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