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', 1 );
  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          */
  62         protected $mCache;
  63
  64         /**
  65          * Should  mean that database cannot be used, but check
  66          * @var bool $mDisable
  67          */
  68         protected $mDisable;
  69
  70         /**
  71          * Lifetime for cache, used by object caching.
  72          * Set on construction, see __construct().
  73          */
  74         protected $mExpiry;
  75
  76         /**
  77          * Message cache has its own parser which it uses to transform
  78          * messages.
  79          */
  80         protected $mParserOptions, $mParser;
  81
  82         /**
  83          * Variable for tracking which variables are already loaded
  84          * @var array $mLoadedLanguages
  85          */
  86         protected $mLoadedLanguages = array();
  87
  88         /**
  89          * @var bool $mInParser
  90          */
  91         protected $mInParser = false;
  92
  93         /** @var BagOStuff */
  94         protected $mMemc;
  95         /** @var WANObjectCache */
  96         protected $wanCache;
  97
  98         /**
  99          * Singleton instance
 100          *
 101          * @var MessageCache $instance
 102          */
 103         private static $instance;
 104
 105         /**
 106          * Get the signleton instance of this class
 107          *
 108          * @since 1.18
 109          * @return MessageCache
 110          */
 111         public static function singleton() {
 112                 if ( is_null( self::$instance ) ) {
 113                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
 114                         self::$instance = new self(
 115                                 wfGetMessageCacheStorage(),
 116                                 $wgUseDatabaseMessages,
 117                                 $wgMsgCacheExpiry
 118                         );
 119                 }
 120
 121                 return self::$instance;
 122         }
 123
 124         /**
 125          * Destroy the singleton instance
 126          *
 127          * @since 1.18
 128          */
 129         public static function destroyInstance() {
 130                 self::$instance = null;
 131         }
 132
 133         /**
 134          * @param BagOStuff $memCached A cache instance. If none, fall back to CACHE_NONE.
 135          * @param bool $useDB
 136          * @param int $expiry Lifetime for cache. @see $mExpiry.
 137          */
 138         function __construct( $memCached, $useDB, $expiry ) {
 139                 if ( !$memCached ) {
 140                         $memCached = wfGetCache( CACHE_NONE );
 141                 }
 142
 143                 $this->mMemc = $memCached;
 144                 $this->mDisable = !$useDB;
 145                 $this->mExpiry = $expiry;
 146
 147                 $this->wanCache = ObjectCache::getMainWANInstance();
 148         }
 149
 150         /**
 151          * ParserOptions is lazy initialised.
 152          *
 153          * @return ParserOptions
 154          */
 155         function getParserOptions() {
 156                 if ( !$this->mParserOptions ) {
 157                         $this->mParserOptions = new ParserOptions;
 158                         $this->mParserOptions->setEditSection( false );
 159                 }
 160
 161                 return $this->mParserOptions;
 162         }
 163
 164         /**
 165          * Try to load the cache from a local file.
 166          *
 167          * @param string $hash The hash of contents, to check validity.
 168          * @param string $code Optional language code, see documenation of load().
 169          * @return array The cache array
 170          */
 171         function getLocalCache( $hash, $code ) {
 172                 global $wgCacheDirectory;
 173
 174                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 175
 176                 # Check file existence
 177                 MediaWiki\suppressWarnings();
 178                 $file = fopen( $filename, 'r' );
 179                 MediaWiki\restoreWarnings();
 180                 if ( !$file ) {
 181                         return false; // No cache file
 182                 }
 183
 184                 // Check to see if the file has the hash specified
 185                 $localHash = fread( $file, 32 );
 186                 if ( $hash === $localHash ) {
 187                         // All good, get the rest of it
 188                         $serialized = '';
 189                         while ( !feof( $file ) ) {
 190                                 $serialized .= fread( $file, 100000 );
 191                         }
 192                         fclose( $file );
 193
 194                         return unserialize( $serialized );
 195                 } else {
 196                         fclose( $file );
 197
 198                         return false; // Wrong hash
 199                 }
 200         }
 201
 202         /**
 203          * Save the cache to a local file.
 204          * @param string $serialized
 205          * @param string $hash
 206          * @param string $code
 207          */
 208         function saveToLocal( $serialized, $hash, $code ) {
 209                 global $wgCacheDirectory;
 210
 211                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 212                 wfMkdirParents( $wgCacheDirectory, null, __METHOD__ ); // might fail
 213
 214                 MediaWiki\suppressWarnings();
 215                 $file = fopen( $filename, 'w' );
 216                 MediaWiki\restoreWarnings();
 217
 218                 if ( !$file ) {
 219                         wfDebug( "Unable to open local cache file for writing\n" );
 220
 221                         return;
 222                 }
 223
 224                 fwrite( $file, $hash . $serialized );
 225                 fclose( $file );
 226                 MediaWiki\suppressWarnings();
 227                 chmod( $filename, 0666 );
 228                 MediaWiki\restoreWarnings();
 229         }
 230
 231         /**
 232          * Loads messages from caches or from database in this order:
 233          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 234          * (2) memcached
 235          * (3) from the database.
 236          *
 237          * When succesfully loading from (2) or (3), all higher level caches are
 238          * updated for the newest version.
 239          *
 240          * Nothing is loaded if member variable mDisable is true, either manually
 241          * set by calling code or if message loading fails (is this possible?).
 242          *
 243          * Returns true if cache is already populated or it was succesfully populated,
 244          * or false if populating empty cache fails. Also returns true if MessageCache
 245          * is disabled.
 246          *
 247          * @param bool|string $code Language to which load messages
 248          * @param integer $mode Use MessageCache::FOR_UPDATE to skip process cache
 249          * @throws MWException
 250          * @return bool
 251          */
 252         function load( $code = false, $mode = null ) {
 253                 global $wgUseLocalMessageCache;
 254
 255                 if ( !is_string( $code ) ) {
 256                         # This isn't really nice, so at least make a note about it and try to
 257                         # fall back
 258                         wfDebug( __METHOD__ . " called without providing a language code\n" );
 259                         $code = 'en';
 260                 }
 261
 262                 # Don't do double loading...
 263                 if ( isset( $this->mLoadedLanguages[$code] ) && $mode != self::FOR_UPDATE ) {
 264                         return true;
 265                 }
 266
 267                 # 8 lines of code just to say (once) that message cache is disabled
 268                 if ( $this->mDisable ) {
 269                         static $shownDisabled = false;
 270                         if ( !$shownDisabled ) {
 271                                 wfDebug( __METHOD__ . ": disabled\n" );
 272                                 $shownDisabled = true;
 273                         }
 274
 275                         return true;
 276                 }
 277
 278                 # Loading code starts
 279                 $success = false; # Keep track of success
 280                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 281                 $hashExpired = false; # whether the cluster-local validation hash is stale
 282                 $where = array(); # Debug info, delayed to avoid spamming debug log too much
 283
 284                 # Local cache
 285                 # Hash of the contents is stored in memcache, to detect if local cache goes
 286                 # out of date (e.g. due to replace() on some other server)
 287                 if ( $wgUseLocalMessageCache ) {
 288                         list( $hash, $hashExpired ) = $this->getValidationHash( $code );
 289                         if ( $hash ) {
 290                                 $cache = $this->getLocalCache( $hash, $code );
 291                                 if ( !$cache ) {
 292                                         $where[] = 'local cache is empty or has the wrong hash';
 293                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 294                                         $where[] = 'local cache is expired';
 295                                         $staleCache = $cache;
 296                                 } elseif ( $hashExpired ) {
 297                                         $where[] = 'local cache validation key is expired';
 298                                         $staleCache = $cache;
 299                                 } else {
 300                                         $where[] = 'got from local cache';
 301                                         $success = true;
 302                                         $this->mCache[$code] = $cache;
 303                                 }
 304                         }
 305                 }
 306
 307                 if ( !$success ) {
 308                         $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 309                         # Try the global cache. If it is empty, try to acquire a lock. If
 310                         # the lock can't be acquired, wait for the other thread to finish
 311                         # and then try the global cache a second time.
 312                         for ( $failedAttempts = 0; $failedAttempts < 2; $failedAttempts++ ) {
 313                                 if ( $hashExpired && $staleCache ) {
 314                                         # Do not bother fetching the whole cache blob to avoid I/O.
 315                                         # Instead, just try to get the non-blocking $statusKey lock
 316                                         # below, and use the local stale value if it was not acquired.
 317                                         $where[] = 'global cache is presumed expired';
 318                                 } else {
 319                                         $cache = $this->mMemc->get( $cacheKey );
 320                                         if ( !$cache ) {
 321                                                 $where[] = 'global cache is empty';
 322                                         } elseif ( $this->isCacheExpired( $cache ) ) {
 323                                                 $where[] = 'global cache is expired';
 324                                                 $staleCache = $cache;
 325                                         } else {
 326                                                 $where[] = 'got from global cache';
 327                                                 $this->mCache[$code] = $cache;
 328                                                 $this->saveToCaches( $cache, 'local-only', $code );
 329                                                 $success = true;
 330                                         }
 331                                 }
 332
 333                                 if ( $success ) {
 334                                         # Done, no need to retry
 335                                         break;
 336                                 }
 337
 338                                 # We need to call loadFromDB. Limit the concurrency to one process.
 339                                 # This prevents the site from going down when the cache expires.
 340                                 if ( $this->loadFromDBWithLock( $code, $where ) ) {
 341                                         # Load from DB complete, no need to retry
 342                                         $success = true;
 343                                         break;
 344                                 } elseif ( $staleCache ) {
 345                                         # Use the stale cache while some other thread constructs the new one
 346                                         $where[] = 'using stale cache';
 347                                         $this->mCache[$code] = $staleCache;
 348                                         $success = true;
 349                                         break;
 350                                 } elseif ( $failedAttempts > 0 ) {
 351                                         # Already retried once, still failed, so don't do another lock/unlock cycle
 352                                         # This case will typically be hit if memcached is down, or if
 353                                         # loadFromDB() takes longer than MSG_WAIT_TIMEOUT
 354                                         $where[] = "could not acquire status key.";
 355                                         break;
 356                                 } else {
 357                                         $statusKey = wfMemcKey( 'messages', $code, 'status' );
 358                                         $status = $this->mMemc->get( $statusKey );
 359                                         if ( $status === 'error' ) {
 360                                                 # Disable cache
 361                                                 break;
 362                                         } else {
 363                                                 # Wait for the other thread to finish, then retry
 364                                                 $where[] = 'waited for other thread to complete';
 365                                                 $this->lock( $cacheKey );
 366                                                 $this->unlock( $cacheKey );
 367                                         }
 368                                 }
 369                         }
 370                 }
 371
 372                 if ( !$success ) {
 373                         $where[] = 'loading FAILED - cache is disabled';
 374                         $this->mDisable = true;
 375                         $this->mCache = false;
 376                         # This used to throw an exception, but that led to nasty side effects like
 377                         # the whole wiki being instantly down if the memcached server died
 378                 } else {
 379                         # All good, just record the success
 380                         $this->mLoadedLanguages[$code] = true;
 381                 }
 382
 383                 $info = implode( ', ', $where );
 384                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 385
 386                 return $success;
 387         }
 388
 389         /**
 390          * @param string $code
 391          * @param array $where List of wfDebug() comments
 392          * @return bool Lock acquired and loadFromDB() called
 393          */
 394         protected function loadFromDBWithLock( $code, array &$where ) {
 395                 global $wgUseLocalMessageCache;
 396
 397                 $memCache = $this->mMemc;
 398
 399                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 400                 if ( !$memCache->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT ) ) {
 401                         return false; // could not acquire lock
 402                 }
 403
 404                 # Unlock the status key if there is an exception
 405                 $statusUnlocker = new ScopedCallback( function () use ( $memCache, $statusKey ) {
 406                         $memCache->delete( $statusKey );
 407                 } );
 408
 409                 # Now let's regenerate
 410                 $where[] = 'loading from database';
 411
 412                 $cacheKey = wfMemcKey( 'messages', $code );
 413                 # Lock the cache to prevent conflicting writes
 414                 # If this lock fails, it doesn't really matter, it just means the
 415                 # write is potentially non-atomic, e.g. the results of a replace()
 416                 # may be discarded.
 417                 if ( $this->lock( $cacheKey ) ) {
 418                         $that = $this;
 419                         $mainUnlocker = new ScopedCallback( function () use ( $that, $cacheKey ) {
 420                                 $that->unlock( $cacheKey );
 421                         } );
 422                 } else {
 423                         $mainUnlocker = null;
 424                         $where[] = 'could not acquire main lock';
 425                 }
 426
 427                 $cache = $this->loadFromDB( $code );
 428                 $this->mCache[$code] = $cache;
 429                 $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 430
 431                 # Unlock
 432                 ScopedCallback::consume( $mainUnlocker );
 433                 ScopedCallback::consume( $statusUnlocker );
 434
 435                 if ( !$saveSuccess ) {
 436                         # Cache save has failed.
 437                         # There are two main scenarios where this could be a problem:
 438                         #
 439                         #   - The cache is more than the maximum size (typically
 440                         #     1MB compressed).
 441                         #
 442                         #   - Memcached has no space remaining in the relevant slab
 443                         #     class. This is unlikely with recent versions of
 444                         #     memcached.
 445                         #
 446                         # Either way, if there is a local cache, nothing bad will
 447                         # happen. If there is no local cache, disabling the message
 448                         # cache for all requests avoids incurring a loadFromDB()
 449                         # overhead on every request, and thus saves the wiki from
 450                         # complete downtime under moderate traffic conditions.
 451                         if ( !$wgUseLocalMessageCache ) {
 452                                 $memCache->set( $statusKey, 'error', 60 * 5 );
 453                                 $where[] = 'could not save cache, disabled globally for 5 minutes';
 454                         } else {
 455                                 $where[] = "could not save global cache";
 456                         }
 457                 }
 458
 459                 return true;
 460         }
 461
 462         /**
 463          * Loads cacheable messages from the database. Messages bigger than
 464          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 465          * on-demand from the database later.
 466          *
 467          * @param string $code Language code.
 468          * @return array Loaded messages for storing in caches.
 469          */
 470         function loadFromDB( $code ) {
 471                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 472
 473                 $dbr = wfGetDB( DB_SLAVE );
 474                 $cache = array();
 475
 476                 # Common conditions
 477                 $conds = array(
 478                         'page_is_redirect' => 0,
 479                         'page_namespace' => NS_MEDIAWIKI,
 480                 );
 481
 482                 $mostused = array();
 483                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 484                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 485                                 $this->load( $wgLanguageCode );
 486                         }
 487                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 488                         foreach ( $mostused as $key => $value ) {
 489                                 $mostused[$key] = "$value/$code";
 490                         }
 491                 }
 492
 493                 if ( count( $mostused ) ) {
 494                         $conds['page_title'] = $mostused;
 495                 } elseif ( $code !== $wgLanguageCode ) {
 496                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 497                 } else {
 498                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 499                         # other than language code.
 500                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 501                 }
 502
 503                 # Conditions to fetch oversized pages to ignore them
 504                 $bigConds = $conds;
 505                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 506
 507                 # Load titles for all oversized pages in the MediaWiki namespace
 508                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 509                 foreach ( $res as $row ) {
 510                         $cache[$row->page_title] = '!TOO BIG';
 511                 }
 512
 513                 # Conditions to load the remaining pages with their contents
 514                 $smallConds = $conds;
 515                 $smallConds[] = 'page_latest=rev_id';
 516                 $smallConds[] = 'rev_text_id=old_id';
 517                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 518
 519                 $res = $dbr->select(
 520                         array( 'page', 'revision', 'text' ),
 521                         array( 'page_title', 'old_text', 'old_flags' ),
 522                         $smallConds,
 523                         __METHOD__ . "($code)-small"
 524                 );
 525
 526                 foreach ( $res as $row ) {
 527                         $text = Revision::getRevisionText( $row );
 528                         if ( $text === false ) {
 529                                 // Failed to fetch data; possible ES errors?
 530                                 // Store a marker to fetch on-demand as a workaround...
 531                                 $entry = '!TOO BIG';
 532                                 wfDebugLog(
 533                                         'MessageCache',
 534                                         __METHOD__
 535                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 536                                 );
 537                         } else {
 538                                 $entry = ' ' . $text;
 539                         }
 540                         $cache[$row->page_title] = $entry;
 541                 }
 542
 543                 $cache['VERSION'] = MSG_CACHE_VERSION;
 544                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 545
 546                 return $cache;
 547         }
 548
 549         /**
 550          * Updates cache as necessary when message page is changed
 551          *
 552          * @param string $title Name of the page changed.
 553          * @param mixed $text New contents of the page.
 554          */
 555         public function replace( $title, $text ) {
 556                 global $wgMaxMsgCacheEntrySize, $wgContLang, $wgLanguageCode;
 557
 558                 if ( $this->mDisable ) {
 559                         return;
 560                 }
 561
 562                 list( $msg, $code ) = $this->figureMessage( $title );
 563                 if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
 564                         # Content language overrides do not use the /<code> suffix
 565                         return;
 566                 }
 567
 568                 $cacheKey = wfMemcKey( 'messages', $code );
 569                 $this->lock( $cacheKey );
 570                 $this->load( $code, self::FOR_UPDATE );
 571
 572                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 573
 574                 if ( $text === false ) {
 575                         # Article was deleted
 576                         $this->mCache[$code][$title] = '!NONEXISTENT';
 577                         $this->mMemc->delete( $titleKey );
 578                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 579                         # Check for size
 580                         $this->mCache[$code][$title] = '!TOO BIG';
 581                         $this->mMemc->set( $titleKey, ' ' . $text, $this->mExpiry );
 582                 } else {
 583                         $this->mCache[$code][$title] = ' ' . $text;
 584                         $this->mMemc->delete( $titleKey );
 585                 }
 586
 587                 # Update caches
 588                 $this->saveToCaches( $this->mCache[$code], 'all', $code );
 589                 $this->unlock( $cacheKey );
 590                 $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
 591
 592                 // Also delete cached sidebar... just in case it is affected
 593                 $codes = array( $code );
 594                 if ( $code === 'en' ) {
 595                         // Delete all sidebars, like for example on action=purge on the
 596                         // sidebar messages
 597                         $codes = array_keys( Language::fetchLanguageNames() );
 598                 }
 599
 600                 foreach ( $codes as $code ) {
 601                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 602                         $this->wanCache->delete( $sidebarKey, 5 );
 603                 }
 604
 605                 // Update the message in the message blob store
 606                 $blobStore = new MessageBlobStore();
 607                 $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );
 608
 609                 Hooks::run( 'MessageCacheReplace', array( $title, $text ) );
 610         }
 611
 612         /**
 613          * Is the given cache array expired due to time passing or a version change?
 614          *
 615          * @param array $cache
 616          * @return bool
 617          */
 618         protected function isCacheExpired( $cache ) {
 619                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 620                         return true;
 621                 }
 622                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 623                         return true;
 624                 }
 625                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 626                         return true;
 627                 }
 628
 629                 return false;
 630         }
 631
 632         /**
 633          * Shortcut to update caches.
 634          *
 635          * @param array $cache Cached messages with a version.
 636          * @param string $dest Either "local-only" to save to local caches only
 637          *   or "all" to save to all caches.
 638          * @param string|bool $code Language code (default: false)
 639          * @return bool
 640          */
 641         protected function saveToCaches( $cache, $dest, $code = false ) {
 642                 global $wgUseLocalMessageCache;
 643
 644                 if ( $dest === 'all' ) {
 645                         $cacheKey = wfMemcKey( 'messages', $code );
 646                         $success = $this->mMemc->set( $cacheKey, $cache );
 647                 } else {
 648                         $success = true;
 649                 }
 650
 651                 # Save to local cache
 652                 if ( $wgUseLocalMessageCache ) {
 653                         $serialized = serialize( $cache );
 654                         $hash = md5( $serialized );
 655                         $this->setValidationHash( $code, $hash );
 656                         $this->saveToLocal( $serialized, $hash, $code );
 657                 }
 658
 659                 return $success;
 660         }
 661
 662         /**
 663          * Get the md5 used to validate the local disk cache
 664          *
 665          * @param string $code
 666          * @return array (hash or false, bool expiry status)
 667          */
 668         protected function getValidationHash( $code ) {
 669                 $curTTL = null;
 670                 $value = $this->wanCache->get(
 671                         wfMemcKey( 'messages', $code, 'hash' ),
 672                         $curTTL,
 673                         array( wfMemcKey( 'messages', $code ) )
 674                 );
 675                 $expired = ( $curTTL === null || $curTTL < 0 );
 676
 677                 return array( $value, $expired );
 678         }
 679
 680         /**
 681          * Set the md5 used to validate the local disk cache
 682          *
 683          * @param string $code
 684          * @param string $hash
 685          */
 686         protected function setValidationHash( $code, $hash ) {
 687                 $this->wanCache->set(
 688                         wfMemcKey( 'messages', $code, 'hash' ),
 689                         $hash,
 690                         WANObjectCache::TTL_NONE
 691                 );
 692         }
 693
 694         /**
 695          * Represents a write lock on the messages key.
 696          *
 697          * Will retry MessageCache::MSG_WAIT_TIMEOUT times, each operations having
 698          * a timeout of MessageCache::MSG_LOCK_TIMEOUT.
 699          *
 700          * @param string $key
 701          * @return bool Success
 702          */
 703         function lock( $key ) {
 704                 $lockKey = $key . ':lock';
 705                 $acquired = false;
 706                 $testDone = false;
 707                 for ( $i = 0; $i < MSG_WAIT_TIMEOUT && !$acquired; $i++ ) {
 708                         $acquired = $this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT );
 709                         if ( $acquired ) {
 710                                 break;
 711                         }
 712
 713                         # Fail fast if memcached is totally down
 714                         if ( !$testDone ) {
 715                                 $testDone = true;
 716                                 if ( !$this->mMemc->set( wfMemcKey( 'test' ), 'test', 1 ) ) {
 717                                         break;
 718                                 }
 719                         }
 720                         sleep( 1 );
 721                 }
 722
 723                 return $acquired;
 724         }
 725
 726         function unlock( $key ) {
 727                 $lockKey = $key . ':lock';
 728                 $this->mMemc->delete( $lockKey );
 729         }
 730
 731         /**
 732          * Get a message from either the content language or the user language.
 733          *
 734          * First, assemble a list of languages to attempt getting the message from. This
 735          * chain begins with the requested language and its fallbacks and then continues with
 736          * the content language and its fallbacks. For each language in the chain, the following
 737          * process will occur (in this order):
 738          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 739          *     Note: for the content language, there is no /lang subpage.
 740          *  2. Fetch from the static CDB cache.
 741          *  3. If available, check the database for fallback language overrides.
 742          *
 743          * This process provides a number of guarantees. When changing this code, make sure all
 744          * of these guarantees are preserved.
 745          *  * If the requested language is *not* the content language, then the CDB cache for that
 746          *    specific language will take precedence over the root database page ([[MW:msg]]).
 747          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 748          *    the message is available *anywhere* in the language for which it is a fallback.
 749          *
 750          * @param string $key The message key
 751          * @param bool $useDB If true, look for the message in the DB, false
 752          *   to use only the compiled l10n cache.
 753          * @param bool|string|object $langcode Code of the language to get the message for.
 754          *   - If string and a valid code, will create a standard language object
 755          *   - If string but not a valid code, will create a basic language object
 756          *   - If boolean and false, create object from the current users language
 757          *   - If boolean and true, create object from the wikis content language
 758          *   - If language object, use it as given
 759          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 760          *
 761          * @throws MWException When given an invalid key
 762          * @return string|bool False if the message doesn't exist, otherwise the
 763          *   message (which can be empty)
 764          */
 765         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 766                 global $wgContLang;
 767
 768                 if ( is_int( $key ) ) {
 769                         // Fix numerical strings that somehow become ints
 770                         // on their way here
 771                         $key = (string)$key;
 772                 } elseif ( !is_string( $key ) ) {
 773                         throw new MWException( 'Non-string key given' );
 774                 } elseif ( $key === '' ) {
 775                         // Shortcut: the empty key is always missing
 776                         return false;
 777                 }
 778
 779                 // For full keys, get the language code from the key
 780                 $pos = strrpos( $key, '/' );
 781                 if ( $isFullKey && $pos !== false ) {
 782                         $langcode = substr( $key, $pos + 1 );
 783                         $key = substr( $key, 0, $pos );
 784                 }
 785
 786                 // Normalise title-case input (with some inlining)
 787                 $lckey = strtr( $key, ' ', '_' );
 788                 if ( ord( $lckey ) < 128 ) {
 789                         $lckey[0] = strtolower( $lckey[0] );
 790                 } else {
 791                         $lckey = $wgContLang->lcfirst( $lckey );
 792                 }
 793
 794                 Hooks::run( 'MessageCache::get', array( &$lckey ) );
 795
 796                 if ( ord( $lckey ) < 128 ) {
 797                         $uckey = ucfirst( $lckey );
 798                 } else {
 799                         $uckey = $wgContLang->ucfirst( $lckey );
 800                 }
 801
 802                 // Loop through each language in the fallback list until we find something useful
 803                 $lang = wfGetLangObj( $langcode );
 804                 $message = $this->getMessageFromFallbackChain(
 805                         $lang,
 806                         $lckey,
 807                         $uckey,
 808                         !$this->mDisable && $useDB
 809                 );
 810
 811                 // If we still have no message, maybe the key was in fact a full key so try that
 812                 if ( $message === false ) {
 813                         $parts = explode( '/', $lckey );
 814                         // We may get calls for things that are http-urls from sidebar
 815                         // Let's not load nonexistent languages for those
 816                         // They usually have more than one slash.
 817                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 818                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 819                                 if ( $message === null ) {
 820                                         $message = false;
 821                                 }
 822                         }
 823                 }
 824
 825                 // Post-processing if the message exists
 826                 if ( $message !== false ) {
 827                         // Fix whitespace
 828                         $message = str_replace(
 829                                 array(
 830                                         # Fix for trailing whitespace, removed by textarea
 831                                         '&#32;',
 832                                         # Fix for NBSP, converted to space by firefox
 833                                         '&nbsp;',
 834                                         '&#160;',
 835                                 ),
 836                                 array(
 837                                         ' ',
 838                                         "\xc2\xa0",
 839                                         "\xc2\xa0"
 840                                 ),
 841                                 $message
 842                         );
 843                 }
 844
 845                 return $message;
 846         }
 847
 848         /**
 849          * Given a language, try and fetch a message from that language, then the
 850          * fallbacks of that language, then the site language, then the fallbacks for the
 851          * site language.
 852          *
 853          * @param Language $lang Requested language
 854          * @param string $lckey Lowercase key for the message
 855          * @param string $uckey Uppercase key for the message
 856          * @param bool $useDB Whether to use the database
 857          *
 858          * @see MessageCache::get
 859          * @return string|bool The message, or false if not found
 860          */
 861         protected function getMessageFromFallbackChain( $lang, $lckey, $uckey, $useDB ) {
 862                 global $wgLanguageCode, $wgContLang;
 863
 864                 $langcode = $lang->getCode();
 865                 $message = false;
 866
 867                 // First try the requested language.
 868                 if ( $useDB ) {
 869                         if ( $langcode === $wgLanguageCode ) {
 870                                 // Messages created in the content language will not have the /lang extension
 871                                 $message = $this->getMsgFromNamespace( $uckey, $langcode );
 872                         } else {
 873                                 $message = $this->getMsgFromNamespace( "$uckey/$langcode", $langcode );
 874                         }
 875                 }
 876
 877                 if ( $message !== false ) {
 878                         return $message;
 879                 }
 880
 881                 // Check the CDB cache
 882                 $message = $lang->getMessage( $lckey );
 883                 if ( $message !== null ) {
 884                         return $message;
 885                 }
 886
 887                 list( $fallbackChain, $siteFallbackChain ) =
 888                         Language::getFallbacksIncludingSiteLanguage( $langcode );
 889
 890                 // Next try checking the database for all of the fallback languages of the requested language.
 891                 if ( $useDB ) {
 892                         foreach ( $fallbackChain as $code ) {
 893                                 if ( $code === $wgLanguageCode ) {
 894                                         // Messages created in the content language will not have the /lang extension
 895                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 896                                 } else {
 897                                         $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 898                                 }
 899
 900                                 if ( $message !== false ) {
 901                                         // Found the message.
 902                                         return $message;
 903                                 }
 904                         }
 905                 }
 906
 907                 // Now try checking the site language.
 908                 if ( $useDB ) {
 909                         $message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
 910                         if ( $message !== false ) {
 911                                 return $message;
 912                         }
 913                 }
 914
 915                 $message = $wgContLang->getMessage( $lckey );
 916                 if ( $message !== null ) {
 917                         return $message;
 918                 }
 919
 920                 // Finally try the DB for the site language's fallbacks.
 921                 if ( $useDB ) {
 922                         foreach ( $siteFallbackChain as $code ) {
 923                                 $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 924                                 if ( $message === false && $code === $wgLanguageCode ) {
 925                                         // Messages created in the content language will not have the /lang extension
 926                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 927                                 }
 928
 929                                 if ( $message !== false ) {
 930                                         // Found the message.
 931                                         return $message;
 932                                 }
 933                         }
 934                 }
 935
 936                 return false;
 937         }
 938
 939         /**
 940          * Get a message from the MediaWiki namespace, with caching. The key must
 941          * first be converted to two-part lang/msg form if necessary.
 942          *
 943          * Unlike self::get(), this function doesn't resolve fallback chains, and
 944          * some callers require this behavior. LanguageConverter::parseCachedTable()
 945          * and self::get() are some examples in core.
 946          *
 947          * @param string $title Message cache key with initial uppercase letter.
 948          * @param string $code Code denoting the language to try.
 949          * @return string|bool The message, or false if it does not exist or on error
 950          */
 951         function getMsgFromNamespace( $title, $code ) {
 952                 $this->load( $code );
 953                 if ( isset( $this->mCache[$code][$title] ) ) {
 954                         $entry = $this->mCache[$code][$title];
 955                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 956                                 // The message exists, so make sure a string
 957                                 // is returned.
 958                                 return (string)substr( $entry, 1 );
 959                         } elseif ( $entry === '!NONEXISTENT' ) {
 960                                 return false;
 961                         } elseif ( $entry === '!TOO BIG' ) {
 962                                 // Fall through and try invididual message cache below
 963                         }
 964                 } else {
 965                         // XXX: This is not cached in process cache, should it?
 966                         $message = false;
 967                         Hooks::run( 'MessagesPreLoad', array( $title, &$message ) );
 968                         if ( $message !== false ) {
 969                                 return $message;
 970                         }
 971
 972                         return false;
 973                 }
 974
 975                 # Try the individual message cache
 976                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 977                 $entry = $this->mMemc->get( $titleKey );
 978                 if ( $entry ) {
 979                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 980                                 $this->mCache[$code][$title] = $entry;
 981
 982                                 // The message exists, so make sure a string
 983                                 // is returned.
 984                                 return (string)substr( $entry, 1 );
 985                         } elseif ( $entry === '!NONEXISTENT' ) {
 986                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 987
 988                                 return false;
 989                         } else {
 990                                 # Corrupt/obsolete entry, delete it
 991                                 $this->mMemc->delete( $titleKey );
 992                         }
 993                 }
 994
 995                 # Try loading it from the database
 996                 $revision = Revision::newFromTitle(
 997                         Title::makeTitle( NS_MEDIAWIKI, $title ), false, Revision::READ_LATEST
 998                 );
 999                 if ( $revision ) {
1000                         $content = $revision->getContent();
1001                         if ( !$content ) {
1002                                 // A possibly temporary loading failure.
1003                                 wfDebugLog(
1004                                         'MessageCache',
1005                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
1006                                 );
1007                                 $message = null; // no negative caching
1008                         } else {
1009                                 // XXX: Is this the right way to turn a Content object into a message?
1010                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
1011                                 //       CssContent. MessageContent is *not* used for storing messages, it's
1012                                 //       only used for wrapping them when needed.
1013                                 $message = $content->getWikitextForTransclusion();
1014
1015                                 if ( $message === false || $message === null ) {
1016                                         wfDebugLog(
1017                                                 'MessageCache',
1018                                                 __METHOD__ . ": message content doesn't provide wikitext "
1019                                                         . "(content model: " . $content->getContentHandler() . ")"
1020                                         );
1021
1022                                         $message = false; // negative caching
1023                                 } else {
1024                                         $this->mCache[$code][$title] = ' ' . $message;
1025                                         $this->mMemc->set( $titleKey, ' ' . $message, $this->mExpiry );
1026                                 }
1027                         }
1028                 } else {
1029                         $message = false; // negative caching
1030                 }
1031
1032                 if ( $message === false ) { // negative caching
1033                         $this->mCache[$code][$title] = '!NONEXISTENT';
1034                         $this->mMemc->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
1035                 }
1036
1037                 return $message;
1038         }
1039
1040         /**
1041          * @param string $message
1042          * @param bool $interface
1043          * @param string $language Language code
1044          * @param Title $title
1045          * @return string
1046          */
1047         function transform( $message, $interface = false, $language = null, $title = null ) {
1048                 // Avoid creating parser if nothing to transform
1049                 if ( strpos( $message, '{{' ) === false ) {
1050                         return $message;
1051                 }
1052
1053                 if ( $this->mInParser ) {
1054                         return $message;
1055                 }
1056
1057                 $parser = $this->getParser();
1058                 if ( $parser ) {
1059                         $popts = $this->getParserOptions();
1060                         $popts->setInterfaceMessage( $interface );
1061                         $popts->setTargetLanguage( $language );
1062
1063                         $userlang = $popts->setUserLang( $language );
1064                         $this->mInParser = true;
1065                         $message = $parser->transformMsg( $message, $popts, $title );
1066                         $this->mInParser = false;
1067                         $popts->setUserLang( $userlang );
1068                 }
1069
1070                 return $message;
1071         }
1072
1073         /**
1074          * @return Parser
1075          */
1076         function getParser() {
1077                 global $wgParser, $wgParserConf;
1078                 if ( !$this->mParser && isset( $wgParser ) ) {
1079                         # Do some initialisation so that we don't have to do it twice
1080                         $wgParser->firstCallInit();
1081                         # Clone it and store it
1082                         $class = $wgParserConf['class'];
1083                         if ( $class == 'ParserDiffTest' ) {
1084                                 # Uncloneable
1085                                 $this->mParser = new $class( $wgParserConf );
1086                         } else {
1087                                 $this->mParser = clone $wgParser;
1088                         }
1089                 }
1090
1091                 return $this->mParser;
1092         }
1093
1094         /**
1095          * @param string $text
1096          * @param Title $title
1097          * @param bool $linestart Whether or not this is at the start of a line
1098          * @param bool $interface Whether this is an interface message
1099          * @param string $language Language code
1100          * @return ParserOutput|string
1101          */
1102         public function parse( $text, $title = null, $linestart = true,
1103                 $interface = false, $language = null
1104         ) {
1105                 if ( $this->mInParser ) {
1106                         return htmlspecialchars( $text );
1107                 }
1108
1109                 $parser = $this->getParser();
1110                 $popts = $this->getParserOptions();
1111                 $popts->setInterfaceMessage( $interface );
1112                 $popts->setTargetLanguage( $language );
1113
1114                 if ( !$title || !$title instanceof Title ) {
1115                         global $wgTitle;
1116                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' . wfGetAllCallers( 5 ) . ' with no title set.' );
1117                         $title = $wgTitle;
1118                 }
1119                 // Sometimes $wgTitle isn't set either...
1120                 if ( !$title ) {
1121                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1122                         # Create a ghost title in such case
1123                         $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
1124                 }
1125
1126                 $this->mInParser = true;
1127                 $res = $parser->parse( $text, $title, $popts, $linestart );
1128                 $this->mInParser = false;
1129
1130                 return $res;
1131         }
1132
1133         function disable() {
1134                 $this->mDisable = true;
1135         }
1136
1137         function enable() {
1138                 $this->mDisable = false;
1139         }
1140
1141         /**
1142          * Clear all stored messages. Mainly used after a mass rebuild.
1143          */
1144         function clear() {
1145                 $langs = Language::fetchLanguageNames( null, 'mw' );
1146                 foreach ( array_keys( $langs ) as $code ) {
1147                         # Global and local caches
1148                         $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
1149                 }
1150
1151                 $this->mLoadedLanguages = array();
1152         }
1153
1154         /**
1155          * @param string $key
1156          * @return array
1157          */
1158         public function figureMessage( $key ) {
1159                 global $wgLanguageCode;
1160
1161                 $pieces = explode( '/', $key );
1162                 if ( count( $pieces ) < 2 ) {
1163                         return array( $key, $wgLanguageCode );
1164                 }
1165
1166                 $lang = array_pop( $pieces );
1167                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1168                         return array( $key, $wgLanguageCode );
1169                 }
1170
1171                 $message = implode( '/', $pieces );
1172
1173                 return array( $message, $lang );
1174         }
1175
1176         /**
1177          * Get all message keys stored in the message cache for a given language.
1178          * If $code is the content language code, this will return all message keys
1179          * for which MediaWiki:msgkey exists. If $code is another language code, this
1180          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1181          * @param string $code Language code
1182          * @return array Array of message keys (strings)
1183          */
1184         public function getAllMessageKeys( $code ) {
1185                 global $wgContLang;
1186                 $this->load( $code );
1187                 if ( !isset( $this->mCache[$code] ) ) {
1188                         // Apparently load() failed
1189                         return null;
1190                 }
1191                 // Remove administrative keys
1192                 $cache = $this->mCache[$code];
1193                 unset( $cache['VERSION'] );
1194                 unset( $cache['EXPIRY'] );
1195                 // Remove any !NONEXISTENT keys
1196                 $cache = array_diff( $cache, array( '!NONEXISTENT' ) );
1197
1198                 // Keys may appear with a capital first letter. lcfirst them.
1199                 return array_map( array( $wgContLang, 'lcfirst' ), array_keys( $cache ) );
1200         }
1201 }