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