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
  26 /**
  27  * MediaWiki message cache structure version.
  28  * Bump this whenever the message cache format has changed.
  29  */
  30 define( 'MSG_CACHE_VERSION', 2 );
  31
  32 /**
  33  * Message cache
  34  * Performs various MediaWiki namespace-related functions
  35  * @ingroup Cache
  36  */
  37 class MessageCache {
  38         const FOR_UPDATE = 1; // force message reload
  39
  40         /** How long to wait for memcached locks */
  41         const WAIT_SEC = 15;
  42         /** How long memcached locks last */
  43         const LOCK_TTL = 30;
  44
  45         /**
  46          * Process local cache of loaded messages that are defined in
  47          * MediaWiki namespace. First array level is a language code,
  48          * second level is message key and the values are either message
  49          * content prefixed with space, or !NONEXISTENT for negative
  50          * caching.
  51          * @var array $mCache
  52          */
  53         protected $mCache;
  54
  55         /**
  56          * Should mean that database cannot be used, but check
  57          * @var bool $mDisable
  58          */
  59         protected $mDisable;
  60
  61         /**
  62          * Lifetime for cache, used by object caching.
  63          * Set on construction, see __construct().
  64          */
  65         protected $mExpiry;
  66
  67         /**
  68          * Message cache has its own parser which it uses to transform
  69          * messages.
  70          */
  71         protected $mParserOptions, $mParser;
  72
  73         /**
  74          * Variable for tracking which variables are already loaded
  75          * @var array $mLoadedLanguages
  76          */
  77         protected $mLoadedLanguages = [];
  78
  79         /**
  80          * @var bool $mInParser
  81          */
  82         protected $mInParser = false;
  83
  84         /** @var BagOStuff */
  85         protected $mMemc;
  86         /** @var WANObjectCache */
  87         protected $wanCache;
  88
  89         /**
  90          * Singleton instance
  91          *
  92          * @var MessageCache $instance
  93          */
  94         private static $instance;
  95
  96         /**
  97          * Get the signleton instance of this class
  98          *
  99          * @since 1.18
 100          * @return MessageCache
 101          */
 102         public static function singleton() {
 103                 if ( self::$instance === null ) {
 104                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
 105                         self::$instance = new self(
 106                                 wfGetMessageCacheStorage(),
 107                                 $wgUseDatabaseMessages,
 108                                 $wgMsgCacheExpiry
 109                         );
 110                 }
 111
 112                 return self::$instance;
 113         }
 114
 115         /**
 116          * Destroy the singleton instance
 117          *
 118          * @since 1.18
 119          */
 120         public static function destroyInstance() {
 121                 self::$instance = null;
 122         }
 123
 124         /**
 125          * Normalize message key input
 126          *
 127          * @param string $key Input message key to be normalized
 128          * @return string Normalized message key
 129          */
 130         public static function normalizeKey( $key ) {
 131                 global $wgContLang;
 132                 $lckey = strtr( $key, ' ', '_' );
 133                 if ( ord( $lckey ) < 128 ) {
 134                         $lckey[0] = strtolower( $lckey[0] );
 135                 } else {
 136                         $lckey = $wgContLang->lcfirst( $lckey );
 137                 }
 138
 139                 return $lckey;
 140         }
 141
 142         /**
 143          * @param BagOStuff $memCached A cache instance. If none, fall back to CACHE_NONE.
 144          * @param bool $useDB
 145          * @param int $expiry Lifetime for cache. @see $mExpiry.
 146          */
 147         function __construct( $memCached, $useDB, $expiry ) {
 148                 global $wgUseLocalMessageCache;
 149
 150                 if ( !$memCached ) {
 151                         $memCached = wfGetCache( CACHE_NONE );
 152                 }
 153
 154                 $this->mMemc = $memCached;
 155                 $this->mDisable = !$useDB;
 156                 $this->mExpiry = $expiry;
 157
 158                 if ( $wgUseLocalMessageCache ) {
 159                         $this->localCache = MediaWikiServices::getInstance()->getLocalServerObjectCache();
 160                 } else {
 161                         $this->localCache = new EmptyBagOStuff();
 162                 }
 163
 164                 $this->wanCache = ObjectCache::getMainWANInstance();
 165         }
 166
 167         /**
 168          * ParserOptions is lazy initialised.
 169          *
 170          * @return ParserOptions
 171          */
 172         function getParserOptions() {
 173                 global $wgUser;
 174
 175                 if ( !$this->mParserOptions ) {
 176                         if ( !$wgUser->isSafeToLoad() ) {
 177                                 // $wgUser isn't unstubbable yet, so don't try to get a
 178                                 // ParserOptions for it. And don't cache this ParserOptions
 179                                 // either.
 180                                 $po = ParserOptions::newFromAnon();
 181                                 $po->setEditSection( false );
 182                                 return $po;
 183                         }
 184
 185                         $this->mParserOptions = new ParserOptions;
 186                         $this->mParserOptions->setEditSection( false );
 187                 }
 188
 189                 return $this->mParserOptions;
 190         }
 191
 192         /**
 193          * Try to load the cache from APC.
 194          *
 195          * @param string $code Optional language code, see documenation of load().
 196          * @return array|bool The cache array, or false if not in cache.
 197          */
 198         protected function getLocalCache( $code ) {
 199                 $cacheKey = wfMemcKey( __CLASS__, $code );
 200
 201                 return $this->localCache->get( $cacheKey );
 202         }
 203
 204         /**
 205          * Save the cache to APC.
 206          *
 207          * @param string $code
 208          * @param array $cache The cache array
 209          */
 210         protected function saveToLocalCache( $code, $cache ) {
 211                 $cacheKey = wfMemcKey( __CLASS__, $code );
 212                 $this->localCache->set( $cacheKey, $cache );
 213         }
 214
 215         /**
 216          * Loads messages from caches or from database in this order:
 217          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 218          * (2) memcached
 219          * (3) from the database.
 220          *
 221          * When succesfully loading from (2) or (3), all higher level caches are
 222          * updated for the newest version.
 223          *
 224          * Nothing is loaded if member variable mDisable is true, either manually
 225          * set by calling code or if message loading fails (is this possible?).
 226          *
 227          * Returns true if cache is already populated or it was succesfully populated,
 228          * or false if populating empty cache fails. Also returns true if MessageCache
 229          * is disabled.
 230          *
 231          * @param string $code Language to which load messages
 232          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache [optional]
 233          * @throws MWException
 234          * @return bool
 235          */
 236         protected function load( $code, $mode = null ) {
 237                 if ( !is_string( $code ) ) {
 238                         throw new InvalidArgumentException( "Missing language code" );
 239                 }
 240
 241                 # Don't do double loading...
 242                 if ( isset( $this->mLoadedLanguages[$code] ) && $mode != self::FOR_UPDATE ) {
 243                         return true;
 244                 }
 245
 246                 # 8 lines of code just to say (once) that message cache is disabled
 247                 if ( $this->mDisable ) {
 248                         static $shownDisabled = false;
 249                         if ( !$shownDisabled ) {
 250                                 wfDebug( __METHOD__ . ": disabled\n" );
 251                                 $shownDisabled = true;
 252                         }
 253
 254                         return true;
 255                 }
 256
 257                 # Loading code starts
 258                 $success = false; # Keep track of success
 259                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 260                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 261
 262                 # Hash of the contents is stored in memcache, to detect if data-center cache
 263                 # or local cache goes out of date (e.g. due to replace() on some other server)
 264                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 265
 266                 # Try the local cache and check against the cluster hash key...
 267                 $cache = $this->getLocalCache( $code );
 268                 if ( !$cache ) {
 269                         $where[] = 'local cache is empty';
 270                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 271                         $where[] = 'local cache has the wrong hash';
 272                         $staleCache = $cache;
 273                 } elseif ( $this->isCacheExpired( $cache ) ) {
 274                         $where[] = 'local cache is expired';
 275                         $staleCache = $cache;
 276                 } elseif ( $hashVolatile ) {
 277                         $where[] = 'local cache validation key is expired/volatile';
 278                         $staleCache = $cache;
 279                 } else {
 280                         $where[] = 'got from local cache';
 281                         $success = true;
 282                         $this->mCache[$code] = $cache;
 283                 }
 284
 285                 if ( !$success ) {
 286                         $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 287                         # Try the global cache. If it is empty, try to acquire a lock. If
 288                         # the lock can't be acquired, wait for the other thread to finish
 289                         # and then try the global cache a second time.
 290                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 291                                 if ( $hashVolatile && $staleCache ) {
 292                                         # Do not bother fetching the whole cache blob to avoid I/O.
 293                                         # Instead, just try to get the non-blocking $statusKey lock
 294                                         # below, and use the local stale value if it was not acquired.
 295                                         $where[] = 'global cache is presumed expired';
 296                                 } else {
 297                                         $cache = $this->mMemc->get( $cacheKey );
 298                                         if ( !$cache ) {
 299                                                 $where[] = 'global cache is empty';
 300                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 301                                                 $where[] = 'global cache is expired';
 302                                                 $staleCache = $cache;
 303                                         } elseif ( $hashVolatile ) {
 304                                                 # DB results are replica DB lag prone until the holdoff TTL passes.
 305                                                 # By then, updates should be reflected in loadFromDBWithLock().
 306                                                 # One thread renerates the cache while others use old values.
 307                                                 $where[] = 'global cache is expired/volatile';
 308                                                 $staleCache = $cache;
 309                                         } else {
 310                                                 $where[] = 'got from global cache';
 311                                                 $this->mCache[$code] = $cache;
 312                                                 $this->saveToCaches( $cache, 'local-only', $code );
 313                                                 $success = true;
 314                                         }
 315                                 }
 316
 317                                 if ( $success ) {
 318                                         # Done, no need to retry
 319                                         break;
 320                                 }
 321
 322                                 # We need to call loadFromDB. Limit the concurrency to one process.
 323                                 # This prevents the site from going down when the cache expires.
 324                                 # Note that the DB slam protection lock here is non-blocking.
 325                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 326                                 if ( $loadStatus === true ) {
 327                                         $success = true;
 328                                         break;
 329                                 } elseif ( $staleCache ) {
 330                                         # Use the stale cache while some other thread constructs the new one
 331                                         $where[] = 'using stale cache';
 332                                         $this->mCache[$code] = $staleCache;
 333                                         $success = true;
 334                                         break;
 335                                 } elseif ( $failedAttempts > 0 ) {
 336                                         # Already blocked once, so avoid another lock/unlock cycle.
 337                                         # This case will typically be hit if memcached is down, or if
 338                                         # loadFromDB() takes longer than LOCK_WAIT.
 339                                         $where[] = "could not acquire status key.";
 340                                         break;
 341                                 } elseif ( $loadStatus === 'cantacquire' ) {
 342                                         # Wait for the other thread to finish, then retry. Normally,
 343                                         # the memcached get() will then yeild the other thread's result.
 344                                         $where[] = 'waited for other thread to complete';
 345                                         $this->getReentrantScopedLock( $cacheKey );
 346                                 } else {
 347                                         # Disable cache; $loadStatus is 'disabled'
 348                                         break;
 349                                 }
 350                         }
 351                 }
 352
 353                 if ( !$success ) {
 354                         $where[] = 'loading FAILED - cache is disabled';
 355                         $this->mDisable = true;
 356                         $this->mCache = false;
 357                         wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
 358                         # This used to throw an exception, but that led to nasty side effects like
 359                         # the whole wiki being instantly down if the memcached server died
 360                 } else {
 361                         # All good, just record the success
 362                         $this->mLoadedLanguages[$code] = true;
 363                 }
 364
 365                 $info = implode( ', ', $where );
 366                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 367
 368                 return $success;
 369         }
 370
 371         /**
 372          * @param string $code
 373          * @param array $where List of wfDebug() comments
 374          * @param integer $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 375          * @return bool|string True on success or one of ("cantacquire", "disabled")
 376          */
 377         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 378                 global $wgUseLocalMessageCache;
 379
 380                 # If cache updates on all levels fail, give up on message overrides.
 381                 # This is to avoid easy site outages; see $saveSuccess comments below.
 382                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 383                 $status = $this->mMemc->get( $statusKey );
 384                 if ( $status === 'error' ) {
 385                         $where[] = "could not load; method is still globally disabled";
 386                         return 'disabled';
 387                 }
 388
 389                 # Now let's regenerate
 390                 $where[] = 'loading from database';
 391
 392                 # Lock the cache to prevent conflicting writes.
 393                 # This lock is non-blocking so stale cache can quickly be used.
 394                 # Note that load() will call a blocking getReentrantScopedLock()
 395                 # after this if it really need to wait for any current thread.
 396                 $cacheKey = wfMemcKey( 'messages', $code );
 397                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 398                 if ( !$scopedLock ) {
 399                         $where[] = 'could not acquire main lock';
 400                         return 'cantacquire';
 401                 }
 402
 403                 $cache = $this->loadFromDB( $code, $mode );
 404                 $this->mCache[$code] = $cache;
 405                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 406
 407                 if ( !$saveSuccess ) {
 408                         /**
 409                          * Cache save has failed.
 410                          *
 411                          * There are two main scenarios where this could be a problem:
 412                          * - The cache is more than the maximum size (typically 1MB compressed).
 413                          * - Memcached has no space remaining in the relevant slab class. This is
 414                          *   unlikely with recent versions of memcached.
 415                          *
 416                          * Either way, if there is a local cache, nothing bad will happen. If there
 417                          * is no local cache, disabling the message cache for all requests avoids
 418                          * incurring a loadFromDB() overhead on every request, and thus saves the
 419                          * wiki from complete downtime under moderate traffic conditions.
 420                          */
 421                         if ( !$wgUseLocalMessageCache ) {
 422                                 $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 423                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 424                         } else {
 425                                 $where[] = "could not save global cache";
 426                         }
 427                 }
 428
 429                 return true;
 430         }
 431
 432         /**
 433          * Loads cacheable messages from the database. Messages bigger than
 434          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 435          * on-demand from the database later.
 436          *
 437          * @param string $code Language code
 438          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 439          * @return array Loaded messages for storing in caches
 440          */
 441         function loadFromDB( $code, $mode = null ) {
 442                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 443
 444                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA );
 445
 446                 $cache = [];
 447
 448                 # Common conditions
 449                 $conds = [
 450                         'page_is_redirect' => 0,
 451                         'page_namespace' => NS_MEDIAWIKI,
 452                 ];
 453
 454                 $mostused = [];
 455                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 456                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 457                                 $this->load( $wgLanguageCode );
 458                         }
 459                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 460                         foreach ( $mostused as $key => $value ) {
 461                                 $mostused[$key] = "$value/$code";
 462                         }
 463                 }
 464
 465                 if ( count( $mostused ) ) {
 466                         $conds['page_title'] = $mostused;
 467                 } elseif ( $code !== $wgLanguageCode ) {
 468                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 469                 } else {
 470                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 471                         # other than language code.
 472                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 473                 }
 474
 475                 # Conditions to fetch oversized pages to ignore them
 476                 $bigConds = $conds;
 477                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 478
 479                 # Load titles for all oversized pages in the MediaWiki namespace
 480                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 481                 foreach ( $res as $row ) {
 482                         $cache[$row->page_title] = '!TOO BIG';
 483                 }
 484
 485                 # Conditions to load the remaining pages with their contents
 486                 $smallConds = $conds;
 487                 $smallConds[] = 'page_latest=rev_id';
 488                 $smallConds[] = 'rev_text_id=old_id';
 489                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 490
 491                 $res = $dbr->select(
 492                         [ 'page', 'revision', 'text' ],
 493                         [ 'page_title', 'old_text', 'old_flags' ],
 494                         $smallConds,
 495                         __METHOD__ . "($code)-small"
 496                 );
 497
 498                 foreach ( $res as $row ) {
 499                         $text = Revision::getRevisionText( $row );
 500                         if ( $text === false ) {
 501                                 // Failed to fetch data; possible ES errors?
 502                                 // Store a marker to fetch on-demand as a workaround...
 503                                 $entry = '!TOO BIG';
 504                                 wfDebugLog(
 505                                         'MessageCache',
 506                                         __METHOD__
 507                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 508                                 );
 509                         } else {
 510                                 $entry = ' ' . $text;
 511                         }
 512                         $cache[$row->page_title] = $entry;
 513                 }
 514
 515                 $cache['VERSION'] = MSG_CACHE_VERSION;
 516                 ksort( $cache );
 517                 $cache['HASH'] = md5( serialize( $cache ) );
 518                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 519
 520                 return $cache;
 521         }
 522
 523         /**
 524          * Updates cache as necessary when message page is changed
 525          *
 526          * @param string|bool $title Name of the page changed (false if deleted)
 527          * @param mixed $text New contents of the page.
 528          */
 529         public function replace( $title, $text ) {
 530                 global $wgMaxMsgCacheEntrySize, $wgContLang, $wgLanguageCode;
 531
 532                 if ( $this->mDisable ) {
 533                         return;
 534                 }
 535
 536                 list( $msg, $code ) = $this->figureMessage( $title );
 537                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 538                         // Content language overrides do not use the /<code> suffix
 539                         return;
 540                 }
 541
 542                 // Note that if the cache is volatile, load() may trigger a DB fetch.
 543                 // In that case we reenter/reuse the existing cache key lock to avoid
 544                 // a self-deadlock. This is safe as no reads happen *directly* in this
 545                 // method between getReentrantScopedLock() and load() below. There is
 546                 // no risk of data "changing under our feet" for replace().
 547                 $cacheKey = wfMemcKey( 'messages', $code );
 548                 $scopedLock = $this->getReentrantScopedLock( $cacheKey );
 549                 $this->load( $code, self::FOR_UPDATE );
 550
 551                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 552                 if ( $text === false ) {
 553                         // Article was deleted
 554                         $this->mCache[$code][$title] = '!NONEXISTENT';
 555                         $this->wanCache->delete( $titleKey );
 556                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 557                         // Check for size
 558                         $this->mCache[$code][$title] = '!TOO BIG';
 559                         $this->wanCache->set( $titleKey, ' ' . $text, $this->mExpiry );
 560                 } else {
 561                         $this->mCache[$code][$title] = ' ' . $text;
 562                         $this->wanCache->delete( $titleKey );
 563                 }
 564
 565                 // Mark this cache as definitely "latest" (non-volatile) so
 566                 // load() calls do try to refresh the cache with replica DB data
 567                 $this->mCache[$code]['LATEST'] = time();
 568
 569                 // Update caches if the lock was acquired
 570                 if ( $scopedLock ) {
 571                         $this->saveToCaches( $this->mCache[$code], 'all', $code );
 572                 }
 573
 574                 ScopedCallback::consume( $scopedLock );
 575                 // Relay the purge to APC and other DCs
 576                 $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
 577
 578                 // Also delete cached sidebar... just in case it is affected
 579                 $codes = [ $code ];
 580                 if ( $code === 'en' ) {
 581                         // Delete all sidebars, like for example on action=purge on the
 582                         // sidebar messages
 583                         $codes = array_keys( Language::fetchLanguageNames() );
 584                 }
 585
 586                 foreach ( $codes as $code ) {
 587                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 588                         $this->wanCache->delete( $sidebarKey );
 589                 }
 590
 591                 // Update the message in the message blob store
 592                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 593                 $blobStore = $resourceloader->getMessageBlobStore();
 594                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 595
 596                 Hooks::run( 'MessageCacheReplace', [ $title, $text ] );
 597         }
 598
 599         /**
 600          * Is the given cache array expired due to time passing or a version change?
 601          *
 602          * @param array $cache
 603          * @return bool
 604          */
 605         protected function isCacheExpired( $cache ) {
 606                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 607                         return true;
 608                 }
 609                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 610                         return true;
 611                 }
 612                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 613                         return true;
 614                 }
 615
 616                 return false;
 617         }
 618
 619         /**
 620          * Shortcut to update caches.
 621          *
 622          * @param array $cache Cached messages with a version.
 623          * @param string $dest Either "local-only" to save to local caches only
 624          *   or "all" to save to all caches.
 625          * @param string|bool $code Language code (default: false)
 626          * @return bool
 627          */
 628         protected function saveToCaches( array $cache, $dest, $code = false ) {
 629                 if ( $dest === 'all' ) {
 630                         $cacheKey = wfMemcKey( 'messages', $code );
 631                         $success = $this->mMemc->set( $cacheKey, $cache );
 632                         $this->setValidationHash( $code, $cache );
 633                 } else {
 634                         $success = true;
 635                 }
 636
 637                 $this->saveToLocalCache( $code, $cache );
 638
 639                 return $success;
 640         }
 641
 642         /**
 643          * Get the md5 used to validate the local APC cache
 644          *
 645          * @param string $code
 646          * @return array (hash or false, bool expiry/volatility status)
 647          */
 648         protected function getValidationHash( $code ) {
 649                 $curTTL = null;
 650                 $value = $this->wanCache->get(
 651                         wfMemcKey( 'messages', $code, 'hash', 'v1' ),
 652                         $curTTL,
 653                         [ wfMemcKey( 'messages', $code ) ]
 654                 );
 655
 656                 if ( !$value ) {
 657                         // No hash found at all; cache must regenerate to be safe
 658                         $hash = false;
 659                         $expired = true;
 660                 } else {
 661                         $hash = $value['hash'];
 662                         if ( ( time() - $value['latest'] ) < WANObjectCache::HOLDOFF_TTL ) {
 663                                 // Cache was recently updated via replace() and should be up-to-date
 664                                 $expired = false;
 665                         } else {
 666                                 // See if the "check" key was bumped after the hash was generated
 667                                 $expired = ( $curTTL < 0 );
 668                         }
 669                 }
 670
 671                 return [ $hash, $expired ];
 672         }
 673
 674         /**
 675          * Set the md5 used to validate the local disk cache
 676          *
 677          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 678          * be treated as "volatile" by getValidationHash() for the next few seconds
 679          *
 680          * @param string $code
 681          * @param array $cache Cached messages with a version
 682          */
 683         protected function setValidationHash( $code, array $cache ) {
 684                 $this->wanCache->set(
 685                         wfMemcKey( 'messages', $code, 'hash', 'v1' ),
 686                         [
 687                                 'hash' => $cache['HASH'],
 688                                 'latest' => isset( $cache['LATEST'] ) ? $cache['LATEST'] : 0
 689                         ],
 690                         WANObjectCache::TTL_INDEFINITE
 691                 );
 692         }
 693
 694         /**
 695          * @param string $key A language message cache key that stores blobs
 696          * @param integer $timeout Wait timeout in seconds
 697          * @return null|ScopedCallback
 698          */
 699         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 700                 return $this->mMemc->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 701         }
 702
 703         /**
 704          * Get a message from either the content language or the user language.
 705          *
 706          * First, assemble a list of languages to attempt getting the message from. This
 707          * chain begins with the requested language and its fallbacks and then continues with
 708          * the content language and its fallbacks. For each language in the chain, the following
 709          * process will occur (in this order):
 710          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 711          *     Note: for the content language, there is no /lang subpage.
 712          *  2. Fetch from the static CDB cache.
 713          *  3. If available, check the database for fallback language overrides.
 714          *
 715          * This process provides a number of guarantees. When changing this code, make sure all
 716          * of these guarantees are preserved.
 717          *  * If the requested language is *not* the content language, then the CDB cache for that
 718          *    specific language will take precedence over the root database page ([[MW:msg]]).
 719          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 720          *    the message is available *anywhere* in the language for which it is a fallback.
 721          *
 722          * @param string $key The message key
 723          * @param bool $useDB If true, look for the message in the DB, false
 724          *   to use only the compiled l10n cache.
 725          * @param bool|string|object $langcode Code of the language to get the message for.
 726          *   - If string and a valid code, will create a standard language object
 727          *   - If string but not a valid code, will create a basic language object
 728          *   - If boolean and false, create object from the current users language
 729          *   - If boolean and true, create object from the wikis content language
 730          *   - If language object, use it as given
 731          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 732          *
 733          * @throws MWException When given an invalid key
 734          * @return string|bool False if the message doesn't exist, otherwise the
 735          *   message (which can be empty)
 736          */
 737         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 738                 if ( is_int( $key ) ) {
 739                         // Fix numerical strings that somehow become ints
 740                         // on their way here
 741                         $key = (string)$key;
 742                 } elseif ( !is_string( $key ) ) {
 743                         throw new MWException( 'Non-string key given' );
 744                 } elseif ( $key === '' ) {
 745                         // Shortcut: the empty key is always missing
 746                         return false;
 747                 }
 748
 749                 // For full keys, get the language code from the key
 750                 $pos = strrpos( $key, '/' );
 751                 if ( $isFullKey && $pos !== false ) {
 752                         $langcode = substr( $key, $pos + 1 );
 753                         $key = substr( $key, 0, $pos );
 754                 }
 755
 756                 // Normalise title-case input (with some inlining)
 757                 $lckey = MessageCache::normalizeKey( $key );
 758
 759                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 760
 761                 // Loop through each language in the fallback list until we find something useful
 762                 $lang = wfGetLangObj( $langcode );
 763                 $message = $this->getMessageFromFallbackChain(
 764                         $lang,
 765                         $lckey,
 766                         !$this->mDisable && $useDB
 767                 );
 768
 769                 // If we still have no message, maybe the key was in fact a full key so try that
 770                 if ( $message === false ) {
 771                         $parts = explode( '/', $lckey );
 772                         // We may get calls for things that are http-urls from sidebar
 773                         // Let's not load nonexistent languages for those
 774                         // They usually have more than one slash.
 775                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 776                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 777                                 if ( $message === null ) {
 778                                         $message = false;
 779                                 }
 780                         }
 781                 }
 782
 783                 // Post-processing if the message exists
 784                 if ( $message !== false ) {
 785                         // Fix whitespace
 786                         $message = str_replace(
 787                                 [
 788                                         # Fix for trailing whitespace, removed by textarea
 789                                         '&#32;',
 790                                         # Fix for NBSP, converted to space by firefox
 791                                         '&nbsp;',
 792                                         '&#160;',
 793                                         '&shy;'
 794                                 ],
 795                                 [
 796                                         ' ',
 797                                         "\xc2\xa0",
 798                                         "\xc2\xa0",
 799                                         "\xc2\xad"
 800                                 ],
 801                                 $message
 802                         );
 803                 }
 804
 805                 return $message;
 806         }
 807
 808         /**
 809          * Given a language, try and fetch messages from that language.
 810          *
 811          * Will also consider fallbacks of that language, the site language, and fallbacks for
 812          * the site language.
 813          *
 814          * @see MessageCache::get
 815          * @param Language|StubObject $lang Preferred language
 816          * @param string $lckey Lowercase key for the message (as for localisation cache)
 817          * @param bool $useDB Whether to include messages from the wiki database
 818          * @return string|bool The message, or false if not found
 819          */
 820         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 821                 global $wgContLang;
 822
 823                 $alreadyTried = [];
 824
 825                  // First try the requested language.
 826                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 827                 if ( $message !== false ) {
 828                         return $message;
 829                 }
 830
 831                 // Now try checking the site language.
 832                 $message = $this->getMessageForLang( $wgContLang, $lckey, $useDB, $alreadyTried );
 833                 return $message;
 834         }
 835
 836         /**
 837          * Given a language, try and fetch messages from that language and its fallbacks.
 838          *
 839          * @see MessageCache::get
 840          * @param Language|StubObject $lang Preferred language
 841          * @param string $lckey Lowercase key for the message (as for localisation cache)
 842          * @param bool $useDB Whether to include messages from the wiki database
 843          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 844          * @return string|bool The message, or false if not found
 845          */
 846         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 847                 global $wgContLang;
 848                 $langcode = $lang->getCode();
 849
 850                 // Try checking the database for the requested language
 851                 if ( $useDB ) {
 852                         $uckey = $wgContLang->ucfirst( $lckey );
 853
 854                         if ( !isset( $alreadyTried[ $langcode ] ) ) {
 855                                 $message = $this->getMsgFromNamespace(
 856                                         $this->getMessagePageName( $langcode, $uckey ),
 857                                         $langcode
 858                                 );
 859
 860                                 if ( $message !== false ) {
 861                                         return $message;
 862                                 }
 863                                 $alreadyTried[ $langcode ] = true;
 864                         }
 865                 } else {
 866                         $uckey = null;
 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(
 885                                         $this->getMessagePageName( $code, $uckey ), $code );
 886
 887                                 if ( $message !== false ) {
 888                                         return $message;
 889                                 }
 890                                 $alreadyTried[ $code ] = true;
 891                         }
 892                 }
 893
 894                 return false;
 895         }
 896
 897         /**
 898          * Get the message page name for a given language
 899          *
 900          * @param string $langcode
 901          * @param string $uckey Uppercase key for the message
 902          * @return string The page name
 903          */
 904         private function getMessagePageName( $langcode, $uckey ) {
 905                 global $wgLanguageCode;
 906                 if ( $langcode === $wgLanguageCode ) {
 907                         // Messages created in the content language will not have the /lang extension
 908                         return $uckey;
 909                 } else {
 910                         return "$uckey/$langcode";
 911                 }
 912         }
 913
 914         /**
 915          * Get a message from the MediaWiki namespace, with caching. The key must
 916          * first be converted to two-part lang/msg form if necessary.
 917          *
 918          * Unlike self::get(), this function doesn't resolve fallback chains, and
 919          * some callers require this behavior. LanguageConverter::parseCachedTable()
 920          * and self::get() are some examples in core.
 921          *
 922          * @param string $title Message cache key with initial uppercase letter.
 923          * @param string $code Code denoting the language to try.
 924          * @return string|bool The message, or false if it does not exist or on error
 925          */
 926         public function getMsgFromNamespace( $title, $code ) {
 927                 $this->load( $code );
 928                 if ( isset( $this->mCache[$code][$title] ) ) {
 929                         $entry = $this->mCache[$code][$title];
 930                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 931                                 // The message exists, so make sure a string
 932                                 // is returned.
 933                                 return (string)substr( $entry, 1 );
 934                         } elseif ( $entry === '!NONEXISTENT' ) {
 935                                 return false;
 936                         } elseif ( $entry === '!TOO BIG' ) {
 937                                 // Fall through and try invididual message cache below
 938                         }
 939                 } else {
 940                         // XXX: This is not cached in process cache, should it?
 941                         $message = false;
 942                         Hooks::run( 'MessagesPreLoad', [ $title, &$message ] );
 943                         if ( $message !== false ) {
 944                                 return $message;
 945                         }
 946
 947                         return false;
 948                 }
 949
 950                 // Try the individual message cache
 951                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 952
 953                 $curTTL = null;
 954                 $entry = $this->wanCache->get(
 955                         $titleKey,
 956                         $curTTL,
 957                         [ wfMemcKey( 'messages', $code ) ]
 958                 );
 959                 $entry = ( $curTTL >= 0 ) ? $entry : false;
 960
 961                 if ( $entry ) {
 962                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 963                                 $this->mCache[$code][$title] = $entry;
 964                                 // The message exists, so make sure a string is returned
 965                                 return (string)substr( $entry, 1 );
 966                         } elseif ( $entry === '!NONEXISTENT' ) {
 967                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 968
 969                                 return false;
 970                         } else {
 971                                 // Corrupt/obsolete entry, delete it
 972                                 $this->wanCache->delete( $titleKey );
 973                         }
 974                 }
 975
 976                 // Try loading it from the database
 977                 $dbr = wfGetDB( DB_REPLICA );
 978                 $cacheOpts = Database::getCacheSetOptions( $dbr );
 979                 // Use newKnownCurrent() to avoid querying revision/user tables
 980                 $titleObj = Title::makeTitle( NS_MEDIAWIKI, $title );
 981                 if ( $titleObj->getLatestRevID() ) {
 982                         $revision = Revision::newKnownCurrent(
 983                                 $dbr,
 984                                 $titleObj->getArticleID(),
 985                                 $titleObj->getLatestRevID()
 986                         );
 987                 } else {
 988                         $revision = false;
 989                 }
 990
 991                 if ( $revision ) {
 992                         $content = $revision->getContent();
 993                         if ( !$content ) {
 994                                 // A possibly temporary loading failure.
 995                                 wfDebugLog(
 996                                         'MessageCache',
 997                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
 998                                 );
 999                                 $message = null; // no negative caching
1000                         } else {
1001                                 // XXX: Is this the right way to turn a Content object into a message?
1002                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1003                                 //       CssContent. MessageContent is *not* used for storing messages, it's
1004                                 //       only used for wrapping them when needed.
1005                                 $message = $content->getWikitextForTransclusion();
1006
1007                                 if ( $message === false || $message === null ) {
1008                                         wfDebugLog(
1009                                                 'MessageCache',
1010                                                 __METHOD__ . ": message content doesn't provide wikitext "
1011                                                         . "(content model: " . $content->getModel() . ")"
1012                                         );
1013
1014                                         $message = false; // negative caching
1015                                 } else {
1016                                         $this->mCache[$code][$title] = ' ' . $message;
1017                                         $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry, $cacheOpts );
1018                                 }
1019                         }
1020                 } else {
1021                         $message = false; // negative caching
1022                 }
1023
1024                 if ( $message === false ) { // negative caching
1025                         $this->mCache[$code][$title] = '!NONEXISTENT';
1026                         $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry, $cacheOpts );
1027                 }
1028
1029                 return $message;
1030         }
1031
1032         /**
1033          * @param string $message
1034          * @param bool $interface
1035          * @param string $language Language code
1036          * @param Title $title
1037          * @return string
1038          */
1039         function transform( $message, $interface = false, $language = null, $title = null ) {
1040                 // Avoid creating parser if nothing to transform
1041                 if ( strpos( $message, '{{' ) === false ) {
1042                         return $message;
1043                 }
1044
1045                 if ( $this->mInParser ) {
1046                         return $message;
1047                 }
1048
1049                 $parser = $this->getParser();
1050                 if ( $parser ) {
1051                         $popts = $this->getParserOptions();
1052                         $popts->setInterfaceMessage( $interface );
1053                         $popts->setTargetLanguage( $language );
1054
1055                         $userlang = $popts->setUserLang( $language );
1056                         $this->mInParser = true;
1057                         $message = $parser->transformMsg( $message, $popts, $title );
1058                         $this->mInParser = false;
1059                         $popts->setUserLang( $userlang );
1060                 }
1061
1062                 return $message;
1063         }
1064
1065         /**
1066          * @return Parser
1067          */
1068         function getParser() {
1069                 global $wgParser, $wgParserConf;
1070                 if ( !$this->mParser && isset( $wgParser ) ) {
1071                         # Do some initialisation so that we don't have to do it twice
1072                         $wgParser->firstCallInit();
1073                         # Clone it and store it
1074                         $class = $wgParserConf['class'];
1075                         if ( $class == 'ParserDiffTest' ) {
1076                                 # Uncloneable
1077                                 $this->mParser = new $class( $wgParserConf );
1078                         } else {
1079                                 $this->mParser = clone $wgParser;
1080                         }
1081                 }
1082
1083                 return $this->mParser;
1084         }
1085
1086         /**
1087          * @param string $text
1088          * @param Title $title
1089          * @param bool $linestart Whether or not this is at the start of a line
1090          * @param bool $interface Whether this is an interface message
1091          * @param Language|string $language Language code
1092          * @return ParserOutput|string
1093          */
1094         public function parse( $text, $title = null, $linestart = true,
1095                 $interface = false, $language = null
1096         ) {
1097                 if ( $this->mInParser ) {
1098                         return htmlspecialchars( $text );
1099                 }
1100
1101                 $parser = $this->getParser();
1102                 $popts = $this->getParserOptions();
1103                 $popts->setInterfaceMessage( $interface );
1104
1105                 if ( is_string( $language ) ) {
1106                         $language = Language::factory( $language );
1107                 }
1108                 $popts->setTargetLanguage( $language );
1109
1110                 if ( !$title || !$title instanceof Title ) {
1111                         global $wgTitle;
1112                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1113                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1114                         $title = $wgTitle;
1115                 }
1116                 // Sometimes $wgTitle isn't set either...
1117                 if ( !$title ) {
1118                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1119                         # Create a ghost title in such case
1120                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1121                 }
1122
1123                 $this->mInParser = true;
1124                 $res = $parser->parse( $text, $title, $popts, $linestart );
1125                 $this->mInParser = false;
1126
1127                 return $res;
1128         }
1129
1130         function disable() {
1131                 $this->mDisable = true;
1132         }
1133
1134         function enable() {
1135                 $this->mDisable = false;
1136         }
1137
1138         /**
1139          * Whether DB/cache usage is disabled for determining messages
1140          *
1141          * If so, this typically indicates either:
1142          *   - a) load() failed to find a cached copy nor query the DB
1143          *   - b) we are in a special context or error mode that cannot use the DB
1144          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1145          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1146          *
1147          * @return bool
1148          * @since 1.27
1149          */
1150         public function isDisabled() {
1151                 return $this->mDisable;
1152         }
1153
1154         /**
1155          * Clear all stored messages. Mainly used after a mass rebuild.
1156          */
1157         function clear() {
1158                 $langs = Language::fetchLanguageNames( null, 'mw' );
1159                 foreach ( array_keys( $langs ) as $code ) {
1160                         # Global and local caches
1161                         $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
1162                 }
1163
1164                 $this->mLoadedLanguages = [];
1165         }
1166
1167         /**
1168          * @param string $key
1169          * @return array
1170          */
1171         public function figureMessage( $key ) {
1172                 global $wgLanguageCode;
1173
1174                 $pieces = explode( '/', $key );
1175                 if ( count( $pieces ) < 2 ) {
1176                         return [ $key, $wgLanguageCode ];
1177                 }
1178
1179                 $lang = array_pop( $pieces );
1180                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1181                         return [ $key, $wgLanguageCode ];
1182                 }
1183
1184                 $message = implode( '/', $pieces );
1185
1186                 return [ $message, $lang ];
1187         }
1188
1189         /**
1190          * Get all message keys stored in the message cache for a given language.
1191          * If $code is the content language code, this will return all message keys
1192          * for which MediaWiki:msgkey exists. If $code is another language code, this
1193          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1194          * @param string $code Language code
1195          * @return array Array of message keys (strings)
1196          */
1197         public function getAllMessageKeys( $code ) {
1198                 global $wgContLang;
1199                 $this->load( $code );
1200                 if ( !isset( $this->mCache[$code] ) ) {
1201                         // Apparently load() failed
1202                         return null;
1203                 }
1204                 // Remove administrative keys
1205                 $cache = $this->mCache[$code];
1206                 unset( $cache['VERSION'] );
1207                 unset( $cache['EXPIRY'] );
1208                 // Remove any !NONEXISTENT keys
1209                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1210
1211                 // Keys may appear with a capital first letter. lcfirst them.
1212                 return array_map( [ $wgContLang, 'lcfirst' ], array_keys( $cache ) );
1213         }
1214 }