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