more than one slash.
 796                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 797                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 798                                 if ( $message === null ) {
 799                                         $message = false;
 800                                 }
 801                         }
 802                 }
 803
 804                 // Post-processing if the message exists
 805                 if ( $message !== false ) {
 806                         // Fix whitespace
 807                         $message = str_replace(
 808                                 [
 809                                         # Fix for trailing whitespace, removed by textarea
 810                                         '&#32;',
 811                                         # Fix for NBSP, converted to space by firefox
 812                                         '&nbsp;',
 813                                         '&#160;',
 814                                         '&shy;'
 815                                 ],
 816                                 [
 817                                         ' ',
 818                                         "\xc2\xa0",
 819                                         "\xc2\xa0",
 820                                         "\xc2\xad"
 821                                 ],
 822                                 $message
 823                         );
 824                 }
 825
 826                 return $message;
 827         }
 828
 829         /**
 830          * Given a language, try and fetch messages from that language.
 831          *
 832          * Will also consider fallbacks of that language, the site language, and fallbacks for
 833          * the site language.
 834          *
 835          * @see MessageCache::get
 836          * @param Language|StubObject $lang Preferred language
 837          * @param string $lckey Lowercase key for the message (as for localisation cache)
 838          * @param bool $useDB Whether to include messages from the wiki database
 839          * @return string|bool The message, or false if not found
 840          */
 841         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 842                 global $wgContLang;
 843
 844                 $alreadyTried = [];
 845
 846                  // First try the requested language.
 847                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 848                 if ( $message !== false ) {
 849                         return $message;
 850                 }
 851
 852                 // Now try checking the site language.
 853                 $message = $this->getMessageForLang( $wgContLang, $lckey, $useDB, $alreadyTried );
 854                 return $message;
 855         }
 856
 857         /**
 858          * Given a language, try and fetch messages from that language and its fallbacks.
 859          *
 860          * @see MessageCache::get
 861          * @param Language|StubObject $lang Preferred language
 862          * @param string $lckey Lowercase key for the message (as for localisation cache)
 863          * @param bool $useDB Whether to include messages from the wiki database
 864          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 865          * @return string|bool The message, or false if not found
 866          */
 867         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 868                 global $wgContLang;
 869
 870                 $langcode = $lang->getCode();
 871
 872                 // Try checking the database for the requested language
 873                 if ( $useDB ) {
 874                         $uckey = $wgContLang->ucfirst( $lckey );
 875
 876                         if ( !isset( $alreadyTried[ $langcode ] ) ) {
 877                                 $message = $this->getMsgFromNamespace(
 878                                         $this->getMessagePageName( $langcode, $uckey ),
 879                                         $langcode
 880                                 );
 881
 882                                 if ( $message !== false ) {
 883                                         return $message;
 884                                 }
 885                                 $alreadyTried[ $langcode ] = true;
 886                         }
 887                 } else {
 888                         $uckey = null;
 889                 }
 890
 891                 // Check the CDB cache
 892                 $message = $lang->getMessage( $lckey );
 893                 if ( $message !== null ) {
 894                         return $message;
 895                 }
 896
 897                 // Try checking the database for all of the fallback languages
 898                 if ( $useDB ) {
 899                         $fallbackChain = Language::getFallbacksFor( $langcode );
 900
 901                         foreach ( $fallbackChain as $code ) {
 902                                 if ( isset( $alreadyTried[ $code ] ) ) {
 903                                         continue;
 904                                 }
 905
 906                                 $message = $this->getMsgFromNamespace(
 907                                         $this->getMessagePageName( $code, $uckey ), $code );
 908
 909                                 if ( $message !== false ) {
 910                                         return $message;
 911                                 }
 912                                 $alreadyTried[ $code ] = true;
 913                         }
 914                 }
 915
 916                 return false;
 917         }
 918
 919         /**
 920          * Get the message page name for a given language
 921          *
 922          * @param string $langcode
 923          * @param string $uckey Uppercase key for the message
 924          * @return string The page name
 925          */
 926         private function getMessagePageName( $langcode, $uckey ) {
 927                 global $wgLanguageCode;
 928
 929                 if ( $langcode === $wgLanguageCode ) {
 930                         // Messages created in the content language will not have the /lang extension
 931                         return $uckey;
 932                 } else {
 933                         return "$uckey/$langcode";
 934                 }
 935         }
 936
 937         /**
 938          * Get a message from the MediaWiki namespace, with caching. The key must
 939          * first be converted to two-part lang/msg form if necessary.
 940          *
 941          * Unlike self::get(), this function doesn't resolve fallback chains, and
 942          * some callers require this behavior. LanguageConverter::parseCachedTable()
 943          * and self::get() are some examples in core.
 944          *
 945          * @param string $title Message cache key with initial uppercase letter.
 946          * @param string $code Code denoting the language to try.
 947          * @return string|bool The message, or false if it does not exist or on error
 948          */
 949         public function getMsgFromNamespace( $title, $code ) {
 950                 $this->load( $code );
 951                 if ( isset( $this->mCache[$code][$title] ) ) {
 952                         $entry = $this->mCache[$code][$title];
 953                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 954                                 // The message exists, so make sure a string is returned.
 955                                 return (string)substr( $entry, 1 );
 956                         } elseif ( $entry === '!NONEXISTENT' ) {
 957                                 return false;
 958                         } elseif ( $entry === '!TOO BIG' ) {
 959                                 // Fall through and try invididual message cache below
 960                         }
 961                 } else {
 962                         // XXX: This is not cached in process cache, should it?
 963                         $message = false;
 964                         Hooks::run( 'MessagesPreLoad', [ $title, &$message ] );
 965                         if ( $message !== false ) {
 966                                 return $message;
 967                         }
 968
 969                         return false;
 970                 }
 971
 972                 // Try the individual message cache
 973                 $titleKey = $this->wanCache->makeKey( 'messages-big', $this->mCache[$code]['HASH'], $title );
 974
 975                 if ( $this->mCacheVolatile[$code] ) {
 976                         $entry = false;
 977                         // Make sure that individual keys respect the WAN cache holdoff period too
 978                         LoggerFactory::getInstance( 'MessageCache' )->debug(
 979                                 __METHOD__ . ': loading volatile key \'{titleKey}\'',
 980                                 [ 'titleKey' => $titleKey, 'code' => $code ] );
 981                 } else {
 982                         $entry = $this->wanCache->get( $titleKey );
 983                 }
 984
 985                 if ( $entry !== false ) {
 986                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 987                                 $this->mCache[$code][$title] = $entry;
 988                                 // The message exists, so make sure a string is returned
 989                                 return (string)substr( $entry, 1 );
 990                         } elseif ( $entry === '!NONEXISTENT' ) {
 991                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 992
 993                                 return false;
 994                         } else {
 995                                 // Corrupt/obsolete entry, delete it
 996                                 $this->wanCache->delete( $titleKey );
 997                         }
 998                 }
 999
1000                 // Try loading the message from the database
1001                 $dbr = wfGetDB( DB_REPLICA );
1002                 $cacheOpts = Database::getCacheSetOptions( $dbr );
1003                 // Use newKnownCurrent() to avoid querying revision/user tables
1004                 $titleObj = Title::makeTitle( NS_MEDIAWIKI, $title );
1005                 if ( $titleObj->getLatestRevID() ) {
1006                         $revision = Revision::newKnownCurrent(
1007                                 $dbr,
1008                                 $titleObj->getArticleID(),
1009                                 $titleObj->getLatestRevID()
1010                         );
1011                 } else {
1012                         $revision = false;
1013                 }
1014
1015                 if ( $revision ) {
1016                         $content = $revision->getContent();
1017                         if ( $content ) {
1018                                 $message = $this->getMessageTextFromContent( $content );
1019                                 if ( is_string( $message ) ) {
1020                                         $this->mCache[$code][$title] = ' ' . $message;
1021                                         $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry, $cacheOpts );
1022                                 }
1023                         } else {
1024                                 // A possibly temporary loading failure
1025                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1026                                         __METHOD__ . ': failed to load message page text for \'{titleKey}\'',
1027                                         [ 'titleKey' => $titleKey, 'code' => $code ] );
1028                                 $message = null; // no negative caching
1029                         }
1030                 } else {
1031                         $message = false; // negative caching
1032                 }
1033
1034                 if ( $message === false ) { // negative caching
1035                         $this->mCache[$code][$title] = '!NONEXISTENT';
1036                         $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry, $cacheOpts );
1037                 }
1038
1039                 return $message;
1040         }
1041
1042         /**
1043          * @param string $message
1044          * @param bool $interface
1045          * @param string $language Language code
1046          * @param Title $title
1047          * @return string
1048          */
1049         function transform( $message, $interface = false, $language = null, $title = null ) {
1050                 // Avoid creating parser if nothing to transform
1051                 if ( strpos( $message, '{{' ) === false ) {
1052                         return $message;
1053                 }
1054
1055                 if ( $this->mInParser ) {
1056                         return $message;
1057                 }
1058
1059                 $parser = $this->getParser();
1060                 if ( $parser ) {
1061                         $popts = $this->getParserOptions();
1062                         $popts->setInterfaceMessage( $interface );
1063                         $popts->setTargetLanguage( $language );
1064
1065                         $userlang = $popts->setUserLang( $language );
1066                         $this->mInParser = true;
1067                         $message = $parser->transformMsg( $message, $popts, $title );
1068                         $this->mInParser = false;
1069                         $popts->setUserLang( $userlang );
1070                 }
1071
1072                 return $message;
1073         }
1074
1075         /**
1076          * @return Parser
1077          */
1078         function getParser() {
1079                 global $wgParser, $wgParserConf;
1080
1081                 if ( !$this->mParser && isset( $wgParser ) ) {
1082                         # Do some initialisation so that we don't have to do it twice
1083                         $wgParser->firstCallInit();
1084                         # Clone it and store it
1085                         $class = $wgParserConf['class'];
1086                         if ( $class == 'ParserDiffTest' ) {
1087                                 # Uncloneable
1088                                 $this->mParser = new $class( $wgParserConf );
1089                         } else {
1090                                 $this->mParser = clone $wgParser;
1091                         }
1092                 }
1093
1094                 return $this->mParser;
1095         }
1096
1097         /**
1098          * @param string $text
1099          * @param Title $title
1100          * @param bool $linestart Whether or not this is at the start of a line
1101          * @param bool $interface Whether this is an interface message
1102          * @param Language|string $language Language code
1103          * @return ParserOutput|string
1104          */
1105         public function parse( $text, $title = null, $linestart = true,
1106                 $interface = false, $language = null
1107         ) {
1108                 global $wgTitle;
1109
1110                 if ( $this->mInParser ) {
1111                         return htmlspecialchars( $text );
1112                 }
1113
1114                 $parser = $this->getParser();
1115                 $popts = $this->getParserOptions();
1116                 $popts->setInterfaceMessage( $interface );
1117
1118                 if ( is_string( $language ) ) {
1119                         $language = Language::factory( $language );
1120                 }
1121                 $popts->setTargetLanguage( $language );
1122
1123                 if ( !$title || !$title instanceof Title ) {
1124                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1125                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1126                         $title = $wgTitle;
1127                 }
1128                 // Sometimes $wgTitle isn't set either...
1129                 if ( !$title ) {
1130                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1131                         # Create a ghost title in such case
1132                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1133                 }
1134
1135                 $this->mInParser = true;
1136                 $res = $parser->parse( $text, $title, $popts, $linestart );
1137                 $this->mInParser = false;
1138
1139                 return $res;
1140         }
1141
1142         function disable() {
1143                 $this->mDisable = true;
1144         }
1145
1146         function enable() {
1147                 $this->mDisable = false;
1148         }
1149
1150         /**
1151          * Whether DB/cache usage is disabled for determining messages
1152          *
1153          * If so, this typically indicates either:
1154          *   - a) load() failed to find a cached copy nor query the DB
1155          *   - b) we are in a special context or error mode that cannot use the DB
1156          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1157          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1158          *
1159          * @return bool
1160          * @since 1.27
1161          */
1162         public function isDisabled() {
1163                 return $this->mDisable;
1164         }
1165
1166         /**
1167          * Clear all stored messages. Mainly used after a mass rebuild.
1168          */
1169         function clear() {
1170                 $langs = Language::fetchLanguageNames( null, 'mw' );
1171                 foreach ( array_keys( $langs ) as $code ) {
1172                         # Global and local caches
1173                         $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
1174                 }
1175
1176                 $this->mLoadedLanguages = [];
1177         }
1178
1179         /**
1180          * @param string $key
1181          * @return array
1182          */
1183         public function figureMessage( $key ) {
1184                 global $wgLanguageCode;
1185
1186                 $pieces = explode( '/', $key );
1187                 if ( count( $pieces ) < 2 ) {
1188                         return [ $key, $wgLanguageCode ];
1189                 }
1190
1191                 $lang = array_pop( $pieces );
1192                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1193                         return [ $key, $wgLanguageCode ];
1194                 }
1195
1196                 $message = implode( '/', $pieces );
1197
1198                 return [ $message, $lang ];
1199         }
1200
1201         /**
1202          * Get all message keys stored in the message cache for a given language.
1203          * If $code is the content language code, this will return all message keys
1204          * for which MediaWiki:msgkey exists. If $code is another language code, this
1205          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1206          * @param string $code Language code
1207          * @return array Array of message keys (strings)
1208          */
1209         public function getAllMessageKeys( $code ) {
1210                 global $wgContLang;
1211
1212                 $this->load( $code );
1213                 if ( !isset( $this->mCache[$code] ) ) {
1214                         // Apparently load() failed
1215                         return null;
1216                 }
1217                 // Remove administrative keys
1218                 $cache = $this->mCache[$code];
1219                 unset( $cache['VERSION'] );
1220                 unset( $cache['EXPIRY'] );
1221                 unset( $cache['EXCESSIVE'] );
1222                 // Remove any !NONEXISTENT keys
1223                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1224
1225                 // Keys may appear with a capital first letter. lcfirst them.
1226                 return array_map( [ $wgContLang, 'lcfirst' ], array_keys( $cache ) );
1227         }
1228
1229         /**
1230          * Purge message caches when a MediaWiki: page is created, updated, or deleted
1231          *
1232          * @param Title $title Message page title
1233          * @param Content|null $content New content for edit/create, null on deletion
1234          * @since 1.29
1235          */
1236         public function updateMessageOverride( Title $title, Content $content = null ) {
1237                 global $wgContLang;
1238
1239                 $msgText = $this->getMessageTextFromContent( $content );
1240                 if ( $msgText === null ) {
1241                         $msgText = false; // treat as not existing
1242                 }
1243
1244                 $this->replace( $title->getDBkey(), $msgText );
1245
1246                 if ( $wgContLang->hasVariants() ) {
1247                         $wgContLang->updateConversionTable( $title );
1248                 }
1249         }
1250
1251         /**
1252          * @param Content|null $content Content or null if the message page does not exist
1253          * @return string|bool|null Returns false if $content is null and null on error
1254          */
1255         private function getMessageTextFromContent( Content $content = null ) {
1256                 // @TODO: could skip pseudo-messages like js/css here, based on content model
1257                 if ( $content ) {
1258                         // Message page exists...
1259                         // XXX: Is this the right way to turn a Content object into a message?
1260                         // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1261                         //       CssContent. MessageContent is *not* used for storing messages, it's
1262                         //       only used for wrapping them when needed.
1263                         $msgText = $content->getWikitextForTransclusion();
1264                         if ( $msgText === false || $msgText === null ) {
1265                                 // This might be due to some kind of misconfiguration...
1266                                 $msgText = null;
1267                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1268                                         __METHOD__ . ": message content doesn't provide wikitext "
1269                                         . "(content model: " . $content->getModel() . ")" );
1270                         }
1271                 } else {
1272                         // Message page does not exist...
1273                         $msgText = false;
1274                 }
1275
1276                 return $msgText;
1277         }
1278 }