* Second try of split message caches with changes suggested by Tim Starling and other...
authorNiklas Laxström <nikerabbit@users.mediawiki.org>
Tue, 3 Jun 2008 20:41:57 +0000 (20:41 +0000)
committerNiklas Laxström <nikerabbit@users.mediawiki.org>
Tue, 3 Jun 2008 20:41:57 +0000 (20:41 +0000)
 * removed use of umask, wfMkdirParents works now
 * splitting of messages per language is now unconditional
 * storing cached messages in 2-d array of code => messages
 * fixed a bug in replace(), now deletion works properly
 * clear() should actually do something now
 * try to delay parser creation in transform()
 * removed the use of $memcPrefix and wfMemcKeyLang() in favour of wfMemcKey()
 * escape $code in loadFromDb()
 * use member variable instead of static variable for tracking loaded languages

includes/MessageCache.php

index 9bd3321..f24d3b4 100644 (file)
@@ -18,35 +18,34 @@ define( 'MSG_CACHE_VERSION', 1 );
  * @ingroup Cache
  */
 class MessageCache {
-       var $mCache, $mUseCache, $mDisable, $mExpiry;
-       var $mMemcKey, $mKeys, $mParserOptions, $mParser;
+       // Holds loaded messages that are defined in MediaWiki namespace.
+       var $mCache;
+
+       var $mUseCache, $mDisable, $mExpiry;
+       var $mKeys, $mParserOptions, $mParser;
        var $mExtensionMessages = array();
        var $mInitialised = false;
-       var $mDeferred = true;
-       var $mAllMessagesLoaded;
+       var $mAllMessagesLoaded; // Extension messages
 
-       function __construct( &$memCached, $useDB, $expiry, $memcPrefix) {
-               wfProfileIn( __METHOD__ );
+       // Variable for tracking which variables are loaded
+       var $mLoadedLanguages = array();
 
+       function __construct( &$memCached, $useDB, $expiry, /*ignored*/ $memcPrefix ) {
                $this->mUseCache = !is_null( $memCached );
                $this->mMemc = &$memCached;
                $this->mDisable = !$useDB;
                $this->mExpiry = $expiry;
                $this->mDisableTransform = false;
-               $this->mMemcKey = $memcPrefix.':messages';
                $this->mKeys = false; # initialised on demand
                $this->mInitialised = true;
                $this->mParser = null;
-
-               # When we first get asked for a message,
-               # then we'll fill up the cache. If we
-               # can return a cache hit, this saves
-               # some extra milliseconds
-               $this->mDeferred = true;
-
-               wfProfileOut( __METHOD__ );
        }
 
+
+       /**
+        * ParserOptions is lazy initialised.
+        * Access should probably be protected.
+        */
        function getParserOptions() {
                if ( !$this->mParserOptions ) {
                        $this->mParserOptions = new ParserOptions;
@@ -55,22 +54,25 @@ class MessageCache {
        }
 
        /**
-        * Try to load the cache from a local file
+        * Try to load the cache from a local file.
+        * Actual format of the file depends on the $wgLocalMessageCacheSerialized
+        * setting.
+        *
+        * @param $hash String: the hash of contents, to check validity.
+        * @param $code Mixed: Optional language code, see documenation of load().
+        * @return false on failure.
         */
-       function loadFromLocal( $hash ) {
+       function loadFromLocal( $hash, $code ) {
                global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;
 
-               if ( $wgLocalMessageCache === false ) {
-                       return;
-               }
-
-               $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
+               $filename = "$wgLocalMessageCache/messages-" . wfWikiID() . "-$code";
 
+               # Check file existence
                wfSuppressWarnings();
                $file = fopen( $filename, 'r' );
                wfRestoreWarnings();
                if ( !$file ) {
-                       return;
+                       return false; // No cache file
                }
 
                if ( $wgLocalMessageCacheSerialized ) {
@@ -82,37 +84,38 @@ class MessageCache {
                                while ( !feof( $file ) ) {
                                        $serialized .= fread( $file, 100000 );
                                }
-                               $this->setCache( unserialize( $serialized ) );
+                               fclose( $file );
+                               return $this->setCache( unserialize( $serialized ), $code );
+                       } else {
+                               fclose( $file );
+                               return false; // Wrong hash
                        }
-                       fclose( $file );
                } else {
                        $localHash=substr(fread($file,40),8);
                        fclose($file);
                        if ($hash!=$localHash) {
-                               return;
+                               return false; // Wrong hash
                        }
 
-                       require("$wgLocalMessageCache/messages-" . wfWikiID());
-                       $this->setCache( $this->mCache);
+                       # Require overwrites the member variable or just shadows it?
+                       require( $filename );
+                       return $this->setCache( $this->mCache, $code );
                }
        }
 
        /**
-        * Save the cache to a local file
+        * Save the cache to a local file.
         */
-       function saveToLocal( $serialized, $hash ) {
-               global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;
-
-               if ( $wgLocalMessageCache === false ) {
-                       return;
-               }
+       function saveToLocal( $serialized, $hash, $code ) {
+               global $wgLocalMessageCache;
 
-               $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
-               $oldUmask = umask( 0 );
-               wfMkdirParents( $wgLocalMessageCache, 0777 );
-               umask( $oldUmask );
+               $filename = "$wgLocalMessageCache/messages-" . wfWikiID() . "-$code";
+               wfMkdirParents( $wgLocalMessageCache, 0777 ); // might fail
 
+               wfSuppressWarnings();
                $file = fopen( $filename, 'w' );
+               wfRestoreWarnings();
+
                if ( !$file ) {
                        wfDebug( "Unable to open local cache file for writing\n" );
                        return;
@@ -123,32 +126,33 @@ class MessageCache {
                @chmod( $filename, 0666 );
        }
 
-       function loadFromScript( $hash ) {
-               wfDeprecated( __METHOD__ );
-               $this->loadFromLocal( $hash );
-       }
-
-       function saveToScript($array, $hash) {
+       function saveToScript( $array, $hash, $code ) {
                global $wgLocalMessageCache;
-               if ( $wgLocalMessageCache === false ) {
+
+               $filename = "$wgLocalMessageCache/messages-" . wfWikiID() . "-$code";
+               $tempFilename = $filename . '.tmp';
+       wfMkdirParents( $wgLocalMessageCache, 0777 ); // might fail
+
+               wfSuppressWarnings();
+               $file = fopen( $tempFilename, 'w');
+               wfRestoreWarnings();
+
+               if ( !$file ) {
+                       wfDebug( "Unable to open local cache file for writing\n" );
                        return;
                }
 
-               $filename = "$wgLocalMessageCache/messages-" . wfWikiID();
-               $oldUmask = umask( 0 );
-               wfMkdirParents( $wgLocalMessageCache, 0777 );
-               umask( $oldUmask );
-               $file = fopen( $filename.'.tmp', 'w');
                fwrite($file,"<?php\n//$hash\n\n \$this->mCache = array(");
 
                foreach ($array as $key => $message) {
-                       fwrite($file, "'". $this->escapeForScript($key).
-                               "' => '" . $this->escapeForScript($message).
-                               "',\n");
+                       $key = $this->escapeForScript($key);
+                       $messages = $this->escapeForScript($message);
+                       fwrite($file, "'$key' => '$message',\n");
                }
+
                fwrite($file,");\n?>");
                fclose($file);
-               rename($filename.'.tmp',$filename);
+               rename($tempFilename, $filename);
        }
 
        function escapeForScript($string) {
@@ -160,222 +164,307 @@ class MessageCache {
        /**
         * Set the cache to $cache, if it is valid. Otherwise set the cache to false.
         */
-       function setCache( $cache ) {
+       function setCache( $cache, $code ) {
                if ( isset( $cache['VERSION'] ) && $cache['VERSION'] == MSG_CACHE_VERSION ) {
-                       $this->mCache = $cache;
+                       $this->mCache[$code] = $cache;
+                       return true;
                } else {
-                       $this->mCache = false;
+                       return false;
                }
        }
 
        /**
-        * Loads messages either from memcached or the database, if not disabled
-        * On error, quietly switches to a fallback mode
-        * Returns false for a reportable error, true otherwise
+        * Loads messages from caches or from database in this order:
+        * (1) local message cache (if $wgLocalMessageCache is enabled)
+        * (2) memcached
+        * (3) from the database.
+        *
+        * When succesfully loading from (2) or (3), all higher level caches are
+        * updated for the newest version.
+        *
+        * Nothing is loaded if  member variable mDisabled is true, either manually
+        * set by calling code or if message loading fails (is this possible?).
+        *
+        * Returns true if cache is already populated or it was succesfully populated,
+        * or false if populating empty cache fails. Also returns true if MessageCache
+        * is disabled.
+        *
+        * @param $code String: language to which load messages
         */
-       function load() {
-               global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;
+       function load( $code = false ) {
+               global $wgLocalMessageCache;
+
+               if ( !$this->mUseCache ) {
+                       return true;
+               }
+
+               if( !is_string( $code ) ) {
+                       # This isn't really nice, so at least make a note about it and try to
+                       # fall back
+                       wfDebug( __METHOD__ . " called without providing a language code\n" );
+                       $code = 'en';
+               }
 
+               # Don't do double loading...
+               if ( isset($this->mLoadedLanguages[$code]) ) return true;
+
+               # 8 lines of code just to say (once) that message cache is disabled
                if ( $this->mDisable ) {
                        static $shownDisabled = false;
                        if ( !$shownDisabled ) {
-                               wfDebug( "MessageCache::load(): disabled\n" );
+                               wfDebug( __METHOD__ . ": disabled\n" );
                                $shownDisabled = true;
                        }
                        return true;
                }
-               if ( !$this->mUseCache ) {
-                       $this->mDeferred = false;
-                       return true;
-               }
 
-               $fname = 'MessageCache::load';
-               wfProfileIn( $fname );
-               $success = true;
+               # Loading code starts
+               wfProfileIn( __METHOD__ );
+               $success = false; # Keep track of success
+               $where = array(); # Debug info, delayed to avoid spamming debug log too much
+               $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 
-               $this->mCache = false;
 
-               # Try local cache
+               # (1) local cache
+               # Hash of the contents is stored in memcache, to detect if local cache goes
+               # out of date (due to update in other thread?)
                if ( $wgLocalMessageCache !== false ) {
-                       wfProfileIn( $fname.'-fromlocal' );
-                       $hash = $this->mMemc->get( "{$this->mMemcKey}-hash" );
+                       wfProfileIn( __METHOD__ . '-fromlocal' );
+
+                       $hash = $this->mMemc->get( wfMemcKey( 'messages', $code, 'hash' ) );
                        if ( $hash ) {
-                               $this->loadFromLocal( $hash );
-                               if ( $this->mCache ) {
-                                       wfDebug( "MessageCache::load(): got from local cache\n" );
-                               }
+                               $success = $this->loadFromLocal( $hash, $code );
+                               if ( $success ) $where[] = 'got from local cache';
                        }
-                       wfProfileOut( $fname.'-fromlocal' );
-               }
-
-               # Try memcached
-               if ( !$this->mCache ) {
-                       wfProfileIn( $fname.'-fromcache' );
-                       $this->setCache( $this->mMemc->get( $this->mMemcKey ) );
-                       if ( $this->mCache ) {
-                               wfDebug( "MessageCache::load(): got from global cache\n" );
-                               # Save to local cache
-                               if ( $wgLocalMessageCache !== false ) {
-                                       $serialized = serialize( $this->mCache );
-                                       if ( !$hash ) {
-                                               $hash = md5( $serialized );
-                                               $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
-                                       }
-                                       if ($wgLocalMessageCacheSerialized) {
-                                               $this->saveToLocal( $serialized,$hash );
-                                       } else {
-                                               $this->saveToScript( $this->mCache, $hash );
-                                       }
-                               }
+                       wfProfileOut( __METHOD__ . '-fromlocal' );
+               }
+
+               # (2) memcache
+               # Fails if nothing in cache, or in the wrong version.
+               if ( !$success ) {
+                       wfProfileIn( __METHOD__ . '-fromcache' );
+                       $cache = $this->mMemc->get( $cacheKey );
+                       $success = $this->setCache( $cache, $code );
+                       if ( $success ) {
+                               $where[] = 'got from global cache';
+                               $this->saveToCaches( $cache, false, $code );
                        }
-                       wfProfileOut( $fname.'-fromcache' );
+                       wfProfileOut( __METHOD__ . '-fromcache' );
                }
 
 
-               # If there's nothing in memcached, load all the messages from the database
-               if ( !$this->mCache ) {
-                       wfDebug( "MessageCache::load(): cache is empty\n" );
-                       $this->lock();
-                       # Other threads don't need to load the messages if another thread is doing it.
-                       $success = $this->mMemc->add( $this->mMemcKey.'-status', "loading", MSG_LOAD_TIMEOUT );
-                       if ( $success ) {
-                               wfProfileIn( $fname.'-load' );
-                               wfDebug( "MessageCache::load(): loading all messages from DB\n" );
-                               $this->loadFromDB();
-                               wfProfileOut( $fname.'-load' );
-
-                               # Save in memcached
-                               # Keep trying if it fails, this is kind of important
-                               wfProfileIn( $fname.'-save' );
-                               for ($i=0; $i<20 &&
-                                                  !$this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
-                                        $i++ ) {
-                                       usleep(mt_rand(500000,1500000));
-                               }
+               # (3)
+               # Nothing in caches... so we need create one and store it in caches
+               if ( !$success ) {
+                       $where[] = 'cache is empty';
+                       $where[] = 'loading from database';
 
-                               # Save to local cache
-                               if ( $wgLocalMessageCache !== false ) {
-                                       $serialized = serialize( $this->mCache );
-                                       $hash = md5( $serialized );
-                                       $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
-                                       if ($wgLocalMessageCacheSerialized) {
-                                               $this->saveToLocal( $serialized,$hash );
-                                       } else {
-                                               $this->saveToScript( $this->mCache, $hash );
-                                       }
-                               }
+                       $this->lock($cacheKey);
 
-                               wfProfileOut( $fname.'-save' );
-                               if ( $i == 20 ) {
-                                       $this->mMemc->set( $this->mMemcKey.'-status', 'error', 60*5 );
-                                       wfDebug( "MemCached set error in MessageCache: restart memcached server!\n" );
-                               } else {
-                                       $this->mMemc->delete( $this->mMemcKey.'-status' );
-                               }
+                       $cache = $this->loadFromDB( $code );
+                       $success = $this->setCache( $cache, $code );
+                       if ( $success ) {
+                               $this->saveToCaches( $cache, true, $code );
                        }
-                       $this->unlock();
+
+                       $this->unlock($cacheKey);
                }
 
-               if ( !is_array( $this->mCache ) ) {
-                       wfDebug( "MessageCache::load(): unable to load cache, disabled\n" );
+               if ( !$success ) {
+                       # Bad luck... this should not happen
+                       $where[] = 'loading FAILED - cache is disabled';
+                       $info = implode( ', ', $where );
+                       wfDebug( __METHOD__ . ": Loading $code... $info\n" );
                        $this->mDisable = true;
                        $this->mCache = false;
+               } else {
+                       # All good, just record the success
+                       $info = implode( ', ', $where );
+                       wfDebug( __METHOD__ . ": Loading $code... $info\n" );
+                       $this->mLoadedLanguages[$code] = true;
                }
-               wfProfileOut( $fname );
-               $this->mDeferred = false;
+               wfProfileOut( __METHOD__ );
                return $success;
        }
 
        /**
-        * Loads all or main part of cacheable messages from the database
+        * Loads cacheable messages from the database. Messages bigger than
+        * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
+        * on-demand from the database later.
+        *
+        * @param $code Optional language code, see documenation of load().
+        * @return Array: Loaded messages for storing in caches.
         */
-       function loadFromDB() {
-               global $wgMaxMsgCacheEntrySize;
-
+       function loadFromDB( $code = false ) {
                wfProfileIn( __METHOD__ );
+               global $wgMaxMsgCacheEntrySize, $wgContLanguageCode;
                $dbr = wfGetDB( DB_SLAVE );
-               $this->mCache = array();
+               $cache = array();
+
+               # Common conditions
+               $conds = array(
+                       'page_is_redirect' => 0,
+                       'page_namespace' => NS_MEDIAWIKI,
+               );
+
+               if ( $code ) {
+                       # Is this fast enough. Should not matter if the filtering is done in the
+                       # database or in code.
+                       if ( $code !== $wgContLanguageCode ) {
+                               # Messages for particular language
+                               $escapedCode = $dbr->escapeLike( $code );
+                               $conds[] = "page_title like '%%/$escapedCode'";
+                       } else {
+                               # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
+                               # other than language code.
+                               $conds[] = "page_title not like '%%/%%'";
+                       }
+               }
+
+               # Conditions to fetch oversized pages to ignore them
+               $bigConds = $conds;
+               $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );
 
                # Load titles for all oversized pages in the MediaWiki namespace
-               $res = $dbr->select( 'page', 'page_title',
-                       array(
-                               'page_len > ' . intval( $wgMaxMsgCacheEntrySize ),
-                               'page_is_redirect' => 0,
-                               'page_namespace' => NS_MEDIAWIKI,
-                       ),
-                       __METHOD__ );
+               $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ );
                while ( $row = $dbr->fetchObject( $res ) ) {
-                       $this->mCache[$row->page_title] = '!TOO BIG';
+                       $cache[$row->page_title] = '!TOO BIG';
                }
                $dbr->freeResult( $res );
 
-               # Load text for the remaining pages
+               # Conditions to load the remaining pages with their contents
+               $smallConds = $conds;
+               $smallConds[] = 'page_latest=rev_id';
+               $smallConds[] = 'rev_text_id=old_id';
+               $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );
+
                $res = $dbr->select( array( 'page', 'revision', 'text' ),
                        array( 'page_title', 'old_text', 'old_flags' ),
-                       array(
-                               'page_is_redirect' => 0,
-                               'page_namespace' => NS_MEDIAWIKI,
-                               'page_latest=rev_id',
-                               'rev_text_id=old_id',
-                               'page_len <= ' . intval( $wgMaxMsgCacheEntrySize ) ),
-                       __METHOD__ );
+                       $smallConds, __METHOD__ );
 
                for ( $row = $dbr->fetchObject( $res ); $row; $row = $dbr->fetchObject( $res ) ) {
-                       $this->mCache[$row->page_title] = ' ' . Revision::getRevisionText( $row );
+                       $cache[$row->page_title] = ' ' . Revision::getRevisionText( $row );
                }
-               $this->mCache['VERSION'] = MSG_CACHE_VERSION;
                $dbr->freeResult( $res );
+
+               $cache['VERSION'] = MSG_CACHE_VERSION;
                wfProfileOut( __METHOD__ );
+               return $cache;
        }
 
-       function replace( $title, $text ) {
-               global $wgLocalMessageCache, $wgLocalMessageCacheSerialized, $parserMemc;
+       /**
+        * Updates cache as necessary when message page is changed
+        *
+        * @param $title String: name of the page changed.
+        * @param $text Mixed: new contents of the page.
+        */
+       public function replace( $title, $text ) {
                global $wgMaxMsgCacheEntrySize;
-
                wfProfileIn( __METHOD__ );
-               $this->lock();
-               $this->load();
-               if ( is_array( $this->mCache ) ) {
+
+
+               list( , $code ) = $this->figureMessage( $title );
+
+               $cacheKey = wfMemcKey( 'messages', $code );
+               $this->load($code);
+               $this->lock($cacheKey);
+
+               if ( is_array($this->mCache[$code]) ) {
+                       $titleKey = wfMemcKey( 'messages', 'individual', $title );
+
                        if ( $text === false ) {
                                # Article was deleted
-                               unset( $this->mCache[$title] );
-                               $this->mMemc->delete( "$this->mMemcKey:{$title}" );
+                               unset( $this->mCache[$code][$title] );
+                               $this->mMemc->delete( $titleKey );
+
                        } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
-                               $this->mCache[$title] = '!TOO BIG';
-                               $this->mMemc->set( "$this->mMemcKey:{$title}", ' '.$text, $this->mExpiry );
+                               # Check for size
+                               $this->mCache[$code][$title] = '!TOO BIG';
+                               $this->mMemc->set( $titleKey, ' ' . $text, $this->mExpiry );
+
                        } else {
-                               $this->mCache[$title] = ' ' . $text;
-                               $this->mMemc->delete( "$this->mMemcKey:{$title}" );
+                               $this->mCache[$code][$title] = ' ' . $text;
+                               $this->mMemc->delete( $titleKey );
                        }
-                       $this->mMemc->set( $this->mMemcKey, $this->mCache, $this->mExpiry );
-
-                       # Save to local cache
-                       if ( $wgLocalMessageCache !== false ) {
-                               $serialized = serialize( $this->mCache );
-                               $hash = md5( $serialized );
-                               $this->mMemc->set( "{$this->mMemcKey}-hash", $hash, $this->mExpiry );
-                               if ($wgLocalMessageCacheSerialized) {
-                                       $this->saveToLocal( $serialized,$hash );
-                               } else {
-                                       $this->saveToScript( $this->mCache, $hash );
-                               }
+
+                       # Update caches
+                       $this->saveToCaches( $this->mCache[$code], true, $code );
+               }
+               $this->unlock($cacheKey);
+
+               // Also delete cached sidebar... just in case it is affected
+               global $parserMemc;
+               $sidebarKey = wfMemcKey( 'sidebar', $code );
+               $parserMemc->delete( $sidebarKey );
+
+               wfProfileOut( __METHOD__ );
+       }
+
+       /**
+        * Shortcut to update caches.
+        *
+        * @param $cache Array: cached messages with a version.
+        * @param $cacheKey String: Identifier for the cache.
+        * @param $memc Bool: Wether to update or not memcache.
+        * @param $code String: Language code.
+        * @return False on somekind of error.
+        */
+       protected function saveToCaches( $cache, $memc = true, $code = false ) {
+               wfProfileIn( __METHOD__ );
+               global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;
+
+               $cacheKey = wfMemcKey( 'messages', $code );
+               $statusKey = wfMemcKey( 'messages', $code, 'status' );
+
+               $success = $this->mMemc->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT );
+               if ( !$success ) return true; # Other process should be updating them now
+
+               $i = 0;
+               if ( $memc ) {
+                       # Save in memcached
+                       # Keep trying if it fails, this is kind of important
+
+                       for ($i=0; $i<20 &&
+                               !$this->mMemc->set( $cacheKey, $cache, $this->mExpiry );
+                               $i++ ) {
+                               usleep(mt_rand(500000,1500000));
                        }
                }
-               $this->unlock();
-               $parserMemc->delete(wfMemcKey('sidebar'));
+
+               # Save to local cache
+               if ( $wgLocalMessageCache !== false ) {
+                       $serialized = serialize( $cache );
+                       $hash = md5( $serialized );
+                       $this->mMemc->set( wfMemcKey( 'messages', $code, 'hash' ), $hash, $this->mExpiry );
+                       if ($wgLocalMessageCacheSerialized) {
+                               $this->saveToLocal( $serialized, $hash, $code );
+                       } else {
+                               $this->saveToScript( $cache, $hash, $code );
+                       }
+               }
+
+               if ( $i == 20 ) {
+                       $this->mMemc->set( $statusKey, 'error', 60*5 );
+                       wfDebug( "MemCached set error in MessageCache: restart memcached server!\n" );
+                       $success = false;
+               } else {
+                       $this->mMemc->delete( $statusKey );
+                       $success = true;
+               }
                wfProfileOut( __METHOD__ );
+               return $success;
        }
 
        /**
         * Returns success
         * Represents a write lock on the messages key
         */
-       function lock() {
+       function lock($key) {
                if ( !$this->mUseCache ) {
                        return true;
                }
 
-               $lockKey = $this->mMemcKey . 'lock';
+               $lockKey = $key . ':lock';
                for ($i=0; $i < MSG_WAIT_TIMEOUT && !$this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT ); $i++ ) {
                        sleep(1);
                }
@@ -383,12 +472,12 @@ class MessageCache {
                return $i >= MSG_WAIT_TIMEOUT;
        }
 
-       function unlock() {
+       function unlock($key) {
                if ( !$this->mUseCache ) {
                        return;
                }
 
-               $lockKey = $this->mMemcKey . 'lock';
+               $lockKey = $key . ':lock';
                $this->mMemc->delete( $lockKey );
        }
 
@@ -438,10 +527,6 @@ class MessageCache {
                if( !$this->mInitialised ) {
                        return '&lt;' . htmlspecialchars($key) . '&gt;';
                }
-               # If cache initialization was deferred, start it now.
-               if( $this->mDeferred && !$this->mDisable && $useDB ) {
-                       $this->load();
-               }
 
                $message = false;
 
@@ -455,10 +540,11 @@ class MessageCache {
                        if(!$isFullKey && ($langcode != $wgContLanguageCode) ) {
                                $title .= '/' . $langcode;
                        }
-                       $message = $this->getMsgFromNamespace( $title );
+                       $message = $this->getMsgFromNamespace( $title, $langcode );
                }
+
                # Try the extension array
-               if( $message === false && isset( $this->mExtensionMessages[$langcode][$lckey] ) ) {
+               if ( $message === false && isset( $this->mExtensionMessages[$langcode][$lckey] ) ) {
                        $message = $this->mExtensionMessages[$langcode][$lckey];
                }
                if ( $message === false && isset( $this->mExtensionMessages['en'][$lckey] ) ) {
@@ -466,11 +552,8 @@ class MessageCache {
                }
 
                # Try the array in the language object
-               if( $message === false ) {
-                       #wfDebug( "Trying language object for message $key\n" );
-                       wfSuppressWarnings();
+               if ( $message === false ) {
                        $message = $lang->getMessage( $lckey );
-                       wfRestoreWarnings();
                        if ( is_null( $message ) ) {
                                $message = false;
                        }
@@ -482,14 +565,14 @@ class MessageCache {
                        $mkey = substr( $lckey, 0, $pos );
                        $code = substr( $lckey, $pos+1 );
                        if ( $code ) {
+                               # We may get calls for things that are http-urls from sidebar
+                               # Let's not load nonexistent languages for those
                                $validCodes = array_keys( Language::getLanguageNames() );
                                if ( in_array( $code, $validCodes ) ) {
                                        $message = Language::getMessageFor( $mkey, $code );
                                        if ( is_null( $message ) ) {
                                                $message = false;
                                        }
-                               } else {
-                                       wfDebug( __METHOD__ . ": Invalid code $code for $mkey/$code, not trying messages array\n" );
                                }
                        }
                }
@@ -498,7 +581,7 @@ class MessageCache {
                if( ($message === false || $message === '-' ) &&
                        !$this->mDisable && $useDB &&
                        !$isFullKey && ($langcode != $wgContLanguageCode) ) {
-                       $message = $this->getMsgFromNamespace( $wgContLang->ucfirst( $lckey ) );
+                       $message = $this->getMsgFromNamespace( $wgContLang->ucfirst( $lckey ), $wgContLanguageCode );
                }
 
                # Final fallback
@@ -512,18 +595,21 @@ class MessageCache {
         * Get a message from the MediaWiki namespace, with caching. The key must
         * first be converted to two-part lang/msg form if necessary.
         *
-        * @param string $title Message cache key with initial uppercase letter
+        * @param $title String: Message cache key with initial uppercase letter.
+        * @param $code String: code denoting the language to try.
         */
-       function getMsgFromNamespace( $title ) {
-               $message = false;
+       function getMsgFromNamespace( $title, $code ) {
                $type = false;
+               $message = false;
 
-               # Try the cache
-               if( $this->mUseCache && isset( $this->mCache[$title] ) ) {
-                       $entry = $this->mCache[$title];
-                       $type = substr( $entry, 0, 1 );
-                       if ( $type == ' ' ) {
-                               return substr( $entry, 1 );
+               if ( $this->mUseCache ) {
+                       $this->load( $code );
+                       if (isset( $this->mCache[$code][$title] ) ) {
+                               $entry = $this->mCache[$code][$title];
+                               $type = substr( $entry, 0, 1 );
+                               if ( $type == ' ' ) {
+                                       return substr( $entry, 1 );
+                               }
                        }
                }
 
@@ -534,27 +620,28 @@ class MessageCache {
                }
 
                # If there is no cache entry and no placeholder, it doesn't exist
-               if ( $type != '!' && $message === false ) {
+               if ( $type !== '!' ) {
                        return false;
                }
 
-               $memcKey = $this->mMemcKey . ':' . $title;
+               $titleKey = wfMemcKey( 'messages', 'individual', $title );
 
                # Try the individual message cache
                if ( $this->mUseCache ) {
-                       $entry = $this->mMemc->get( $memcKey );
+                       $entry = $this->mMemc->get( $titleKey );
                        if ( $entry ) {
                                $type = substr( $entry, 0, 1 );
 
-                               if ( $type == ' ' ) {
+                               if ( $type === ' ' ) {
+                                       # Ok!
                                        $message = substr( $entry, 1 );
-                                       $this->mCache[$title] = $entry;
+                                       $this->mCache[$code][$title] = $entry;
                                        return $message;
-                               } elseif ( $entry == '!NONEXISTENT' ) {
+                               } elseif ( $entry === '!NONEXISTENT' ) {
                                        return false;
                                } else {
                                        # Corrupt/obsolete entry, delete it
-                                       $this->mMemc->delete( $memcKey );
+                                       $this->mMemc->delete( $titleKey );
                                }
 
                        }
@@ -565,40 +652,43 @@ class MessageCache {
                if( $revision ) {
                        $message = $revision->getText();
                        if ($this->mUseCache) {
-                               $this->mCache[$title] = ' ' . $message;
-                               $this->mMemc->set( $memcKey, $message, $this->mExpiry );
+                               $this->mCache[$code][$title] = ' ' . $message;
+                               $this->mMemc->set( $titleKey, $message, $this->mExpiry );
                        }
                } else {
                        # Negative caching
                        # Use some special text instead of false, because false gets converted to '' somewhere
-                       $this->mMemc->set( $memcKey, '!NONEXISTENT', $this->mExpiry );
-                       $this->mCache[$title] = false;
+                       $this->mMemc->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
+                       $this->mCache[$code][$title] = false;
                }
-
                return $message;
        }
 
        function transform( $message, $interface = false ) {
+               // Avoid creating parser if nothing to transfrom
+               if( strpos( $message, '{{' ) === false ) {
+                       return $message;
+               }
+
                global $wgParser;
                if ( !$this->mParser && isset( $wgParser ) ) {
                        # Do some initialisation so that we don't have to do it twice
                        $wgParser->firstCallInit();
                        # Clone it and store it
                        $this->mParser = clone $wgParser;
+                       #wfDebug( __METHOD__ . ": following contents triggered transform: $message\n" );
                }
                if ( $this->mParser ) {
-                       if( strpos( $message, '{{' ) !== false ) {
-                               $popts = $this->getParserOptions();
-                               $popts->setInterfaceMessage( $interface );
-                               $message = $this->mParser->transformMsg( $message, $popts );
-                       }
+                       $popts = $this->getParserOptions();
+                       $popts->setInterfaceMessage( $interface );
+                       $message = $this->mParser->transformMsg( $message, $popts );
                }
                return $message;
        }
 
        function disable() { $this->mDisable = true; }
        function enable() { $this->mDisable = false; }
-
        /** @deprecated */
        function disableTransform(){
                wfDeprecated( __METHOD__ );
@@ -680,12 +770,14 @@ class MessageCache {
         * Clear all stored messages. Mainly used after a mass rebuild.
         */
        function clear() {
-               global $wgLocalMessageCache;
                if( $this->mUseCache ) {
-                       # Global cache
-                       $this->mMemc->delete( $this->mMemcKey );
-                       # Invalidate all local caches
-                       $this->mMemc->delete( "{$this->mMemcKey}-hash" );
+                       $langs = Language::getLanguageNames( false );
+                       foreach ( array_keys($langs) as $code ) {
+                               # Global cache
+                               $this->mMemc->delete( wfMemcKey( 'messages', $code ) );
+                               # Invalidate all local caches
+                               $this->mMemc->delete( wfMemcKey( 'messages', $code, 'hash' ) );
+                       }
                }
        }
 
@@ -761,4 +853,15 @@ class MessageCache {
                        $this->addMessages( $mergedMessages, $langcode );
        }
 
+       public function figureMessage( $key ) {
+               global $wgContLanguageCode;
+               $pieces = explode('/', $key, 2);
+
+               $key = $pieces[0];
+
+               # Language the user is translating to
+               $langCode = isset($pieces[1]) ? $pieces[1] : $wgContLanguageCode;
+               return array( $key, $langCode );
+       }
+
 }