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         /**
  54          * Process local cache of loaded messages that are defined in
  55          * MediaWiki namespace. First array level is a language code,
  56          * second level is message key and the values are either message
  57          * content prefixed with space, or !NONEXISTENT for negative
  58          * caching.
  59          */
  60         protected $mCache;
  61
  62         /**
  63          * Should  mean that database cannot be used, but check
  64          * @var bool $mDisable
  65          */
  66         protected $mDisable;
  67
  68         /**
  69          * Lifetime for cache, used by object caching.
  70          * Set on construction, see __construct().
  71          */
  72         protected $mExpiry;
  73
  74         /**
  75          * Message cache has its own parser which it uses to transform
  76          * messages.
  77          */
  78         protected $mParserOptions, $mParser;
  79
  80         /**
  81          * Variable for tracking which variables are already loaded
  82          * @var array $mLoadedLanguages
  83          */
  84         protected $mLoadedLanguages = array();
  85
  86         /**
  87          * Singleton instance
  88          *
  89          * @var MessageCache $instance
  90          */
  91         private static $instance;
  92
  93         /**
  94          * @var bool $mInParser
  95          */
  96         protected $mInParser = false;
  97
  98         /**
  99          * Get the signleton instance of this class
 100          *
 101          * @since 1.18
 102          * @return MessageCache
 103          */
 104         public static function singleton() {
 105                 if ( is_null( self::$instance ) ) {
 106                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
 107                         self::$instance = new self(
 108                                 wfGetMessageCacheStorage(),
 109                                 $wgUseDatabaseMessages,
 110                                 $wgMsgCacheExpiry
 111                         );
 112                 }
 113
 114                 return self::$instance;
 115         }
 116
 117         /**
 118          * Destroy the singleton instance
 119          *
 120          * @since 1.18
 121          */
 122         public static function destroyInstance() {
 123                 self::$instance = null;
 124         }
 125
 126         /**
 127          * @param BagOStuff $memCached A cache instance. If none, fall back to CACHE_NONE.
 128          * @param bool $useDB
 129          * @param int $expiry Lifetime for cache. @see $mExpiry.
 130          */
 131         function __construct( $memCached, $useDB, $expiry ) {
 132                 if ( !$memCached ) {
 133                         $memCached = wfGetCache( CACHE_NONE );
 134                 }
 135
 136                 $this->mMemc = $memCached;
 137                 $this->mDisable = !$useDB;
 138                 $this->mExpiry = $expiry;
 139         }
 140
 141         /**
 142          * ParserOptions is lazy initialised.
 143          *
 144          * @return ParserOptions
 145          */
 146         function getParserOptions() {
 147                 if ( !$this->mParserOptions ) {
 148                         $this->mParserOptions = new ParserOptions;
 149                         $this->mParserOptions->setEditSection( false );
 150                 }
 151
 152                 return $this->mParserOptions;
 153         }
 154
 155         /**
 156          * Try to load the cache from a local file.
 157          *
 158          * @param string $hash The hash of contents, to check validity.
 159          * @param string $code Optional language code, see documenation of load().
 160          * @return array The cache array
 161          */
 162         function getLocalCache( $hash, $code ) {
 163                 global $wgCacheDirectory;
 164
 165                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 166
 167                 # Check file existence
 168                 wfSuppressWarnings();
 169                 $file = fopen( $filename, 'r' );
 170                 wfRestoreWarnings();
 171                 if ( !$file ) {
 172                         return false; // No cache file
 173                 }
 174
 175                 // Check to see if the file has the hash specified
 176                 $localHash = fread( $file, 32 );
 177                 if ( $hash === $localHash ) {
 178                         // All good, get the rest of it
 179                         $serialized = '';
 180                         while ( !feof( $file ) ) {
 181                                 $serialized .= fread( $file, 100000 );
 182                         }
 183                         fclose( $file );
 184
 185                         return unserialize( $serialized );
 186                 } else {
 187                         fclose( $file );
 188
 189                         return false; // Wrong hash
 190                 }
 191         }
 192
 193         /**
 194          * Save the cache to a local file.
 195          * @param string $serialized
 196          * @param string $hash
 197          * @param string $code
 198          */
 199         function saveToLocal( $serialized, $hash, $code ) {
 200                 global $wgCacheDirectory;
 201
 202                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 203                 wfMkdirParents( $wgCacheDirectory, null, __METHOD__ ); // might fail
 204
 205                 wfSuppressWarnings();
 206                 $file = fopen( $filename, 'w' );
 207                 wfRestoreWarnings();
 208
 209                 if ( !$file ) {
 210                         wfDebug( "Unable to open local cache file for writing\n" );
 211
 212                         return;
 213                 }
 214
 215                 fwrite( $file, $hash . $serialized );
 216                 fclose( $file );
 217                 wfSuppressWarnings();
 218                 chmod( $filename, 0666 );
 219                 wfRestoreWarnings();
 220         }
 221
 222         /**
 223          * Loads messages from caches or from database in this order:
 224          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 225          * (2) memcached
 226          * (3) from the database.
 227          *
 228          * When succesfully loading from (2) or (3), all higher level caches are
 229          * updated for the newest version.
 230          *
 231          * Nothing is loaded if member variable mDisable is true, either manually
 232          * set by calling code or if message loading fails (is this possible?).
 233          *
 234          * Returns true if cache is already populated or it was succesfully populated,
 235          * or false if populating empty cache fails. Also returns true if MessageCache
 236          * is disabled.
 237          *
 238          * @param bool|string $code Language to which load messages
 239          * @throws MWException
 240          * @return bool
 241          */
 242         function load( $code = false ) {
 243                 global $wgUseLocalMessageCache;
 244
 245                 if ( !is_string( $code ) ) {
 246                         # This isn't really nice, so at least make a note about it and try to
 247                         # fall back
 248                         wfDebug( __METHOD__ . " called without providing a language code\n" );
 249                         $code = 'en';
 250                 }
 251
 252                 # Don't do double loading...
 253                 if ( isset( $this->mLoadedLanguages[$code] ) ) {
 254                         return true;
 255                 }
 256
 257                 # 8 lines of code just to say (once) that message cache is disabled
 258                 if ( $this->mDisable ) {
 259                         static $shownDisabled = false;
 260                         if ( !$shownDisabled ) {
 261                                 wfDebug( __METHOD__ . ": disabled\n" );
 262                                 $shownDisabled = true;
 263                         }
 264
 265                         return true;
 266                 }
 267
 268                 # Loading code starts
 269                 $success = false; # Keep track of success
 270                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 271                 $where = array(); # Debug info, delayed to avoid spamming debug log too much
 272                 $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 273
 274                 # Local cache
 275                 # Hash of the contents is stored in memcache, to detect if local cache goes
 276                 # out of date (e.g. due to replace() on some other server)
 277                 if ( $wgUseLocalMessageCache ) {
 278                         wfProfileIn( __METHOD__ . '-fromlocal' );
 279
 280                         $hash = $this->mMemc->get( wfMemcKey( 'messages', $code, 'hash' ) );
 281                         if ( $hash ) {
 282                                 $cache = $this->getLocalCache( $hash, $code );
 283                                 if ( !$cache ) {
 284                                         $where[] = 'local cache is empty or has the wrong hash';
 285                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 286                                         $where[] = 'local cache is expired';
 287                                         $staleCache = $cache;
 288                                 } else {
 289                                         $where[] = 'got from local cache';
 290                                         $success = true;
 291                                         $this->mCache[$code] = $cache;
 292                                 }
 293                         }
 294                         wfProfileOut( __METHOD__ . '-fromlocal' );
 295                 }
 296
 297                 if ( !$success ) {
 298                         # Try the global cache. If it is empty, try to acquire a lock. If
 299                         # the lock can't be acquired, wait for the other thread to finish
 300                         # and then try the global cache a second time.
 301                         for ( $failedAttempts = 0; $failedAttempts < 2; $failedAttempts++ ) {
 302                                 wfProfileIn( __METHOD__ . '-fromcache' );
 303                                 $cache = $this->mMemc->get( $cacheKey );
 304                                 if ( !$cache ) {
 305                                         $where[] = 'global cache is empty';
 306                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 307                                         $where[] = 'global cache is expired';
 308                                         $staleCache = $cache;
 309                                 } else {
 310                                         $where[] = 'got from global cache';
 311                                         $this->mCache[$code] = $cache;
 312                                         $this->saveToCaches( $cache, 'local-only', $code );
 313                                         $success = true;
 314                                 }
 315
 316                                 wfProfileOut( __METHOD__ . '-fromcache' );
 317
 318                                 if ( $success ) {
 319                                         # Done, no need to retry
 320                                         break;
 321                                 }
 322
 323                                 # We need to call loadFromDB. Limit the concurrency to a single
 324                                 # process. This prevents the site from going down when the cache
 325                                 # expires.
 326                                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 327                                 $acquired = $this->mMemc->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT );
 328                                 if ( $acquired ) {
 329                                         # Unlock the status key if there is an exception
 330                                         $that = $this;
 331                                         $statusUnlocker = new ScopedCallback( function () use ( $that, $statusKey ) {
 332                                                 $that->mMemc->delete( $statusKey );
 333                                         } );
 334
 335                                         # Now let's regenerate
 336                                         $where[] = 'loading from database';
 337
 338                                         # Lock the cache to prevent conflicting writes
 339                                         # If this lock fails, it doesn't really matter, it just means the
 340                                         # write is potentially non-atomic, e.g. the results of a replace()
 341                                         # may be discarded.
 342                                         if ( $this->lock( $cacheKey ) ) {
 343                                                 $mainUnlocker = new ScopedCallback( function () use ( $that, $cacheKey ) {
 344                                                         $that->unlock( $cacheKey );
 345                                                 } );
 346                                         } else {
 347                                                 $mainUnlocker = null;
 348                                                 $where[] = 'could not acquire main lock';
 349                                         }
 350
 351                                         $cache = $this->loadFromDB( $code );
 352                                         $this->mCache[$code] = $cache;
 353                                         $success = true;
 354                                         $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 355
 356                                         # Unlock
 357                                         ScopedCallback::consume( $mainUnlocker );
 358                                         ScopedCallback::consume( $statusUnlocker );
 359
 360                                         if ( !$saveSuccess ) {
 361                                                 # Cache save has failed.
 362                                                 # There are two main scenarios where this could be a problem:
 363                                                 #
 364                                                 #   - The cache is more than the maximum size (typically
 365                                                 #     1MB compressed).
 366                                                 #
 367                                                 #   - Memcached has no space remaining in the relevant slab
 368                                                 #     class. This is unlikely with recent versions of
 369                                                 #     memcached.
 370                                                 #
 371                                                 # Either way, if there is a local cache, nothing bad will
 372                                                 # happen. If there is no local cache, disabling the message
 373                                                 # cache for all requests avoids incurring a loadFromDB()
 374                                                 # overhead on every request, and thus saves the wiki from
 375                                                 # complete downtime under moderate traffic conditions.
 376                                                 if ( !$wgUseLocalMessageCache ) {
 377                                                         $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 378                                                         $where[] = 'could not save cache, disabled globally for 5 minutes';
 379                                                 } else {
 380                                                         $where[] = "could not save global cache";
 381                                                 }
 382                                         }
 383
 384                                         # Load from DB complete, no need to retry
 385                                         break;
 386                                 } elseif ( $staleCache ) {
 387                                         # Use the stale cache while some other thread constructs the new one
 388                                         $where[] = 'using stale cache';
 389                                         $this->mCache[$code] = $staleCache;
 390                                         $success = true;
 391                                         break;
 392                                 } elseif ( $failedAttempts > 0 ) {
 393                                         # Already retried once, still failed, so don't do another lock/unlock cycle
 394                                         # This case will typically be hit if memcached is down, or if
 395                                         # loadFromDB() takes longer than MSG_WAIT_TIMEOUT
 396                                         $where[] = "could not acquire status key.";
 397                                         break;
 398                                 } else {
 399                                         $status = $this->mMemc->get( $statusKey );
 400                                         if ( $status === 'error' ) {
 401                                                 # Disable cache
 402                                                 break;
 403                                         } else {
 404                                                 # Wait for the other thread to finish, then retry
 405                                                 $where[] = 'waited for other thread to complete';
 406                                                 $this->lock( $cacheKey );
 407                                                 $this->unlock( $cacheKey );
 408                                         }
 409                                 }
 410                         }
 411                 }
 412
 413                 if ( !$success ) {
 414                         $where[] = 'loading FAILED - cache is disabled';
 415                         $this->mDisable = true;
 416                         $this->mCache = false;
 417                         # This used to throw an exception, but that led to nasty side effects like
 418                         # the whole wiki being instantly down if the memcached server died
 419                 } else {
 420                         # All good, just record the success
 421                         $this->mLoadedLanguages[$code] = true;
 422                 }
 423                 $info = implode( ', ', $where );
 424                 wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );
 425
 426                 return $success;
 427         }
 428
 429         /**
 430          * Loads cacheable messages from the database. Messages bigger than
 431          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 432          * on-demand from the database later.
 433          *
 434          * @param string $code Language code.
 435          * @return array Loaded messages for storing in caches.
 436          */
 437         function loadFromDB( $code ) {
 438                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 439                 $dbr = wfGetDB( DB_SLAVE );
 440                 $cache = array();
 441
 442                 # Common conditions
 443                 $conds = array(
 444                         'page_is_redirect' => 0,
 445                         'page_namespace' => NS_MEDIAWIKI,
 446                 );
 447
 448                 $mostused = array();
 449                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 450                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 451                                 $this->load( $wgLanguageCode );
 452                         }
 453                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 454                         foreach ( $mostused as $key => $value ) {
 455                                 $mostused[$key] = "$value/$code";
 456                         }
 457                 }
 458
 459                 if ( count( $mostused ) ) {
 460                         $conds['page_title'] = $mostused;
 461                 } elseif ( $code !== $wgLanguageCode ) {
 462                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 463                 } else {
 464                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 465                         # other than language code.
 466                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 467                 }
 468
 469                 # Conditions to fetch oversized pages to ignore them
 470                 $bigConds = $conds;
 471                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 472
 473                 # Load titles for all oversized pages in the MediaWiki namespace
 474                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 475                 foreach ( $res as $row ) {
 476                         $cache[$row->page_title] = '!TOO BIG';
 477                 }
 478
 479                 # Conditions to load the remaining pages with their contents
 480                 $smallConds = $conds;
 481                 $smallConds[] = 'page_latest=rev_id';
 482                 $smallConds[] = 'rev_text_id=old_id';
 483                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 484
 485                 $res = $dbr->select(
 486                         array( 'page', 'revision', 'text' ),
 487                         array( 'page_title', 'old_text', 'old_flags' ),
 488                         $smallConds,
 489                         __METHOD__ . "($code)-small"
 490                 );
 491
 492                 foreach ( $res as $row ) {
 493                         $text = Revision::getRevisionText( $row );
 494                         if ( $text === false ) {
 495                                 // Failed to fetch data; possible ES errors?
 496                                 // Store a marker to fetch on-demand as a workaround...
 497                                 $entry = '!TOO BIG';
 498                                 wfDebugLog(
 499                                         'MessageCache',
 500                                         __METHOD__
 501                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 502                                 );
 503                         } else {
 504                                 $entry = ' ' . $text;
 505                         }
 506                         $cache[$row->page_title] = $entry;
 507                 }
 508
 509                 $cache['VERSION'] = MSG_CACHE_VERSION;
 510                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 511
 512                 return $cache;
 513         }
 514
 515         /**
 516          * Updates cache as necessary when message page is changed
 517          *
 518          * @param string $title Name of the page changed.
 519          * @param mixed $text New contents of the page.
 520          */
 521         public function replace( $title, $text ) {
 522                 global $wgMaxMsgCacheEntrySize;
 523
 524                 if ( $this->mDisable ) {
 525
 526                         return;
 527                 }
 528
 529                 list( $msg, $code ) = $this->figureMessage( $title );
 530
 531                 $cacheKey = wfMemcKey( 'messages', $code );
 532                 $this->load( $code );
 533                 $this->lock( $cacheKey );
 534
 535                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 536
 537                 if ( $text === false ) {
 538                         # Article was deleted
 539                         $this->mCache[$code][$title] = '!NONEXISTENT';
 540                         $this->mMemc->delete( $titleKey );
 541                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 542                         # Check for size
 543                         $this->mCache[$code][$title] = '!TOO BIG';
 544                         $this->mMemc->set( $titleKey, ' ' . $text, $this->mExpiry );
 545                 } else {
 546                         $this->mCache[$code][$title] = ' ' . $text;
 547                         $this->mMemc->delete( $titleKey );
 548                 }
 549
 550                 # Update caches
 551                 $this->saveToCaches( $this->mCache[$code], 'all', $code );
 552                 $this->unlock( $cacheKey );
 553
 554                 // Also delete cached sidebar... just in case it is affected
 555                 $codes = array( $code );
 556                 if ( $code === 'en' ) {
 557                         // Delete all sidebars, like for example on action=purge on the
 558                         // sidebar messages
 559                         $codes = array_keys( Language::fetchLanguageNames() );
 560                 }
 561
 562                 global $wgMemc;
 563                 foreach ( $codes as $code ) {
 564                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 565                         $wgMemc->delete( $sidebarKey );
 566                 }
 567
 568                 // Update the message in the message blob store
 569                 global $wgContLang;
 570                 MessageBlobStore::getInstance()->updateMessage( $wgContLang->lcfirst( $msg ) );
 571
 572                 Hooks::run( 'MessageCacheReplace', array( $title, $text ) );
 573
 574         }
 575
 576         /**
 577          * Is the given cache array expired due to time passing or a version change?
 578          *
 579          * @param array $cache
 580          * @return bool
 581          */
 582         protected function isCacheExpired( $cache ) {
 583                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 584                         return true;
 585                 }
 586                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 587                         return true;
 588                 }
 589                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 590                         return true;
 591                 }
 592
 593                 return false;
 594         }
 595
 596         /**
 597          * Shortcut to update caches.
 598          *
 599          * @param array $cache Cached messages with a version.
 600          * @param string $dest Either "local-only" to save to local caches only
 601          *   or "all" to save to all caches.
 602          * @param string|bool $code Language code (default: false)
 603          * @return bool
 604          */
 605         protected function saveToCaches( $cache, $dest, $code = false ) {
 606                 global $wgUseLocalMessageCache;
 607
 608                 $cacheKey = wfMemcKey( 'messages', $code );
 609
 610                 if ( $dest === 'all' ) {
 611                         $success = $this->mMemc->set( $cacheKey, $cache );
 612                 } else {
 613                         $success = true;
 614                 }
 615
 616                 # Save to local cache
 617                 if ( $wgUseLocalMessageCache ) {
 618                         $serialized = serialize( $cache );
 619                         $hash = md5( $serialized );
 620                         $this->mMemc->set( wfMemcKey( 'messages', $code, 'hash' ), $hash );
 621                         $this->saveToLocal( $serialized, $hash, $code );
 622                 }
 623
 624
 625                 return $success;
 626         }
 627
 628         /**
 629          * Represents a write lock on the messages key.
 630          *
 631          * Will retry MessageCache::MSG_WAIT_TIMEOUT times, each operations having
 632          * a timeout of MessageCache::MSG_LOCK_TIMEOUT.
 633          *
 634          * @param string $key
 635          * @return bool Success
 636          */
 637         function lock( $key ) {
 638                 $lockKey = $key . ':lock';
 639                 $acquired = false;
 640                 $testDone = false;
 641                 for ( $i = 0; $i < MSG_WAIT_TIMEOUT && !$acquired; $i++ ) {
 642                         $acquired = $this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT );
 643                         if ( $acquired ) {
 644                                 break;
 645                         }
 646
 647                         # Fail fast if memcached is totally down
 648                         if ( !$testDone ) {
 649                                 $testDone = true;
 650                                 if ( !$this->mMemc->set( wfMemcKey( 'test' ), 'test', 1 ) ) {
 651                                         break;
 652                                 }
 653                         }
 654                         sleep( 1 );
 655                 }
 656
 657                 return $acquired;
 658         }
 659
 660         function unlock( $key ) {
 661                 $lockKey = $key . ':lock';
 662                 $this->mMemc->delete( $lockKey );
 663         }
 664
 665         /**
 666          * Get a message from either the content language or the user language.
 667          *
 668          * First, assemble a list of languages to attempt getting the message from. This
 669          * chain begins with the requested language and its fallbacks and then continues with
 670          * the content language and its fallbacks. For each language in the chain, the following
 671          * process will occur (in this order):
 672          *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
 673          *     Note: for the content language, there is no /lang subpage.
 674          *  2. Fetch from the static CDB cache.
 675          *  3. If available, check the database for fallback language overrides.
 676          *
 677          * This process provides a number of guarantees. When changing this code, make sure all
 678          * of these guarantees are preserved.
 679          *  * If the requested language is *not* the content language, then the CDB cache for that
 680          *    specific language will take precedence over the root database page ([[MW:msg]]).
 681          *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
 682          *    the message is available *anywhere* in the language for which it is a fallback.
 683          *
 684          * @param string $key The message key
 685          * @param bool $useDB If true, look for the message in the DB, false
 686          *   to use only the compiled l10n cache.
 687          * @param bool|string|object $langcode Code of the language to get the message for.
 688          *   - If string and a valid code, will create a standard language object
 689          *   - If string but not a valid code, will create a basic language object
 690          *   - If boolean and false, create object from the current users language
 691          *   - If boolean and true, create object from the wikis content language
 692          *   - If language object, use it as given
 693          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 694          *
 695          * @throws MWException When given an invalid key
 696          * @return string|bool False if the message doesn't exist, otherwise the
 697          *   message (which can be empty)
 698          */
 699         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 700                 global $wgContLang;
 701
 702
 703                 if ( is_int( $key ) ) {
 704                         // Fix numerical strings that somehow become ints
 705                         // on their way here
 706                         $key = (string)$key;
 707                 } elseif ( !is_string( $key ) ) {
 708                         throw new MWException( 'Non-string key given' );
 709                 } elseif ( $key === '' ) {
 710                         // Shortcut: the empty key is always missing
 711                         return false;
 712                 }
 713
 714                 // For full keys, get the language code from the key
 715                 $pos = strrpos( $key, '/' );
 716                 if ( $isFullKey && $pos !== false ) {
 717                         $langcode = substr( $key, $pos + 1 );
 718                         $key = substr( $key, 0, $pos );
 719                 }
 720
 721                 // Normalise title-case input (with some inlining)
 722                 $lckey = strtr( $key, ' ', '_' );
 723                 if ( ord( $lckey ) < 128 ) {
 724                         $lckey[0] = strtolower( $lckey[0] );
 725                 } else {
 726                         $lckey = $wgContLang->lcfirst( $lckey );
 727                 }
 728
 729                 Hooks::run( 'MessageCache::get', array( &$lckey ) );
 730
 731                 if ( ord( $lckey ) < 128 ) {
 732                         $uckey = ucfirst( $lckey );
 733                 } else {
 734                         $uckey = $wgContLang->ucfirst( $lckey );
 735                 }
 736
 737                 // Loop through each language in the fallback list until we find something useful
 738                 $lang = wfGetLangObj( $langcode );
 739                 $message = $this->getMessageFromFallbackChain(
 740                         $lang,
 741                         $lckey,
 742                         $uckey,
 743                         !$this->mDisable && $useDB
 744                 );
 745
 746                 // If we still have no message, maybe the key was in fact a full key so try that
 747                 if ( $message === false ) {
 748                         $parts = explode( '/', $lckey );
 749                         // We may get calls for things that are http-urls from sidebar
 750                         // Let's not load nonexistent languages for those
 751                         // They usually have more than one slash.
 752                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 753                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 754                                 if ( $message === null ) {
 755                                         $message = false;
 756                                 }
 757                         }
 758                 }
 759
 760                 // Post-processing if the message exists
 761                 if ( $message !== false ) {
 762                         // Fix whitespace
 763                         $message = str_replace(
 764                                 array(
 765                                         # Fix for trailing whitespace, removed by textarea
 766                                         '&#32;',
 767                                         # Fix for NBSP, converted to space by firefox
 768                                         '&nbsp;',
 769                                         '&#160;',
 770                                 ),
 771                                 array(
 772                                         ' ',
 773                                         "\xc2\xa0",
 774                                         "\xc2\xa0"
 775                                 ),
 776                                 $message
 777                         );
 778                 }
 779
 780                 return $message;
 781         }
 782
 783         /**
 784          * Given a language, try and fetch a message from that language, then the
 785          * fallbacks of that language, then the site language, then the fallbacks for the
 786          * site language.
 787          *
 788          * @param Language $lang Requested language
 789          * @param string $lckey Lowercase key for the message
 790          * @param string $uckey Uppercase key for the message
 791          * @param bool $useDB Whether to use the database
 792          *
 793          * @see MessageCache::get
 794          * @return string|bool The message, or false if not found
 795          */
 796         protected function getMessageFromFallbackChain( $lang, $lckey, $uckey, $useDB ) {
 797                 global $wgLanguageCode, $wgContLang;
 798
 799                 $langcode = $lang->getCode();
 800                 $message = false;
 801
 802                 // First try the requested language.
 803                 if ( $useDB ) {
 804                         if ( $langcode === $wgLanguageCode ) {
 805                                 // Messages created in the content language will not have the /lang extension
 806                                 $message = $this->getMsgFromNamespace( $uckey, $langcode );
 807                         } else {
 808                                 $message = $this->getMsgFromNamespace( "$uckey/$langcode", $langcode );
 809                         }
 810                 }
 811
 812                 if ( $message !== false ) {
 813                         return $message;
 814                 }
 815
 816                 // Check the CDB cache
 817                 $message = $lang->getMessage( $lckey );
 818                 if ( $message !== null ) {
 819                         return $message;
 820                 }
 821
 822                 list( $fallbackChain, $siteFallbackChain ) =
 823                         Language::getFallbacksIncludingSiteLanguage( $langcode );
 824
 825                 // Next try checking the database for all of the fallback languages of the requested language.
 826                 if ( $useDB ) {
 827                         foreach ( $fallbackChain as $code ) {
 828                                 if ( $code === $wgLanguageCode ) {
 829                                         // Messages created in the content language will not have the /lang extension
 830                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 831                                 } else {
 832                                         $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 833                                 }
 834
 835                                 if ( $message !== false ) {
 836                                         // Found the message.
 837                                         return $message;
 838                                 }
 839                         }
 840                 }
 841
 842                 // Now try checking the site language.
 843                 if ( $useDB ) {
 844                         $message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
 845                         if ( $message !== false ) {
 846                                 return $message;
 847                         }
 848                 }
 849
 850                 $message = $wgContLang->getMessage( $lckey );
 851                 if ( $message !== null ) {
 852                         return $message;
 853                 }
 854
 855                 // Finally try the DB for the site language's fallbacks.
 856                 if ( $useDB ) {
 857                         foreach ( $siteFallbackChain as $code ) {
 858                                 $message = $this->getMsgFromNamespace( "$uckey/$code", $code );
 859                                 if ( $message === false && $code === $wgLanguageCode ) {
 860                                         // Messages created in the content language will not have the /lang extension
 861                                         $message = $this->getMsgFromNamespace( $uckey, $code );
 862                                 }
 863
 864                                 if ( $message !== false ) {
 865                                         // Found the message.
 866                                         return $message;
 867                                 }
 868                         }
 869                 }
 870
 871                 return false;
 872         }
 873
 874         /**
 875          * Get a message from the MediaWiki namespace, with caching. The key must
 876          * first be converted to two-part lang/msg form if necessary.
 877          *
 878          * Unlike self::get(), this function doesn't resolve fallback chains, and
 879          * some callers require this behavior. LanguageConverter::parseCachedTable()
 880          * and self::get() are some examples in core.
 881          *
 882          * @param string $title Message cache key with initial uppercase letter.
 883          * @param string $code Code denoting the language to try.
 884          * @return string|bool The message, or false if it does not exist or on error
 885          */
 886         function getMsgFromNamespace( $title, $code ) {
 887                 $this->load( $code );
 888                 if ( isset( $this->mCache[$code][$title] ) ) {
 889                         $entry = $this->mCache[$code][$title];
 890                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 891                                 // The message exists, so make sure a string
 892                                 // is returned.
 893                                 return (string)substr( $entry, 1 );
 894                         } elseif ( $entry === '!NONEXISTENT' ) {
 895                                 return false;
 896                         } elseif ( $entry === '!TOO BIG' ) {
 897                                 // Fall through and try invididual message cache below
 898                         }
 899                 } else {
 900                         // XXX: This is not cached in process cache, should it?
 901                         $message = false;
 902                         Hooks::run( 'MessagesPreLoad', array( $title, &$message ) );
 903                         if ( $message !== false ) {
 904                                 return $message;
 905                         }
 906
 907                         return false;
 908                 }
 909
 910                 # Try the individual message cache
 911                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 912                 $entry = $this->mMemc->get( $titleKey );
 913                 if ( $entry ) {
 914                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 915                                 $this->mCache[$code][$title] = $entry;
 916
 917                                 // The message exists, so make sure a string
 918                                 // is returned.
 919                                 return (string)substr( $entry, 1 );
 920                         } elseif ( $entry === '!NONEXISTENT' ) {
 921                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 922
 923                                 return false;
 924                         } else {
 925                                 # Corrupt/obsolete entry, delete it
 926                                 $this->mMemc->delete( $titleKey );
 927                         }
 928                 }
 929
 930                 # Try loading it from the database
 931                 $revision = Revision::newFromTitle(
 932                         Title::makeTitle( NS_MEDIAWIKI, $title ), false, Revision::READ_LATEST
 933                 );
 934                 if ( $revision ) {
 935                         $content = $revision->getContent();
 936                         if ( !$content ) {
 937                                 // A possibly temporary loading failure.
 938                                 wfDebugLog(
 939                                         'MessageCache',
 940                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
 941                                 );
 942                                 $message = null; // no negative caching
 943                         } else {
 944                                 // XXX: Is this the right way to turn a Content object into a message?
 945                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
 946                                 //       CssContent. MessageContent is *not* used for storing messages, it's
 947                                 //       only used for wrapping them when needed.
 948                                 $message = $content->getWikitextForTransclusion();
 949
 950                                 if ( $message === false || $message === null ) {
 951                                         wfDebugLog(
 952                                                 'MessageCache',
 953                                                 __METHOD__ . ": message content doesn't provide wikitext "
 954                                                         . "(content model: " . $content->getContentHandler() . ")"
 955                                         );
 956
 957                                         $message = false; // negative caching
 958                                 } else {
 959                                         $this->mCache[$code][$title] = ' ' . $message;
 960                                         $this->mMemc->set( $titleKey, ' ' . $message, $this->mExpiry );
 961                                 }
 962                         }
 963                 } else {
 964                         $message = false; // negative caching
 965                 }
 966
 967                 if ( $message === false ) { // negative caching
 968                         $this->mCache[$code][$title] = '!NONEXISTENT';
 969                         $this->mMemc->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
 970                 }
 971
 972                 return $message;
 973         }
 974
 975         /**
 976          * @param string $message
 977          * @param bool $interface
 978          * @param string $language Language code
 979          * @param Title $title
 980          * @return string
 981          */
 982         function transform( $message, $interface = false, $language = null, $title = null ) {
 983                 // Avoid creating parser if nothing to transform
 984                 if ( strpos( $message, '{{' ) === false ) {
 985                         return $message;
 986                 }
 987
 988                 if ( $this->mInParser ) {
 989                         return $message;
 990                 }
 991
 992                 $parser = $this->getParser();
 993                 if ( $parser ) {
 994                         $popts = $this->getParserOptions();
 995                         $popts->setInterfaceMessage( $interface );
 996                         $popts->setTargetLanguage( $language );
 997
 998                         $userlang = $popts->setUserLang( $language );
 999                         $this->mInParser = true;
1000                         $message = $parser->transformMsg( $message, $popts, $title );
1001                         $this->mInParser = false;
1002                         $popts->setUserLang( $userlang );
1003                 }
1004
1005                 return $message;
1006         }
1007
1008         /**
1009          * @return Parser
1010          */
1011         function getParser() {
1012                 global $wgParser, $wgParserConf;
1013                 if ( !$this->mParser && isset( $wgParser ) ) {
1014                         # Do some initialisation so that we don't have to do it twice
1015                         $wgParser->firstCallInit();
1016                         # Clone it and store it
1017                         $class = $wgParserConf['class'];
1018                         if ( $class == 'ParserDiffTest' ) {
1019                                 # Uncloneable
1020                                 $this->mParser = new $class( $wgParserConf );
1021                         } else {
1022                                 $this->mParser = clone $wgParser;
1023                         }
1024                 }
1025
1026                 return $this->mParser;
1027         }
1028
1029         /**
1030          * @param string $text
1031          * @param Title $title
1032          * @param bool $linestart Whether or not this is at the start of a line
1033          * @param bool $interface Whether this is an interface message
1034          * @param string $language Language code
1035          * @return ParserOutput|string
1036          */
1037         public function parse( $text, $title = null, $linestart = true,
1038                 $interface = false, $language = null
1039         ) {
1040                 if ( $this->mInParser ) {
1041                         return htmlspecialchars( $text );
1042                 }
1043
1044                 $parser = $this->getParser();
1045                 $popts = $this->getParserOptions();
1046                 $popts->setInterfaceMessage( $interface );
1047                 $popts->setTargetLanguage( $language );
1048
1049                 if ( !$title || !$title instanceof Title ) {
1050                         global $wgTitle;
1051                         wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' . wfGetAllCallers( 5 ) . ' with no title set.' );
1052                         $title = $wgTitle;
1053                 }
1054                 // Sometimes $wgTitle isn't set either...
1055                 if ( !$title ) {
1056                         # It's not uncommon having a null $wgTitle in scripts. See r80898
1057                         # Create a ghost title in such case
1058                         $title = Title::newFromText( 'Dwimmerlaik' );
1059                 }
1060
1061                 $this->mInParser = true;
1062                 $res = $parser->parse( $text, $title, $popts, $linestart );
1063                 $this->mInParser = false;
1064
1065
1066                 return $res;
1067         }
1068
1069         function disable() {
1070                 $this->mDisable = true;
1071         }
1072
1073         function enable() {
1074                 $this->mDisable = false;
1075         }
1076
1077         /**
1078          * Clear all stored messages. Mainly used after a mass rebuild.
1079          */
1080         function clear() {
1081                 $langs = Language::fetchLanguageNames( null, 'mw' );
1082                 foreach ( array_keys( $langs ) as $code ) {
1083                         # Global cache
1084                         $this->mMemc->delete( wfMemcKey( 'messages', $code ) );
1085                         # Invalidate all local caches
1086                         $this->mMemc->delete( wfMemcKey( 'messages', $code, 'hash' ) );
1087                 }
1088                 $this->mLoadedLanguages = array();
1089         }
1090
1091         /**
1092          * @param string $key
1093          * @return array
1094          */
1095         public function figureMessage( $key ) {
1096                 global $wgLanguageCode;
1097                 $pieces = explode( '/', $key );
1098                 if ( count( $pieces ) < 2 ) {
1099                         return array( $key, $wgLanguageCode );
1100                 }
1101
1102                 $lang = array_pop( $pieces );
1103                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
1104                         return array( $key, $wgLanguageCode );
1105                 }
1106
1107                 $message = implode( '/', $pieces );
1108
1109                 return array( $message, $lang );
1110         }
1111
1112         /**
1113          * Get all message keys stored in the message cache for a given language.
1114          * If $code is the content language code, this will return all message keys
1115          * for which MediaWiki:msgkey exists. If $code is another language code, this
1116          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
1117          * @param string $code Language code
1118          * @return array Array of message keys (strings)
1119          */
1120         public function getAllMessageKeys( $code ) {
1121                 global $wgContLang;
1122                 $this->load( $code );
1123                 if ( !isset( $this->mCache[$code] ) ) {
1124                         // Apparently load() failed
1125                         return null;
1126                 }
1127                 // Remove administrative keys
1128                 $cache = $this->mCache[$code];
1129                 unset( $cache['VERSION'] );
1130                 unset( $cache['EXPIRY'] );
1131                 // Remove any !NONEXISTENT keys
1132                 $cache = array_diff( $cache, array( '!NONEXISTENT' ) );
1133
1134                 // Keys may appear with a capital first letter. lcfirst them.
1135                 return array_map( array( $wgContLang, 'lcfirst' ), array_keys( $cache ) );
1136         }
1137 }