includes/cache/MessageCache.php

   1 <?php
   2 /**
   3  * Localisation messages cache.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Cache
  22  */
  23 use MediaWiki\MediaWikiServices;
  24 use Wikimedia\ScopedCallback;
  25 use MediaWiki\Logger\LoggerFactory;
  26
  27 /**
  28  * MediaWiki message cache structure version.
  29  * Bump this whenever the message cache format has changed.
  30  */
  31 define( 'MSG_CACHE_VERSION', 2 );
  32
  33 /**
  34  * Message cache
  35  * Performs various MediaWiki namespace-related functions
  36  * @ingroup Cache
  37  */
  38 class MessageCache {
  39         const FOR_UPDATE = 1; // force message reload
  40
  41         /** How long to wait for memcached locks */
  42         const WAIT_SEC = 15;
  43         /** How long memcached locks last */
  44         const LOCK_TTL = 30;
  45
  46         /**
  47          * Process local cache of loaded messages that are defined in
  48          * MediaWiki namespace. First array level is a language code,
  49          * second level is message key and the values are either message
  50          * content prefixed with space, or !NONEXISTENT for negative
  51          * caching.
  52          * @var array $mCache
  53          */
  54         protected $mCache;
  55
  56         /**
  57          * @var bool[] Map of (language code => boolean)
  58          */
  59         protected $mCacheVolatile = [];
  60
  61         /**
  62          * Should mean that database cannot be used, but check
  63          * @var bool $mDisable
  64          */
  65         protected $mDisable;
  66
  67         /**
  68          * Lifetime for cache, used by object caching.
  69          * Set on construction, see __construct().
  70          */
  71         protected $mExpiry;
  72
  73         /**
  74          * Message cache has its own parser which it uses to transform messages
  75          * @var ParserOptions
  76          */
  77         protected $mParserOptions;
  78         /** @var Parser */
  79         protected $mParser;
  80
  81         /**
  82          * Variable for tracking which variables are already loaded
  83          * @var array $mLoadedLanguages
  84          */
  85         protected $mLoadedLanguages = [];
  86
  87         /**
  88          * @var bool $mInParser
  89          */
  90         protected $mInParser = false;
  91
  92         /** @var BagOStuff */
  93         protected $mMemc;
  94         /** @var WANObjectCache */
  95         protected $wanCache;
  96
  97         /**
  98          * Singleton instance
  99          *
 100          * @var MessageCache $instance
 101          */
 102         private static $instance;
 103
 104         /**
 105          * Get the signleton instance of this class
 106          *
 107          * @since 1.18
 108          * @return MessageCache
 109          */
 110         public static function singleton() {
 111                 if ( self::$instance === null ) {
 112                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
 113                         self::$instance = new self(
 114                                 wfGetMessageCacheStorage(),
 115                                 $wgUseDatabaseMessages,
 116                                 $wgMsgCacheExpiry
 117                         );
 118                 }
 119
 120                 return self::$instance;
 121         }
 122
 123         /**
 124          * Destroy the singleton instance
 125          *
 126          * @since 1.18
 127          */
 128         public static function destroyInstance() {
 129                 self::$instance = null;
 130         }
 131
 132         /**
 133          * Normalize message key input
 134          *
 135          * @param string $key Input message key to be normalized
 136          * @return string Normalized message key
 137          */
 138         public static function normalizeKey( $key ) {
 139                 global $wgContLang;
 140
 141                 $lckey = strtr( $key, ' ', '_' );
 142                 if ( ord( $lckey ) < 128 ) {
 143                         $lckey[0] = strtolower( $lckey[0] );
 144                 } else {
 145                         $lckey = $wgContLang->lcfirst( $lckey );
 146                 }
 147
 148                 return $lckey;
 149         }
 150
 151         /**
 152          * @param BagOStuff $memCached A cache instance. If none, fall back to CACHE_NONE.
 153          * @param bool $useDB
 154          * @param int $expiry Lifetime for cache. @see $mExpiry.
 155          */
 156         function __construct( BagOStuff $memCached, $useDB, $expiry ) {
 157                 global $wgUseLocalMessageCache;
 158
 159                 $this->mMemc = $memCached;
 160                 $this->mDisable = !$useDB;
 161                 $this->mExpiry = $expiry;
 162
 163                 if ( $wgUseLocalMessageCache ) {
 164                         $this->localCache = MediaWikiServices::getInstance()->getLocalServerObjectCache();
 165                 } else {
 166                         $this->localCache = new EmptyBagOStuff();
 167                 }
 168
 169                 $this->wanCache = ObjectCache::getMainWANInstance();
 170         }
 171
 172         /**
 173          * ParserOptions is lazy initialised.
 174          *
 175          * @return ParserOptions
 176          */
 177         function getParserOptions() {
 178                 global $wgUser;
 179
 180                 if ( !$this->mParserOptions ) {
 181                         if ( !$wgUser->isSafeToLoad() ) {
 182                                 // $wgUser isn't unstubbable yet, so don't try to get a
 183                                 // ParserOptions for it. And don't cache this ParserOptions
 184                                 // either.
 185                                 $po = ParserOptions::newFromAnon();
 186                                 $po->setEditSection( false );
 187                                 return $po;
 188                         }
 189
 190                         $this->mParserOptions = new ParserOptions;
 191                         $this->mParserOptions->setEditSection( false );
 192                 }
 193
 194                 return $this->mParserOptions;
 195         }
 196
 197         /**
 198          * Try to load the cache from APC.
 199          *
 200          * @param string $code Optional language code, see documenation of load().
 201          * @return array|bool The cache array, or false if not in cache.
 202          */
 203         protected function getLocalCache( $code ) {
 204                 $cacheKey = wfMemcKey( __CLASS__, $code );
 205
 206                 return $this->localCache->get( $cacheKey );
 207         }
 208
 209         /**
 210          * Save the cache to APC.
 211          *
 212          * @param string $code
 213          * @param array $cache The cache array
 214          */
 215         protected function saveToLocalCache( $code, $cache ) {
 216                 $cacheKey = wfMemcKey( __CLASS__, $code );
 217                 $this->localCache->set( $cacheKey, $cache );
 218         }
 219
 220         /**
 221          * Loads messages from caches or from database in this order:
 222          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 223          * (2) memcached
 224          * (3) from the database.
 225          *
 226          * When succesfully loading from (2) or (3), all higher level caches are
 227          * updated for the newest version.
 228          *
 229          * Nothing is loaded if member variable mDisable is true, either manually
 230          * set by calling code or if message loading fails (is this possible?).
 231          *
 232          * Returns true if cache is already populated or it was succesfully populated,
 233          * or false if populating empty cache fails. Also returns true if MessageCache
 234          * is disabled.
 235          *
 236          * @param string $code Language to which load messages
 237          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache [optional]
 238          * @throws MWException
 239          * @return bool
 240          */
 241         protected function load( $code, $mode = null ) {
 242                 if ( !is_string( $code ) ) {
 243                         throw new InvalidArgumentException( "Missing language code" );
 244                 }
 245
 246                 # Don't do double loading...
 247                 if ( isset( $this->mLoadedLanguages[$code] ) && $mode != self::FOR_UPDATE ) {
 248                         return true;
 249                 }
 250
 251                 # 8 lines of code just to say (once) that message cache is disabled
 252                 if ( $this->mDisable ) {
 253                         static $shownDisabled = false;
 254                         if ( !$shownDisabled ) {
 255                                 wfDebug( __METHOD__ . ": disabled\n" );
 256                                 $shownDisabled = true;
 257                         }
 258
 259                         return true;
 260                 }
 261
 262                 # Loading code starts
 263                 $success = false; # Keep track of success
 264                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 265                 $where = []; # Debug info, delayed to avoid spamming debug log too much
 266
 267                 # Hash of the contents is stored in memcache, to detect if data-center cache
 268                 # or local cache goes out of date (e.g. due to replace() on some other server)
 269                 list( $hash, $hashVolatile ) = $this->getValidationHash( $code );
 270                 $this->mCacheVolatile[$code] = $hashVolatile;
 271
 272                 # Try the local cache and check against the cluster hash key...
 273                 $cache = $this->getLocalCache( $code );
 274                 if ( !$cache ) {
 275                         $where[] = 'local cache is empty';
 276                 } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
 277                         $where[] = 'local cache has the wrong hash';
 278                         $staleCache = $cache;
 279                 } elseif ( $this->isCacheExpired( $cache ) ) {
 280                         $where[] = 'local cache is expired';
 281                         $staleCache = $cache;
 282                 } elseif ( $hashVolatile ) {
 283                         $where[] = 'local cache validation key is expired/volatile';
 284                         $staleCache = $cache;
 285                 } else {
 286                         $where[] = 'got from local cache';
 287                         $success = true;
 288                         $this->mCache[$code] = $cache;
 289                 }
 290
 291                 if ( !$success ) {
 292                         $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 293                         # Try the global cache. If it is empty, try to acquire a lock. If
 294                         # the lock can't be acquired, wait for the other thread to finish
 295                         # and then try the global cache a second time.
 296                         for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
 297                                 if ( $hashVolatile && $staleCache ) {
 298                                         # Do not bother fetching the whole cache blob to avoid I/O.
 299                                         # Instead, just try to get the non-blocking $statusKey lock
 300                                         # below, and use the local stale value if it was not acquired.
 301                                         $where[] = 'global cache is presumed expired';
 302                                 } else {
 303                                         $cache = $this->mMemc->get( $cacheKey );
 304                                         if ( !$cache ) {
 305                                                 $where[] = 'global cache is empty';
 306                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 307                                                 $where[] = 'global cache is expired';
 308                                                 $staleCache = $cache;
 309                                         } elseif ( $hashVolatile ) {
 310                                                 # DB results are replica DB lag prone until the holdoff TTL passes.
 311                                                 # By then, updates should be reflected in loadFromDBWithLock().
 312                                                 # One thread renerates the cache while others use old values.
 313                                                 $where[] = 'global cache is expired/volatile';
 314                                                 $staleCache = $cache;
 315                                         } else {
 316                                                 $where[] = 'got from global cache';
 317                                                 $this->mCache[$code] = $cache;
 318                                                 $this->saveToCaches( $cache, 'local-only', $code );
 319                                                 $success = true;
 320                                         }
 321                                 }
 322
 323                                 if ( $success ) {
 324                                         # Done, no need to retry
 325                                         break;
 326                                 }
 327
 328                                 # We need to call loadFromDB. Limit the concurrency to one process.
 329                                 # This prevents the site from going down when the cache expires.
 330                                 # Note that the DB slam protection lock here is non-blocking.
 331                                 $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
 332                                 if ( $loadStatus === true ) {
 333                                         $success = true;
 334                                         break;
 335                                 } elseif ( $staleCache ) {
 336                                         # Use the stale cache while some other thread constructs the new one
 337                                         $where[] = 'using stale cache';
 338                                         $this->mCache[$code] = $staleCache;
 339                                         $success = true;
 340                                         break;
 341                                 } elseif ( $failedAttempts > 0 ) {
 342                                         # Already blocked once, so avoid another lock/unlock cycle.
 343                                         # This case will typically be hit if memcached is down, or if
 344                                         # loadFromDB() takes longer than LOCK_WAIT.
 345                                         $where[] = "could not acquire status key.";
 346                                         break;
 347                                 } elseif ( $loadStatus === 'cantacquire' ) {
 348                                         # Wait for the other thread to finish, then retry. Normally,
 349                                         # the memcached get() will then yeild the other thread's result.
 350                                         $where[] = 'waited for other thread to complete';
 351                                         $this->getReentrantScopedLock( $cacheKey );
 352                                 } else {
 353                                         # Disable cache; $loadStatus is 'disabled'
 354                                         break;
 355                                 }
 356                         }
 357                 }
 358
 359                 if ( !$success ) {
 360                         $where[] = 'loading FAILED - cache is disabled';
 361                         $this->mDisable = true;
 362                         $this->mCache = false;
 363                         wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
 364                         # This used to throw an exception, but that led to nasty side effects like
 365                         # the whole wiki being instantly down if the memcached server died
 366                 } else {
 367                         # All good, just record the success
 368                         $this->mLoadedLanguages[$code] = true;
 369                 }
 370
 371                 $info = implode( ', ', $where );
 372                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 373
 374                 return $success;
 375         }
 376
 377         /**
 378          * @param string $code
 379          * @param array $where List of wfDebug() comments
 380          * @param integer $mode Use MessageCache::FOR_UPDATE to use DB_MASTER
 381          * @return bool|string True on success or one of ("cantacquire", "disabled")
 382          */
 383         protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
 384                 global $wgUseLocalMessageCache;
 385
 386                 # If cache updates on all levels fail, give up on message overrides.
 387                 # This is to avoid easy site outages; see $saveSuccess comments below.
 388                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 389                 $status = $this->mMemc->get( $statusKey );
 390                 if ( $status === 'error' ) {
 391                         $where[] = "could not load; method is still globally disabled";
 392                         return 'disabled';
 393                 }
 394
 395                 # Now let's regenerate
 396                 $where[] = 'loading from database';
 397
 398                 # Lock the cache to prevent conflicting writes.
 399                 # This lock is non-blocking so stale cache can quickly be used.
 400                 # Note that load() will call a blocking getReentrantScopedLock()
 401                 # after this if it really need to wait for any current thread.
 402                 $cacheKey = wfMemcKey( 'messages', $code );
 403                 $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
 404                 if ( !$scopedLock ) {
 405                         $where[] = 'could not acquire main lock';
 406                         return 'cantacquire';
 407                 }
 408
 409                 $cache = $this->loadFromDB( $code, $mode );
 410                 $this->mCache[$code] = $cache;
 411                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 412
 413                 if ( !$saveSuccess ) {
 414                         /**
 415                          * Cache save has failed.
 416                          *
 417                          * There are two main scenarios where this could be a problem:
 418                          * - The cache is more than the maximum size (typically 1MB compressed).
 419                          * - Memcached has no space remaining in the relevant slab class. This is
 420                          *   unlikely with recent versions of memcached.
 421                          *
 422                          * Either way, if there is a local cache, nothing bad will happen. If there
 423                          * is no local cache, disabling the message cache for all requests avoids
 424                          * incurring a loadFromDB() overhead on every request, and thus saves the
 425                          * wiki from complete downtime under moderate traffic conditions.
 426                          */
 427                         if ( !$wgUseLocalMessageCache ) {
 428                                 $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 429                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 430                         } else {
 431                                 $where[] = "could not save global cache";
 432                         }
 433                 }
 434
 435                 return true;
 436         }
 437
 438         /**
 439          * Loads cacheable messages from the database. Messages bigger than
 440          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 441          * on-demand from the database later.
 442          *
 443          * @param string $code Language code
 444          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 445          * @return array Loaded messages for storing in caches
 446          */
 447         function loadFromDB( $code, $mode = null ) {
 448                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 449
 450                 $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA );
 451
 452                 $cache = [];
 453
 454                 # Common conditions
 455                 $conds = [
 456                         'page_is_redirect' => 0,
 457                         'page_namespace' => NS_MEDIAWIKI,
 458                 ];
 459
 460                 $mostused = [];
 461                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 462                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 463                                 $this->load( $wgLanguageCode );
 464                         }
 465                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 466                         foreach ( $mostused as $key => $value ) {
 467                                 $mostused[$key] = "$value/$code";
 468                         }
 469                 }
 470
 471                 if ( count( $mostused ) ) {
 472                         $conds['page_title'] = $mostused;
 473                 } elseif ( $code !== $wgLanguageCode ) {
 474                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 475                 } else {
 476                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 477                         # other than language code.
 478                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 479                 }
 480
 481                 # Conditions to fetch oversized pages to ignore them
 482                 $bigConds = $conds;
 483                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 484
 485                 # Load titles for all oversized pages in the MediaWiki namespace
 486                 $res = $dbr->select(
 487                         'page',
 488                         [ 'page_title', 'page_latest' ],
 489                         $bigConds,
 490                         __METHOD__ . "($code)-big"
 491                 );
 492                 foreach ( $res as $row ) {
 493                         $cache[$row->page_title] = '!TOO BIG';
 494                         // At least include revision ID so page changes are reflected in the hash
 495                         $cache['EXCESSIVE'][$row->page_title] = $row->page_latest;
 496                 }
 497
 498                 # Conditions to load the remaining pages with their contents
 499                 $smallConds = $conds;
 500                 $smallConds[] = 'page_latest=rev_id';
 501                 $smallConds[] = 'rev_text_id=old_id';
 502                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 503
 504                 $res = $dbr->select(
 505                         [ 'page', 'revision', 'text' ],
 506                         [ 'page_title', 'old_text', 'old_flags' ],
 507                         $smallConds,
 508                         __METHOD__ . "($code)-small"
 509                 );
 510
 511                 foreach ( $res as $row ) {
 512                         $text = Revision::getRevisionText( $row );
 513                         if ( $text === false ) {
 514                                 // Failed to fetch data; possible ES errors?
 515                                 // Store a marker to fetch on-demand as a workaround...
 516                                 // TODO Use a differnt marker
 517                                 $entry = '!TOO BIG';
 518                                 wfDebugLog(
 519                                         'MessageCache',
 520                                         __METHOD__
 521                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 522                                 );
 523                         } else {
 524                                 $entry = ' ' . $text;
 525                         }
 526                         $cache[$row->page_title] = $entry;
 527                 }
 528
 529                 $cache['VERSION'] = MSG_CACHE_VERSION;
 530                 ksort( $cache );
 531
 532                 # Hash for validating local cache (APC). No need to take into account
 533                 # messages larger than $wgMaxMsgCacheEntrySize, since those are only
 534                 # stored and fetched from memcache.
 535                 $cache['HASH'] = md5( serialize( $cache ) );
 536                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 537
 538                 return $cache;
 539         }
 540
 541         /**
 542          * Updates cache as necessary when message page is changed
 543          *
 544          * @param string|bool $title Name of the page changed (false if deleted)
 545          * @param string|bool $text New contents of the page (false if deleted)
 546          */
 547         public function replace( $title, $text ) {
 548                 global $wgMaxMsgCacheEntrySize, $wgContLang, $wgLanguageCode;
 549
 550                 if ( $this->mDisable ) {
 551                         return;
 552                 }
 553
 554                 list( $msg, $code ) = $this->figureMessage( $title );
 555                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 556                         // Content language overrides do not use the /<code> suffix
 557                         return;
 558                 }
 559
 560                 // Note that if the cache is volatile, load() may trigger a DB fetch.
 561                 // In that case we reenter/reuse the existing cache key lock to avoid
 562                 // a self-deadlock. This is safe as no reads happen *directly* in this
 563                 // method between getReentrantScopedLock() and load() below. There is
 564                 // no risk of data "changing under our feet" for replace().
 565                 $scopedLock = $this->getReentrantScopedLock( wfMemcKey( 'messages', $code ) );
 566                 // Load the messages from the master DB to avoid race conditions
 567                 $this->load( $code, self::FOR_UPDATE );
 568
 569                 // Load the new value into the process cache...
 570                 if ( $text === false ) {
 571                         $this->mCache[$code][$title] = '!NONEXISTENT';
 572                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 573                         $this->mCache[$code][$title] = '!TOO BIG';
 574                         // Pre-fill the individual key cache with the known latest message text
 575                         $key = $this->wanCache->makeKey( 'messages-big', $this->mCache[$code]['HASH'], $title );
 576                         $this->wanCache->set( $key, " $text", $this->mExpiry );
 577                 } else {
 578                         $this->mCache[$code][$title] = ' ' . $text;
 579                 }
 580                 // Mark this cache as definitely being "latest" (non-volatile) so
 581                 // load() calls do not try to refresh the cache with replica DB data
 582                 $this->mCache[$code]['LATEST'] = time();
 583
 584                 // Update caches if the lock was acquired
 585                 if ( $scopedLock ) {
 586                         $this->saveToCaches( $this->mCache[$code], 'all', $code );
 587                 } else {
 588                         LoggerFactory::getInstance( 'MessageCache' )->error(
 589                                 __METHOD__ . ': could not acquire lock to update {title} ({code})',
 590                                 [ 'title' => $title, 'code' => $code ] );
 591                 }
 592
 593                 ScopedCallback::consume( $scopedLock );
 594                 // Relay the purge. Touching this check key expires cache contents
 595                 // and local cache (APC) validation hash across all datacenters.
 596                 $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
 597
 598                 // Also delete cached sidebar... just in case it is affected
 599                 $codes = [ $code ];
 600                 if ( $code === 'en' ) {
 601                         // Delete all sidebars, like for example on action=purge on the
 602                         // sidebar messages
 603                         $codes = array_keys( Language::fetchLanguageNames() );
 604                 }
 605
 606                 foreach ( $codes as $code ) {
 607                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 608                         $this->wanCache->delete( $sidebarKey );
 609                 }
 610
 611                 // Update the message in the message blob store
 612                 $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
 613                 $blobStore = $resourceloader->getMessageBlobStore();
 614                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 615
 616                 Hooks::run( 'MessageCacheReplace', [ $title, $text ] );
 617         }
 618
 619         /**
 620          * Is the given cache array expired due to time passing or a version change?
 621          *
 622          * @param array $cache
 623          * @return bool
 624          */
 625         protected function isCacheExpired( $cache ) {
 626                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 627                         return true;
 628                 }
 629                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 630                         return true;
 631                 }
 632                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 633                         return true;
 634                 }
 635
 636                 return false;
 637         }
 638
 639         /**
 640          * Shortcut to update caches.
 641          *
 642          * @param array $cache Cached messages with a version.
 643          * @param string $dest Either "local-only" to save to local caches only
 644          *   or "all" to save to all caches.
 645          * @param string|bool $code Language code (default: false)
 646          * @return bool
 647          */
 648         protected function saveToCaches( array $cache, $dest, $code = false ) {
 649                 if ( $dest === 'all' ) {
 650                         $cacheKey = wfMemcKey( 'messages', $code );
 651                         $success = $this->mMemc->set( $cacheKey, $cache );
 652                         $this->setValidationHash( $code, $cache );
 653                 } else {
 654                         $success = true;
 655                 }
 656
 657                 $this->saveToLocalCache( $code, $cache );
 658
 659                 return $success;
 660         }
 661
 662         /**
 663          * Get the md5 used to validate the local APC cache
 664          *
 665          * @param string $code
 666          * @return array (hash or false, bool expiry/volatility status)
 667          */
 668         protected function getValidationHash( $code ) {
 669                 $curTTL = null;
 670                 $value = $this->wanCache->get(
 671                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 672                         $curTTL,
 673                         [ wfMemcKey( 'messages', $code ) ]
 674                 );
 675
 676                 if ( $value ) {
 677                         $hash = $value['hash'];
 678                         if ( ( time() - $value['latest'] ) < WANObjectCache::TTL_MINUTE ) {
 679                                 // Cache was recently updated via replace() and should be up-to-date.
 680                                 // That method is only called in the primary datacenter and uses FOR_UPDATE.
 681                                 // Also, it is unlikely that the current datacenter is *now* secondary one.
 682                                 $expired = false;
 683                         } else {
 684                                 // See if the "check" key was bumped after the hash was generated
 685                                 $expired = ( $curTTL < 0 );
 686                         }
 687                 } else {
 688                         // No hash found at all; cache must regenerate to be safe
 689                         $hash = false;
 690                         $expired = true;
 691                 }
 692
 693                 return [ $hash, $expired ];
 694         }
 695
 696         /**
 697          * Set the md5 used to validate the local disk cache
 698          *
 699          * If $cache has a 'LATEST' UNIX timestamp key, then the hash will not
 700          * be treated as "volatile" by getValidationHash() for the next few seconds.
 701          * This is triggered when $cache is generated using FOR_UPDATE mode.
 702          *
 703          * @param string $code
 704          * @param array $cache Cached messages with a version
 705          */
 706         protected function setValidationHash( $code, array $cache ) {
 707                 $this->wanCache->set(
 708                         $this->wanCache->makeKey( 'messages', $code, 'hash', 'v1' ),
 709                         [
 710                                 'hash' => $cache['HASH'],
 711                                 'latest' => isset( $cache['LATEST'] ) ? $cache['LATEST'] : 0
 712                         ],
 713                         WANObjectCache::TTL_INDEFINITE
 714                 );
 715         }
 716
 717         /**
 718          * @param string $key A language message cache key that stores blobs
 719          * @param integer $timeout Wait timeout in seconds
 720          * @return null|ScopedCallback
 721          */
 722         protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
 723                 return $this->mMemc->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
 724         }
 725
 726         /**
 727          * Get a message from either the content language or the user language.
 728          *
 729          * First, assemble a list of languages to attempt getting the message from. This
 730          * chain begins with the requested language and its fallbacks and then continues with
 731          * the content language and its fallbacks. For each language in the chain, the following
 732          * process will occur (in this order):
 733          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 734          *     Note: for the content language, there is no /lang subpage.
 735          *  2. Fetch from the static CDB cache.
 736          *  3. If available, check the database for fallback language overrides.
 737          *
 738          * This process provides a number of guarantees. When changing this code, make sure all
 739          * of these guarantees are preserved.
 740          *  * If the requested language is *not* the content language, then the CDB cache for that
 741          *    specific language will take precedence over the root database page ([[MW:msg]]).
 742          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 743          *    the message is available *anywhere* in the language for which it is a fallback.
 744          *
 745          * @param string $key The message key
 746          * @param bool $useDB If true, look for the message in the DB, false
 747          *   to use only the compiled l10n cache.
 748          * @param bool|string|object $langcode Code of the language to get the message for.
 749          *   - If string and a valid code, will create a standard language object
 750          *   - If string but not a valid code, will create a basic language object
 751          *   - If boolean and false, create object from the current users language
 752          *   - If boolean and true, create object from the wikis content language
 753          *   - If language object, use it as given
 754          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 755          *
 756          * @throws MWException When given an invalid key
 757          * @return string|bool False if the message doesn't exist, otherwise the
 758          *   message (which can be empty)
 759          */
 760         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 761                 if ( is_int( $key ) ) {
 762                         // Fix numerical strings that somehow become ints
 763                         // on their way here
 764                         $key = (string)$key;
 765                 } elseif ( !is_string( $key ) ) {
 766                         throw new MWException( 'Non-string key given' );
 767                 } elseif ( $key === '' ) {
 768                         // Shortcut: the empty key is always missing
 769                         return false;
 770                 }
 771
 772                 // For full keys, get the language code from the key
 773                 $pos = strrpos( $key, '/' );
 774                 if ( $isFullKey && $pos !== false ) {
 775                         $langcode = substr( $key, $pos + 1 );
 776                         $key = substr( $key, 0, $pos );
 777                 }
 778
 779                 // Normalise title-case input (with some inlining)
 780                 $lckey = MessageCache::normalizeKey( $key );
 781
 782                 Hooks::run( 'MessageCache::get', [ &$lckey ] );
 783
 784                 // Loop through each language in the fallback list until we find something useful
 785                 $lang = wfGetLangObj( $langcode );
 786                 $message = $this->getMessageFromFallbackChain(
 787                         $lang,
 788                         $lckey,
 789                         !$this->mDisable && $useDB
 790                 );
 791
 792                 // If we still have no message, maybe the key was in fact a full key so try that
 793                 if ( $message === false ) {
 794                         $parts = explode( '/', $lckey );
 795                         // We may get calls for things that are http-urls from sidebar
 796                         // Let's not load nonexistent languages for those
 797                         // They usually have more than one slash.
 798                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 799                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 800                                 if ( $message === null ) {
 801                                         $message = false;
 802                                 }
 803                         }
 804                 }
 805
 806                 // Post-processing if the message exists
 807                 if ( $message !== false ) {
 808                         // Fix whitespace
 809                         $message = str_replace(
 810                                 [
 811                                         # Fix for trailing whitespace, removed by textarea
 812                                         '&#32;',
 813                                         # Fix for NBSP, converted to space by firefox
 814                                         '&nbsp;',
 815                                         '&#160;',
 816                                         '&shy;'
 817                                 ],
 818                                 [
 819                                         ' ',
 820                                         "\xc2\xa0",
 821                                         "\xc2\xa0",
 822                                         "\xc2\xad"
 823                                 ],
 824                                 $message
 825                         );
 826                 }
 827
 828                 return $message;
 829         }
 830
 831         /**
 832          * Given a language, try and fetch messages from that language.
 833          *
 834          * Will also consider fallbacks of that language, the site language, and fallbacks for
 835          * the site language.
 836          *
 837          * @see MessageCache::get
 838          * @param Language|StubObject $lang Preferred language
 839          * @param string $lckey Lowercase key for the message (as for localisation cache)
 840          * @param bool $useDB Whether to include messages from the wiki database
 841          * @return string|bool The message, or false if not found
 842          */
 843         protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
 844                 global $wgContLang;
 845
 846                 $alreadyTried = [];
 847
 848                  // First try the requested language.
 849                 $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
 850                 if ( $message !== false ) {
 851                         return $message;
 852                 }
 853
 854                 // Now try checking the site language.
 855                 $message = $this->getMessageForLang( $wgContLang, $lckey, $useDB, $alreadyTried );
 856                 return $message;
 857         }
 858
 859         /**
 860          * Given a language, try and fetch messages from that language and its fallbacks.
 861          *
 862          * @see MessageCache::get
 863          * @param Language|StubObject $lang Preferred language
 864          * @param string $lckey Lowercase key for the message (as for localisation cache)
 865          * @param bool $useDB Whether to include messages from the wiki database
 866          * @param bool[] $alreadyTried Contains true for each language that has been tried already
 867          * @return string|bool The message, or false if not found
 868          */
 869         private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
 870                 global $wgContLang;
 871
 872                 $langcode = $lang->getCode();
 873
 874                 // Try checking the database for the requested language
 875                 if ( $useDB ) {
 876                         $uckey = $wgContLang->ucfirst( $lckey );
 877
 878                         if ( !isset( $alreadyTried[ $langcode ] ) ) {
 879                                 $message = $this->getMsgFromNamespace(
 880                                         $this->getMessagePageName( $langcode, $uckey ),
 881                                         $langcode
 882                                 );
 883
 884                                 if ( $message !== false ) {
 885                                         return $message;
 886                                 }
 887                                 $alreadyTried[ $langcode ] = true;
 888                         }
 889                 } else {
 890                         $uckey = null;
 891                 }
 892
 893                 // Check the CDB cache
 894                 $message = $lang->getMessage( $lckey );
 895                 if ( $message !== null ) {
 896                         return $message;
 897                 }
 898
 899                 // Try checking the database for all of the fallback languages
 900                 if ( $useDB ) {
 901                         $fallbackChain = Language::getFallbacksFor( $langcode );
 902
 903                         foreach ( $fallbackChain as $code ) {
 904                                 if ( isset( $alreadyTried[ $code ] ) ) {
 905                                         continue;
 906                                 }
 907
 908                                 $message = $this->getMsgFromNamespace(
 909                                         $this->getMessagePageName( $code, $uckey ), $code );
 910
 911                                 if ( $message !== false ) {
 912                                         return $message;
 913                                 }
 914                                 $alreadyTried[ $code ] = true;
 915                         }
 916                 }
 917
 918                 return false;
 919         }
 920
 921         /**
 922          * Get the message page name for a given language
 923          *
 924          * @param string $langcode
 925          * @param string $uckey Uppercase key for the message
 926          * @return string The page name
 927          */
 928         private function getMessagePageName( $langcode, $uckey ) {
 929                 global $wgLanguageCode;
 930
 931                 if ( $langcode === $wgLanguageCode ) {
 932                         // Messages created in the content language will not have the /lang extension
 933                         return $uckey;
 934                 } else {
 935                         return "$uckey/$langcode";
 936                 }
 937         }
 938
 939         /**
 940          * Get a message from the MediaWiki namespace, with caching. The key must
 941          * first be converted to two-part lang/msg form if necessary.
 942          *
 943          * Unlike self::get(), this function doesn't resolve fallback chains, and
 944          * some callers require this behavior. LanguageConverter::parseCachedTable()
 945          * and self::get() are some examples in core.
 946          *
 947          * @param string $title Message cache key with initial uppercase letter.
 948          * @param string $code Code denoting the language to try.
 949          * @return string|bool The message, or false if it does not exist or on error
 950          */
 951         public function getMsgFromNamespace( $title, $code ) {
 952                 $this->load( $code );
 953                 if ( isset( $this->mCache[$code][$title] ) ) {
 954                         $entry = $this->mCache[$code][$title];
 955                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 956                                 // The message exists, so make sure a string is returned.
 957                                 return (string)substr( $entry, 1 );
 958                         } elseif ( $entry === '!NONEXISTENT' ) {
 959                                 return false;
 960                         } elseif ( $entry === '!TOO BIG' ) {
 961                                 // Fall through and try invididual message cache below
 962                         }
 963                 } else {
 964                         // XXX: This is not cached in process cache, should it?
 965                         $message = false;
 966                         Hooks::run( 'MessagesPreLoad', [ $title, &$message ] );
 967                         if ( $message !== false ) {
 968                                 return $message;
 969                         }
 970
 971                         return false;
 972                 }
 973
 974                 // Try the individual message cache
 975                 $titleKey = $this->wanCache->makeKey( 'messages-big', $this->mCache[$code]['HASH'], $title );
 976
 977                 if ( $this->mCacheVolatile[$code] ) {
 978                         $entry = false;
 979                         // Make sure that individual keys respect the WAN cache holdoff period too
 980                         LoggerFactory::getInstance( 'MessageCache' )->debug(
 981                                 __METHOD__ . ': loading volatile key \'{titleKey}\'',
 982                                 [ 'titleKey' => $titleKey, 'code' => $code ] );
 983                 } else {
 984                         $entry = $this->wanCache->get( $titleKey );
 985                 }
 986
 987                 if ( $entry !== false ) {
 988                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 989                                 $this->mCache[$code][$title] = $entry;
 990                                 // The message exists, so make sure a string is returned
 991                                 return (string)substr( $entry, 1 );
 992                         } elseif ( $entry === '!NONEXISTENT' ) {
 993                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 994
 995                                 return false;
 996                         } else {
 997                                 // Corrupt/obsolete entry, delete it
 998                                 $this->wanCache->delete( $titleKey );
 999                         }
1000                 }
1001
1002                 // Try loading the message from the database
1003                 $dbr = wfGetDB( DB_REPLICA );
1004                 $cacheOpts = Database::getCacheSetOptions( $dbr );
1005                 // Use newKnownCurrent() to avoid querying revision/user tables
1006                 $titleObj = Title::makeTitle( NS_MEDIAWIKI, $title );
1007                 if ( $titleObj->getLatestRevID() ) {
1008                         $revision = Revision::newKnownCurrent(
1009                                 $dbr,
1010                                 $titleObj->getArticleID(),
1011                                 $titleObj->getLatestRevID()
1012                         );
1013                 } else {
1014                         $revision = false;
1015                 }
1016
1017                 if ( $revision ) {
1018                         $content = $revision->getContent();
1019                         if ( $content ) {
1020                                 $message = $this->getMessageTextFromContent( $content );
1021                                 if ( is_string( $message ) ) {
1022                                         $this->mCache[$code][$title] = ' ' . $message;
1023                                         $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry, $cacheOpts );
1024                                 }
1025                         } else {
1026                                 // A possibly temporary loading failure
1027                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1028                                         __METHOD__ . ': failed to load message page text for \'{titleKey}\'',
1029                                         [ 'titleKey' => $titleKey, 'code' => $code ] );
1030                                 $message = null; // no negative caching
1031                         }
1032                 } else {
1033                         $message = false; // negative caching
1034                 }
1035
1036                 if ( $message === false ) { // negative caching
1037                         $this->mCache[$code][$title] = '!NONEXISTENT';
1038                         $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry, $cacheOpts );
1039                 }
1040
1041                 return $message;
1042         }
1043
1044         /**
1045          * @param string $message
1046          * @param bool $interface
1047          * @param string $language Language code
1048          * @param Title $title
1049          * @return string
1050          */
1051         function transform( $message, $interface = false, $language = null, $title = null ) {
1052                 // Avoid creating parser if nothing to transform
1053                 if ( strpos( $message, '{{' ) === false ) {
1054                         return $message;
1055                 }
1056
1057                 if ( $this->mInParser ) {
1058                         return $message;
1059                 }
1060
1061                 $parser = $this->getParser();
1062                 if ( $parser ) {
1063                         $popts = $this->getParserOptions();
1064                         $popts->setInterfaceMessage( $interface );
1065                         $popts->setTargetLanguage( $language );
1066
1067                         $userlang = $popts->setUserLang( $language );
1068                         $this->mInParser = true;
1069                         $message = $parser->transformMsg( $message, $popts, $title );
1070                         $this->mInParser = false;
1071                         $popts->setUserLang( $userlang );
1072                 }
1073
1074                 return $message;
1075         }
1076
1077         /**
1078          * @return Parser
1079          */
1080         function getParser() {
1081                 global $wgParser, $wgParserConf;
1082
1083                 if ( !$this->mParser && isset( $wgParser ) ) {
1084                         # Do some initialisation so that we don't have to do it twice
1085                         $wgParser->firstCallInit();
1086                         # Clone it and store it
1087                         $class = $wgParserConf['class'];
1088                         if ( $class == 'ParserDiffTest' ) {
1089                                 # Uncloneable
1090                                 $this->mParser = new $class( $wgParserConf );
1091                         } else {
1092                                 $this->mParser = clone $wgParser;
1093                         }
1094                 }
1095
1096                 return $this->mParser;
1097         }
1098
1099         /**
1100          * @param string $text
1101          * @param Title $title
1102          * @param bool $linestart Whether or not this is at the start of a line
1103          * @param bool $interface Whether this is an interface message
1104          * @param Language|string $language Language code
1105          * @return ParserOutput|string
1106          */
1107         public function parse( $text, $title = null, $linestart = true,
1108                 $interface = false, $language = null
1109         ) {
1110                 global $wgTitle;
1111
1112                 if ( $this->mInParser ) {
1113                         return htmlspecialchars( $text );
1114                 }
1115
1116                 $parser = $this->getParser();
1117                 $popts = $this->getParserOptions();
1118                 $popts->setInterfaceMessage( $interface );
1119
1120                 if ( is_string( $language ) ) {
1121                         $language = Language::factory( $language );
1122                 }
1123                 $popts->setTargetLanguage( $language );
1124
1125                 if ( !$title || !$title instanceof Title ) {
1126                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1127                                 wfGetAllCallers( 6 ) . ' with no title set.' );
1128                         $title = $wgTitle;
1129                 }
1130                 // Sometimes $wgTitle isn't set either...
1131                 if ( !$title ) {
1132                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1133                         # Create a ghost title in such case
1134                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1135                 }
1136
1137                 $this->mInParser = true;
1138                 $res = $parser->parse( $text, $title, $popts, $linestart );
1139                 $this->mInParser = false;
1140
1141                 return $res;
1142         }
1143
1144         function disable() {
1145                 $this->mDisable = true;
1146         }
1147
1148         function enable() {
1149                 $this->mDisable = false;
1150         }
1151
1152         /**
1153          * Whether DB/cache usage is disabled for determining messages
1154          *
1155          * If so, this typically indicates either:
1156          *   - a) load() failed to find a cached copy nor query the DB
1157          *   - b) we are in a special context or error mode that cannot use the DB
1158          * If the DB is ignored, any derived HTML output or cached objects may be wrong.
1159          * To avoid long-term cache pollution, TTLs can be adjusted accordingly.
1160          *
1161          * @return bool
1162          * @since 1.27
1163          */
1164         public function isDisabled() {
1165                 return $this->mDisable;
1166         }
1167
1168         /**
1169          * Clear all stored messages. Mainly used after a mass rebuild.
1170          */
1171         function clear() {
1172                 $langs = Language::fetchLanguageNames( null, 'mw' );
1173                 foreach ( array_keys( $langs ) as $code ) {
1174                         # Global and local caches
1175                         $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
1176                 }
1177
1178                 $this->mLoadedLanguages = [];
1179         }
1180
1181         /**
1182          * @param string $key
1183          * @return array
1184          */
1185         public function figureMessage( $key ) {
1186                 global $wgLanguageCode;
1187
1188                 $pieces = explode( '/', $key );
1189                 if ( count( $pieces ) < 2 ) {
1190                         return [ $key, $wgLanguageCode ];
1191                 }
1192
1193                 $lang = array_pop( $pieces );
1194                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1195                         return [ $key, $wgLanguageCode ];
1196                 }
1197
1198                 $message = implode( '/', $pieces );
1199
1200                 return [ $message, $lang ];
1201         }
1202
1203         /**
1204          * Get all message keys stored in the message cache for a given language.
1205          * If $code is the content language code, this will return all message keys
1206          * for which MediaWiki:msgkey exists. If $code is another language code, this
1207          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1208          * @param string $code Language code
1209          * @return array Array of message keys (strings)
1210          */
1211         public function getAllMessageKeys( $code ) {
1212                 global $wgContLang;
1213
1214                 $this->load( $code );
1215                 if ( !isset( $this->mCache[$code] ) ) {
1216                         // Apparently load() failed
1217                         return null;
1218                 }
1219                 // Remove administrative keys
1220                 $cache = $this->mCache[$code];
1221                 unset( $cache['VERSION'] );
1222                 unset( $cache['EXPIRY'] );
1223                 unset( $cache['EXCESSIVE'] );
1224                 // Remove any !NONEXISTENT keys
1225                 $cache = array_diff( $cache, [ '!NONEXISTENT' ] );
1226
1227                 // Keys may appear with a capital first letter. lcfirst them.
1228                 return array_map( [ $wgContLang, 'lcfirst' ], array_keys( $cache ) );
1229         }
1230
1231         /**
1232          * Purge message caches when a MediaWiki: page is created, updated, or deleted
1233          *
1234          * @param Title $title Message page title
1235          * @param Content|null $content New content for edit/create, null on deletion
1236          * @since 1.29
1237          */
1238         public function updateMessageOverride( Title $title, Content $content = null ) {
1239                 global $wgContLang;
1240
1241                 $msgText = $this->getMessageTextFromContent( $content );
1242                 if ( $msgText === null ) {
1243                         $msgText = false; // treat as not existing
1244                 }
1245
1246                 $this->replace( $title->getDBkey(), $msgText );
1247
1248                 if ( $wgContLang->hasVariants() ) {
1249                         $wgContLang->updateConversionTable( $title );
1250                 }
1251         }
1252
1253         /**
1254          * @param Content|null $content Content or null if the message page does not exist
1255          * @return string|bool|null Returns false if $content is null and null on error
1256          */
1257         private function getMessageTextFromContent( Content $content = null ) {
1258                 // @TODO: could skip pseudo-messages like js/css here, based on content model
1259                 if ( $content ) {
1260                         // Message page exists...
1261                         // XXX: Is this the right way to turn a Content object into a message?
1262                         // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1263                         //       CssContent. MessageContent is *not* used for storing messages, it's
1264                         //       only used for wrapping them when needed.
1265                         $msgText = $content->getWikitextForTransclusion();
1266                         if ( $msgText === false || $msgText === null ) {
1267                                 // This might be due to some kind of misconfiguration...
1268                                 $msgText = null;
1269                                 LoggerFactory::getInstance( 'MessageCache' )->warning(
1270                                         __METHOD__ . ": message content doesn't provide wikitext "
1271                                         . "(content model: " . $content->getModel() . ")" );
1272                         }
1273                 } else {
1274                         // Message page does not exist...
1275                         $msgText = false;
1276                 }
1277
1278                 return $msgText;
1279         }
1280 }