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
  24 /**
  25  * MediaWiki message cache structure version.
  26  * Bump this whenever the message cache format has changed.
  27  */
  28 define( 'MSG_CACHE_VERSION', 2 );
  29
  30 /**
  31  * Memcached timeout when loading a key.
  32  * See MessageCache::load()
  33  */
  34 define( 'MSG_LOAD_TIMEOUT', 60 );
  35
  36 /**
  37  * Message cache
  38  * Performs various MediaWiki namespace-related functions
  39  * @ingroup Cache
  40  */
  41 class MessageCache {
  42         const FOR_UPDATE = 1; // force message reload
  43
  44         /** How long memcached locks last */
  45         const WAIT_SEC = 30;
  46         /** How long to wait for memcached locks */
  47         const LOCK_TTL = 30;
  48
  49         /**
  50          * Process local cache of loaded messages that are defined in
  51          * MediaWiki namespace. First array level is a language code,
  52          * second level is message key and the values are either message
  53          * content prefixed with space, or !NONEXISTENT for negative
  54          * caching.
  55          * @var array $mCache
  56          */
  57         protected $mCache;
  58
  59         /**
  60          * Should  mean that database cannot be used, but check
  61          * @var bool $mDisable
  62          */
  63         protected $mDisable;
  64
  65         /**
  66          * Lifetime for cache, used by object caching.
  67          * Set on construction, see __construct().
  68          */
  69         protected $mExpiry;
  70
  71         /**
  72          * Message cache has its own parser which it uses to transform
  73          * messages.
  74          */
  75         protected $mParserOptions, $mParser;
  76
  77         /**
  78          * Variable for tracking which variables are already loaded
  79          * @var array $mLoadedLanguages
  80          */
  81         protected $mLoadedLanguages = array();
  82
  83         /**
  84          * @var bool $mInParser
  85          */
  86         protected $mInParser = false;
  87
  88         /** @var BagOStuff */
  89         protected $mMemc;
  90         /** @var WANObjectCache */
  91         protected $wanCache;
  92
  93         /**
  94          * Singleton instance
  95          *
  96          * @var MessageCache $instance
  97          */
  98         private static $instance;
  99
 100         /**
 101          * Get the signleton instance of this class
 102          *
 103          * @since 1.18
 104          * @return MessageCache
 105          */
 106         public static function singleton() {
 107                 if ( is_null( self::$instance ) ) {
 108                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
 109                         self::$instance = new self(
 110                                 wfGetMessageCacheStorage(),
 111                                 $wgUseDatabaseMessages,
 112                                 $wgMsgCacheExpiry
 113                         );
 114                 }
 115
 116                 return self::$instance;
 117         }
 118
 119         /**
 120          * Destroy the singleton instance
 121          *
 122          * @since 1.18
 123          */
 124         public static function destroyInstance() {
 125                 self::$instance = null;
 126         }
 127
 128         /**
 129          * Normalize message key input
 130          *
 131          * @param string $key Input message key to be normalized
 132          * @return string Normalized message key
 133          */
 134         public static function normalizeKey( $key ) {
 135                 global $wgContLang;
 136                 $lckey = strtr( $key, ' ', '_' );
 137                 if ( ord( $lckey ) < 128 ) {
 138                         $lckey[0] = strtolower( $lckey[0] );
 139                 } else {
 140                         $lckey = $wgContLang->lcfirst( $lckey );
 141                 }
 142
 143                 return $lckey;
 144         }
 145
 146         /**
 147          * @param BagOStuff $memCached A cache instance. If none, fall back to CACHE_NONE.
 148          * @param bool $useDB
 149          * @param int $expiry Lifetime for cache. @see $mExpiry.
 150          */
 151         function __construct( $memCached, $useDB, $expiry ) {
 152                 global $wgUseLocalMessageCache;
 153
 154                 if ( !$memCached ) {
 155                         $memCached = wfGetCache( CACHE_NONE );
 156                 }
 157
 158                 $this->mMemc = $memCached;
 159                 $this->mDisable = !$useDB;
 160                 $this->mExpiry = $expiry;
 161
 162                 if ( $wgUseLocalMessageCache ) {
 163                         $this->localCache = ObjectCache::newAccelerator( CACHE_NONE );
 164                 } else {
 165                         $this->localCache = wfGetCache( CACHE_NONE );
 166                 }
 167
 168                 $this->wanCache = ObjectCache::getMainWANInstance();
 169         }
 170
 171         /**
 172          * ParserOptions is lazy initialised.
 173          *
 174          * @return ParserOptions
 175          */
 176         function getParserOptions() {
 177                 if ( !$this->mParserOptions ) {
 178                         $this->mParserOptions = new ParserOptions;
 179                         $this->mParserOptions->setEditSection( false );
 180                 }
 181
 182                 return $this->mParserOptions;
 183         }
 184
 185         /**
 186          * Try to load the cache from APC.
 187          *
 188          * @param string $code Optional language code, see documenation of load().
 189          * @return array|bool The cache array, or false if not in cache.
 190          */
 191         protected function getLocalCache( $code ) {
 192                 $cacheKey = wfMemcKey( __CLASS__, $code );
 193
 194                 return $this->localCache->get( $cacheKey );
 195         }
 196
 197         /**
 198          * Save the cache to APC.
 199          *
 200          * @param string $code
 201          * @param array $cache The cache array
 202          */
 203         protected function saveToLocalCache( $code, $cache ) {
 204                 $cacheKey = wfMemcKey( __CLASS__, $code );
 205                 $this->localCache->set( $cacheKey, $cache );
 206         }
 207
 208         /**
 209          * Loads messages from caches or from database in this order:
 210          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 211          * (2) memcached
 212          * (3) from the database.
 213          *
 214          * When succesfully loading from (2) or (3), all higher level caches are
 215          * updated for the newest version.
 216          *
 217          * Nothing is loaded if member variable mDisable is true, either manually
 218          * set by calling code or if message loading fails (is this possible?).
 219          *
 220          * Returns true if cache is already populated or it was succesfully populated,
 221          * or false if populating empty cache fails. Also returns true if MessageCache
 222          * is disabled.
 223          *
 224          * @param bool|string $code Language to which load messages
 225          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 226          * @throws MWException
 227          * @return bool
 228          */
 229         function load( $code = false, $mode = null ) {
 230                 if ( !is_string( $code ) ) {
 231                         # This isn't really nice, so at least make a note about it and try to
 232                         # fall back
 233                         wfDebug( __METHOD__ . " called without providing a language code\n" );
 234                         $code = 'en';
 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 = array(); # 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 < 2; $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 slave 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 slam-protection lock here is non-blocking.
 321                                 if ( $this->loadFromDBWithLock( $code, $where ) ) {
 322                                         $success = true;
 323                                         break;
 324                                 } elseif ( $staleCache ) {
 325                                         # Use the stale cache while some other thread constructs the new one
 326                                         $where[] = 'using stale cache';
 327                                         $this->mCache[$code] = $staleCache;
 328                                         $success = true;
 329                                         break;
 330                                 } elseif ( $failedAttempts > 0 ) {
 331                                         # Already retried once, still failed, so don't do another lock/unlock cycle
 332                                         # This case will typically be hit if memcached is down, or if
 333                                         # loadFromDB() takes longer than MSG_WAIT_TIMEOUT
 334                                         $where[] = "could not acquire status key.";
 335                                         break;
 336                                 } else {
 337                                         $statusKey = wfMemcKey( 'messages', $code, 'status' );
 338                                         $status = $this->mMemc->get( $statusKey );
 339                                         if ( $status === 'error' ) {
 340                                                 # Disable cache
 341                                                 break;
 342                                         } else {
 343                                                 # Wait for the other thread to finish, then retry. Normally,
 344                                                 # the memcached get() will then yeild the other thread's result.
 345                                                 $where[] = 'waited for other thread to complete';
 346                                                 $this->getReentrantScopedLock( $cacheKey );
 347                                         }
 348                                 }
 349                         }
 350                 }
 351
 352                 if ( !$success ) {
 353                         $where[] = 'loading FAILED - cache is disabled';
 354                         $this->mDisable = true;
 355                         $this->mCache = false;
 356                         # This used to throw an exception, but that led to nasty side effects like
 357                         # the whole wiki being instantly down if the memcached server died
 358                 } else {
 359                         # All good, just record the success
 360                         $this->mLoadedLanguages[$code] = true;
 361                 }
 362
 363                 $info = implode( ', ', $where );
 364                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 365
 366                 return $success;
 367         }
 368
 369         /**
 370          * @param string $code
 371          * @param array $where List of wfDebug() comments
 372          * @return bool Lock acquired and loadFromDB() called
 373          */
 374         protected function loadFromDBWithLock( $code, array &$where ) {
 375                 global $wgUseLocalMessageCache;
 376
 377                 $memCache = $this->mMemc;
 378
 379                 # Get the non-blocking status key lock. This lets the caller quickly know
 380                 # to use any stale cache lying around. Otherwise, it may do a blocking
 381                 # lock to try to obtain the messages.
 382                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 383                 if ( !$memCache->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT ) ) {
 384                         return false; // could not acquire lock
 385                 }
 386
 387                 # Unlock the status key if there is an exception
 388                 $statusUnlocker = new ScopedCallback( function () use ( $memCache, $statusKey ) {
 389                         $memCache->delete( $statusKey );
 390                 } );
 391
 392                 # Now let's regenerate
 393                 $where[] = 'loading from database';
 394
 395                 $cacheKey = wfMemcKey( 'messages', $code );
 396                 # Lock the cache to prevent conflicting writes
 397                 # If this lock fails, it doesn't really matter, it just means the
 398                 # write is potentially non-atomic, e.g. the results of a replace()
 399                 # may be discarded.
 400                 $mainUnlocker = $this->getReentrantScopedLock( $cacheKey );
 401                 if ( !$mainUnlocker ) {
 402                         $where[] = 'could not acquire main lock';
 403                 }
 404
 405                 $cache = $this->loadFromDB( $code );
 406                 $this->mCache[$code] = $cache;
 407                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 408
 409                 # Unlock
 410                 ScopedCallback::consume( $mainUnlocker );
 411                 ScopedCallback::consume( $statusUnlocker );
 412
 413                 if ( !$saveSuccess ) {
 414                         # Cache save has failed.
 415                         # There are two main scenarios where this could be a problem:
 416                         #
 417                         #   - The cache is more than the maximum size (typically
 418                         #     1MB compressed).
 419                         #
 420                         #   - Memcached has no space remaining in the relevant slab
 421                         #     class. This is unlikely with recent versions of
 422                         #     memcached.
 423                         #
 424                         # Either way, if there is a local cache, nothing bad will
 425                         # happen. If there is no local cache, disabling the message
 426                         # cache for all requests avoids incurring a loadFromDB()
 427                         # overhead on every request, and thus saves the wiki from
 428                         # complete downtime under moderate traffic conditions.
 429                         if ( !$wgUseLocalMessageCache ) {
 430                                 $memCache->set( $statusKey, 'error', 60 * 5 );
 431                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 432                         } else {
 433                                 $where[] = "could not save global cache";
 434                         }
 435                 }
 436
 437                 return true;
 438         }
 439
 440         /**
 441          * Loads cacheable messages from the database. Messages bigger than
 442          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 443          * on-demand from the database later.
 444          *
 445          * @param string $code Language code.
 446          * @return array Loaded messages for storing in caches.
 447          */
 448         function loadFromDB( $code ) {
 449                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 450
 451                 $dbr = wfGetDB( DB_SLAVE );
 452                 $cache = array();
 453
 454                 # Common conditions
 455                 $conds = array(
 456                         'page_is_redirect' => 0,
 457                         'page_namespace' => NS_MEDIAWIKI,
 458                 );
 459
 460                 $mostused = array();
 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( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 487                 foreach ( $res as $row ) {
 488                         $cache[$row->page_title] = '!TOO BIG';
 489                 }
 490
 491                 # Conditions to load the remaining pages with their contents
 492                 $smallConds = $conds;
 493                 $smallConds[] = 'page_latest=rev_id';
 494                 $smallConds[] = 'rev_text_id=old_id';
 495                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 496
 497                 $res = $dbr->select(
 498                         array( 'page', 'revision', 'text' ),
 499                         array( 'page_title', 'old_text', 'old_flags' ),
 500                         $smallConds,
 501                         __METHOD__ . "($code)-small"
 502                 );
 503
 504                 foreach ( $res as $row ) {
 505                         $text = Revision::getRevisionText( $row );
 506                         if ( $text === false ) {
 507                                 // Failed to fetch data; possible ES errors?
 508                                 // Store a marker to fetch on-demand as a workaround...
 509                                 $entry = '!TOO BIG';
 510                                 wfDebugLog(
 511                                         'MessageCache',
 512                                         __METHOD__
 513                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 514                                 );
 515                         } else {
 516                                 $entry = ' ' . $text;
 517                         }
 518                         $cache[$row->page_title] = $entry;
 519                 }
 520
 521                 $cache['VERSION'] = MSG_CACHE_VERSION;
 522                 ksort( $cache );
 523                 $cache['HASH'] = md5( serialize( $cache ) );
 524                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 525
 526                 return $cache;
 527         }
 528
 529         /**
 530          * Updates cache as necessary when message page is changed
 531          *
 532          * @param string $title Name of the page changed.
 533          * @param mixed $text New contents of the page.
 534          */
 535         public function replace( $title, $text ) {
 536                 global $wgMaxMsgCacheEntrySize, $wgContLang, $wgLanguageCode;
 537
 538                 if ( $this->mDisable ) {
 539                         return;
 540                 }
 541
 542                 list( $msg, $code ) = $this->figureMessage( $title );
 543                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 544                         # Content language overrides do not use the /<code> suffix
 545                         return;
 546                 }
 547
 548                 # Note that if the cache is volatile, load() may trigger a DB fetch.
 549                 # In that case we reenter/reuse the existing cache key lock to avoid
 550                 # a self-deadlock. This is safe as no reads happen *directly* in this
 551                 # method between getReentrantScopedLock() and load() below. There is
 552                 # no risk of data "changing under our feet" for replace().
 553                 $cacheKey = wfMemcKey( 'messages', $code );
 554                 $scopedLock = $this->getReentrantScopedLock( $cacheKey );
 555                 $this->load( $code, self::FOR_UPDATE );
 556
 557                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 558
 559                 if ( $text === false ) {
 560                         # Article was deleted
 561                         $this->mCache[$code][$title] = '!NONEXISTENT';
 562                         $this->wanCache->delete( $titleKey );
 563                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 564                         # Check for size
 565                         $this->mCache[$code][$title] = '!TOO BIG';
 566                         $this->wanCache->set( $titleKey, ' ' . $text, $this->mExpiry );
 567                 } else {
 568                         $this->mCache[$code][$title] = ' ' . $text;
 569                         $this->wanCache->delete( $titleKey );
 570                 }
 571
 572                 # Update caches
 573                 $this->saveToCaches( $this->mCache[$code], 'all', $code );
 574                 ScopedCallback::consume( $scopedLock );
 575                 $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
 576
 577                 // Also delete cached sidebar... just in case it is affected
 578                 $codes = array( $code );
 579                 if ( $code === 'en' ) {
 580                         // Delete all sidebars, like for example on action=purge on the
 581                         // sidebar messages
 582                         $codes = array_keys( Language::fetchLanguageNames() );
 583                 }
 584
 585                 foreach ( $codes as $code ) {
 586                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 587                         $this->wanCache->delete( $sidebarKey, 5 );
 588                 }
 589
 590                 // Update the message in the message blob store
 591                 $blobStore = new MessageBlobStore();
 592                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 593
 594                 Hooks::run( 'MessageCacheReplace', array( $title, $text ) );
 595         }
 596
 597         /**
 598          * Is the given cache array expired due to time passing or a version change?
 599          *
 600          * @param array $cache
 601          * @return bool
 602          */
 603         protected function isCacheExpired( $cache ) {
 604                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 605                         return true;
 606                 }
 607                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 608                         return true;
 609                 }
 610                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 611                         return true;
 612                 }
 613
 614                 return false;
 615         }
 616
 617         /**
 618          * Shortcut to update caches.
 619          *
 620          * @param array $cache Cached messages with a version.
 621          * @param string $dest Either "local-only" to save to local caches only
 622          *   or "all" to save to all caches.
 623          * @param string|bool $code Language code (default: false)
 624          * @return bool
 625          */
 626         protected function saveToCaches( $cache, $dest, $code = false ) {
 627                 if ( $dest === 'all' ) {
 628                         $cacheKey = wfMemcKey( 'messages', $code );
 629                         $success = $this->mMemc->set( $cacheKey, $cache );
 630                 } else {
 631                         $success = true;
 632                 }
 633
 634                 $this->setValidationHash( $code, $cache['HASH'] );
 635
 636                 # Save to local cache
 637                 $this->saveToLocalCache( $code, $cache );
 638
 639                 return $success;
 640         }
 641
 642         /**
 643          * Get the md5 used to validate the local disk cache
 644          *
 645          * @param string $code
 646          * @return array (hash or false, bool expiry/volatility status)
 647          */
 648         protected function getValidationHash( $code ) {
 649                 $curTTL = null;
 650                 $value = $this->wanCache->get(
 651                         wfMemcKey( 'messages', $code, 'hash' ),
 652                         $curTTL,
 653                         array( wfMemcKey( 'messages', $code ) )
 654                 );
 655                 $expired = ( $curTTL === null || $curTTL < 0 );
 656
 657                 return array( $value, $expired );
 658         }
 659
 660         /**
 661          * Set the md5 used to validate the local disk cache
 662          *
 663          * @param string $code
 664          * @param string $hash
 665          */
 666         protected function setValidationHash( $code, $hash ) {
 667                 $this->wanCache->set(
 668                         wfMemcKey( 'messages', $code, 'hash' ),
 669                         $hash,
 670                         WANObjectCache::TTL_NONE
 671                 );
 672         }
 673
 674         /**
 675          * @param string $key A language message cache key that stores blobs
 676          * @return null|ScopedCallback
 677          */
 678         protected function getReentrantScopedLock( $key ) {
 679                 return $this->mMemc->getScopedLock( $key, self::WAIT_SEC, self::LOCK_TTL, __METHOD__ );
 680         }
 681
 682         /**
 683          * Get a message from either the content language or the user language.
 684          *
 685          * First, assemble a list of languages to attempt getting the message from. This
 686          * chain begins with the requested language and its fallbacks and then continues with
 687          * the content language and its fallbacks. For each language in the chain, the following
 688          * process will occur (in this order):
 689          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 690          *     Note: for the content language, there is no /lang subpage.
 691          *  2. Fetch from the static CDB cache.
 692          *  3. If available, check the database for fallback language overrides.
 693          *
 694          * This process provides a number of guarantees. When changing this code, make sure all
 695          * of these guarantees are preserved.
 696          *  * If the requested language is *not* the content language, then the CDB cache for that
 697          *    specific language will take precedence over the root database page ([[MW:msg]]).
 698          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 699          *    the message is available *anywhere* in the language for which it is a fallback.
 700          *
 701          * @param string $key The message key
 702          * @param bool $useDB If true, look for the message in the DB, false
 703          *   to use only the compiled l10n cache.
 704          * @param bool|string|object $langcode Code of the language to get the message for.
 705          *   - If string and a valid code, will create a standard language object
 706          *   - If string but not a valid code, will create a basic language object
 707          *   - If boolean and false, create object from the current users language
 708          *   - If boolean and true, create object from the wikis content language
 709          *   - If language object, use it as given
 710          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 711          *
 712          * @throws MWException When given an invalid key
 713          * @return string|bool False if the message doesn't exist, otherwise the
 714          *   message (which can be empty)
 715          */
 716         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 717                 global $wgContLang;
 718
 719                 if ( is_int( $key ) ) {
 720                         // Fix numerical strings that somehow become ints
 721                         // on their way here
 722                         $key = (string)$key;
 723                 } elseif ( !is_string( $key ) ) {
 724                         throw new MWException( 'Non-string key given' );
 725                 } elseif ( $key === '' ) {
 726                         // Shortcut: the empty key is always missing
 727                         return false;
 728                 }
 729
 730                 // For full keys, get the language code from the key
 731                 $pos = strrpos( $key, '/' );
 732                 if ( $isFullKey && $pos !== false ) {
 733                         $langcode = substr( $key, $pos + 1 );
 734                         $key = substr( $key, 0, $pos );
 735                 }
 736
 737                 // Normalise title-case input (with some inlining)
 738                 $lckey = MessageCache::normalizeKey( $key );
 739
 740                 Hooks::run( 'MessageCache::get', array( &$lckey ) );
 741
 742                 if ( ord( $lckey ) < 128 ) {
 743                         $uckey = ucfirst( $lckey );
 744                 } else {
 745                         $uckey = $wgContLang->ucfirst( $lckey );
 746                 }
 747
 748                 // Loop through each language in the fallback list until we find something useful
 749                 $lang = wfGetLangObj( $langcode );
 750                 $message = $this->getMessageFromFallbackChain(
 751                         $lang,
 752                         $lckey,
 753                         $uckey,
 754                         !$this->mDisable && $useDB
 755                 );
 756
 757                 // If we still have no message, maybe the key was in fact a full key so try that
 758                 if ( $message === false ) {
 759                         $parts = explode( '/', $lckey );
 760                         // We may get calls for things that are http-urls from sidebar
 761                         // Let's not load nonexistent languages for those
 762                         // They usually have more than one slash.
 763                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 764                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 765                                 if ( $message === null ) {
 766                                         $message = false;
 767                                 }
 768                         }
 769                 }
 770
 771                 // Post-processing if the message exists
 772                 if ( $message !== false ) {
 773                         // Fix whitespace
 774                         $message = str_replace(
 775                                 array(
 776                                         # Fix for trailing whitespace, removed by textarea
 777                                         '&#32;',
 778                                         # Fix for NBSP, converted to space by firefox
 779                                         '&nbsp;',
 780                                         '&#160;',
 781                                 ),
 782                                 array(
 783                                         ' ',
 784                                         "\xc2\xa0",
 785                                         "\xc2\xa0"
 786                                 ),
 787                                 $message
 788                         );
 789                 }
 790
 791                 return $message;
 792         }
 793
 794         /**
 795          * Given a language, try and fetch a message from that language, then the
 796          * fallbacks of that language, then the site language, then the fallbacks for the
 797          * site language.
 798          *
 799          * @param Language $lang Requested language
 800          * @param string $lckey Lowercase key for the message
 801          * @param string $uckey Uppercase key for the message
 802          * @param bool $useDB Whether to use the database
 803          *
 804          * @see MessageCache::get
 805          * @return string|bool The message, or false if not found
 806          */
 807         protected function getMessageFromFallbackChain( $lang, $lckey, $uckey, $useDB ) {
 808                 global $wgLanguageCode, $wgContLang;
 809
 810                 $langcode = $lang->getCode();
 811                 $message = false;
 812
 813                 // First try the requested language.
 814                 if ( $useDB ) {
 815                         if ( $langcode === $wgLanguageCode ) {
 816                                 // Messages created in the content language will not have the /lang extension
 817                                 $message = $this->getMsgFromNamespace( $uckey, $langcode );
 818                         } else {
 819                                 $message = $this->getMsgFromNamespace( "$uckey/$langcode", $langcode );
 820                         }
 821                 }
 822
 823                 if ( $message !== false ) {
 824                         return $message;
 825                 }
 826
 827                 // Check the CDB cache
 828                 $message = $lang->getMessage( $lckey );
 829                 if ( $message !== null ) {
 830                         return $message;
 831                 }
 832
 833                 list( $fallbackChain, $siteFallbackChain ) =
 834                         Language::getFallbacksIncludingSiteLanguage( $langcode );
 835
 836                 // Next try checking the database for all of the fallback languages of the requested language.
 837                 if ( $useDB ) {
 838                         foreach ( $fallbackChain as $code ) {
 839                                 if ( $code === $wgLanguageCode ) {
 840                                         // Messages created in the content language will not have the /lang extension
 841                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 842                                 } else {
 843                                         $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 844                                 }
 845
 846                                 if ( $message !== false ) {
 847                                         // Found the message.
 848                                         return $message;
 849                                 }
 850                         }
 851                 }
 852
 853                 // Now try checking the site language.
 854                 if ( $useDB ) {
 855                         $message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
 856                         if ( $message !== false ) {
 857                                 return $message;
 858                         }
 859                 }
 860
 861                 $message = $wgContLang->getMessage( $lckey );
 862                 if ( $message !== null ) {
 863                         return $message;
 864                 }
 865
 866                 // Finally try the DB for the site language's fallbacks.
 867                 if ( $useDB ) {
 868                         foreach ( $siteFallbackChain as $code ) {
 869                                 $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 870                                 if ( $message === false && $code === $wgLanguageCode ) {
 871                                         // Messages created in the content language will not have the /lang extension
 872                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 873                                 }
 874
 875                                 if ( $message !== false ) {
 876                                         // Found the message.
 877                                         return $message;
 878                                 }
 879                         }
 880                 }
 881
 882                 return false;
 883         }
 884
 885         /**
 886          * Get a message from the MediaWiki namespace, with caching. The key must
 887          * first be converted to two-part lang/msg form if necessary.
 888          *
 889          * Unlike self::get(), this function doesn't resolve fallback chains, and
 890          * some callers require this behavior. LanguageConverter::parseCachedTable()
 891          * and self::get() are some examples in core.
 892          *
 893          * @param string $title Message cache key with initial uppercase letter.
 894          * @param string $code Code denoting the language to try.
 895          * @return string|bool The message, or false if it does not exist or on error
 896          */
 897         function getMsgFromNamespace( $title, $code ) {
 898                 $this->load( $code );
 899                 if ( isset( $this->mCache[$code][$title] ) ) {
 900                         $entry = $this->mCache[$code][$title];
 901                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 902                                 // The message exists, so make sure a string
 903                                 // is returned.
 904                                 return (string)substr( $entry, 1 );
 905                         } elseif ( $entry === '!NONEXISTENT' ) {
 906                                 return false;
 907                         } elseif ( $entry === '!TOO BIG' ) {
 908                                 // Fall through and try invididual message cache below
 909                         }
 910                 } else {
 911                         // XXX: This is not cached in process cache, should it?
 912                         $message = false;
 913                         Hooks::run( 'MessagesPreLoad', array( $title, &$message ) );
 914                         if ( $message !== false ) {
 915                                 return $message;
 916                         }
 917
 918                         return false;
 919                 }
 920
 921                 # Try the individual message cache
 922                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 923                 $entry = $this->wanCache->get( $titleKey );
 924                 if ( $entry ) {
 925                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 926                                 $this->mCache[$code][$title] = $entry;
 927
 928                                 // The message exists, so make sure a string
 929                                 // is returned.
 930                                 return (string)substr( $entry, 1 );
 931                         } elseif ( $entry === '!NONEXISTENT' ) {
 932                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 933
 934                                 return false;
 935                         } else {
 936                                 # Corrupt/obsolete entry, delete it
 937                                 $this->wanCache->delete( $titleKey );
 938                         }
 939                 }
 940
 941                 # Try loading it from the database
 942                 $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
 943                 if ( $revision ) {
 944                         $content = $revision->getContent();
 945                         if ( !$content ) {
 946                                 // A possibly temporary loading failure.
 947                                 wfDebugLog(
 948                                         'MessageCache',
 949                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
 950                                 );
 951                                 $message = null; // no negative caching
 952                         } else {
 953                                 // XXX: Is this the right way to turn a Content object into a message?
 954                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
 955                                 //       CssContent. MessageContent is *not* used for storing messages, it's
 956                                 //       only used for wrapping them when needed.
 957                                 $message = $content->getWikitextForTransclusion();
 958
 959                                 if ( $message === false || $message === null ) {
 960                                         wfDebugLog(
 961                                                 'MessageCache',
 962                                                 __METHOD__ . ": message content doesn't provide wikitext "
 963                                                         . "(content model: " . $content->getContentHandler() . ")"
 964                                         );
 965
 966                                         $message = false; // negative caching
 967                                 } else {
 968                                         $this->mCache[$code][$title] = ' ' . $message;
 969                                         $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry );
 970                                 }
 971                         }
 972                 } else {
 973                         $message = false; // negative caching
 974                 }
 975
 976                 if ( $message === false ) { // negative caching
 977                         $this->mCache[$code][$title] = '!NONEXISTENT';
 978                         $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
 979                 }
 980
 981                 return $message;
 982         }
 983
 984         /**
 985          * @param string $message
 986          * @param bool $interface
 987          * @param string $language Language code
 988          * @param Title $title
 989          * @return string
 990          */
 991         function transform( $message, $interface = false, $language = null, $title = null ) {
 992                 // Avoid creating parser if nothing to transform
 993                 if ( strpos( $message, '{{' ) === false ) {
 994                         return $message;
 995                 }
 996
 997                 if ( $this->mInParser ) {
 998                         return $message;
 999                 }
1000
1001                 $parser = $this->getParser();
1002                 if ( $parser ) {
1003                         $popts = $this->getParserOptions();
1004                         $popts->setInterfaceMessage( $interface );
1005                         $popts->setTargetLanguage( $language );
1006
1007                         $userlang = $popts->setUserLang( $language );
1008                         $this->mInParser = true;
1009                         $message = $parser->transformMsg( $message, $popts, $title );
1010                         $this->mInParser = false;
1011                         $popts->setUserLang( $userlang );
1012                 }
1013
1014                 return $message;
1015         }
1016
1017         /**
1018          * @return Parser
1019          */
1020         function getParser() {
1021                 global $wgParser, $wgParserConf;
1022                 if ( !$this->mParser && isset( $wgParser ) ) {
1023                         # Do some initialisation so that we don't have to do it twice
1024                         $wgParser->firstCallInit();
1025                         # Clone it and store it
1026                         $class = $wgParserConf['class'];
1027                         if ( $class == 'ParserDiffTest' ) {
1028                                 # Uncloneable
1029                                 $this->mParser = new $class( $wgParserConf );
1030                         } else {
1031                                 $this->mParser = clone $wgParser;
1032                         }
1033                 }
1034
1035                 return $this->mParser;
1036         }
1037
1038         /**
1039          * @param string $text
1040          * @param Title $title
1041          * @param bool $linestart Whether or not this is at the start of a line
1042          * @param bool $interface Whether this is an interface message
1043          * @param string $language Language code
1044          * @return ParserOutput|string
1045          */
1046         public function parse( $text, $title = null, $linestart = true,
1047                 $interface = false, $language = null
1048         ) {
1049                 if ( $this->mInParser ) {
1050                         return htmlspecialchars( $text );
1051                 }
1052
1053                 $parser = $this->getParser();
1054                 $popts = $this->getParserOptions();
1055                 $popts->setInterfaceMessage( $interface );
1056                 $popts->setTargetLanguage( $language );
1057
1058                 if ( !$title || !$title instanceof Title ) {
1059                         global $wgTitle;
1060                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
1061                                 wfGetAllCallers( 5 ) . ' with no title set.' );
1062                         $title = $wgTitle;
1063                 }
1064                 // Sometimes $wgTitle isn't set either...
1065                 if ( !$title ) {
1066                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1067                         # Create a ghost title in such case
1068                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1069                 }
1070
1071                 $this->mInParser = true;
1072                 $res = $parser->parse( $text, $title, $popts, $linestart );
1073                 $this->mInParser = false;
1074
1075                 return $res;
1076         }
1077
1078         function disable() {
1079                 $this->mDisable = true;
1080         }
1081
1082         function enable() {
1083                 $this->mDisable = false;
1084         }
1085
1086         /**
1087          * Clear all stored messages. Mainly used after a mass rebuild.
1088          */
1089         function clear() {
1090                 $langs = Language::fetchLanguageNames( null, 'mw' );
1091                 foreach ( array_keys( $langs ) as $code ) {
1092                         # Global and local caches
1093                         $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
1094                 }
1095
1096                 $this->mLoadedLanguages = array();
1097         }
1098
1099         /**
1100          * @param string $key
1101          * @return array
1102          */
1103         public function figureMessage( $key ) {
1104                 global $wgLanguageCode;
1105
1106                 $pieces = explode( '/', $key );
1107                 if ( count( $pieces ) < 2 ) {
1108                         return array( $key, $wgLanguageCode );
1109                 }
1110
1111                 $lang = array_pop( $pieces );
1112                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1113                         return array( $key, $wgLanguageCode );
1114                 }
1115
1116                 $message = implode( '/', $pieces );
1117
1118                 return array( $message, $lang );
1119         }
1120
1121         /**
1122          * Get all message keys stored in the message cache for a given language.
1123          * If $code is the content language code, this will return all message keys
1124          * for which MediaWiki:msgkey exists. If $code is another language code, this
1125          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1126          * @param string $code Language code
1127          * @return array Array of message keys (strings)
1128          */
1129         public function getAllMessageKeys( $code ) {
1130                 global $wgContLang;
1131                 $this->load( $code );
1132                 if ( !isset( $this->mCache[$code] ) ) {
1133                         // Apparently load() failed
1134                         return null;
1135                 }
1136                 // Remove administrative keys
1137                 $cache = $this->mCache[$code];
1138                 unset( $cache['VERSION'] );
1139                 unset( $cache['EXPIRY'] );
1140                 // Remove any !NONEXISTENT keys
1141                 $cache = array_diff( $cache, array( '!NONEXISTENT' ) );
1142
1143                 // Keys may appear with a capital first letter. lcfirst them.
1144                 return array_map( array( $wgContLang, 'lcfirst' ), array_keys( $cache ) );
1145         }
1146 }