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  *
  26  */
  27 define( 'MSG_LOAD_TIMEOUT', 60 );
  28 define( 'MSG_LOCK_TIMEOUT', 30 );
  29 define( 'MSG_WAIT_TIMEOUT', 30 );
  30 define( 'MSG_CACHE_VERSION', 1 );
  31
  32 /**
  33  * Message cache
  34  * Performs various MediaWiki namespace-related functions
  35  * @ingroup Cache
  36  */
  37 class MessageCache {
  38         /**
  39          * Process local cache of loaded messages that are defined in
  40          * MediaWiki namespace. First array level is a language code,
  41          * second level is message key and the values are either message
  42          * content prefixed with space, or !NONEXISTENT for negative
  43          * caching.
  44          */
  45         protected $mCache;
  46
  47         // Should  mean that database cannot be used, but check
  48         protected $mDisable;
  49
  50         /// Lifetime for cache, used by object caching
  51         protected $mExpiry;
  52
  53         /**
  54          * Message cache has it's own parser which it uses to transform
  55          * messages.
  56          */
  57         protected $mParserOptions, $mParser;
  58
  59         /// Variable for tracking which variables are already loaded
  60         protected $mLoadedLanguages = array();
  61
  62         /**
  63          * Singleton instance
  64          *
  65          * @var MessageCache
  66          */
  67         private static $instance;
  68
  69         /**
  70          * @var bool
  71          */
  72         protected $mInParser = false;
  73
  74         /**
  75          * Get the signleton instance of this class
  76          *
  77          * @since 1.18
  78          * @return MessageCache
  79          */
  80         public static function singleton() {
  81                 if ( is_null( self::$instance ) ) {
  82                         global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
  83                         self::$instance = new self(
  84                                 wfGetMessageCacheStorage(),
  85                                 $wgUseDatabaseMessages,
  86                                 $wgMsgCacheExpiry
  87                         );
  88                 }
  89                 return self::$instance;
  90         }
  91
  92         /**
  93          * Destroy the singleton instance
  94          *
  95          * @since 1.18
  96          */
  97         public static function destroyInstance() {
  98                 self::$instance = null;
  99         }
 100
 101         function __construct( $memCached, $useDB, $expiry ) {
 102                 if ( !$memCached ) {
 103                         $memCached = wfGetCache( CACHE_NONE );
 104                 }
 105
 106                 $this->mMemc = $memCached;
 107                 $this->mDisable = !$useDB;
 108                 $this->mExpiry = $expiry;
 109         }
 110
 111         /**
 112          * ParserOptions is lazy initialised.
 113          *
 114          * @return ParserOptions
 115          */
 116         function getParserOptions() {
 117                 if ( !$this->mParserOptions ) {
 118                         $this->mParserOptions = new ParserOptions;
 119                         $this->mParserOptions->setEditSection( false );
 120                 }
 121                 return $this->mParserOptions;
 122         }
 123
 124         /**
 125          * Try to load the cache from a local file.
 126          *
 127          * @param string $hash the hash of contents, to check validity.
 128          * @param Mixed $code Optional language code, see documenation of load().
 129          * @return array The cache array
 130          */
 131         function getLocalCache( $hash, $code ) {
 132                 global $wgCacheDirectory;
 133
 134                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 135
 136                 # Check file existence
 137                 wfSuppressWarnings();
 138                 $file = fopen( $filename, 'r' );
 139                 wfRestoreWarnings();
 140                 if ( !$file ) {
 141                         return false; // No cache file
 142                 }
 143
 144                 // Check to see if the file has the hash specified
 145                 $localHash = fread( $file, 32 );
 146                 if ( $hash === $localHash ) {
 147                         // All good, get the rest of it
 148                         $serialized = '';
 149                         while ( !feof( $file ) ) {
 150                                 $serialized .= fread( $file, 100000 );
 151                         }
 152                         fclose( $file );
 153                         return unserialize( $serialized );
 154                 } else {
 155                         fclose( $file );
 156                         return false; // Wrong hash
 157                 }
 158         }
 159
 160         /**
 161          * Save the cache to a local file.
 162          */
 163         function saveToLocal( $serialized, $hash, $code ) {
 164                 global $wgCacheDirectory;
 165
 166                 $filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 167                 wfMkdirParents( $wgCacheDirectory, null, __METHOD__ ); // might fail
 168
 169                 wfSuppressWarnings();
 170                 $file = fopen( $filename, 'w' );
 171                 wfRestoreWarnings();
 172
 173                 if ( !$file ) {
 174                         wfDebug( "Unable to open local cache file for writing\n" );
 175                         return;
 176                 }
 177
 178                 fwrite( $file, $hash . $serialized );
 179                 fclose( $file );
 180                 wfSuppressWarnings();
 181                 chmod( $filename, 0666 );
 182                 wfRestoreWarnings();
 183         }
 184
 185         /**
 186          * Loads messages from caches or from database in this order:
 187          * (1) local message cache (if $wgUseLocalMessageCache is enabled)
 188          * (2) memcached
 189          * (3) from the database.
 190          *
 191          * When succesfully loading from (2) or (3), all higher level caches are
 192          * updated for the newest version.
 193          *
 194          * Nothing is loaded if member variable mDisable is true, either manually
 195          * set by calling code or if message loading fails (is this possible?).
 196          *
 197          * Returns true if cache is already populated or it was succesfully populated,
 198          * or false if populating empty cache fails. Also returns true if MessageCache
 199          * is disabled.
 200          *
 201          * @param bool|String $code Language to which load messages
 202          * @throws MWException
 203          * @return bool
 204          */
 205         function load( $code = false ) {
 206                 global $wgUseLocalMessageCache;
 207
 208                 if ( !is_string( $code ) ) {
 209                         # This isn't really nice, so at least make a note about it and try to
 210                         # fall back
 211                         wfDebug( __METHOD__ . " called without providing a language code\n" );
 212                         $code = 'en';
 213                 }
 214
 215                 # Don't do double loading...
 216                 if ( isset( $this->mLoadedLanguages[$code] ) ) {
 217                         return true;
 218                 }
 219
 220                 # 8 lines of code just to say (once) that message cache is disabled
 221                 if ( $this->mDisable ) {
 222                         static $shownDisabled = false;
 223                         if ( !$shownDisabled ) {
 224                                 wfDebug( __METHOD__ . ": disabled\n" );
 225                                 $shownDisabled = true;
 226                         }
 227                         return true;
 228                 }
 229
 230                 # Loading code starts
 231                 wfProfileIn( __METHOD__ );
 232                 $success = false; # Keep track of success
 233                 $staleCache = false; # a cache array with expired data, or false if none has been loaded
 234                 $where = array(); # Debug info, delayed to avoid spamming debug log too much
 235                 $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 236
 237                 # Local cache
 238                 # Hash of the contents is stored in memcache, to detect if local cache goes
 239                 # out of date (e.g. due to replace() on some other server)
 240                 if ( $wgUseLocalMessageCache ) {
 241                         wfProfileIn( __METHOD__ . '-fromlocal' );
 242
 243                         $hash = $this->mMemc->get( wfMemcKey( 'messages', $code, 'hash' ) );
 244                         if ( $hash ) {
 245                                 $cache = $this->getLocalCache( $hash, $code );
 246                                 if ( !$cache ) {
 247                                         $where[] = 'local cache is empty or has the wrong hash';
 248                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 249                                         $where[] = 'local cache is expired';
 250                                         $staleCache = $cache;
 251                                 } else {
 252                                         $where[] = 'got from local cache';
 253                                         $success = true;
 254                                         $this->mCache[$code] = $cache;
 255                                 }
 256                         }
 257                         wfProfileOut( __METHOD__ . '-fromlocal' );
 258                 }
 259
 260                 if ( !$success ) {
 261                         # Try the global cache. If it is empty, try to acquire a lock. If
 262                         # the lock can't be acquired, wait for the other thread to finish
 263                         # and then try the global cache a second time.
 264                         for ( $failedAttempts = 0; $failedAttempts < 2; $failedAttempts++ ) {
 265                                 wfProfileIn( __METHOD__ . '-fromcache' );
 266                                 $cache = $this->mMemc->get( $cacheKey );
 267                                 if ( !$cache ) {
 268                                         $where[] = 'global cache is empty';
 269                                 } elseif ( $this->isCacheExpired( $cache ) ) {
 270                                         $where[] = 'global cache is expired';
 271                                         $staleCache = $cache;
 272                                 } else {
 273                                         $where[] = 'got from global cache';
 274                                         $this->mCache[$code] = $cache;
 275                                         $this->saveToCaches( $cache, 'local-only', $code );
 276                                         $success = true;
 277                                 }
 278
 279                                 wfProfileOut( __METHOD__ . '-fromcache' );
 280
 281                                 if ( $success ) {
 282                                         # Done, no need to retry
 283                                         break;
 284                                 }
 285
 286                                 # We need to call loadFromDB. Limit the concurrency to a single
 287                                 # process. This prevents the site from going down when the cache
 288                                 # expires.
 289                                 $statusKey = wfMemcKey( 'messages', $code, 'status' );
 290                                 $acquired = $this->mMemc->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT );
 291                                 if ( $acquired ) {
 292                                         # Unlock the status key if there is an exception
 293                                         $that = $this;
 294                                         $statusUnlocker = new ScopedCallback( function () use ( $that, $statusKey ) {
 295                                                 $that->mMemc->delete( $statusKey );
 296                                         } );
 297
 298                                         # Now let's regenerate
 299                                         $where[] = 'loading from database';
 300
 301                                         # Lock the cache to prevent conflicting writes
 302                                         # If this lock fails, it doesn't really matter, it just means the
 303                                         # write is potentially non-atomic, e.g. the results of a replace()
 304                                         # may be discarded.
 305                                         if ( $this->lock( $cacheKey ) ) {
 306                                                 $mainUnlocker = new ScopedCallback( function () use ( $that, $cacheKey ) {
 307                                                         $that->unlock( $cacheKey );
 308                                                 } );
 309                                         } else {
 310                                                 $mainUnlocker = null;
 311                                                 $where[] = 'could not acquire main lock';
 312                                         }
 313
 314                                         $cache = $this->loadFromDB( $code );
 315                                         $this->mCache[$code] = $cache;
 316                                         $success = true;
 317                                         $saveSuccess = $this->saveToCaches( $cache, 'all', $code );
 318
 319                                         # Unlock
 320                                         ScopedCallback::consume( $mainUnlocker );
 321                                         ScopedCallback::consume( $statusUnlocker );
 322
 323                                         if ( !$saveSuccess ) {
 324                                                 # Cache save has failed.
 325                                                 # There are two main scenarios where this could be a problem:
 326                                                 #
 327                                                 #   - The cache is more than the maximum size (typically
 328                                                 #     1MB compressed).
 329                                                 #
 330                                                 #   - Memcached has no space remaining in the relevant slab
 331                                                 #     class. This is unlikely with recent versions of
 332                                                 #     memcached.
 333                                                 #
 334                                                 # Either way, if there is a local cache, nothing bad will
 335                                                 # happen. If there is no local cache, disabling the message
 336                                                 # cache for all requests avoids incurring a loadFromDB()
 337                                                 # overhead on every request, and thus saves the wiki from
 338                                                 # complete downtime under moderate traffic conditions.
 339                                                 if ( !$wgUseLocalMessageCache ) {
 340                                                         $this->mMemc->set( $statusKey, 'error', 60 * 5 );
 341                                                         $where[] = 'could not save cache, disabled globally for 5 minutes';
 342                                                 } else {
 343                                                         $where[] = "could not save global cache";
 344                                                 }
 345                                         }
 346
 347                                         # Load from DB complete, no need to retry
 348                                         break;
 349                                 } elseif ( $staleCache ) {
 350                                         # Use the stale cache while some other thread constructs the new one
 351                                         $where[] = 'using stale cache';
 352                                         $this->mCache[$code] = $staleCache;
 353                                         $success = true;
 354                                         break;
 355                                 } elseif ( $failedAttempts > 0 ) {
 356                                         # Already retried once, still failed, so don't do another lock/unlock cycle
 357                                         # This case will typically be hit if memcached is down, or if
 358                                         # loadFromDB() takes longer than MSG_WAIT_TIMEOUT
 359                                         $where[] = "could not acquire status key.";
 360                                         break;
 361                                 } else {
 362                                         $status = $this->mMemc->get( $statusKey );
 363                                         if ( $status === 'error' ) {
 364                                                 # Disable cache
 365                                                 break;
 366                                         } else {
 367                                                 # Wait for the other thread to finish, then retry
 368                                                 $where[] = 'waited for other thread to complete';
 369                                                 $this->lock( $cacheKey );
 370                                                 $this->unlock( $cacheKey );
 371                                         }
 372                                 }
 373                         }
 374                 }
 375
 376                 if ( !$success ) {
 377                         $where[] = 'loading FAILED - cache is disabled';
 378                         $this->mDisable = true;
 379                         $this->mCache = false;
 380                         # This used to throw an exception, but that led to nasty side effects like
 381                         # the whole wiki being instantly down if the memcached server died
 382                 } else {
 383                         # All good, just record the success
 384                         $this->mLoadedLanguages[$code] = true;
 385                 }
 386                 $info = implode( ', ', $where );
 387                 wfDebug( __METHOD__ . ": Loading $code... $info\n" );
 388                 wfProfileOut( __METHOD__ );
 389                 return $success;
 390         }
 391
 392         /**
 393          * Loads cacheable messages from the database. Messages bigger than
 394          * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 395          * on-demand from the database later.
 396          *
 397          * @param string $code Language code.
 398          * @return array Loaded messages for storing in caches.
 399          */
 400         function loadFromDB( $code ) {
 401                 wfProfileIn( __METHOD__ );
 402                 global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;
 403                 $dbr = wfGetDB( DB_SLAVE );
 404                 $cache = array();
 405
 406                 # Common conditions
 407                 $conds = array(
 408                         'page_is_redirect' => 0,
 409                         'page_namespace' => NS_MEDIAWIKI,
 410                 );
 411
 412                 $mostused = array();
 413                 if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
 414                         if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
 415                                 $this->load( $wgLanguageCode );
 416                         }
 417                         $mostused = array_keys( $this->mCache[$wgLanguageCode] );
 418                         foreach ( $mostused as $key => $value ) {
 419                                 $mostused[$key] = "$value/$code";
 420                         }
 421                 }
 422
 423                 if ( count( $mostused ) ) {
 424                         $conds['page_title'] = $mostused;
 425                 } elseif ( $code !== $wgLanguageCode ) {
 426                         $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 427                 } else {
 428                         # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 429                         # other than language code.
 430                         $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
 431                 }
 432
 433                 # Conditions to fetch oversized pages to ignore them
 434                 $bigConds = $conds;
 435                 $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 436
 437                 # Load titles for all oversized pages in the MediaWiki namespace
 438                 $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
 439                 foreach ( $res as $row ) {
 440                         $cache[$row->page_title] = '!TOO BIG';
 441                 }
 442
 443                 # Conditions to load the remaining pages with their contents
 444                 $smallConds = $conds;
 445                 $smallConds[] = 'page_latest=rev_id';
 446                 $smallConds[] = 'rev_text_id=old_id';
 447                 $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
 448
 449                 $res = $dbr->select(
 450                         array( 'page', 'revision', 'text' ),
 451                         array( 'page_title', 'old_text', 'old_flags' ),
 452                         $smallConds,
 453                         __METHOD__ . "($code)-small"
 454                 );
 455
 456                 foreach ( $res as $row ) {
 457                         $text = Revision::getRevisionText( $row );
 458                         if ( $text === false ) {
 459                                 // Failed to fetch data; possible ES errors?
 460                                 // Store a marker to fetch on-demand as a workaround...
 461                                 $entry = '!TOO BIG';
 462                                 wfDebugLog(
 463                                         'MessageCache',
 464                                         __METHOD__
 465                                                 . ": failed to load message page text for {$row->page_title} ($code)"
 466                                 );
 467                         } else {
 468                                 $entry = ' ' . $text;
 469                         }
 470                         $cache[$row->page_title] = $entry;
 471                 }
 472
 473                 $cache['VERSION'] = MSG_CACHE_VERSION;
 474                 $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 475                 wfProfileOut( __METHOD__ );
 476                 return $cache;
 477         }
 478
 479         /**
 480          * Updates cache as necessary when message page is changed
 481          *
 482          * @param string $title Name of the page changed.
 483          * @param mixed $text New contents of the page.
 484          */
 485         public function replace( $title, $text ) {
 486                 global $wgMaxMsgCacheEntrySize;
 487                 wfProfileIn( __METHOD__ );
 488
 489                 if ( $this->mDisable ) {
 490                         wfProfileOut( __METHOD__ );
 491                         return;
 492                 }
 493
 494                 list( $msg, $code ) = $this->figureMessage( $title );
 495
 496                 $cacheKey = wfMemcKey( 'messages', $code );
 497                 $this->load( $code );
 498                 $this->lock( $cacheKey );
 499
 500                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 501
 502                 if ( $text === false ) {
 503                         # Article was deleted
 504                         $this->mCache[$code][$title] = '!NONEXISTENT';
 505                         $this->mMemc->delete( $titleKey );
 506                 } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
 507                         # Check for size
 508                         $this->mCache[$code][$title] = '!TOO BIG';
 509                         $this->mMemc->set( $titleKey, ' ' . $text, $this->mExpiry );
 510                 } else {
 511                         $this->mCache[$code][$title] = ' ' . $text;
 512                         $this->mMemc->delete( $titleKey );
 513                 }
 514
 515                 # Update caches
 516                 $this->saveToCaches( $this->mCache[$code], 'all', $code );
 517                 $this->unlock( $cacheKey );
 518
 519                 // Also delete cached sidebar... just in case it is affected
 520                 $codes = array( $code );
 521                 if ( $code === 'en' ) {
 522                         // Delete all sidebars, like for example on action=purge on the
 523                         // sidebar messages
 524                         $codes = array_keys( Language::fetchLanguageNames() );
 525                 }
 526
 527                 global $wgMemc;
 528                 foreach ( $codes as $code ) {
 529                         $sidebarKey = wfMemcKey( 'sidebar', $code );
 530                         $wgMemc->delete( $sidebarKey );
 531                 }
 532
 533                 // Update the message in the message blob store
 534                 global $wgContLang;
 535                 MessageBlobStore::updateMessage( $wgContLang->lcfirst( $msg ) );
 536
 537                 wfRunHooks( 'MessageCacheReplace', array( $title, $text ) );
 538
 539                 wfProfileOut( __METHOD__ );
 540         }
 541
 542         /**
 543          * Is the given cache array expired due to time passing or a version change?
 544          *
 545          * @param $cache
 546          * @return bool
 547          */
 548         protected function isCacheExpired( $cache ) {
 549                 if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
 550                         return true;
 551                 }
 552                 if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
 553                         return true;
 554                 }
 555                 if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
 556                         return true;
 557                 }
 558                 return false;
 559         }
 560
 561         /**
 562          * Shortcut to update caches.
 563          *
 564          * @param array $cache Cached messages with a version.
 565          * @param string $dest Either "local-only" to save to local caches only
 566          *   or "all" to save to all caches.
 567          * @param string|bool $code Language code (default: false)
 568          * @return bool
 569          */
 570         protected function saveToCaches( $cache, $dest, $code = false ) {
 571                 wfProfileIn( __METHOD__ );
 572                 global $wgUseLocalMessageCache;
 573
 574                 $cacheKey = wfMemcKey( 'messages', $code );
 575
 576                 if ( $dest === 'all' ) {
 577                         $success = $this->mMemc->set( $cacheKey, $cache );
 578                 } else {
 579                         $success = true;
 580                 }
 581
 582                 # Save to local cache
 583                 if ( $wgUseLocalMessageCache ) {
 584                         $serialized = serialize( $cache );
 585                         $hash = md5( $serialized );
 586                         $this->mMemc->set( wfMemcKey( 'messages', $code, 'hash' ), $hash );
 587                         $this->saveToLocal( $serialized, $hash, $code );
 588                 }
 589
 590                 wfProfileOut( __METHOD__ );
 591                 return $success;
 592         }
 593
 594         /**
 595          * Represents a write lock on the messages key
 596          *
 597          * @param string $key
 598          * @return Boolean: success
 599          */
 600         function lock( $key ) {
 601                 $lockKey = $key . ':lock';
 602                 $acquired = false;
 603                 $testDone = false;
 604                 for ( $i = 0; $i < MSG_WAIT_TIMEOUT && !$acquired; $i++ ) {
 605                         $acquired = $this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT );
 606                         if ( $acquired ) {
 607                                 break;
 608                         }
 609
 610                         # Fail fast if memcached is totally down
 611                         if ( !$testDone ) {
 612                                 $testDone = true;
 613                                 if ( !$this->mMemc->set( wfMemcKey( 'test' ), 'test', 1 ) ) {
 614                                         break;
 615                                 }
 616                         }
 617                         sleep( 1 );
 618                 }
 619
 620                 return $acquired;
 621         }
 622
 623         function unlock( $key ) {
 624                 $lockKey = $key . ':lock';
 625                 $this->mMemc->delete( $lockKey );
 626         }
 627
 628         /**
 629          * Get a message from either the content language or the user language.
 630          *
 631          * @param string $key The message cache key
 632          * @param bool $useDB Get the message from the DB, false to use only
 633          *               the localisation
 634          * @param bool|string $langcode Code of the language to get the message for, if
 635          *                  it is a valid code create a language for that language,
 636          *                  if it is a string but not a valid code then make a basic
 637          *                  language object, if it is a false boolean then use the
 638          *                  current users language (as a fallback for the old
 639          *                  parameter functionality), or if it is a true boolean
 640          *                  then use the wikis content language (also as a
 641          *                  fallback).
 642          * @param bool $isFullKey Specifies whether $key is a two part key "msg/lang".
 643          *
 644          * @throws MWException
 645          * @return string|bool
 646          */
 647         function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
 648                 global $wgLanguageCode, $wgContLang;
 649
 650                 if ( is_int( $key ) ) {
 651                         // "Non-string key given" exception sometimes happens for numerical
 652                         // strings that become ints somewhere on their way here
 653                         $key = strval( $key );
 654                 }
 655
 656                 if ( !is_string( $key ) ) {
 657                         throw new MWException( 'Non-string key given' );
 658                 }
 659
 660                 if ( strval( $key ) === '' ) {
 661                         # Shortcut: the empty key is always missing
 662                         return false;
 663                 }
 664
 665                 $lang = wfGetLangObj( $langcode );
 666                 if ( !$lang ) {
 667                         throw new MWException( "Bad lang code $langcode given" );
 668                 }
 669
 670                 $langcode = $lang->getCode();
 671
 672                 $message = false;
 673
 674                 # Normalise title-case input (with some inlining)
 675                 $lckey = str_replace( ' ', '_', $key );
 676                 if ( ord( $key ) < 128 ) {
 677                         $lckey[0] = strtolower( $lckey[0] );
 678                         $uckey = ucfirst( $lckey );
 679                 } else {
 680                         $lckey = $wgContLang->lcfirst( $lckey );
 681                         $uckey = $wgContLang->ucfirst( $lckey );
 682                 }
 683
 684                 # Try the MediaWiki namespace
 685                 if ( !$this->mDisable && $useDB ) {
 686                         $title = $uckey;
 687                         if ( !$isFullKey && ( $langcode != $wgLanguageCode ) ) {
 688                                 $title .= '/' . $langcode;
 689                         }
 690                         $message = $this->getMsgFromNamespace( $title, $langcode );
 691                 }
 692
 693                 # Try the array in the language object
 694                 if ( $message === false ) {
 695                         $message = $lang->getMessage( $lckey );
 696                         if ( is_null( $message ) ) {
 697                                 $message = false;
 698                         }
 699                 }
 700
 701                 # Try the array of another language
 702                 if ( $message === false ) {
 703                         $parts = explode( '/', $lckey );
 704                         # We may get calls for things that are http-urls from sidebar
 705                         # Let's not load nonexistent languages for those
 706                         # They usually have more than one slash.
 707                         if ( count( $parts ) == 2 && $parts[1] !== '' ) {
 708                                 $message = Language::getMessageFor( $parts[0], $parts[1] );
 709                                 if ( is_null( $message ) ) {
 710                                         $message = false;
 711                                 }
 712                         }
 713                 }
 714
 715                 # Is this a custom message? Try the default language in the db...
 716                 if ( ( $message === false || $message === '-' ) &&
 717                         !$this->mDisable && $useDB &&
 718                         !$isFullKey && ( $langcode != $wgLanguageCode )
 719                 ) {
 720                         $message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
 721                 }
 722
 723                 # Final fallback
 724                 if ( $message === false ) {
 725                         return false;
 726                 }
 727
 728                 # Fix whitespace
 729                 $message = strtr( $message,
 730                         array(
 731                                 # Fix for trailing whitespace, removed by textarea
 732                                 '&#32;' => ' ',
 733                                 # Fix for NBSP, converted to space by firefox
 734                                 '&nbsp;' => "\xc2\xa0",
 735                                 '&#160;' => "\xc2\xa0",
 736                         ) );
 737
 738                 return $message;
 739         }
 740
 741         /**
 742          * Get a message from the MediaWiki namespace, with caching. The key must
 743          * first be converted to two-part lang/msg form if necessary.
 744          *
 745          * Unlike self::get(), this function doesn't resolve fallback chains, and
 746          * some callers require this behavior. LanguageConverter::parseCachedTable()
 747          * and self::get() are some examples in core.
 748          *
 749          * @param string $title Message cache key with initial uppercase letter.
 750          * @param string $code Code denoting the language to try.
 751          * @return string|bool False on failure
 752          */
 753         function getMsgFromNamespace( $title, $code ) {
 754                 $this->load( $code );
 755                 if ( isset( $this->mCache[$code][$title] ) ) {
 756                         $entry = $this->mCache[$code][$title];
 757                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 758                                 return substr( $entry, 1 );
 759                         } elseif ( $entry === '!NONEXISTENT' ) {
 760                                 return false;
 761                         } elseif ( $entry === '!TOO BIG' ) {
 762                                 // Fall through and try invididual message cache below
 763                         }
 764                 } else {
 765                         // XXX: This is not cached in process cache, should it?
 766                         $message = false;
 767                         wfRunHooks( 'MessagesPreLoad', array( $title, &$message ) );
 768                         if ( $message !== false ) {
 769                                 return $message;
 770                         }
 771
 772                         return false;
 773                 }
 774
 775                 # Try the individual message cache
 776                 $titleKey = wfMemcKey( 'messages', 'individual', $title );
 777                 $entry = $this->mMemc->get( $titleKey );
 778                 if ( $entry ) {
 779                         if ( substr( $entry, 0, 1 ) === ' ' ) {
 780                                 $this->mCache[$code][$title] = $entry;
 781                                 return substr( $entry, 1 );
 782                         } elseif ( $entry === '!NONEXISTENT' ) {
 783                                 $this->mCache[$code][$title] = '!NONEXISTENT';
 784                                 return false;
 785                         } else {
 786                                 # Corrupt/obsolete entry, delete it
 787                                 $this->mMemc->delete( $titleKey );
 788                         }
 789                 }
 790
 791                 # Try loading it from the database
 792                 $revision = Revision::newFromTitle(
 793                         Title::makeTitle( NS_MEDIAWIKI, $title ), false, Revision::READ_LATEST
 794                 );
 795                 if ( $revision ) {
 796                         $content = $revision->getContent();
 797                         if ( !$content ) {
 798                                 // A possibly temporary loading failure.
 799                                 wfDebugLog(
 800                                         'MessageCache',
 801                                         __METHOD__ . ": failed to load message page text for {$title} ($code)"
 802                                 );
 803                                 $message = null; // no negative caching
 804                         } else {
 805                                 // XXX: Is this the right way to turn a Content object into a message?
 806                                 // NOTE: $content is typically either WikitextContent, JavaScriptContent or
 807                                 //       CssContent. MessageContent is *not* used for storing messages, it's
 808                                 //       only used for wrapping them when needed.
 809                                 $message = $content->getWikitextForTransclusion();
 810
 811                                 if ( $message === false || $message === null ) {
 812                                         wfDebugLog(
 813                                                 'MessageCache',
 814                                                 __METHOD__ . ": message content doesn't provide wikitext "
 815                                                         . "(content model: " . $content->getContentHandler() . ")"
 816                                         );
 817
 818                                         $message = false; // negative caching
 819                                 } else {
 820                                         $this->mCache[$code][$title] = ' ' . $message;
 821                                         $this->mMemc->set( $titleKey, ' ' . $message, $this->mExpiry );
 822                                 }
 823                         }
 824                 } else {
 825                         $message = false; // negative caching
 826                 }
 827
 828                 if ( $message === false ) { // negative caching
 829                         $this->mCache[$code][$title] = '!NONEXISTENT';
 830                         $this->mMemc->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
 831                 }
 832
 833                 return $message;
 834         }
 835
 836         /**
 837          * @param string $message
 838          * @param bool $interface
 839          * @param string $language Language code
 840          * @param Title $title
 841          * @return string
 842          */
 843         function transform( $message, $interface = false, $language = null, $title = null ) {
 844                 // Avoid creating parser if nothing to transform
 845                 if ( strpos( $message, '{{' ) === false ) {
 846                         return $message;
 847                 }
 848
 849                 if ( $this->mInParser ) {
 850                         return $message;
 851                 }
 852
 853                 $parser = $this->getParser();
 854                 if ( $parser ) {
 855                         $popts = $this->getParserOptions();
 856                         $popts->setInterfaceMessage( $interface );
 857                         $popts->setTargetLanguage( $language );
 858
 859                         $userlang = $popts->setUserLang( $language );
 860                         $this->mInParser = true;
 861                         $message = $parser->transformMsg( $message, $popts, $title );
 862                         $this->mInParser = false;
 863                         $popts->setUserLang( $userlang );
 864                 }
 865                 return $message;
 866         }
 867
 868         /**
 869          * @return Parser
 870          */
 871         function getParser() {
 872                 global $wgParser, $wgParserConf;
 873                 if ( !$this->mParser && isset( $wgParser ) ) {
 874                         # Do some initialisation so that we don't have to do it twice
 875                         $wgParser->firstCallInit();
 876                         # Clone it and store it
 877                         $class = $wgParserConf['class'];
 878                         if ( $class == 'Parser_DiffTest' ) {
 879                                 # Uncloneable
 880                                 $this->mParser = new $class( $wgParserConf );
 881                         } else {
 882                                 $this->mParser = clone $wgParser;
 883                         }
 884                 }
 885                 return $this->mParser;
 886         }
 887
 888         /**
 889          * @param string $text
 890          * @param Title $title
 891          * @param bool $linestart Whether or not this is at the start of a line
 892          * @param bool $interface Whether this is an interface message
 893          * @param string $language Language code
 894          * @return ParserOutput|string
 895          */
 896         public function parse( $text, $title = null, $linestart = true,
 897                 $interface = false, $language = null
 898         ) {
 899                 if ( $this->mInParser ) {
 900                         return htmlspecialchars( $text );
 901                 }
 902
 903                 $parser = $this->getParser();
 904                 $popts = $this->getParserOptions();
 905                 $popts->setInterfaceMessage( $interface );
 906                 $popts->setTargetLanguage( $language );
 907
 908                 wfProfileIn( __METHOD__ );
 909                 if ( !$title || !$title instanceof Title ) {
 910                         global $wgTitle;
 911                         $title = $wgTitle;
 912                 }
 913                 // Sometimes $wgTitle isn't set either...
 914                 if ( !$title ) {
 915                         # It's not uncommon having a null $wgTitle in scripts. See r80898
 916                         # Create a ghost title in such case
 917                         $title = Title::newFromText( 'Dwimmerlaik' );
 918                 }
 919
 920                 $this->mInParser = true;
 921                 $res = $parser->parse( $text, $title, $popts, $linestart );
 922                 $this->mInParser = false;
 923
 924                 wfProfileOut( __METHOD__ );
 925                 return $res;
 926         }
 927
 928         function disable() {
 929                 $this->mDisable = true;
 930         }
 931
 932         function enable() {
 933                 $this->mDisable = false;
 934         }
 935
 936         /**
 937          * Clear all stored messages. Mainly used after a mass rebuild.
 938          */
 939         function clear() {
 940                 $langs = Language::fetchLanguageNames( null, 'mw' );
 941                 foreach ( array_keys( $langs ) as $code ) {
 942                         # Global cache
 943                         $this->mMemc->delete( wfMemcKey( 'messages', $code ) );
 944                         # Invalidate all local caches
 945                         $this->mMemc->delete( wfMemcKey( 'messages', $code, 'hash' ) );
 946                 }
 947                 $this->mLoadedLanguages = array();
 948         }
 949
 950         /**
 951          * @param $key
 952          * @return array
 953          */
 954         public function figureMessage( $key ) {
 955                 global $wgLanguageCode;
 956                 $pieces = explode( '/', $key );
 957                 if ( count( $pieces ) < 2 ) {
 958                         return array( $key, $wgLanguageCode );
 959                 }
 960
 961                 $lang = array_pop( $pieces );
 962                 if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
 963                         return array( $key, $wgLanguageCode );
 964                 }
 965
 966                 $message = implode( '/', $pieces );
 967                 return array( $message, $lang );
 968         }
 969
 970         /**
 971          * Get all message keys stored in the message cache for a given language.
 972          * If $code is the content language code, this will return all message keys
 973          * for which MediaWiki:msgkey exists. If $code is another language code, this
 974          * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
 975          * @param string $code Language code
 976          * @return array of message keys (strings)
 977          */
 978         public function getAllMessageKeys( $code ) {
 979                 global $wgContLang;
 980                 $this->load( $code );
 981                 if ( !isset( $this->mCache[$code] ) ) {
 982                         // Apparently load() failed
 983                         return null;
 984                 }
 985                 // Remove administrative keys
 986                 $cache = $this->mCache[$code];
 987                 unset( $cache['VERSION'] );
 988                 unset( $cache['EXPIRY'] );
 989                 // Remove any !NONEXISTENT keys
 990                 $cache = array_diff( $cache, array( '!NONEXISTENT' ) );
 991                 // Keys may appear with a capital first letter. lcfirst them.
 992                 return array_map( array( $wgContLang, 'lcfirst' ), array_keys( $cache ) );
 993         }
 994 }