14 files changed, 2603 insertions, 742 deletions

diff --git a/includes/cache/BacklinkCache.php b/includes/cache/BacklinkCache.php
new file mode 100644
index 00000000..193f20fe
--- /dev/null
+++ b/includes/cache/BacklinkCache.php
@@ -0,0 +1,468 @@
+<?php
+/**
+ * Class for fetching backlink lists, approximate backlink counts and
+ * partitions.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @author Tim Starling
+ * @author Aaron Schulz
+ * @copyright © 2009, Tim Starling, Domas Mituzas
+ * @copyright © 2010, Max Sem
+ * @copyright © 2011, Antoine Musso
+ */
+
+/**
+ * Class for fetching backlink lists, approximate backlink counts and
+ * partitions. This is a shared cache.
+ *
+ * Instances of this class should typically be fetched with the method
+ * $title->getBacklinkCache().
+ *
+ * Ideally you should only get your backlinks from here when you think
+ * there is some advantage in caching them. Otherwise it's just a waste
+ * of memory.
+ *
+ * Introduced by r47317
+ *
+ * @internal documentation reviewed on 18 Mar 2011 by hashar
+ */
+class BacklinkCache {
+	/** @var ProcessCacheLRU */
+	protected static $cache;
+
+	/**
+	 * Multi dimensions array representing batches. Keys are:
+	 *  > (string) links table name
+	 *    > 'numRows' : Number of rows for this link table
+	 *    > 'batches' : array( $start, $end )
+	 *
+	 * @see BacklinkCache::partitionResult()
+	 *
+	 * Cleared with BacklinkCache::clear()
+	 */
+	protected $partitionCache = array();
+
+	/**
+	 * Contains the whole links from a database result.
+	 * This is raw data that will be partitioned in $partitionCache
+	 *
+	 * Initialized with BacklinkCache::getLinks()
+	 * Cleared with BacklinkCache::clear()
+	 */
+	protected $fullResultCache = array();
+
+	/**
+	 * Local copy of a database object.
+	 *
+	 * Accessor: BacklinkCache::getDB()
+	 * Mutator : BacklinkCache::setDB()
+	 * Cleared with BacklinkCache::clear()
+	 */
+	protected $db;
+
+	/**
+	 * Local copy of a Title object
+	 */
+	protected $title;
+
+	const CACHE_EXPIRY = 3600;
+
+	/**
+	 * Create a new BacklinkCache
+	 *
+	 * @param Title $title : Title object to create a backlink cache for
+	 */
+	public function __construct( Title $title ) {
+		$this->title = $title;
+	}
+
+	/**
+	 * Create a new BacklinkCache or reuse any existing one.
+	 * Currently, only one cache instance can exist; callers that
+	 * need multiple backlink cache objects should keep them in scope.
+	 *
+	 * @param Title $title : Title object to get a backlink cache for
+	 * @return BacklinkCache
+	 */
+	public static function get( Title $title ) {
+		if ( !self::$cache ) { // init cache
+			self::$cache = new ProcessCacheLRU( 1 );
+		}
+		$dbKey = $title->getPrefixedDBkey();
+		if ( !self::$cache->has( $dbKey, 'obj', 3600 ) ) {
+			self::$cache->set( $dbKey, 'obj', new self( $title ) );
+		}
+		return self::$cache->get( $dbKey, 'obj' );
+	}
+
+	/**
+	 * Serialization handler, diasallows to serialize the database to prevent
+	 * failures after this class is deserialized from cache with dead DB
+	 * connection.
+	 *
+	 * @return array
+	 */
+	function __sleep() {
+		return array( 'partitionCache', 'fullResultCache', 'title' );
+	}
+
+	/**
+	 * Clear locally stored data and database object.
+	 */
+	public function clear() {
+		$this->partitionCache = array();
+		$this->fullResultCache = array();
+		unset( $this->db );
+	}
+
+	/**
+	 * Set the Database object to use
+	 *
+	 * @param $db DatabaseBase
+	 */
+	public function setDB( $db ) {
+		$this->db = $db;
+	}
+
+	/**
+	 * Get the slave connection to the database
+	 * When non existing, will initialize the connection.
+	 * @return DatabaseBase object
+	 */
+	protected function getDB() {
+		if ( !isset( $this->db ) ) {
+			$this->db = wfGetDB( DB_SLAVE );
+		}
+		return $this->db;
+	}
+
+	/**
+	 * Get the backlinks for a given table. Cached in process memory only.
+	 * @param $table String
+	 * @param $startId Integer|false
+	 * @param $endId Integer|false
+	 * @param $max Integer|INF
+	 * @return TitleArrayFromResult
+	 */
+	public function getLinks( $table, $startId = false, $endId = false, $max = INF ) {
+		return TitleArray::newFromResult( $this->queryLinks( $table, $startId, $endId, $max ) );
+	}
+
+	/**
+	 * Get the backlinks for a given table. Cached in process memory only.
+	 * @param $table String
+	 * @param $startId Integer|false
+	 * @param $endId Integer|false
+	 * @param $max Integer|INF
+	 * @return ResultWrapper
+	 */
+	protected function queryLinks( $table, $startId, $endId, $max ) {
+		wfProfileIn( __METHOD__ );
+
+		$fromField = $this->getPrefix( $table ) . '_from';
+
+		if ( !$startId && !$endId && is_infinite( $max )
+			&& isset( $this->fullResultCache[$table] ) )
+		{
+			wfDebug( __METHOD__ . ": got results from cache\n" );
+			$res = $this->fullResultCache[$table];
+		} else {
+			wfDebug( __METHOD__ . ": got results from DB\n" );
+			$conds = $this->getConditions( $table );
+			// Use the from field in the condition rather than the joined page_id,
+			// because databases are stupid and don't necessarily propagate indexes.
+			if ( $startId ) {
+				$conds[] = "$fromField >= " . intval( $startId );
+			}
+			if ( $endId ) {
+				$conds[] = "$fromField <= " . intval( $endId );
+			}
+			$options = array( 'STRAIGHT_JOIN', 'ORDER BY' => $fromField );
+			if ( is_finite( $max ) && $max > 0 ) {
+				$options['LIMIT'] = $max;
+			}
+
+			$res = $this->getDB()->select(
+				array( $table, 'page' ),
+				array( 'page_namespace', 'page_title', 'page_id' ),
+				$conds,
+				__METHOD__,
+				$options
+			);
+
+			if ( !$startId && !$endId && $res->numRows() < $max ) {
+				// The full results fit within the limit, so cache them
+				$this->fullResultCache[$table] = $res;
+			} else {
+				wfDebug( __METHOD__ . ": results from DB were uncacheable\n" );
+			}
+		}
+
+		wfProfileOut( __METHOD__ );
+		return $res;
+	}
+
+	/**
+	 * Get the field name prefix for a given table
+	 * @param $table String
+	 * @throws MWException
+	 * @return null|string
+	 */
+	protected function getPrefix( $table ) {
+		static $prefixes = array(
+			'pagelinks' => 'pl',
+			'imagelinks' => 'il',
+			'categorylinks' => 'cl',
+			'templatelinks' => 'tl',
+			'redirect' => 'rd',
+		);
+
+		if ( isset( $prefixes[$table] ) ) {
+			return $prefixes[$table];
+		} else {
+			$prefix = null;
+			wfRunHooks( 'BacklinkCacheGetPrefix', array( $table, &$prefix ) );
+			if ( $prefix ) {
+				return $prefix;
+			} else {
+				throw new MWException( "Invalid table \"$table\" in " . __CLASS__ );
+			}
+		}
+	}
+
+	/**
+	 * Get the SQL condition array for selecting backlinks, with a join
+	 * on the page table.
+	 * @param $table String
+	 * @throws MWException
+	 * @return array|null
+	 */
+	protected function getConditions( $table ) {
+		$prefix = $this->getPrefix( $table );
+
+		// @todo FIXME: imagelinks and categorylinks do not rely on getNamespace,
+		// they could be moved up for nicer case statements
+		switch ( $table ) {
+			case 'pagelinks':
+			case 'templatelinks':
+				$conds = array(
+					"{$prefix}_namespace" => $this->title->getNamespace(),
+					"{$prefix}_title" => $this->title->getDBkey(),
+					"page_id={$prefix}_from"
+				);
+				break;
+			case 'redirect':
+				$conds = array(
+					"{$prefix}_namespace" => $this->title->getNamespace(),
+					"{$prefix}_title" => $this->title->getDBkey(),
+					$this->getDb()->makeList( array(
+						"{$prefix}_interwiki" => '',
+						"{$prefix}_interwiki IS NULL",
+					), LIST_OR ),
+					"page_id={$prefix}_from"
+				);
+				break;
+			case 'imagelinks':
+				$conds = array(
+					'il_to' => $this->title->getDBkey(),
+					'page_id=il_from'
+				);
+				break;
+			case 'categorylinks':
+				$conds = array(
+					'cl_to' => $this->title->getDBkey(),
+					'page_id=cl_from',
+				);
+				break;
+			default:
+				$conds = null;
+				wfRunHooks( 'BacklinkCacheGetConditions', array( $table, $this->title, &$conds ) );
+				if ( !$conds ) {
+					throw new MWException( "Invalid table \"$table\" in " . __CLASS__ );
+				}
+		}
+
+		return $conds;
+	}
+
+	/**
+	 * Check if there are any backlinks
+	 * @param $table String
+	 * @return bool
+	 */
+	public function hasLinks( $table ) {
+		return ( $this->getNumLinks( $table, 1 ) > 0 );
+	}
+
+	/**
+	 * Get the approximate number of backlinks
+	 * @param $table String
+	 * @param $max integer|INF Only count up to this many backlinks
+	 * @return integer
+	 */
+	public function getNumLinks( $table, $max = INF ) {
+		global $wgMemc;
+
+		// 1) try partition cache ...
+		if ( isset( $this->partitionCache[$table] ) ) {
+			$entry = reset( $this->partitionCache[$table] );
+			return min( $max, $entry['numRows'] );
+		}
+
+		// 2) ... then try full result cache ...
+		if ( isset( $this->fullResultCache[$table] ) ) {
+			return min( $max, $this->fullResultCache[$table]->numRows() );
+		}
+
+		$memcKey = wfMemcKey( 'numbacklinks', md5( $this->title->getPrefixedDBkey() ), $table );
+
+		// 3) ... fallback to memcached ...
+		$count = $wgMemc->get( $memcKey );
+		if ( $count ) {
+			return min( $max, $count );
+		}
+
+		// 4) fetch from the database ...
+		$count = $this->getLinks( $table, false, false, $max )->count();
+		if ( $count < $max ) { // full count
+			$wgMemc->set( $memcKey, $count, self::CACHE_EXPIRY );
+		}
+
+		return min( $max, $count );
+	}
+
+	/**
+	 * Partition the backlinks into batches.
+	 * Returns an array giving the start and end of each range. The first
+	 * batch has a start of false, and the last batch has an end of false.
+	 *
+	 * @param string $table the links table name
+	 * @param $batchSize Integer
+	 * @return Array
+	 */
+	public function partition( $table, $batchSize ) {
+		global $wgMemc;
+
+		// 1) try partition cache ...
+		if ( isset( $this->partitionCache[$table][$batchSize] ) ) {
+			wfDebug( __METHOD__ . ": got from partition cache\n" );
+			return $this->partitionCache[$table][$batchSize]['batches'];
+		}
+
+		$this->partitionCache[$table][$batchSize] = false;
+		$cacheEntry =& $this->partitionCache[$table][$batchSize];
+
+		// 2) ... then try full result cache ...
+		if ( isset( $this->fullResultCache[$table] ) ) {
+			$cacheEntry = $this->partitionResult( $this->fullResultCache[$table], $batchSize );
+			wfDebug( __METHOD__ . ": got from full result cache\n" );
+			return $cacheEntry['batches'];
+		}
+
+		$memcKey = wfMemcKey(
+			'backlinks',
+			md5( $this->title->getPrefixedDBkey() ),
+			$table,
+			$batchSize
+		);
+
+		// 3) ... fallback to memcached ...
+		$memcValue = $wgMemc->get( $memcKey );
+		if ( is_array( $memcValue ) ) {
+			$cacheEntry = $memcValue;
+			wfDebug( __METHOD__ . ": got from memcached $memcKey\n" );
+			return $cacheEntry['batches'];
+		}
+
+		// 4) ... finally fetch from the slow database :(
+		$cacheEntry = array( 'numRows' => 0, 'batches' => array() ); // final result
+		// Do the selects in batches to avoid client-side OOMs (bug 43452).
+		// Use a LIMIT that plays well with $batchSize to keep equal sized partitions.
+		$selectSize = max( $batchSize, 200000 - ( 200000 % $batchSize ) );
+		$start = false;
+		do {
+			$res = $this->queryLinks( $table, $start, false, $selectSize );
+			$partitions = $this->partitionResult( $res, $batchSize, false );
+			// Merge the link count and range partitions for this chunk
+			$cacheEntry['numRows'] += $partitions['numRows'];
+			$cacheEntry['batches'] = array_merge( $cacheEntry['batches'], $partitions['batches'] );
+			if ( count( $partitions['batches'] ) ) {
+				list( $lStart, $lEnd ) = end( $partitions['batches'] );
+				$start = $lEnd + 1; // pick up after this inclusive range
+			}
+		} while ( $partitions['numRows'] >= $selectSize );
+		// Make sure the first range has start=false and the last one has end=false
+		if ( count( $cacheEntry['batches'] ) ) {
+			$cacheEntry['batches'][0][0] = false;
+			$cacheEntry['batches'][count( $cacheEntry['batches'] ) - 1][1] = false;
+		}
+
+		// Save partitions to memcached
+		$wgMemc->set( $memcKey, $cacheEntry, self::CACHE_EXPIRY );
+
+		// Save backlink count to memcached
+		$memcKey = wfMemcKey( 'numbacklinks', md5( $this->title->getPrefixedDBkey() ), $table );
+		$wgMemc->set( $memcKey, $cacheEntry['numRows'], self::CACHE_EXPIRY );
+
+		wfDebug( __METHOD__ . ": got from database\n" );
+		return $cacheEntry['batches'];
+	}
+
+	/**
+	 * Partition a DB result with backlinks in it into batches
+	 * @param $res ResultWrapper database result
+	 * @param $batchSize integer
+	 * @param $isComplete bool Whether $res includes all the backlinks
+	 * @throws MWException
+	 * @return array
+	 */
+	protected function partitionResult( $res, $batchSize, $isComplete = true ) {
+		$batches = array();
+		$numRows = $res->numRows();
+		$numBatches = ceil( $numRows / $batchSize );
+
+		for ( $i = 0; $i < $numBatches; $i++ ) {
+			if ( $i == 0 && $isComplete ) {
+				$start = false;
+			} else {
+				$rowNum = $i * $batchSize;
+				$res->seek( $rowNum );
+				$row = $res->fetchObject();
+				$start = (int)$row->page_id;
+			}
+
+			if ( $i == ( $numBatches - 1 ) && $isComplete ) {
+				$end = false;
+			} else {
+				$rowNum = min( $numRows - 1, ( $i + 1 ) * $batchSize - 1 );
+				$res->seek( $rowNum );
+				$row = $res->fetchObject();
+				$end = (int)$row->page_id;
+			}
+
+			# Sanity check order
+			if ( $start && $end && $start > $end ) {
+				throw new MWException( __METHOD__ . ': Internal error: query result out of order' );
+			}
+
+			$batches[] = array( $start, $end );
+		}
+
+		return array( 'numRows' => $numRows, 'batches' => $batches );
+	}
+}
diff --git a/includes/cache/CacheDependency.php b/includes/cache/CacheDependency.php
index a3c2b52a..32bcdf7f 100644
--- a/includes/cache/CacheDependency.php
+++ b/includes/cache/CacheDependency.php
@@ -74,7 +74,7 @@ class DependencyWrapper {
 
 	/**
 	 * Get the user-defined value
-	 * @return bool|\Mixed
+	 * @return bool|Mixed
 	 */
 	function getValue() {
 		return $this->value;
@@ -98,11 +98,11 @@ class DependencyWrapper {
 	 * calculated value will be stored to the cache in a wrapper.
 	 *
 	 * @param $cache BagOStuff a cache object such as $wgMemc
-	 * @param $key String: the cache key
+	 * @param string $key the cache key
 	 * @param $expiry Integer: the expiry timestamp or interval in seconds
 	 * @param $callback Mixed: the callback for generating the value, or false
-	 * @param $callbackParams Array: the function parameters for the callback
-	 * @param $deps Array: the dependencies to store on a cache miss. Note: these
+	 * @param array $callbackParams the function parameters for the callback
+	 * @param array $deps the dependencies to store on a cache miss. Note: these
 	 *    are not the dependencies used on a cache hit! Cache hits use the stored
 	 *    dependency array.
 	 *
@@ -153,7 +153,7 @@ class FileDependency extends CacheDependency {
 	/**
 	 * Create a file dependency
 	 *
-	 * @param $filename String: the name of the file, preferably fully qualified
+	 * @param string $filename the name of the file, preferably fully qualified
 	 * @param $timestamp Mixed: the unix last modified timestamp, or false if the
 	 *        file does not exist. If omitted, the timestamp will be loaded from
 	 *        the file.
@@ -404,7 +404,7 @@ class GlobalDependency extends CacheDependency {
 	 * @return bool
 	 */
 	function isExpired() {
-		if( !isset($GLOBALS[$this->name]) ) {
+		if ( !isset( $GLOBALS[$this->name] ) ) {
 			return true;
 		}
 		return $GLOBALS[$this->name] != $this->value;
diff --git a/includes/cache/FileCacheBase.php b/includes/cache/FileCacheBase.php
index c0c5609c..d4bf5ee6 100644
--- a/includes/cache/FileCacheBase.php
+++ b/includes/cache/FileCacheBase.php
@@ -35,7 +35,7 @@ abstract class FileCacheBase {
 	/* lazy loaded */
 	protected $mCached;
 
-	/* @TODO: configurable? */
+	/* @todo configurable? */
 	const MISS_FACTOR = 15; // log 1 every MISS_FACTOR cache misses
 	const MISS_TTL_SEC = 3600; // how many seconds ago is "recent"
 
@@ -107,7 +107,7 @@ abstract class FileCacheBase {
 
 	/**
 	 * Check if up to date cache file exists
-	 * @param $timestamp string MW_TS timestamp
+	 * @param string $timestamp MW_TS timestamp
 	 *
 	 * @return bool
 	 */
@@ -138,7 +138,7 @@ abstract class FileCacheBase {
 	 * @return string
 	 */
 	public function fetchText() {
-		if( $this->useGzip() ) {
+		if ( $this->useGzip() ) {
 			$fh = gzopen( $this->cachePath(), 'rb' );
 			return stream_get_contents( $fh );
 		} else {
@@ -163,7 +163,7 @@ abstract class FileCacheBase {
 
 		$this->checkCacheDirs(); // build parent dir
 		if ( !file_put_contents( $this->cachePath(), $text, LOCK_EX ) ) {
-			wfDebug( __METHOD__ . "() failed saving ". $this->cachePath() . "\n");
+			wfDebug( __METHOD__ . "() failed saving " . $this->cachePath() . "\n" );
 			$this->mCached = null;
 			return false;
 		}
@@ -229,7 +229,7 @@ abstract class FileCacheBase {
 	public function incrMissesRecent( WebRequest $request ) {
 		global $wgMemc;
 		if ( mt_rand( 0, self::MISS_FACTOR - 1 ) == 0 ) {
-			# Get a large IP range that should include the user  even if that 
+			# Get a large IP range that should include the user  even if that
 			# person's IP address changes
 			$ip = $request->getIP();
 			if ( !IP::isValid( $ip ) ) {
diff --git a/includes/cache/GenderCache.php b/includes/cache/GenderCache.php
index 2a169bb3..a933527a 100644
--- a/includes/cache/GenderCache.php
+++ b/includes/cache/GenderCache.php
@@ -59,22 +59,21 @@ class GenderCache {
 
 	/**
 	 * Returns the gender for given username.
-	 * @param $username String or User: username
-	 * @param $caller String: the calling method
+	 * @param string $username or User: username
+	 * @param string $caller the calling method
 	 * @return String
 	 */
 	public function getGenderOf( $username, $caller = '' ) {
 		global $wgUser;
 
-		if( $username instanceof User ) {
+		if ( $username instanceof User ) {
 			$username = $username->getName();
 		}
 
 		$username = self::normalizeUsername( $username );
 		if ( !isset( $this->cache[$username] ) ) {
-
 			if ( $this->misses >= $this->missLimit && $wgUser->getName() !== $username ) {
-				if( $this->misses === $this->missLimit ) {
+				if ( $this->misses === $this->missLimit ) {
 					$this->misses++;
 					wfDebug( __METHOD__ . ": too many misses, returning default onwards\n" );
 				}
@@ -84,7 +83,6 @@ class GenderCache {
 				$this->misses++;
 				$this->doQuery( $username, $caller );
 			}
-
 		}
 
 		/* Undefined if there is a valid username which for some reason doesn't
@@ -102,7 +100,9 @@ class GenderCache {
 	public function doLinkBatch( $data, $caller = '' ) {
 		$users = array();
 		foreach ( $data as $ns => $pagenames ) {
-			if ( !MWNamespace::hasGenderDistinction( $ns ) ) continue;
+			if ( !MWNamespace::hasGenderDistinction( $ns ) ) {
+				continue;
+			}
 			foreach ( array_keys( $pagenames ) as $username ) {
 				$users[$username] = true;
 			}
@@ -116,7 +116,7 @@ class GenderCache {
 	 *
 	 * @since 1.20
 	 * @param $titles List: array of Title objects or strings
-	 * @param $caller String: the calling method
+	 * @param string $caller the calling method
 	 */
 	public function doTitlesArray( $titles, $caller = '' ) {
 		$users = array();
@@ -137,20 +137,20 @@ class GenderCache {
 	/**
 	 * Preloads genders for given list of users.
 	 * @param $users List|String: usernames
-	 * @param $caller String: the calling method
+	 * @param string $caller the calling method
 	 */
 	public function doQuery( $users, $caller = '' ) {
 		$default = $this->getDefault();
 
 		$usersToCheck = array();
-		foreach ( (array) $users as $value ) {
+		foreach ( (array)$users as $value ) {
 			$name = self::normalizeUsername( $value );
 			// Skip users whose gender setting we already know
 			if ( !isset( $this->cache[$name] ) ) {
 				// For existing users, this value will be overwritten by the correct value
 				$this->cache[$name] = $default;
 				// query only for valid names, which can be in the database
-				if( User::isValidUserName( $name ) ) {
+				if ( User::isValidUserName( $name ) ) {
 					$usersToCheck[] = $name;
 				}
 			}
diff --git a/includes/cache/HTMLCacheUpdate.php b/includes/cache/HTMLCacheUpdate.php
index 0a3c0023..992809ef 100644
--- a/includes/cache/HTMLCacheUpdate.php
+++ b/includes/cache/HTMLCacheUpdate.php
@@ -23,24 +23,6 @@
 
 /**
  * Class to invalidate the HTML cache of all the pages linking to a given title.
- * Small numbers of links will be done immediately, large numbers are pushed onto
- * the job queue.
- *
- * This class is designed to work efficiently with small numbers of links, and
- * to work reasonably well with up to ~10^5 links. Above ~10^6 links, the memory
- * and time requirements of loading all backlinked IDs in doUpdate() might become
- * prohibitive. The requirements measured at Wikimedia are approximately:
- *
- *   memory: 48 bytes per row
- *   time: 16us per row for the query plus processing
- *
- * The reason this query is done is to support partitioning of the job
- * by backlinked ID. The memory issue could be allieviated by doing this query in
- * batches, but of course LIMIT with an offset is inefficient on the DB side.
- *
- * The class is nevertheless a vast improvement on the previous method of using
- * File::getLinksTo() and Title::touchArray(), which uses about 2KB of memory per
- * link.
  *
  * @ingroup Cache
  */
@@ -50,8 +32,7 @@ class HTMLCacheUpdate implements DeferrableUpdate {
 	 */
 	public $mTitle;
 
-	public $mTable, $mPrefix, $mStart, $mEnd;
-	public $mRowsPerJob, $mRowsPerQuery;
+	public $mTable;
 
 	/**
 	 * @param $titleTo
@@ -59,202 +40,34 @@ class HTMLCacheUpdate implements DeferrableUpdate {
 	 * @param $start bool
 	 * @param $end bool
 	 */
-	function __construct( $titleTo, $table, $start = false, $end = false ) {
-		global $wgUpdateRowsPerJob, $wgUpdateRowsPerQuery;
-
+	function __construct( Title $titleTo, $table ) {
 		$this->mTitle = $titleTo;
 		$this->mTable = $table;
-		$this->mStart = $start;
-		$this->mEnd = $end;
-		$this->mRowsPerJob = $wgUpdateRowsPerJob;
-		$this->mRowsPerQuery = $wgUpdateRowsPerQuery;
-		$this->mCache = $this->mTitle->getBacklinkCache();
 	}
 
 	public function doUpdate() {
-		if ( $this->mStart || $this->mEnd ) {
-			$this->doPartialUpdate();
-			return;
-		}
-
-		# Get an estimate of the number of rows from the BacklinkCache
-		$numRows = $this->mCache->getNumLinks( $this->mTable );
-		if ( $numRows > $this->mRowsPerJob * 2 ) {
-			# Do fast cached partition
-			$this->insertJobs();
-		} else {
-			# Get the links from the DB
-			$titleArray = $this->mCache->getLinks( $this->mTable );
-			# Check if the row count estimate was correct
-			if ( $titleArray->count() > $this->mRowsPerJob * 2 ) {
-				# Not correct, do accurate partition
-				wfDebug( __METHOD__.": row count estimate was incorrect, repartitioning\n" );
-				$this->insertJobsFromTitles( $titleArray );
-			} else {
-				$this->invalidateTitles( $titleArray );
-			}
-		}
-	}
-
-	/**
-	 * Update some of the backlinks, defined by a page ID range
-	 */
-	protected function doPartialUpdate() {
-		$titleArray = $this->mCache->getLinks( $this->mTable, $this->mStart, $this->mEnd );
-		if ( $titleArray->count() <= $this->mRowsPerJob * 2 ) {
-			# This partition is small enough, do the update
-			$this->invalidateTitles( $titleArray );
-		} else {
-			# Partitioning was excessively inaccurate. Divide the job further.
-			# This can occur when a large number of links are added in a short
-			# period of time, say by updating a heavily-used template.
-			$this->insertJobsFromTitles( $titleArray );
-		}
-	}
+		wfProfileIn( __METHOD__ );
 
-	/**
-	 * Partition the current range given by $this->mStart and $this->mEnd,
-	 * using a pre-calculated title array which gives the links in that range.
-	 * Queue the resulting jobs.
-	 *
-	 * @param $titleArray array
-	 */
-	protected function insertJobsFromTitles( $titleArray ) {
-		# We make subpartitions in the sense that the start of the first job
-		# will be the start of the parent partition, and the end of the last
-		# job will be the end of the parent partition.
-		$jobs = array();
-		$start = $this->mStart; # start of the current job
-		$numTitles = 0;
-		foreach ( $titleArray as $title ) {
-			$id = $title->getArticleID();
-			# $numTitles is now the number of titles in the current job not
-			# including the current ID
-			if ( $numTitles >= $this->mRowsPerJob ) {
-				# Add a job up to but not including the current ID
-				$params = array(
-					'table' => $this->mTable,
-					'start' => $start,
-					'end' => $id - 1
-				);
-				$jobs[] = new HTMLCacheUpdateJob( $this->mTitle, $params );
-				$start = $id;
-				$numTitles = 0;
-			}
-			$numTitles++;
-		}
-		# Last job
-		$params = array(
-			'table' => $this->mTable,
-			'start' => $start,
-			'end' => $this->mEnd
-		);
-		$jobs[] = new HTMLCacheUpdateJob( $this->mTitle, $params );
-		wfDebug( __METHOD__.": repartitioning into " . count( $jobs ) . " jobs\n" );
-
-		if ( count( $jobs ) < 2 ) {
-			# I don't think this is possible at present, but handling this case
-			# makes the code a bit more robust against future code updates and
-			# avoids a potential infinite loop of repartitioning
-			wfDebug( __METHOD__.": repartitioning failed!\n" );
-			$this->invalidateTitles( $titleArray );
-			return;
-		}
-
-		Job::batchInsert( $jobs );
-	}
-
-	/**
-	 * @return mixed
-	 */
-	protected function insertJobs() {
-		$batches = $this->mCache->partition( $this->mTable, $this->mRowsPerJob );
-		if ( !$batches ) {
-			return;
-		}
-		$jobs = array();
-		foreach ( $batches as $batch ) {
-			$params = array(
+		$job = new HTMLCacheUpdateJob(
+			$this->mTitle,
+			array(
 				'table' => $this->mTable,
-				'start' => $batch[0],
-				'end' => $batch[1],
-			);
-			$jobs[] = new HTMLCacheUpdateJob( $this->mTitle, $params );
-		}
-		Job::batchInsert( $jobs );
-	}
-
-	/**
-	 * Invalidate an array (or iterator) of Title objects, right now
-	 * @param $titleArray array
-	 */
-	protected function invalidateTitles( $titleArray ) {
-		global $wgUseFileCache, $wgUseSquid;
-
-		$dbw = wfGetDB( DB_MASTER );
-		$timestamp = $dbw->timestamp();
-
-		# Get all IDs in this query into an array
-		$ids = array();
-		foreach ( $titleArray as $title ) {
-			$ids[] = $title->getArticleID();
-		}
-
-		if ( !$ids ) {
-			return;
-		}
-
-		# Update page_touched
-		$batches = array_chunk( $ids, $this->mRowsPerQuery );
-		foreach ( $batches as $batch ) {
-			$dbw->update( 'page',
-				array( 'page_touched' => $timestamp ),
-				array( 'page_id' => $batch ),
-				__METHOD__
-			);
-		}
-
-		# Update squid
-		if ( $wgUseSquid ) {
-			$u = SquidUpdate::newFromTitles( $titleArray );
-			$u->doUpdate();
-		}
+			) + Job::newRootJobParams( // "overall" refresh links job info
+				"htmlCacheUpdate:{$this->mTable}:{$this->mTitle->getPrefixedText()}"
+			)
+		);
 
-		# Update file cache
-		if  ( $wgUseFileCache ) {
-			foreach ( $titleArray as $title ) {
-				HTMLFileCache::clearFileCache( $title );
-			}
+		$count = $this->mTitle->getBacklinkCache()->getNumLinks( $this->mTable, 200 );
+		if ( $count >= 200 ) { // many backlinks
+			JobQueueGroup::singleton()->push( $job );
+			JobQueueGroup::singleton()->deduplicateRootJob( $job );
+		} else { // few backlinks ($count might be off even if 0)
+			$dbw = wfGetDB( DB_MASTER );
+			$dbw->onTransactionIdle( function() use ( $job ) {
+				$job->run(); // just do the purge query now
+			} );
 		}
-	}
-}
-
-
-/**
- * Job wrapper for HTMLCacheUpdate. Gets run whenever a related
- * job gets called from the queue.
- *
- * @ingroup JobQueue
- */
-class HTMLCacheUpdateJob extends Job {
-	var $table, $start, $end;
-
-	/**
-	 * Construct a job
-	 * @param $title Title: the title linked to
-	 * @param $params Array: job parameters (table, start and end page_ids)
-	 * @param $id Integer: job id
-	 */
-	function __construct( $title, $params, $id = 0 ) {
-		parent::__construct( 'htmlCacheUpdate', $title, $params, $id );
-		$this->table = $params['table'];
-		$this->start = $params['start'];
-		$this->end = $params['end'];
-	}
 
-	public function run() {
-		$update = new HTMLCacheUpdate( $this->title, $this->table, $this->start, $this->end );
-		$update->doUpdate();
-		return true;
+		wfProfileOut( __METHOD__ );
 	}
 }
diff --git a/includes/cache/HTMLFileCache.php b/includes/cache/HTMLFileCache.php
index 6bfeed32..ab379116 100644
--- a/includes/cache/HTMLFileCache.php
+++ b/includes/cache/HTMLFileCache.php
@@ -33,6 +33,7 @@ class HTMLFileCache extends FileCacheBase {
 	 * Construct an ObjectFileCache from a Title and an action
 	 * @param $title Title|string Title object or prefixed DB key string
 	 * @param $action string
+	 * @throws MWException
 	 * @return HTMLFileCache
 	 */
 	public static function newFromTitle( $title, $action ) {
@@ -127,7 +128,7 @@ class HTMLFileCache extends FileCacheBase {
 	public function loadFromFileCache( IContextSource $context ) {
 		global $wgMimeType, $wgLanguageCode;
 
-		wfDebug( __METHOD__ . "()\n");
+		wfDebug( __METHOD__ . "()\n" );
 		$filename = $this->cachePath();
 
 		$context->getOutput()->sendCacheControl();
@@ -162,15 +163,15 @@ class HTMLFileCache extends FileCacheBase {
 			return $text;
 		}
 
-		wfDebug( __METHOD__ . "()\n", false);
+		wfDebug( __METHOD__ . "()\n", false );
 
 		$now = wfTimestampNow();
 		if ( $this->useGzip() ) {
 			$text = str_replace(
-				'</html>', '<!-- Cached/compressed '.$now." -->\n</html>", $text );
+				'</html>', '<!-- Cached/compressed ' . $now . " -->\n</html>", $text );
 		} else {
 			$text = str_replace(
-				'</html>', '<!-- Cached '.$now." -->\n</html>", $text );
+				'</html>', '<!-- Cached ' . $now . " -->\n</html>", $text );
 		}
 
 		// Store text to FS...
@@ -181,7 +182,7 @@ class HTMLFileCache extends FileCacheBase {
 
 		// gzip output to buffer as needed and set headers...
 		if ( $this->useGzip() ) {
-			// @TODO: ugly wfClientAcceptsGzip() function - use context!
+			// @todo Ugly wfClientAcceptsGzip() function - use context!
 			if ( wfClientAcceptsGzip() ) {
 				header( 'Content-Encoding: gzip' );
 				return $compressed;
diff --git a/includes/cache/LinkBatch.php b/includes/cache/LinkBatch.php
index 372f983b..48b60aa9 100644
--- a/includes/cache/LinkBatch.php
+++ b/includes/cache/LinkBatch.php
@@ -39,7 +39,7 @@ class LinkBatch {
 	protected $caller;
 
 	function __construct( $arr = array() ) {
-		foreach( $arr as $item ) {
+		foreach ( $arr as $item ) {
 			$this->addObj( $item );
 		}
 	}
@@ -98,7 +98,7 @@ class LinkBatch {
 	 * @return bool
 	 */
 	public function isEmpty() {
-		return ($this->getSize() == 0);
+		return $this->getSize() == 0;
 	}
 
 	/**
@@ -223,7 +223,7 @@ class LinkBatch {
 	/**
 	 * Construct a WHERE clause which will match all the given titles.
 	 *
-	 * @param $prefix String: the appropriate table's field name prefix ('page', 'pl', etc)
+	 * @param string $prefix the appropriate table's field name prefix ('page', 'pl', etc)
 	 * @param $db DatabaseBase object to use
 	 * @return mixed string with SQL where clause fragment, or false if no items.
 	 */
diff --git a/includes/cache/LinkCache.php b/includes/cache/LinkCache.php
index f759c020..54de1989 100644
--- a/includes/cache/LinkCache.php
+++ b/includes/cache/LinkCache.php
@@ -35,18 +35,44 @@ class LinkCache {
 	private $mGoodLinkFields = array();
 	private $mBadLinks = array();
 	private $mForUpdate = false;
+	private $useDatabase = true;
 
 	/**
-	 * Get an instance of this class
+	 * @var LinkCache
+	 */
+	protected static $instance;
+
+	/**
+	 * Get an instance of this class.
 	 *
 	 * @return LinkCache
 	 */
 	static function &singleton() {
-		static $instance;
-		if ( !isset( $instance ) ) {
-			$instance = new LinkCache;
+		if ( self::$instance ) {
+			return self::$instance;
 		}
-		return $instance;
+		self::$instance = new LinkCache;
+		return self::$instance;
+	}
+
+	/**
+	 * Destroy the singleton instance, a new one will be created next time
+	 * singleton() is called.
+	 * @since 1.22
+	 */
+	static function destroySingleton() {
+		self::$instance = null;
+	}
+
+	/**
+	 * Set the singleton instance to a given object.
+	 * Since we do not have an interface for LinkCache, you have to be sure the
+	 * given object implements all the LinkCache public methods.
+	 * @param LinkCache $instance
+	 * @since 1.22
+	 */
+	static function setSingleton( LinkCache $instance ) {
+		self::$instance = $instance;
 	}
 
 	/**
@@ -74,11 +100,11 @@ class LinkCache {
 	 * Get a field of a title object from cache.
 	 * If this link is not good, it will return NULL.
 	 * @param $title Title
-	 * @param $field String: ('length','redirect','revision')
+	 * @param string $field ('length','redirect','revision','model')
 	 * @return mixed
 	 */
 	public function getGoodLinkFieldObj( $title, $field ) {
-		$dbkey = $title->getPrefixedDbKey();
+		$dbkey = $title->getPrefixedDBkey();
 		if ( array_key_exists( $dbkey, $this->mGoodLinkFields ) ) {
 			return $this->mGoodLinkFields[$dbkey][$field];
 		} else {
@@ -102,14 +128,16 @@ class LinkCache {
 	 * @param $len Integer: text's length
 	 * @param $redir Integer: whether the page is a redirect
 	 * @param $revision Integer: latest revision's ID
+	 * @param $model Integer: latest revision's content model ID
 	 */
-	public function addGoodLinkObj( $id, $title, $len = -1, $redir = null, $revision = false ) {
-		$dbkey = $title->getPrefixedDbKey();
+	public function addGoodLinkObj( $id, $title, $len = -1, $redir = null, $revision = false, $model = false ) {
+		$dbkey = $title->getPrefixedDBkey();
 		$this->mGoodLinks[$dbkey] = intval( $id );
 		$this->mGoodLinkFields[$dbkey] = array(
 			'length' => intval( $len ),
 			'redirect' => intval( $redir ),
-			'revision' => intval( $revision ) );
+			'revision' => intval( $revision ),
+			'model' => intval( $model ) );
 	}
 
 	/**
@@ -117,15 +145,16 @@ class LinkCache {
 	 * @since 1.19
 	 * @param $title Title
 	 * @param $row object which has the fields page_id, page_is_redirect,
-	 *  page_latest
+	 *  page_latest and page_content_model
 	 */
 	public function addGoodLinkObjFromRow( $title, $row ) {
-		$dbkey = $title->getPrefixedDbKey();
+		$dbkey = $title->getPrefixedDBkey();
 		$this->mGoodLinks[$dbkey] = intval( $row->page_id );
 		$this->mGoodLinkFields[$dbkey] = array(
 			'length' => intval( $row->page_len ),
 			'redirect' => intval( $row->page_is_redirect ),
 			'revision' => intval( $row->page_latest ),
+			'model' => !empty( $row->page_content_model ) ? strval( $row->page_content_model ) : null,
 		);
 	}
 
@@ -133,7 +162,7 @@ class LinkCache {
 	 * @param $title Title
 	 */
 	public function addBadLinkObj( $title ) {
-		$dbkey = $title->getPrefixedDbKey();
+		$dbkey = $title->getPrefixedDBkey();
 		if ( !$this->isBadLink( $dbkey ) ) {
 			$this->mBadLinks[$dbkey] = 1;
 		}
@@ -147,24 +176,29 @@ class LinkCache {
 	 * @param $title Title
 	 */
 	public function clearLink( $title ) {
-		$dbkey = $title->getPrefixedDbKey();
+		$dbkey = $title->getPrefixedDBkey();
 		unset( $this->mBadLinks[$dbkey] );
 		unset( $this->mGoodLinks[$dbkey] );
 		unset( $this->mGoodLinkFields[$dbkey] );
 	}
 
-	public function getGoodLinks() { return $this->mGoodLinks; }
-	public function getBadLinks() { return array_keys( $this->mBadLinks ); }
+	public function getGoodLinks() {
+		return $this->mGoodLinks;
+	}
+
+	public function getBadLinks() {
+		return array_keys( $this->mBadLinks );
+	}
 
 	/**
 	 * Add a title to the link cache, return the page_id or zero if non-existent
 	 *
-	 * @param $title String: title to add
+	 * @param string $title title to add
 	 * @return Integer
 	 */
 	public function addLink( $title ) {
 		$nt = Title::newFromDBkey( $title );
-		if( $nt ) {
+		if ( $nt ) {
 			return $this->addLinkObj( $nt );
 		} else {
 			return 0;
@@ -172,13 +206,27 @@ class LinkCache {
 	}
 
 	/**
+	 * Enable or disable database use.
+	 * @since 1.22
+	 * @param $value Boolean
+	 * @return Boolean
+	 */
+	public function useDatabase( $value = null ) {
+		if ( $value !== null ) {
+			$this->useDatabase = (bool)$value;
+		}
+		return $this->useDatabase;
+	}
+
+	/**
 	 * Add a title to the link cache, return the page_id or zero if non-existent
 	 *
 	 * @param $nt Title object to add
 	 * @return Integer
 	 */
 	public function addLinkObj( $nt ) {
-		global $wgAntiLockFlags;
+		global $wgAntiLockFlags, $wgContentHandlerUseDB;
+
 		wfProfileIn( __METHOD__ );
 
 		$key = $nt->getPrefixedDBkey();
@@ -197,6 +245,10 @@ class LinkCache {
 			return 0;
 		}
 
+		if( !$this->useDatabase ) {
+			return 0;
+		}
+
 		# Some fields heavily used for linking...
 		if ( $this->mForUpdate ) {
 			$db = wfGetDB( DB_MASTER );
@@ -210,8 +262,12 @@ class LinkCache {
 			$options = array();
 		}
 
-		$s = $db->selectRow( 'page',
-			array( 'page_id', 'page_len', 'page_is_redirect', 'page_latest' ),
+		$f = array( 'page_id', 'page_len', 'page_is_redirect', 'page_latest' );
+		if ( $wgContentHandlerUseDB ) {
+			$f[] = 'page_content_model';
+		}
+
+		$s = $db->selectRow( 'page', $f,
 			array( 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ),
 			__METHOD__, $options );
 		# Set fields...
diff --git a/includes/cache/LocalisationCache.php b/includes/cache/LocalisationCache.php
new file mode 100644
index 00000000..25a1e196
--- /dev/null
+++ b/includes/cache/LocalisationCache.php
@@ -0,0 +1,1371 @@
+<?php
+/**
+ * Cache of the contents of localisation files.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+
+define( 'MW_LC_VERSION', 2 );
+
+/**
+ * Class for caching the contents of localisation files, Messages*.php
+ * and *.i18n.php.
+ *
+ * An instance of this class is available using Language::getLocalisationCache().
+ *
+ * The values retrieved from here are merged, containing items from extension
+ * files, core messages files and the language fallback sequence (e.g. zh-cn ->
+ * zh-hans -> en ). Some common errors are corrected, for example namespace
+ * names with spaces instead of underscores, but heavyweight processing, such
+ * as grammatical transformation, is done by the caller.
+ */
+class LocalisationCache {
+	/** Configuration associative array */
+	var $conf;
+
+	/**
+	 * True if recaching should only be done on an explicit call to recache().
+	 * Setting this reduces the overhead of cache freshness checking, which
+	 * requires doing a stat() for every extension i18n file.
+	 */
+	var $manualRecache = false;
+
+	/**
+	 * True to treat all files as expired until they are regenerated by this object.
+	 */
+	var $forceRecache = false;
+
+	/**
+	 * The cache data. 3-d array, where the first key is the language code,
+	 * the second key is the item key e.g. 'messages', and the third key is
+	 * an item specific subkey index. Some items are not arrays and so for those
+	 * items, there are no subkeys.
+	 */
+	var $data = array();
+
+	/**
+	 * The persistent store object. An instance of LCStore.
+	 *
+	 * @var LCStore
+	 */
+	var $store;
+
+	/**
+	 * A 2-d associative array, code/key, where presence indicates that the item
+	 * is loaded. Value arbitrary.
+	 *
+	 * For split items, if set, this indicates that all of the subitems have been
+	 * loaded.
+	 */
+	var $loadedItems = array();
+
+	/**
+	 * A 3-d associative array, code/key/subkey, where presence indicates that
+	 * the subitem is loaded. Only used for the split items, i.e. messages.
+	 */
+	var $loadedSubitems = array();
+
+	/**
+	 * An array where presence of a key indicates that that language has been
+	 * initialised. Initialisation includes checking for cache expiry and doing
+	 * any necessary updates.
+	 */
+	var $initialisedLangs = array();
+
+	/**
+	 * An array mapping non-existent pseudo-languages to fallback languages. This
+	 * is filled by initShallowFallback() when data is requested from a language
+	 * that lacks a Messages*.php file.
+	 */
+	var $shallowFallbacks = array();
+
+	/**
+	 * An array where the keys are codes that have been recached by this instance.
+	 */
+	var $recachedLangs = array();
+
+	/**
+	 * All item keys
+	 */
+	static public $allKeys = array(
+		'fallback', 'namespaceNames', 'bookstoreList',
+		'magicWords', 'messages', 'rtl', 'capitalizeAllNouns', 'digitTransformTable',
+		'separatorTransformTable', 'fallback8bitEncoding', 'linkPrefixExtension',
+		'linkTrail', 'namespaceAliases',
+		'dateFormats', 'datePreferences', 'datePreferenceMigrationMap',
+		'defaultDateFormat', 'extraUserToggles', 'specialPageAliases',
+		'imageFiles', 'preloadedMessages', 'namespaceGenderAliases',
+		'digitGroupingPattern', 'pluralRules', 'pluralRuleTypes', 'compiledPluralRules',
+	);
+
+	/**
+	 * Keys for items which consist of associative arrays, which may be merged
+	 * by a fallback sequence.
+	 */
+	static public $mergeableMapKeys = array( 'messages', 'namespaceNames',
+		'dateFormats', 'imageFiles', 'preloadedMessages'
+	);
+
+	/**
+	 * Keys for items which are a numbered array.
+	 */
+	static public $mergeableListKeys = array( 'extraUserToggles' );
+
+	/**
+	 * Keys for items which contain an array of arrays of equivalent aliases
+	 * for each subitem. The aliases may be merged by a fallback sequence.
+	 */
+	static public $mergeableAliasListKeys = array( 'specialPageAliases' );
+
+	/**
+	 * Keys for items which contain an associative array, and may be merged if
+	 * the primary value contains the special array key "inherit". That array
+	 * key is removed after the first merge.
+	 */
+	static public $optionalMergeKeys = array( 'bookstoreList' );
+
+	/**
+	 * Keys for items that are formatted like $magicWords
+	 */
+	static public $magicWordKeys = array( 'magicWords' );
+
+	/**
+	 * Keys for items where the subitems are stored in the backend separately.
+	 */
+	static public $splitKeys = array( 'messages' );
+
+	/**
+	 * Keys which are loaded automatically by initLanguage()
+	 */
+	static public $preloadedKeys = array( 'dateFormats', 'namespaceNames' );
+
+	/**
+	 * Associative array of cached plural rules. The key is the language code,
+	 * the value is an array of plural rules for that language.
+	 */
+	var $pluralRules = null;
+
+	/**
+	 * Associative array of cached plural rule types. The key is the language
+	 * code, the value is an array of plural rule types for that language. For
+	 * example, $pluralRuleTypes['ar'] = ['zero', 'one', 'two', 'few', 'many'].
+	 * The index for each rule type matches the index for the rule in
+	 * $pluralRules, thus allowing correlation between the two. The reason we
+	 * don't just use the type names as the keys in $pluralRules is because
+	 * Language::convertPlural applies the rules based on numeric order (or
+	 * explicit numeric parameter), not based on the name of the rule type. For
+	 * example, {{plural:count|wordform1|wordform2|wordform3}}, rather than
+	 * {{plural:count|one=wordform1|two=wordform2|many=wordform3}}.
+	 */
+	var $pluralRuleTypes = null;
+
+	var $mergeableKeys = null;
+
+	/**
+	 * Constructor.
+	 * For constructor parameters, see the documentation in DefaultSettings.php
+	 * for $wgLocalisationCacheConf.
+	 *
+	 * @param $conf Array
+	 * @throws MWException
+	 */
+	function __construct( $conf ) {
+		global $wgCacheDirectory;
+
+		$this->conf = $conf;
+		$storeConf = array();
+		if ( !empty( $conf['storeClass'] ) ) {
+			$storeClass = $conf['storeClass'];
+		} else {
+			switch ( $conf['store'] ) {
+				case 'files':
+				case 'file':
+					$storeClass = 'LCStore_CDB';
+					break;
+				case 'db':
+					$storeClass = 'LCStore_DB';
+					break;
+				case 'accel':
+					$storeClass = 'LCStore_Accel';
+					break;
+				case 'detect':
+					$storeClass = $wgCacheDirectory ? 'LCStore_CDB' : 'LCStore_DB';
+					break;
+				default:
+					throw new MWException(
+						'Please set $wgLocalisationCacheConf[\'store\'] to something sensible.' );
+			}
+		}
+
+		wfDebug( get_class( $this ) . ": using store $storeClass\n" );
+		if ( !empty( $conf['storeDirectory'] ) ) {
+			$storeConf['directory'] = $conf['storeDirectory'];
+		}
+
+		$this->store = new $storeClass( $storeConf );
+		foreach ( array( 'manualRecache', 'forceRecache' ) as $var ) {
+			if ( isset( $conf[$var] ) ) {
+				$this->$var = $conf[$var];
+			}
+		}
+	}
+
+	/**
+	 * Returns true if the given key is mergeable, that is, if it is an associative
+	 * array which can be merged through a fallback sequence.
+	 * @param $key
+	 * @return bool
+	 */
+	public function isMergeableKey( $key ) {
+		if ( $this->mergeableKeys === null ) {
+			$this->mergeableKeys = array_flip( array_merge(
+				self::$mergeableMapKeys,
+				self::$mergeableListKeys,
+				self::$mergeableAliasListKeys,
+				self::$optionalMergeKeys,
+				self::$magicWordKeys
+			) );
+		}
+		return isset( $this->mergeableKeys[$key] );
+	}
+
+	/**
+	 * Get a cache item.
+	 *
+	 * Warning: this may be slow for split items (messages), since it will
+	 * need to fetch all of the subitems from the cache individually.
+	 * @param $code
+	 * @param $key
+	 * @return mixed
+	 */
+	public function getItem( $code, $key ) {
+		if ( !isset( $this->loadedItems[$code][$key] ) ) {
+			wfProfileIn( __METHOD__ . '-load' );
+			$this->loadItem( $code, $key );
+			wfProfileOut( __METHOD__ . '-load' );
+		}
+
+		if ( $key === 'fallback' && isset( $this->shallowFallbacks[$code] ) ) {
+			return $this->shallowFallbacks[$code];
+		}
+
+		return $this->data[$code][$key];
+	}
+
+	/**
+	 * Get a subitem, for instance a single message for a given language.
+	 * @param $code
+	 * @param $key
+	 * @param $subkey
+	 * @return null
+	 */
+	public function getSubitem( $code, $key, $subkey ) {
+		if ( !isset( $this->loadedSubitems[$code][$key][$subkey] ) &&
+			 !isset( $this->loadedItems[$code][$key] ) ) {
+			wfProfileIn( __METHOD__ . '-load' );
+			$this->loadSubitem( $code, $key, $subkey );
+			wfProfileOut( __METHOD__ . '-load' );
+		}
+
+		if ( isset( $this->data[$code][$key][$subkey] ) ) {
+			return $this->data[$code][$key][$subkey];
+		} else {
+			return null;
+		}
+	}
+
+	/**
+	 * Get the list of subitem keys for a given item.
+	 *
+	 * This is faster than array_keys($lc->getItem(...)) for the items listed in
+	 * self::$splitKeys.
+	 *
+	 * Will return null if the item is not found, or false if the item is not an
+	 * array.
+	 * @param $code
+	 * @param $key
+	 * @return bool|null|string
+	 */
+	public function getSubitemList( $code, $key ) {
+		if ( in_array( $key, self::$splitKeys ) ) {
+			return $this->getSubitem( $code, 'list', $key );
+		} else {
+			$item = $this->getItem( $code, $key );
+			if ( is_array( $item ) ) {
+				return array_keys( $item );
+			} else {
+				return false;
+			}
+		}
+	}
+
+	/**
+	 * Load an item into the cache.
+	 * @param $code
+	 * @param $key
+	 */
+	protected function loadItem( $code, $key ) {
+		if ( !isset( $this->initialisedLangs[$code] ) ) {
+			$this->initLanguage( $code );
+		}
+
+		// Check to see if initLanguage() loaded it for us
+		if ( isset( $this->loadedItems[$code][$key] ) ) {
+			return;
+		}
+
+		if ( isset( $this->shallowFallbacks[$code] ) ) {
+			$this->loadItem( $this->shallowFallbacks[$code], $key );
+			return;
+		}
+
+		if ( in_array( $key, self::$splitKeys ) ) {
+			$subkeyList = $this->getSubitem( $code, 'list', $key );
+			foreach ( $subkeyList as $subkey ) {
+				if ( isset( $this->data[$code][$key][$subkey] ) ) {
+					continue;
+				}
+				$this->data[$code][$key][$subkey] = $this->getSubitem( $code, $key, $subkey );
+			}
+		} else {
+			$this->data[$code][$key] = $this->store->get( $code, $key );
+		}
+
+		$this->loadedItems[$code][$key] = true;
+	}
+
+	/**
+	 * Load a subitem into the cache
+	 * @param $code
+	 * @param $key
+	 * @param $subkey
+	 */
+	protected function loadSubitem( $code, $key, $subkey ) {
+		if ( !in_array( $key, self::$splitKeys ) ) {
+			$this->loadItem( $code, $key );
+			return;
+		}
+
+		if ( !isset( $this->initialisedLangs[$code] ) ) {
+			$this->initLanguage( $code );
+		}
+
+		// Check to see if initLanguage() loaded it for us
+		if ( isset( $this->loadedItems[$code][$key] ) ||
+			 isset( $this->loadedSubitems[$code][$key][$subkey] ) ) {
+			return;
+		}
+
+		if ( isset( $this->shallowFallbacks[$code] ) ) {
+			$this->loadSubitem( $this->shallowFallbacks[$code], $key, $subkey );
+			return;
+		}
+
+		$value = $this->store->get( $code, "$key:$subkey" );
+		$this->data[$code][$key][$subkey] = $value;
+		$this->loadedSubitems[$code][$key][$subkey] = true;
+	}
+
+	/**
+	 * Returns true if the cache identified by $code is missing or expired.
+	 *
+	 * @param string $code
+	 *
+	 * @return bool
+	 */
+	public function isExpired( $code ) {
+		if ( $this->forceRecache && !isset( $this->recachedLangs[$code] ) ) {
+			wfDebug( __METHOD__ . "($code): forced reload\n" );
+			return true;
+		}
+
+		$deps = $this->store->get( $code, 'deps' );
+		$keys = $this->store->get( $code, 'list' );
+		$preload = $this->store->get( $code, 'preload' );
+		// Different keys may expire separately, at least in LCStore_Accel
+		if ( $deps === null || $keys === null || $preload === null ) {
+			wfDebug( __METHOD__ . "($code): cache missing, need to make one\n" );
+			return true;
+		}
+
+		foreach ( $deps as $dep ) {
+			// Because we're unserializing stuff from cache, we
+			// could receive objects of classes that don't exist
+			// anymore (e.g. uninstalled extensions)
+			// When this happens, always expire the cache
+			if ( !$dep instanceof CacheDependency || $dep->isExpired() ) {
+				wfDebug( __METHOD__ . "($code): cache for $code expired due to " .
+					get_class( $dep ) . "\n" );
+				return true;
+			}
+		}
+
+		return false;
+	}
+
+	/**
+	 * Initialise a language in this object. Rebuild the cache if necessary.
+	 * @param $code
+	 * @throws MWException
+	 */
+	protected function initLanguage( $code ) {
+		if ( isset( $this->initialisedLangs[$code] ) ) {
+			return;
+		}
+
+		$this->initialisedLangs[$code] = true;
+
+		# If the code is of the wrong form for a Messages*.php file, do a shallow fallback
+		if ( !Language::isValidBuiltInCode( $code ) ) {
+			$this->initShallowFallback( $code, 'en' );
+			return;
+		}
+
+		# Recache the data if necessary
+		if ( !$this->manualRecache && $this->isExpired( $code ) ) {
+			if ( file_exists( Language::getMessagesFileName( $code ) ) ) {
+				$this->recache( $code );
+			} elseif ( $code === 'en' ) {
+				throw new MWException( 'MessagesEn.php is missing.' );
+			} else {
+				$this->initShallowFallback( $code, 'en' );
+			}
+			return;
+		}
+
+		# Preload some stuff
+		$preload = $this->getItem( $code, 'preload' );
+		if ( $preload === null ) {
+			if ( $this->manualRecache ) {
+				// No Messages*.php file. Do shallow fallback to en.
+				if ( $code === 'en' ) {
+					throw new MWException( 'No localisation cache found for English. ' .
+						'Please run maintenance/rebuildLocalisationCache.php.' );
+				}
+				$this->initShallowFallback( $code, 'en' );
+				return;
+			} else {
+				throw new MWException( 'Invalid or missing localisation cache.' );
+			}
+		}
+		$this->data[$code] = $preload;
+		foreach ( $preload as $key => $item ) {
+			if ( in_array( $key, self::$splitKeys ) ) {
+				foreach ( $item as $subkey => $subitem ) {
+					$this->loadedSubitems[$code][$key][$subkey] = true;
+				}
+			} else {
+				$this->loadedItems[$code][$key] = true;
+			}
+		}
+	}
+
+	/**
+	 * Create a fallback from one language to another, without creating a
+	 * complete persistent cache.
+	 * @param $primaryCode
+	 * @param $fallbackCode
+	 */
+	public function initShallowFallback( $primaryCode, $fallbackCode ) {
+		$this->data[$primaryCode] =& $this->data[$fallbackCode];
+		$this->loadedItems[$primaryCode] =& $this->loadedItems[$fallbackCode];
+		$this->loadedSubitems[$primaryCode] =& $this->loadedSubitems[$fallbackCode];
+		$this->shallowFallbacks[$primaryCode] = $fallbackCode;
+	}
+
+	/**
+	 * Read a PHP file containing localisation data.
+	 * @param $_fileName
+	 * @param $_fileType
+	 * @throws MWException
+	 * @return array
+	 */
+	protected function readPHPFile( $_fileName, $_fileType ) {
+		wfProfileIn( __METHOD__ );
+		// Disable APC caching
+		$_apcEnabled = ini_set( 'apc.cache_by_default', '0' );
+		include $_fileName;
+		ini_set( 'apc.cache_by_default', $_apcEnabled );
+
+		if ( $_fileType == 'core' || $_fileType == 'extension' ) {
+			$data = compact( self::$allKeys );
+		} elseif ( $_fileType == 'aliases' ) {
+			$data = compact( 'aliases' );
+		} else {
+			wfProfileOut( __METHOD__ );
+			throw new MWException( __METHOD__ . ": Invalid file type: $_fileType" );
+		}
+		wfProfileOut( __METHOD__ );
+		return $data;
+	}
+
+	/**
+	 * Get the compiled plural rules for a given language from the XML files.
+	 * @since 1.20
+	 */
+	public function getCompiledPluralRules( $code ) {
+		$rules = $this->getPluralRules( $code );
+		if ( $rules === null ) {
+			return null;
+		}
+		try {
+			$compiledRules = CLDRPluralRuleEvaluator::compile( $rules );
+		} catch ( CLDRPluralRuleError $e ) {
+			wfDebugLog( 'l10n', $e->getMessage() . "\n" );
+			return array();
+		}
+		return $compiledRules;
+	}
+
+	/**
+	 * Get the plural rules for a given language from the XML files.
+	 * Cached.
+	 * @since 1.20
+	 */
+	public function getPluralRules( $code ) {
+		if ( $this->pluralRules === null ) {
+			$this->loadPluralFiles();
+		}
+		if ( !isset( $this->pluralRules[$code] ) ) {
+			return null;
+		} else {
+			return $this->pluralRules[$code];
+		}
+	}
+
+	/**
+	 * Get the plural rule types for a given language from the XML files.
+	 * Cached.
+	 * @since 1.22
+	 */
+	public function getPluralRuleTypes( $code ) {
+		if ( $this->pluralRuleTypes === null ) {
+			$this->loadPluralFiles();
+		}
+		if ( !isset( $this->pluralRuleTypes[$code] ) ) {
+			return null;
+		} else {
+			return $this->pluralRuleTypes[$code];
+		}
+	}
+
+	/**
+	 * Load the plural XML files.
+	 */
+	protected function loadPluralFiles() {
+		global $IP;
+		$cldrPlural = "$IP/languages/data/plurals.xml";
+		$mwPlural = "$IP/languages/data/plurals-mediawiki.xml";
+		// Load CLDR plural rules
+		$this->loadPluralFile( $cldrPlural );
+		if ( file_exists( $mwPlural ) ) {
+			// Override or extend
+			$this->loadPluralFile( $mwPlural );
+		}
+	}
+
+	/**
+	 * Load a plural XML file with the given filename, compile the relevant
+	 * rules, and save the compiled rules in a process-local cache.
+	 */
+	protected function loadPluralFile( $fileName ) {
+		$doc = new DOMDocument;
+		$doc->load( $fileName );
+		$rulesets = $doc->getElementsByTagName( "pluralRules" );
+		foreach ( $rulesets as $ruleset ) {
+			$codes = $ruleset->getAttribute( 'locales' );
+			$rules = array();
+			$ruleTypes = array();
+			$ruleElements = $ruleset->getElementsByTagName( "pluralRule" );
+			foreach ( $ruleElements as $elt ) {
+				$ruleType = $elt->getAttribute( 'count' );
+				if ( $ruleType === 'other' ) {
+					// Don't record "other" rules, which have an empty condition
+					continue;
+				}
+				$rules[] = $elt->nodeValue;
+				$ruleTypes[] = $ruleType;
+			}
+			foreach ( explode( ' ', $codes ) as $code ) {
+				$this->pluralRules[$code] = $rules;
+				$this->pluralRuleTypes[$code] = $ruleTypes;
+			}
+		}
+	}
+
+	/**
+	 * Read the data from the source files for a given language, and register
+	 * the relevant dependencies in the $deps array. If the localisation
+	 * exists, the data array is returned, otherwise false is returned.
+	 */
+	protected function readSourceFilesAndRegisterDeps( $code, &$deps ) {
+		global $IP;
+		wfProfileIn( __METHOD__ );
+
+		$fileName = Language::getMessagesFileName( $code );
+		if ( !file_exists( $fileName ) ) {
+			wfProfileOut( __METHOD__ );
+			return false;
+		}
+
+		$deps[] = new FileDependency( $fileName );
+		$data = $this->readPHPFile( $fileName, 'core' );
+
+		# Load CLDR plural rules for JavaScript
+		$data['pluralRules'] = $this->getPluralRules( $code );
+		# And for PHP
+		$data['compiledPluralRules'] = $this->getCompiledPluralRules( $code );
+		# Load plural rule types
+		$data['pluralRuleTypes'] = $this->getPluralRuleTypes( $code );
+
+		$deps['plurals'] = new FileDependency( "$IP/languages/data/plurals.xml" );
+		$deps['plurals-mw'] = new FileDependency( "$IP/languages/data/plurals-mediawiki.xml" );
+
+		wfProfileOut( __METHOD__ );
+		return $data;
+	}
+
+	/**
+	 * Merge two localisation values, a primary and a fallback, overwriting the
+	 * primary value in place.
+	 * @param $key
+	 * @param $value
+	 * @param $fallbackValue
+	 */
+	protected function mergeItem( $key, &$value, $fallbackValue ) {
+		if ( !is_null( $value ) ) {
+			if ( !is_null( $fallbackValue ) ) {
+				if ( in_array( $key, self::$mergeableMapKeys ) ) {
+					$value = $value + $fallbackValue;
+				} elseif ( in_array( $key, self::$mergeableListKeys ) ) {
+					$value = array_unique( array_merge( $fallbackValue, $value ) );
+				} elseif ( in_array( $key, self::$mergeableAliasListKeys ) ) {
+					$value = array_merge_recursive( $value, $fallbackValue );
+				} elseif ( in_array( $key, self::$optionalMergeKeys ) ) {
+					if ( !empty( $value['inherit'] ) ) {
+						$value = array_merge( $fallbackValue, $value );
+					}
+
+					if ( isset( $value['inherit'] ) ) {
+						unset( $value['inherit'] );
+					}
+				} elseif ( in_array( $key, self::$magicWordKeys ) ) {
+					$this->mergeMagicWords( $value, $fallbackValue );
+				}
+			}
+		} else {
+			$value = $fallbackValue;
+		}
+	}
+
+	/**
+	 * @param $value
+	 * @param $fallbackValue
+	 */
+	protected function mergeMagicWords( &$value, $fallbackValue ) {
+		foreach ( $fallbackValue as $magicName => $fallbackInfo ) {
+			if ( !isset( $value[$magicName] ) ) {
+				$value[$magicName] = $fallbackInfo;
+			} else {
+				$oldSynonyms = array_slice( $fallbackInfo, 1 );
+				$newSynonyms = array_slice( $value[$magicName], 1 );
+				$synonyms = array_values( array_unique( array_merge(
+					$newSynonyms, $oldSynonyms ) ) );
+				$value[$magicName] = array_merge( array( $fallbackInfo[0] ), $synonyms );
+			}
+		}
+	}
+
+	/**
+	 * Given an array mapping language code to localisation value, such as is
+	 * found in extension *.i18n.php files, iterate through a fallback sequence
+	 * to merge the given data with an existing primary value.
+	 *
+	 * Returns true if any data from the extension array was used, false
+	 * otherwise.
+	 * @param $codeSequence
+	 * @param $key
+	 * @param $value
+	 * @param $fallbackValue
+	 * @return bool
+	 */
+	protected function mergeExtensionItem( $codeSequence, $key, &$value, $fallbackValue ) {
+		$used = false;
+		foreach ( $codeSequence as $code ) {
+			if ( isset( $fallbackValue[$code] ) ) {
+				$this->mergeItem( $key, $value, $fallbackValue[$code] );
+				$used = true;
+			}
+		}
+
+		return $used;
+	}
+
+	/**
+	 * Load localisation data for a given language for both core and extensions
+	 * and save it to the persistent cache store and the process cache
+	 * @param $code
+	 * @throws MWException
+	 */
+	public function recache( $code ) {
+		global $wgExtensionMessagesFiles;
+		wfProfileIn( __METHOD__ );
+
+		if ( !$code ) {
+			wfProfileOut( __METHOD__ );
+			throw new MWException( "Invalid language code requested" );
+		}
+		$this->recachedLangs[$code] = true;
+
+		# Initial values
+		$initialData = array_combine(
+			self::$allKeys,
+			array_fill( 0, count( self::$allKeys ), null ) );
+		$coreData = $initialData;
+		$deps = array();
+
+		# Load the primary localisation from the source file
+		$data = $this->readSourceFilesAndRegisterDeps( $code, $deps );
+		if ( $data === false ) {
+			wfDebug( __METHOD__ . ": no localisation file for $code, using fallback to en\n" );
+			$coreData['fallback'] = 'en';
+		} else {
+			wfDebug( __METHOD__ . ": got localisation for $code from source\n" );
+
+			# Merge primary localisation
+			foreach ( $data as $key => $value ) {
+				$this->mergeItem( $key, $coreData[$key], $value );
+			}
+
+		}
+
+		# Fill in the fallback if it's not there already
+		if ( is_null( $coreData['fallback'] ) ) {
+			$coreData['fallback'] = $code === 'en' ? false : 'en';
+		}
+		if ( $coreData['fallback'] === false ) {
+			$coreData['fallbackSequence'] = array();
+		} else {
+			$coreData['fallbackSequence'] = array_map( 'trim', explode( ',', $coreData['fallback'] ) );
+			$len = count( $coreData['fallbackSequence'] );
+
+			# Ensure that the sequence ends at en
+			if ( $coreData['fallbackSequence'][$len - 1] !== 'en' ) {
+				$coreData['fallbackSequence'][] = 'en';
+			}
+
+			# Load the fallback localisation item by item and merge it
+			foreach ( $coreData['fallbackSequence'] as $fbCode ) {
+				# Load the secondary localisation from the source file to
+				# avoid infinite cycles on cyclic fallbacks
+				$fbData = $this->readSourceFilesAndRegisterDeps( $fbCode, $deps );
+				if ( $fbData === false ) {
+					continue;
+				}
+
+				foreach ( self::$allKeys as $key ) {
+					if ( !isset( $fbData[$key] ) ) {
+						continue;
+					}
+
+					if ( is_null( $coreData[$key] ) || $this->isMergeableKey( $key ) ) {
+						$this->mergeItem( $key, $coreData[$key], $fbData[$key] );
+					}
+				}
+			}
+		}
+
+		$codeSequence = array_merge( array( $code ), $coreData['fallbackSequence'] );
+
+		# Load the extension localisations
+		# This is done after the core because we know the fallback sequence now.
+		# But it has a higher precedence for merging so that we can support things
+		# like site-specific message overrides.
+		wfProfileIn( __METHOD__ . '-extensions' );
+		$allData = $initialData;
+		foreach ( $wgExtensionMessagesFiles as $fileName ) {
+			$data = $this->readPHPFile( $fileName, 'extension' );
+			$used = false;
+
+			foreach ( $data as $key => $item ) {
+				if ( $this->mergeExtensionItem( $codeSequence, $key, $allData[$key], $item ) ) {
+					$used = true;
+				}
+			}
+
+			if ( $used ) {
+				$deps[] = new FileDependency( $fileName );
+			}
+		}
+
+		# Merge core data into extension data
+		foreach ( $coreData as $key => $item ) {
+			$this->mergeItem( $key, $allData[$key], $item );
+		}
+		wfProfileOut( __METHOD__ . '-extensions' );
+
+		# Add cache dependencies for any referenced globals
+		$deps['wgExtensionMessagesFiles'] = new GlobalDependency( 'wgExtensionMessagesFiles' );
+		$deps['version'] = new ConstantDependency( 'MW_LC_VERSION' );
+
+		# Add dependencies to the cache entry
+		$allData['deps'] = $deps;
+
+		# Replace spaces with underscores in namespace names
+		$allData['namespaceNames'] = str_replace( ' ', '_', $allData['namespaceNames'] );
+
+		# And do the same for special page aliases. $page is an array.
+		foreach ( $allData['specialPageAliases'] as &$page ) {
+			$page = str_replace( ' ', '_', $page );
+		}
+		# Decouple the reference to prevent accidental damage
+		unset( $page );
+
+		# If there were no plural rules, return an empty array
+		if ( $allData['pluralRules'] === null ) {
+			$allData['pluralRules'] = array();
+		}
+		if ( $allData['compiledPluralRules'] === null ) {
+			$allData['compiledPluralRules'] = array();
+		}
+		# If there were no plural rule types, return an empty array
+		if ( $allData['pluralRuleTypes'] === null ) {
+			$allData['pluralRuleTypes'] = array();
+		}
+
+		# Set the list keys
+		$allData['list'] = array();
+		foreach ( self::$splitKeys as $key ) {
+			$allData['list'][$key] = array_keys( $allData[$key] );
+		}
+		# Run hooks
+		wfRunHooks( 'LocalisationCacheRecache', array( $this, $code, &$allData ) );
+
+		if ( is_null( $allData['namespaceNames'] ) ) {
+			wfProfileOut( __METHOD__ );
+			throw new MWException( __METHOD__ . ': Localisation data failed sanity check! ' .
+				'Check that your languages/messages/MessagesEn.php file is intact.' );
+		}
+
+		# Set the preload key
+		$allData['preload'] = $this->buildPreload( $allData );
+
+		# Save to the process cache and register the items loaded
+		$this->data[$code] = $allData;
+		foreach ( $allData as $key => $item ) {
+			$this->loadedItems[$code][$key] = true;
+		}
+
+		# Save to the persistent cache
+		wfProfileIn( __METHOD__ . '-write' );
+		$this->store->startWrite( $code );
+		foreach ( $allData as $key => $value ) {
+			if ( in_array( $key, self::$splitKeys ) ) {
+				foreach ( $value as $subkey => $subvalue ) {
+					$this->store->set( "$key:$subkey", $subvalue );
+				}
+			} else {
+				$this->store->set( $key, $value );
+			}
+		}
+		$this->store->finishWrite();
+		wfProfileOut( __METHOD__ . '-write' );
+
+		# Clear out the MessageBlobStore
+		# HACK: If using a null (i.e. disabled) storage backend, we
+		# can't write to the MessageBlobStore either
+		if ( !$this->store instanceof LCStore_Null ) {
+			MessageBlobStore::clear();
+		}
+
+		wfProfileOut( __METHOD__ );
+	}
+
+	/**
+	 * Build the preload item from the given pre-cache data.
+	 *
+	 * The preload item will be loaded automatically, improving performance
+	 * for the commonly-requested items it contains.
+	 * @param $data
+	 * @return array
+	 */
+	protected function buildPreload( $data ) {
+		$preload = array( 'messages' => array() );
+		foreach ( self::$preloadedKeys as $key ) {
+			$preload[$key] = $data[$key];
+		}
+
+		foreach ( $data['preloadedMessages'] as $subkey ) {
+			if ( isset( $data['messages'][$subkey] ) ) {
+				$subitem = $data['messages'][$subkey];
+			} else {
+				$subitem = null;
+			}
+			$preload['messages'][$subkey] = $subitem;
+		}
+
+		return $preload;
+	}
+
+	/**
+	 * Unload the data for a given language from the object cache.
+	 * Reduces memory usage.
+	 * @param $code
+	 */
+	public function unload( $code ) {
+		unset( $this->data[$code] );
+		unset( $this->loadedItems[$code] );
+		unset( $this->loadedSubitems[$code] );
+		unset( $this->initialisedLangs[$code] );
+		unset( $this->shallowFallbacks[$code] );
+
+		foreach ( $this->shallowFallbacks as $shallowCode => $fbCode ) {
+			if ( $fbCode === $code ) {
+				$this->unload( $shallowCode );
+			}
+		}
+	}
+
+	/**
+	 * Unload all data
+	 */
+	public function unloadAll() {
+		foreach ( $this->initialisedLangs as $lang => $unused ) {
+			$this->unload( $lang );
+		}
+	}
+
+	/**
+	 * Disable the storage backend
+	 */
+	public function disableBackend() {
+		$this->store = new LCStore_Null;
+		$this->manualRecache = false;
+	}
+
+	/**
+	 * Return an array with initialised languages.
+	 *
+	 * @return array
+	 */
+	public function getInitialisedLanguages() {
+		return $this->initialisedLangs;
+	}
+
+	/**
+	 * Set initialised languages.
+	 *
+	 * @param array $languages Optional array of initialised languages.
+	 */
+	public function setInitialisedLanguages( $languages = array() ) {
+		$this->initialisedLangs = $languages;
+	}
+
+}
+
+/**
+ * Interface for the persistence layer of LocalisationCache.
+ *
+ * The persistence layer is two-level hierarchical cache. The first level
+ * is the language, the second level is the item or subitem.
+ *
+ * Since the data for a whole language is rebuilt in one operation, it needs
+ * to have a fast and atomic method for deleting or replacing all of the
+ * current data for a given language. The interface reflects this bulk update
+ * operation. Callers writing to the cache must first call startWrite(), then
+ * will call set() a couple of thousand times, then will call finishWrite()
+ * to commit the operation. When finishWrite() is called, the cache is
+ * expected to delete all data previously stored for that language.
+ *
+ * The values stored are PHP variables suitable for serialize(). Implementations
+ * of LCStore are responsible for serializing and unserializing.
+ */
+interface LCStore {
+	/**
+	 * Get a value.
+	 * @param string $code Language code
+	 * @param string $key Cache key
+	 */
+	function get( $code, $key );
+
+	/**
+	 * Start a write transaction.
+	 * @param string $code Language code
+	 */
+	function startWrite( $code );
+
+	/**
+	 * Finish a write transaction.
+	 */
+	function finishWrite();
+
+	/**
+	 * Set a key to a given value. startWrite() must be called before this
+	 * is called, and finishWrite() must be called afterwards.
+	 * @param string $key
+	 * @param mixed $value
+	 */
+	function set( $key, $value );
+}
+
+/**
+ * LCStore implementation which uses PHP accelerator to store data.
+ * This will work if one of XCache, WinCache or APC cacher is configured.
+ * (See ObjectCache.php)
+ */
+class LCStore_Accel implements LCStore {
+	var $currentLang;
+	var $keys;
+
+	public function __construct() {
+		$this->cache = wfGetCache( CACHE_ACCEL );
+	}
+
+	public function get( $code, $key ) {
+		$k = wfMemcKey( 'l10n', $code, 'k', $key );
+		$r = $this->cache->get( $k );
+		return $r === false ? null : $r;
+	}
+
+	public function startWrite( $code ) {
+		$k = wfMemcKey( 'l10n', $code, 'l' );
+		$keys = $this->cache->get( $k );
+		if ( $keys ) {
+			foreach ( $keys as $k ) {
+				$this->cache->delete( $k );
+			}
+		}
+		$this->currentLang = $code;
+		$this->keys = array();
+	}
+
+	public function finishWrite() {
+		if ( $this->currentLang ) {
+			$k = wfMemcKey( 'l10n', $this->currentLang, 'l' );
+			$this->cache->set( $k, array_keys( $this->keys ) );
+		}
+		$this->currentLang = null;
+		$this->keys = array();
+	}
+
+	public function set( $key, $value ) {
+		if ( $this->currentLang ) {
+			$k = wfMemcKey( 'l10n', $this->currentLang, 'k', $key );
+			$this->keys[$k] = true;
+			$this->cache->set( $k, $value );
+		}
+	}
+}
+
+/**
+ * LCStore implementation which uses the standard DB functions to store data.
+ * This will work on any MediaWiki installation.
+ */
+class LCStore_DB implements LCStore {
+	var $currentLang;
+	var $writesDone = false;
+
+	/**
+	 * @var DatabaseBase
+	 */
+	var $dbw;
+	var $batch;
+	var $readOnly = false;
+
+	public function get( $code, $key ) {
+		if ( $this->writesDone ) {
+			$db = wfGetDB( DB_MASTER );
+		} else {
+			$db = wfGetDB( DB_SLAVE );
+		}
+		$row = $db->selectRow( 'l10n_cache', array( 'lc_value' ),
+			array( 'lc_lang' => $code, 'lc_key' => $key ), __METHOD__ );
+		if ( $row ) {
+			return unserialize( $row->lc_value );
+		} else {
+			return null;
+		}
+	}
+
+	public function startWrite( $code ) {
+		if ( $this->readOnly ) {
+			return;
+		}
+
+		if ( !$code ) {
+			throw new MWException( __METHOD__ . ": Invalid language \"$code\"" );
+		}
+
+		$this->dbw = wfGetDB( DB_MASTER );
+		try {
+			$this->dbw->begin( __METHOD__ );
+			$this->dbw->delete( 'l10n_cache', array( 'lc_lang' => $code ), __METHOD__ );
+		} catch ( DBQueryError $e ) {
+			if ( $this->dbw->wasReadOnlyError() ) {
+				$this->readOnly = true;
+				$this->dbw->rollback( __METHOD__ );
+				return;
+			} else {
+				throw $e;
+			}
+		}
+
+		$this->currentLang = $code;
+		$this->batch = array();
+	}
+
+	public function finishWrite() {
+		if ( $this->readOnly ) {
+			return;
+		}
+
+		if ( $this->batch ) {
+			$this->dbw->insert( 'l10n_cache', $this->batch, __METHOD__ );
+		}
+
+		$this->dbw->commit( __METHOD__ );
+		$this->currentLang = null;
+		$this->dbw = null;
+		$this->batch = array();
+		$this->writesDone = true;
+	}
+
+	public function set( $key, $value ) {
+		if ( $this->readOnly ) {
+			return;
+		}
+
+		if ( is_null( $this->currentLang ) ) {
+			throw new MWException( __CLASS__ . ': must call startWrite() before calling set()' );
+		}
+
+		$this->batch[] = array(
+			'lc_lang' => $this->currentLang,
+			'lc_key' => $key,
+			'lc_value' => serialize( $value ) );
+
+		if ( count( $this->batch ) >= 100 ) {
+			$this->dbw->insert( 'l10n_cache', $this->batch, __METHOD__ );
+			$this->batch = array();
+		}
+	}
+}
+
+/**
+ * LCStore implementation which stores data as a collection of CDB files in the
+ * directory given by $wgCacheDirectory. If $wgCacheDirectory is not set, this
+ * will throw an exception.
+ *
+ * Profiling indicates that on Linux, this implementation outperforms MySQL if
+ * the directory is on a local filesystem and there is ample kernel cache
+ * space. The performance advantage is greater when the DBA extension is
+ * available than it is with the PHP port.
+ *
+ * See Cdb.php and http://cr.yp.to/cdb.html
+ */
+class LCStore_CDB implements LCStore {
+	var $readers, $writer, $currentLang, $directory;
+
+	function __construct( $conf = array() ) {
+		global $wgCacheDirectory;
+
+		if ( isset( $conf['directory'] ) ) {
+			$this->directory = $conf['directory'];
+		} else {
+			$this->directory = $wgCacheDirectory;
+		}
+	}
+
+	public function get( $code, $key ) {
+		if ( !isset( $this->readers[$code] ) ) {
+			$fileName = $this->getFileName( $code );
+
+			if ( !file_exists( $fileName ) ) {
+				$this->readers[$code] = false;
+			} else {
+				$this->readers[$code] = CdbReader::open( $fileName );
+			}
+		}
+
+		if ( !$this->readers[$code] ) {
+			return null;
+		} else {
+			$value = $this->readers[$code]->get( $key );
+
+			if ( $value === false ) {
+				return null;
+			}
+			return unserialize( $value );
+		}
+	}
+
+	public function startWrite( $code ) {
+		if ( !file_exists( $this->directory ) ) {
+			if ( !wfMkdirParents( $this->directory, null, __METHOD__ ) ) {
+				throw new MWException( "Unable to create the localisation store " .
+					"directory \"{$this->directory}\"" );
+			}
+		}
+
+		// Close reader to stop permission errors on write
+		if ( !empty( $this->readers[$code] ) ) {
+			$this->readers[$code]->close();
+		}
+
+		$this->writer = CdbWriter::open( $this->getFileName( $code ) );
+		$this->currentLang = $code;
+	}
+
+	public function finishWrite() {
+		// Close the writer
+		$this->writer->close();
+		$this->writer = null;
+		unset( $this->readers[$this->currentLang] );
+		$this->currentLang = null;
+	}
+
+	public function set( $key, $value ) {
+		if ( is_null( $this->writer ) ) {
+			throw new MWException( __CLASS__ . ': must call startWrite() before calling set()' );
+		}
+		$this->writer->set( $key, serialize( $value ) );
+	}
+
+	protected function getFileName( $code ) {
+		if ( strval( $code ) === '' || strpos( $code, '/' ) !== false ) {
+			throw new MWException( __METHOD__ . ": Invalid language \"$code\"" );
+		}
+		return "{$this->directory}/l10n_cache-$code.cdb";
+	}
+}
+
+/**
+ * Null store backend, used to avoid DB errors during install
+ */
+class LCStore_Null implements LCStore {
+	public function get( $code, $key ) {
+		return null;
+	}
+
+	public function startWrite( $code ) {}
+	public function finishWrite() {}
+	public function set( $key, $value ) {}
+}
+
+/**
+ * A localisation cache optimised for loading large amounts of data for many
+ * languages. Used by rebuildLocalisationCache.php.
+ */
+class LocalisationCache_BulkLoad extends LocalisationCache {
+	/**
+	 * A cache of the contents of data files.
+	 * Core files are serialized to avoid using ~1GB of RAM during a recache.
+	 */
+	var $fileCache = array();
+
+	/**
+	 * Most recently used languages. Uses the linked-list aspect of PHP hashtables
+	 * to keep the most recently used language codes at the end of the array, and
+	 * the language codes that are ready to be deleted at the beginning.
+	 */
+	var $mruLangs = array();
+
+	/**
+	 * Maximum number of languages that may be loaded into $this->data
+	 */
+	var $maxLoadedLangs = 10;
+
+	/**
+	 * @param $fileName
+	 * @param $fileType
+	 * @return array|mixed
+	 */
+	protected function readPHPFile( $fileName, $fileType ) {
+		$serialize = $fileType === 'core';
+		if ( !isset( $this->fileCache[$fileName][$fileType] ) ) {
+			$data = parent::readPHPFile( $fileName, $fileType );
+
+			if ( $serialize ) {
+				$encData = serialize( $data );
+			} else {
+				$encData = $data;
+			}
+
+			$this->fileCache[$fileName][$fileType] = $encData;
+
+			return $data;
+		} elseif ( $serialize ) {
+			return unserialize( $this->fileCache[$fileName][$fileType] );
+		} else {
+			return $this->fileCache[$fileName][$fileType];
+		}
+	}
+
+	/**
+	 * @param $code
+	 * @param $key
+	 * @return mixed
+	 */
+	public function getItem( $code, $key ) {
+		unset( $this->mruLangs[$code] );
+		$this->mruLangs[$code] = true;
+		return parent::getItem( $code, $key );
+	}
+
+	/**
+	 * @param $code
+	 * @param $key
+	 * @param $subkey
+	 * @return
+	 */
+	public function getSubitem( $code, $key, $subkey ) {
+		unset( $this->mruLangs[$code] );
+		$this->mruLangs[$code] = true;
+		return parent::getSubitem( $code, $key, $subkey );
+	}
+
+	/**
+	 * @param $code
+	 */
+	public function recache( $code ) {
+		parent::recache( $code );
+		unset( $this->mruLangs[$code] );
+		$this->mruLangs[$code] = true;
+		$this->trimCache();
+	}
+
+	/**
+	 * @param $code
+	 */
+	public function unload( $code ) {
+		unset( $this->mruLangs[$code] );
+		parent::unload( $code );
+	}
+
+	/**
+	 * Unload cached languages until there are less than $this->maxLoadedLangs
+	 */
+	protected function trimCache() {
+		while ( count( $this->data ) > $this->maxLoadedLangs && count( $this->mruLangs ) ) {
+			reset( $this->mruLangs );
+			$code = key( $this->mruLangs );
+			wfDebug( __METHOD__ . ": unloading $code\n" );
+			$this->unload( $code );
+		}
+	}
+}
diff --git a/includes/cache/MessageCache.php b/includes/cache/MessageCache.php
index b854a2ec..a92c87f4 100644
--- a/includes/cache/MessageCache.php
+++ b/includes/cache/MessageCache.php
@@ -22,14 +22,29 @@
  */
 
 /**
- *
+ * MediaWiki message cache structure version.
+ * Bump this whenever the message cache format has changed.
  */
-define( 'MSG_LOAD_TIMEOUT', 60 );
-define( 'MSG_LOCK_TIMEOUT', 10 );
-define( 'MSG_WAIT_TIMEOUT', 10 );
 define( 'MSG_CACHE_VERSION', 1 );
 
 /**
+ * Memcached timeout when loading a key.
+ * See MessageCache::load()
+ */
+define( 'MSG_LOAD_TIMEOUT', 60 );
+
+/**
+ * Memcached timeout when locking a key for a writing operation.
+ * See MessageCache::lock()
+ */
+define( 'MSG_LOCK_TIMEOUT', 30 );
+/**
+ * Number of times we will try to acquire a lock from Memcached.
+ * This comes in addition to MSG_LOCK_TIMEOUT.
+ */
+define( 'MSG_WAIT_TIMEOUT', 30 );
+
+/**
  * Message cache
  * Performs various MediaWiki namespace-related functions
  * @ingroup Cache
@@ -44,10 +59,16 @@ class MessageCache {
 	 */
 	protected $mCache;
 
-	// Should  mean that database cannot be used, but check
+	/**
+	 * Should  mean that database cannot be used, but check
+	 * @var bool $mDisable
+	 */
 	protected $mDisable;
 
-	/// Lifetime for cache, used by object caching
+	/**
+	 * Lifetime for cache, used by object caching.
+	 * Set on construction, see __construct().
+	 */
 	protected $mExpiry;
 
 	/**
@@ -56,38 +77,21 @@ class MessageCache {
 	 */
 	protected $mParserOptions, $mParser;
 
-	/// Variable for tracking which variables are already loaded
-	protected $mLoadedLanguages = array();
-
-	/**
-	 * Used for automatic detection of most used messages.
-	 */
-	protected $mRequestedMessages = array();
-
 	/**
-	 * How long the message request counts are stored. Longer period gives
-	 * better sample, but also takes longer to adapt changes. The counts
-	 * are aggregrated per day, regardless of the value of this variable.
+	 * Variable for tracking which variables are already loaded
+	 * @var array $mLoadedLanguages
 	 */
-	protected static $mAdaptiveDataAge = 604800; // Is 7*24*3600
-
-	/**
-	 * Filter the tail of less used messages that are requested more seldom
-	 * than this factor times the number of request of most requested message.
-	 * These messages are not loaded in the default set, but are still cached
-	 * individually on demand with the normal cache expiry time.
-	 */
-	protected static $mAdaptiveInclusionThreshold = 0.05;
+	protected $mLoadedLanguages = array();
 
 	/**
 	 * Singleton instance
 	 *
-	 * @var MessageCache
+	 * @var MessageCache $instance
 	 */
 	private static $instance;
 
 	/**
-	 * @var bool
+	 * @var bool $mInParser
 	 */
 	protected $mInParser = false;
 
@@ -95,12 +99,16 @@ class MessageCache {
 	 * Get the signleton instance of this class
 	 *
 	 * @since 1.18
-	 * @return MessageCache object
+	 * @return MessageCache
 	 */
 	public static function singleton() {
 		if ( is_null( self::$instance ) ) {
 			global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
-			self::$instance = new self( wfGetMessageCacheStorage(), $wgUseDatabaseMessages, $wgMsgCacheExpiry );
+			self::$instance = new self(
+				wfGetMessageCacheStorage(),
+				$wgUseDatabaseMessages,
+				$wgMsgCacheExpiry
+			);
 		}
 		return self::$instance;
 	}
@@ -114,6 +122,11 @@ class MessageCache {
 		self::$instance = null;
 	}
 
+	/**
+	 * @param ObjectCache $memCached A cache instance. If none, fall back to CACHE_NONE.
+	 * @param bool $useDB
+	 * @param int $expiry Lifetime for cache. @see $mExpiry.
+	 */
 	function __construct( $memCached, $useDB, $expiry ) {
 		if ( !$memCached ) {
 			$memCached = wfGetCache( CACHE_NONE );
@@ -139,15 +152,13 @@ class MessageCache {
 
 	/**
 	 * 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 bool on failure.
+	 * @param string $hash the hash of contents, to check validity.
+	 * @param Mixed $code Optional language code, see documenation of load().
+	 * @return array The cache array
 	 */
-	function loadFromLocal( $hash, $code ) {
-		global $wgCacheDirectory, $wgLocalMessageCacheSerialized;
+	function getLocalCache( $hash, $code ) {
+		global $wgCacheDirectory;
 
 		$filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
 
@@ -159,31 +170,19 @@ class MessageCache {
 			return false; // No cache file
 		}
 
-		if ( $wgLocalMessageCacheSerialized ) {
-			// Check to see if the file has the hash specified
-			$localHash = fread( $file, 32 );
-			if ( $hash === $localHash ) {
-				// All good, get the rest of it
-				$serialized = '';
-				while ( !feof( $file ) ) {
-					$serialized .= fread( $file, 100000 );
-				}
-				fclose( $file );
-				return $this->setCache( unserialize( $serialized ), $code );
-			} else {
-				fclose( $file );
-				return false; // Wrong hash
+		// Check to see if the file has the hash specified
+		$localHash = fread( $file, 32 );
+		if ( $hash === $localHash ) {
+			// All good, get the rest of it
+			$serialized = '';
+			while ( !feof( $file ) ) {
+				$serialized .= fread( $file, 100000 );
 			}
+			fclose( $file );
+			return unserialize( $serialized );
 		} else {
-			$localHash = substr( fread( $file, 40 ), 8 );
 			fclose( $file );
-			if ( $hash != $localHash ) {
-				return false; // Wrong hash
-			}
-
-			# Require overwrites the member variable or just shadows it?
-			require( $filename );
-			return $this->setCache( $this->mCache, $code );
+			return false; // Wrong hash
 		}
 	}
 
@@ -212,55 +211,6 @@ class MessageCache {
 		wfRestoreWarnings();
 	}
 
-	function saveToScript( $array, $hash, $code ) {
-		global $wgCacheDirectory;
-
-		$filename = "$wgCacheDirectory/messages-" . wfWikiID() . "-$code";
-		$tempFilename = $filename . '.tmp';
-		wfMkdirParents( $wgCacheDirectory, null, __METHOD__ ); // might fail
-
-		wfSuppressWarnings();
-		$file = fopen( $tempFilename, 'w' );
-		wfRestoreWarnings();
-
-		if ( !$file ) {
-			wfDebug( "Unable to open local cache file for writing\n" );
-			return;
-		}
-
-		fwrite( $file, "<?php\n//$hash\n\n \$this->mCache = array(" );
-
-		foreach ( $array as $key => $message ) {
-			$key = $this->escapeForScript( $key );
-			$message = $this->escapeForScript( $message );
-			fwrite( $file, "'$key' => '$message',\n" );
-		}
-
-		fwrite( $file, ");\n?>" );
-		fclose( $file);
-		rename( $tempFilename, $filename );
-	}
-
-	function escapeForScript( $string ) {
-		$string = str_replace( '\\', '\\\\', $string );
-		$string = str_replace( '\'', '\\\'', $string );
-		return $string;
-	}
-
-	/**
-	 * Set the cache to $cache, if it is valid. Otherwise set the cache to false.
-	 *
-	 * @return bool
-	 */
-	function setCache( $cache, $code ) {
-		if ( isset( $cache['VERSION'] ) && $cache['VERSION'] == MSG_CACHE_VERSION ) {
-			$this->mCache[$code] = $cache;
-			return true;
-		} else {
-			return false;
-		}
-	}
-
 	/**
 	 * Loads messages from caches or from database in this order:
 	 * (1) local message cache (if $wgUseLocalMessageCache is enabled)
@@ -277,13 +227,14 @@ class MessageCache {
 	 * or false if populating empty cache fails. Also returns true if MessageCache
 	 * is disabled.
 	 *
-	 * @param $code String: language to which load messages
+	 * @param bool|String $code Language to which load messages
+	 * @throws MWException
 	 * @return bool
 	 */
 	function load( $code = false ) {
 		global $wgUseLocalMessageCache;
 
-		if( !is_string( $code ) ) {
+		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" );
@@ -308,77 +259,161 @@ class MessageCache {
 		# Loading code starts
 		wfProfileIn( __METHOD__ );
 		$success = false; # Keep track of success
+		$staleCache = false; # a cache array with expired data, or false if none has been loaded
 		$where = array(); # Debug info, delayed to avoid spamming debug log too much
 		$cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
 
-		# (1) local cache
+		# 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?)
+		# out of date (e.g. due to replace() on some other server)
 		if ( $wgUseLocalMessageCache ) {
 			wfProfileIn( __METHOD__ . '-fromlocal' );
 
 			$hash = $this->mMemc->get( wfMemcKey( 'messages', $code, 'hash' ) );
 			if ( $hash ) {
-				$success = $this->loadFromLocal( $hash, $code );
-				if ( $success ) $where[] = 'got from local cache';
+				$cache = $this->getLocalCache( $hash, $code );
+				if ( !$cache ) {
+					$where[] = 'local cache is empty or has the wrong hash';
+				} elseif ( $this->isCacheExpired( $cache ) ) {
+					$where[] = 'local cache is expired';
+					$staleCache = $cache;
+				} else {
+					$where[] = 'got from local cache';
+					$success = true;
+					$this->mCache[$code] = $cache;
+				}
 			}
 			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( __METHOD__ . '-fromcache' );
-		}
+			# Try the global cache. If it is empty, try to acquire a lock. If
+			# the lock can't be acquired, wait for the other thread to finish
+			# and then try the global cache a second time.
+			for ( $failedAttempts = 0; $failedAttempts < 2; $failedAttempts++ ) {
+				wfProfileIn( __METHOD__ . '-fromcache' );
+				$cache = $this->mMemc->get( $cacheKey );
+				if ( !$cache ) {
+					$where[] = 'global cache is empty';
+				} elseif ( $this->isCacheExpired( $cache ) ) {
+					$where[] = 'global cache is expired';
+					$staleCache = $cache;
+				} else {
+					$where[] = 'got from global cache';
+					$this->mCache[$code] = $cache;
+					$this->saveToCaches( $cache, 'local-only', $code );
+					$success = true;
+				}
+
+				wfProfileOut( __METHOD__ . '-fromcache' );
 
-		# (3)
-		# Nothing in caches... so we need create one and store it in caches
-		if ( !$success ) {
-			$where[] = 'cache is empty';
-			$where[] = 'loading from database';
-
-			$this->lock( $cacheKey );
-
-			# Limit the concurrency of loadFromDB to a single process
-			# This prevents the site from going down when the cache expires
-			$statusKey = wfMemcKey( 'messages', $code, 'status' );
-			$success = $this->mMemc->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT );
-			if ( $success ) {
-				$cache = $this->loadFromDB( $code );
-				$success = $this->setCache( $cache, $code );
-			}
-			if ( $success ) {
-				$success = $this->saveToCaches( $cache, true, $code );
 				if ( $success ) {
-					$this->mMemc->delete( $statusKey );
+					# Done, no need to retry
+					break;
+				}
+
+				# We need to call loadFromDB. Limit the concurrency to a single
+				# process. This prevents the site from going down when the cache
+				# expires.
+				$statusKey = wfMemcKey( 'messages', $code, 'status' );
+				$acquired = $this->mMemc->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT );
+				if ( $acquired ) {
+					# Unlock the status key if there is an exception
+					$that = $this;
+					$statusUnlocker = new ScopedCallback( function () use ( $that, $statusKey ) {
+						$that->mMemc->delete( $statusKey );
+					} );
+
+					# Now let's regenerate
+					$where[] = 'loading from database';
+
+					# Lock the cache to prevent conflicting writes
+					# If this lock fails, it doesn't really matter, it just means the
+					# write is potentially non-atomic, e.g. the results of a replace()
+					# may be discarded.
+					if ( $this->lock( $cacheKey ) ) {
+						$mainUnlocker = new ScopedCallback( function () use ( $that, $cacheKey ) {
+							$that->unlock( $cacheKey );
+						} );
+					} else {
+						$mainUnlocker = null;
+						$where[] = 'could not acquire main lock';
+					}
+
+					$cache = $this->loadFromDB( $code );
+					$this->mCache[$code] = $cache;
+					$success = true;
+					$saveSuccess = $this->saveToCaches( $cache, 'all', $code );
+
+					# Unlock
+					ScopedCallback::consume( $mainUnlocker );
+					ScopedCallback::consume( $statusUnlocker );
+
+					if ( !$saveSuccess ) {
+						# Cache save has failed.
+						# There are two main scenarios where this could be a problem:
+						#
+						#   - The cache is more than the maximum size (typically
+						#     1MB compressed).
+						#
+						#   - Memcached has no space remaining in the relevant slab
+						#     class. This is unlikely with recent versions of
+						#     memcached.
+						#
+						# Either way, if there is a local cache, nothing bad will
+						# happen. If there is no local cache, disabling the message
+						# cache for all requests avoids incurring a loadFromDB()
+						# overhead on every request, and thus saves the wiki from
+						# complete downtime under moderate traffic conditions.
+						if ( !$wgUseLocalMessageCache ) {
+							$this->mMemc->set( $statusKey, 'error', 60 * 5 );
+							$where[] = 'could not save cache, disabled globally for 5 minutes';
+						} else {
+							$where[] = "could not save global cache";
+						}
+					}
+
+					# Load from DB complete, no need to retry
+					break;
+				} elseif ( $staleCache ) {
+					# Use the stale cache while some other thread constructs the new one
+					$where[] = 'using stale cache';
+					$this->mCache[$code] = $staleCache;
+					$success = true;
+					break;
+				} elseif ( $failedAttempts > 0 ) {
+					# Already retried once, still failed, so don't do another lock/unlock cycle
+					# This case will typically be hit if memcached is down, or if
+					# loadFromDB() takes longer than MSG_WAIT_TIMEOUT
+					$where[] = "could not acquire status key.";
+					break;
 				} else {
-					$this->mMemc->set( $statusKey, 'error', 60 * 5 );
-					wfDebug( "MemCached set error in MessageCache: restart memcached server!\n" );
+					$status = $this->mMemc->get( $statusKey );
+					if ( $status === 'error' ) {
+						# Disable cache
+						break;
+					} else {
+						# Wait for the other thread to finish, then retry
+						$where[] = 'waited for other thread to complete';
+						$this->lock( $cacheKey );
+						$this->unlock( $cacheKey );
+					}
 				}
 			}
-			$this->unlock($cacheKey);
 		}
 
 		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;
+			# This used to throw an exception, but that led to nasty side effects like
+			# the whole wiki being instantly down if the memcached server died
 		} else {
 			# All good, just record the success
-			$info = implode( ', ', $where );
-			wfDebug( __METHOD__ . ": Loading $code... $info\n" );
 			$this->mLoadedLanguages[$code] = true;
 		}
+		$info = implode( ', ', $where );
+		wfDebug( __METHOD__ . ": Loading $code... $info\n" );
 		wfProfileOut( __METHOD__ );
 		return $success;
 	}
@@ -388,8 +423,8 @@ class MessageCache {
 	 * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
 	 * on-demand from the database later.
 	 *
-	 * @param $code String: language code.
-	 * @return Array: loaded messages for storing in caches.
+	 * @param string $code Language code.
+	 * @return array Loaded messages for storing in caches.
 	 */
 	function loadFromDB( $code ) {
 		wfProfileIn( __METHOD__ );
@@ -404,19 +439,20 @@ class MessageCache {
 		);
 
 		$mostused = array();
-		if ( $wgAdaptiveMessageCache ) {
-			$mostused = $this->getMostUsedMessages();
-			if ( $code !== $wgLanguageCode ) {
-				foreach ( $mostused as $key => $value ) {
-					$mostused[$key] = "$value/$code";
-				}
+		if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
+			if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
+				$this->load( $wgLanguageCode );
+			}
+			$mostused = array_keys( $this->mCache[$wgLanguageCode] );
+			foreach ( $mostused as $key => $value ) {
+				$mostused[$key] = "$value/$code";
 			}
 		}
 
 		if ( count( $mostused ) ) {
 			$conds['page_title'] = $mostused;
 		} elseif ( $code !== $wgLanguageCode ) {
-			$conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), "/$code" );
+			$conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
 		} else {
 			# Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
 			# other than language code.
@@ -448,24 +484,23 @@ class MessageCache {
 
 		foreach ( $res as $row ) {
 			$text = Revision::getRevisionText( $row );
-			if( $text === false ) {
+			if ( $text === false ) {
 				// Failed to fetch data; possible ES errors?
 				// Store a marker to fetch on-demand as a workaround...
 				$entry = '!TOO BIG';
-				wfDebugLog( 'MessageCache', __METHOD__ . ": failed to load message page text for {$row->page_title} ($code)" );
+				wfDebugLog(
+					'MessageCache',
+					__METHOD__
+						. ": failed to load message page text for {$row->page_title} ($code)"
+				);
 			} else {
 				$entry = ' ' . $text;
 			}
 			$cache[$row->page_title] = $entry;
 		}
 
-		foreach ( $mostused as $key ) {
-			if ( !isset( $cache[$key] ) ) {
-				$cache[$key] = '!NONEXISTENT';
-			}
-		}
-
 		$cache['VERSION'] = MSG_CACHE_VERSION;
+		$cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 		wfProfileOut( __METHOD__ );
 		return $cache;
 	}
@@ -473,8 +508,8 @@ class MessageCache {
 	/**
 	 * 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.
+	 * @param string $title Name of the page changed.
+	 * @param mixed $text New contents of the page.
 	 */
 	public function replace( $title, $text ) {
 		global $wgMaxMsgCacheEntrySize;
@@ -507,12 +542,12 @@ class MessageCache {
 		}
 
 		# Update caches
-		$this->saveToCaches( $this->mCache[$code], true, $code );
+		$this->saveToCaches( $this->mCache[$code], 'all', $code );
 		$this->unlock( $cacheKey );
 
 		// Also delete cached sidebar... just in case it is affected
 		$codes = array( $code );
-		if ( $code === 'en'  ) {
+		if ( $code === 'en' ) {
 			// Delete all sidebars, like for example on action=purge on the
 			// sidebar messages
 			$codes = array_keys( Language::fetchLanguageNames() );
@@ -534,21 +569,41 @@ class MessageCache {
 	}
 
 	/**
+	 * Is the given cache array expired due to time passing or a version change?
+	 *
+	 * @param $cache
+	 * @return bool
+	 */
+	protected function isCacheExpired( $cache ) {
+		if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
+			return true;
+		}
+		if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
+			return true;
+		}
+		if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
+			return true;
+		}
+		return false;
+	}
+
+	/**
 	 * Shortcut to update caches.
 	 *
-	 * @param $cache Array: cached messages with a version.
-	 * @param $memc Bool: Wether to update or not memcache.
-	 * @param $code String: Language code.
-	 * @return bool on somekind of error.
+	 * @param array $cache Cached messages with a version.
+	 * @param string $dest Either "local-only" to save to local caches only
+	 *   or "all" to save to all caches.
+	 * @param string|bool $code Language code (default: false)
+	 * @return bool
 	 */
-	protected function saveToCaches( $cache, $memc = true, $code = false ) {
+	protected function saveToCaches( $cache, $dest, $code = false ) {
 		wfProfileIn( __METHOD__ );
-		global $wgUseLocalMessageCache, $wgLocalMessageCacheSerialized;
+		global $wgUseLocalMessageCache;
 
 		$cacheKey = wfMemcKey( 'messages', $code );
 
-		if ( $memc ) {
-			$success = $this->mMemc->set( $cacheKey, $cache, $this->mExpiry );
+		if ( $dest === 'all' ) {
+			$success = $this->mMemc->set( $cacheKey, $cache );
 		} else {
 			$success = true;
 		}
@@ -557,12 +612,8 @@ class MessageCache {
 		if ( $wgUseLocalMessageCache ) {
 			$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 );
-			}
+			$this->mMemc->set( wfMemcKey( 'messages', $code, 'hash' ), $hash );
+			$this->saveToLocal( $serialized, $hash, $code );
 		}
 
 		wfProfileOut( __METHOD__ );
@@ -570,19 +621,35 @@ class MessageCache {
 	}
 
 	/**
-	 * Represents a write lock on the messages key
+	 * Represents a write lock on the messages key.
 	 *
-	 * @param $key string
+	 * Will retry MessageCache::MSG_WAIT_TIMEOUT times, each operations having
+	 * a timeout of MessageCache::MSG_LOCK_TIMEOUT.
 	 *
+	 * @param string $key
 	 * @return Boolean: success
 	 */
 	function lock( $key ) {
 		$lockKey = $key . ':lock';
-		for ( $i = 0; $i < MSG_WAIT_TIMEOUT && !$this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT ); $i++ ) {
+		$acquired = false;
+		$testDone = false;
+		for ( $i = 0; $i < MSG_WAIT_TIMEOUT && !$acquired; $i++ ) {
+			$acquired = $this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT );
+			if ( $acquired ) {
+				break;
+			}
+
+			# Fail fast if memcached is totally down
+			if ( !$testDone ) {
+				$testDone = true;
+				if ( !$this->mMemc->set( wfMemcKey( 'test' ), 'test', 1 ) ) {
+					break;
+				}
+			}
 			sleep( 1 );
 		}
 
-		return $i >= MSG_WAIT_TIMEOUT;
+		return $acquired;
 	}
 
 	function unlock( $key ) {
@@ -593,50 +660,62 @@ class MessageCache {
 	/**
 	 * Get a message from either the content language or the user language.
 	 *
-	 * @param $key String: the message cache key
-	 * @param $useDB Boolean: get the message from the DB, false to use only
-	 *               the localisation
-	 * @param $langcode String: code of the language to get the message for, if
-	 *                  it is a valid code create a language for that language,
-	 *                  if it is a string but not a valid code then make a basic
-	 *                  language object, if it is a false boolean then use the
-	 *                  current users language (as a fallback for the old
-	 *                  parameter functionality), or if it is a true boolean
-	 *                  then use the wikis content language (also as a
-	 *                  fallback).
-	 * @param $isFullKey Boolean: specifies whether $key is a two part key
+	 * First, assemble a list of languages to attempt getting the message from. This
+	 * chain begins with the requested language and its fallbacks and then continues with
+	 * the content language and its fallbacks. For each language in the chain, the following
+	 * process will occur (in this order):
+	 *  1. If a language-specific override, i.e., [[MW:msg/lang]], is available, use that.
+	 *     Note: for the content language, there is no /lang subpage.
+	 *  2. Fetch from the static CDB cache.
+	 *  3. If available, check the database for fallback language overrides.
+	 *
+	 * This process provides a number of guarantees. When changing this code, make sure all
+	 * of these guarantees are preserved.
+	 *  * If the requested language is *not* the content language, then the CDB cache for that
+	 *    specific language will take precedence over the root database page ([[MW:msg]]).
+	 *  * Fallbacks will be just that: fallbacks. A fallback language will never be reached if
+	 *    the message is available *anywhere* in the language for which it is a fallback.
+	 *
+	 * @param string $key the message key
+	 * @param bool $useDB If true, look for the message in the DB, false
+	 *                    to use only the compiled l10n cache.
+	 * @param bool|string|object $langcode Code of the language to get the message for.
+	 *        - If string and a valid code, will create a standard language object
+	 *        - If string but not a valid code, will create a basic language object
+	 *        - If boolean and false, create object from the current users language
+	 *        - If boolean and true, create object from the wikis content language
+	 *        - If language object, use it as given
+	 * @param bool $isFullKey specifies whether $key is a two part key
 	 *                   "msg/lang".
 	 *
-	 * @return string|bool
+	 * @throws MWException when given an invalid key
+	 * @return string|bool False if the message doesn't exist, otherwise the message (which can be empty)
 	 */
 	function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
-		global $wgLanguageCode, $wgContLang;
+		global $wgContLang;
 
-		if ( is_int( $key ) ) {
-			// "Non-string key given" exception sometimes happens for numerical strings that become ints somewhere on their way here
-			$key = strval( $key );
-		}
+		$section = new ProfileSection( __METHOD__ );
 
-		if ( !is_string( $key ) ) {
+		if ( is_int( $key ) ) {
+			// Fix numerical strings that somehow become ints
+			// on their way here
+			$key = (string)$key;
+		} elseif ( !is_string( $key ) ) {
 			throw new MWException( 'Non-string key given' );
-		}
-
-		if ( strval( $key ) === '' ) {
-			# Shortcut: the empty key is always missing
+		} elseif ( $key === '' ) {
+			// Shortcut: the empty key is always missing
 			return false;
 		}
 
-		$lang = wfGetLangObj( $langcode );
-		if ( !$lang ) {
-			throw new MWException( "Bad lang code $langcode given" );
+		// For full keys, get the language code from the key
+		$pos = strrpos( $key, '/' );
+		if ( $isFullKey && $pos !== false ) {
+			$langcode = substr( $key, $pos + 1 );
+			$key = substr( $key, 0, $pos );
 		}
 
-		$langcode = $lang->getCode();
-
-		$message = false;
-
-		# Normalise title-case input (with some inlining)
-		$lckey = str_replace( ' ', '_', $key );
+		// Normalise title-case input (with some inlining)
+		$lckey = strtr( $key, ' ', '_' );
 		if ( ord( $key ) < 128 ) {
 			$lckey[0] = strtolower( $lckey[0] );
 			$uckey = ucfirst( $lckey );
@@ -645,89 +724,160 @@ class MessageCache {
 			$uckey = $wgContLang->ucfirst( $lckey );
 		}
 
-		/**
-		 * Record each message request, but only once per request.
-		 * This information is not used unless $wgAdaptiveMessageCache
-		 * is enabled.
-		 */
-		$this->mRequestedMessages[$uckey] = true;
+		// Loop through each language in the fallback list until we find something useful
+		$lang = wfGetLangObj( $langcode );
+		$message = $this->getMessageFromFallbackChain( $lang, $lckey, $uckey, !$this->mDisable && $useDB );
 
-		# Try the MediaWiki namespace
-		if( !$this->mDisable && $useDB ) {
-			$title = $uckey;
-			if( !$isFullKey && ( $langcode != $wgLanguageCode ) ) {
-				$title .= '/' . $langcode;
+		// If we still have no message, maybe the key was in fact a full key so try that
+		if ( $message === false ) {
+			$parts = explode( '/', $lckey );
+			// We may get calls for things that are http-urls from sidebar
+			// Let's not load nonexistent languages for those
+			// They usually have more than one slash.
+			if ( count( $parts ) == 2 && $parts[1] !== '' ) {
+				$message = Language::getMessageFor( $parts[0], $parts[1] );
+				if ( $message === null ) {
+					$message = false;
+				}
 			}
-			$message = $this->getMsgFromNamespace( $title, $langcode );
 		}
 
-		# Try the array in the language object
-		if ( $message === false ) {
-			$message = $lang->getMessage( $lckey );
-			if ( is_null( $message ) ) {
-				$message = false;
+		// Post-processing if the message exists
+		if ( $message !== false ) {
+			// Fix whitespace
+			$message = str_replace(
+				array(
+					# Fix for trailing whitespace, removed by textarea
+					'&#32;',
+					# Fix for NBSP, converted to space by firefox
+					'&nbsp;',
+					'&#160;',
+				),
+				array(
+					' ',
+					"\xc2\xa0",
+					"\xc2\xa0"
+				),
+				$message
+			);
+		}
+
+		return $message;
+	}
+
+	/**
+	 * Given a language, try and fetch a message from that language, then the
+	 * fallbacks of that language, then the site language, then the fallbacks for the
+	 * site language.
+	 *
+	 * @param Language $lang Requested language
+	 * @param string $lckey Lowercase key for the message
+	 * @param string $uckey Uppercase key for the message
+	 * @param bool $useDB Whether to use the database
+	 *
+	 * @see MessageCache::get
+	 * @return string|bool The message, or false if not found
+	 */
+	protected function getMessageFromFallbackChain( $lang, $lckey, $uckey, $useDB ) {
+		global $wgLanguageCode, $wgContLang;
+
+		$langcode = $lang->getCode();
+		$message = false;
+
+		// First try the requested language.
+		if ( $useDB ) {
+			if ( $langcode === $wgLanguageCode ) {
+				// Messages created in the content language will not have the /lang extension
+				$message = $this->getMsgFromNamespace( $uckey, $langcode );
+			} else {
+				$message = $this->getMsgFromNamespace( "$uckey/$langcode", $langcode );
 			}
 		}
 
-		# Try the array of another language
-		if( $message === false ) {
-			$parts = explode( '/', $lckey );
-			# We may get calls for things that are http-urls from sidebar
-			# Let's not load nonexistent languages for those
-			# They usually have more than one slash.
-			if ( count( $parts ) == 2 && $parts[1] !== '' ) {
-				$message = Language::getMessageFor( $parts[0], $parts[1] );
-				if ( is_null( $message ) ) {
-					$message = false;
+		if ( $message !== false ) {
+			return $message;
+		}
+
+		// Check the CDB cache
+		$message = $lang->getMessage( $lckey );
+		if ( $message !== null ) {
+			return $message;
+		}
+
+		list( $fallbackChain, $siteFallbackChain ) = Language::getFallbacksIncludingSiteLanguage( $langcode );
+
+		// Next try checking the database for all of the fallback languages of the requested language.
+		if ( $useDB ) {
+			foreach ( $fallbackChain as $code ) {
+				if ( $code === $wgLanguageCode ) {
+					// Messages created in the content language will not have the /lang extension
+					$message = $this->getMsgFromNamespace( $uckey, $code );
+				} else {
+					$message = $this->getMsgFromNamespace( "$uckey/$code", $code );
+				}
+
+				if ( $message !== false ) {
+					// Found the message.
+					return $message;
 				}
 			}
 		}
 
-		# Is this a custom message? Try the default language in the db...
-		if( ( $message === false || $message === '-' ) &&
-			!$this->mDisable && $useDB &&
-			!$isFullKey && ( $langcode != $wgLanguageCode ) ) {
+		// Now try checking the site language.
+		if ( $useDB ) {
 			$message = $this->getMsgFromNamespace( $uckey, $wgLanguageCode );
+			if ( $message !== false ) {
+				return $message;
+			}
 		}
 
-		# Final fallback
-		if( $message === false ) {
-			return false;
+		$message = $wgContLang->getMessage( $lckey );
+		if ( $message !== null ) {
+			return $message;
 		}
 
-		# Fix whitespace
-		$message = strtr( $message,
-			array(
-				# Fix for trailing whitespace, removed by textarea
-				'&#32;' => ' ',
-				# Fix for NBSP, converted to space by firefox
-				'&nbsp;' => "\xc2\xa0",
-				'&#160;' => "\xc2\xa0",
-			) );
+		// Finally try the DB for the site language's fallbacks.
+		if ( $useDB ) {
+			foreach ( $siteFallbackChain as $code ) {
+				$message = $this->getMsgFromNamespace( "$uckey/$code", $code );
+				if ( $message === false && $code === $wgLanguageCode ) {
+					// Messages created in the content language will not have the /lang extension
+					$message = $this->getMsgFromNamespace( $uckey, $code );
+				}
 
-		return $message;
+				if ( $message !== false ) {
+					// Found the message.
+					return $message;
+				}
+			}
+		}
+
+		return false;
 	}
 
 	/**
 	 * Get a message from the MediaWiki namespace, with caching. The key must
 	 * first be converted to two-part lang/msg form if necessary.
 	 *
-	 * @param $title String: Message cache key with initial uppercase letter.
-	 * @param $code String: code denoting the language to try.
+	 * Unlike self::get(), this function doesn't resolve fallback chains, and
+	 * some callers require this behavior. LanguageConverter::parseCachedTable()
+	 * and self::get() are some examples in core.
 	 *
-	 * @return string|bool False on failure
+	 * @param string $title Message cache key with initial uppercase letter.
+	 * @param string $code Code denoting the language to try.
+	 * @return string|bool The message, or false if it does not exist or on error
 	 */
 	function getMsgFromNamespace( $title, $code ) {
-		global $wgAdaptiveMessageCache;
-
 		$this->load( $code );
 		if ( isset( $this->mCache[$code][$title] ) ) {
 			$entry = $this->mCache[$code][$title];
 			if ( substr( $entry, 0, 1 ) === ' ' ) {
-				return substr( $entry, 1 );
+				// The message exists, so make sure a string
+				// is returned.
+				return (string)substr( $entry, 1 );
 			} elseif ( $entry === '!NONEXISTENT' ) {
 				return false;
-			} elseif( $entry === '!TOO BIG' ) {
+			} elseif ( $entry === '!TOO BIG' ) {
 				// Fall through and try invididual message cache below
 			}
 		} else {
@@ -738,15 +888,7 @@ class MessageCache {
 				return $message;
 			}
 
-			/**
-			 * If message cache is in normal mode, it is guaranteed
-			 * (except bugs) that there is always entry (or placeholder)
-			 * in the cache if message exists. Thus we can do minor
-			 * performance improvement and return false early.
-			 */
-			if ( !$wgAdaptiveMessageCache ) {
-				return false;
-			}
+			return false;
 		}
 
 		# Try the individual message cache
@@ -755,7 +897,9 @@ class MessageCache {
 		if ( $entry ) {
 			if ( substr( $entry, 0, 1 ) === ' ' ) {
 				$this->mCache[$code][$title] = $entry;
-				return substr( $entry, 1 );
+				// The message exists, so make sure a string
+				// is returned.
+				return (string)substr( $entry, 1 );
 			} elseif ( $entry === '!NONEXISTENT' ) {
 				$this->mCache[$code][$title] = '!NONEXISTENT';
 				return false;
@@ -770,16 +914,39 @@ class MessageCache {
 			Title::makeTitle( NS_MEDIAWIKI, $title ), false, Revision::READ_LATEST
 		);
 		if ( $revision ) {
-			$message = $revision->getText();
-			if ($message === false) {
+			$content = $revision->getContent();
+			if ( !$content ) {
 				// A possibly temporary loading failure.
-				wfDebugLog( 'MessageCache', __METHOD__ . ": failed to load message page text for {$title} ($code)" );
+				wfDebugLog(
+					'MessageCache',
+					__METHOD__ . ": failed to load message page text for {$title} ($code)"
+				);
+				$message = null; // no negative caching
 			} else {
-				$this->mCache[$code][$title] = ' ' . $message;
-				$this->mMemc->set( $titleKey, ' ' . $message, $this->mExpiry );
+				// XXX: Is this the right way to turn a Content object into a message?
+				// NOTE: $content is typically either WikitextContent, JavaScriptContent or
+				//       CssContent. MessageContent is *not* used for storing messages, it's
+				//       only used for wrapping them when needed.
+				$message = $content->getWikitextForTransclusion();
+
+				if ( $message === false || $message === null ) {
+					wfDebugLog(
+						'MessageCache',
+						__METHOD__ . ": message content doesn't provide wikitext "
+							. "(content model: " . $content->getContentHandler() . ")"
+					);
+
+					$message = false; // negative caching
+				} else {
+					$this->mCache[$code][$title] = ' ' . $message;
+					$this->mMemc->set( $titleKey, ' ' . $message, $this->mExpiry );
+				}
 			}
 		} else {
-			$message = false;
+			$message = false; // negative caching
+		}
+
+		if ( $message === false ) { // negative caching
 			$this->mCache[$code][$title] = '!NONEXISTENT';
 			$this->mMemc->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
 		}
@@ -788,15 +955,15 @@ class MessageCache {
 	}
 
 	/**
-	 * @param $message string
-	 * @param $interface bool
-	 * @param $language
-	 * @param $title Title
+	 * @param string $message
+	 * @param bool $interface
+	 * @param string $language Language code
+	 * @param Title $title
 	 * @return string
 	 */
 	function transform( $message, $interface = false, $language = null, $title = null ) {
 		// Avoid creating parser if nothing to transform
-		if( strpos( $message, '{{' ) === false ) {
+		if ( strpos( $message, '{{' ) === false ) {
 			return $message;
 		}
 
@@ -840,14 +1007,16 @@ class MessageCache {
 	}
 
 	/**
-	 * @param $text string
-	 * @param $title Title
-	 * @param $linestart bool
-	 * @param $interface bool
-	 * @param $language
-	 * @return ParserOutput
+	 * @param string $text
+	 * @param Title $title
+	 * @param bool $linestart Whether or not this is at the start of a line
+	 * @param bool $interface Whether this is an interface message
+	 * @param string $language Language code
+	 * @return ParserOutput|string
 	 */
-	public function parse( $text, $title = null, $linestart = true, $interface = false, $language = null  ) {
+	public function parse( $text, $title = null, $linestart = true,
+		$interface = false, $language = null
+	) {
 		if ( $this->mInParser ) {
 			return htmlspecialchars( $text );
 		}
@@ -890,7 +1059,7 @@ class MessageCache {
 	 */
 	function clear() {
 		$langs = Language::fetchLanguageNames( null, 'mw' );
-		foreach ( array_keys($langs) as $code ) {
+		foreach ( array_keys( $langs ) as $code ) {
 			# Global cache
 			$this->mMemc->delete( wfMemcKey( 'messages', $code ) );
 			# Invalidate all local caches
@@ -906,12 +1075,12 @@ class MessageCache {
 	public function figureMessage( $key ) {
 		global $wgLanguageCode;
 		$pieces = explode( '/', $key );
-		if( count( $pieces ) < 2 ) {
+		if ( count( $pieces ) < 2 ) {
 			return array( $key, $wgLanguageCode );
 		}
 
 		$lang = array_pop( $pieces );
-		if( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
+		if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
 			return array( $key, $wgLanguageCode );
 		}
 
@@ -919,88 +1088,12 @@ class MessageCache {
 		return array( $message, $lang );
 	}
 
-	public static function logMessages() {
-		wfProfileIn( __METHOD__ );
-		global $wgAdaptiveMessageCache;
-		if ( !$wgAdaptiveMessageCache || !self::$instance instanceof MessageCache ) {
-			wfProfileOut( __METHOD__ );
-			return;
-		}
-
-		$cachekey = wfMemckey( 'message-profiling' );
-		$cache = wfGetCache( CACHE_DB );
-		$data = $cache->get( $cachekey );
-
-		if ( !$data ) {
-			$data = array();
-		}
-
-		$age = self::$mAdaptiveDataAge;
-		$filterDate = substr( wfTimestamp( TS_MW, time() - $age ), 0, 8 );
-		foreach ( array_keys( $data ) as $key ) {
-			if ( $key < $filterDate ) {
-				unset( $data[$key] );
-			}
-		}
-
-		$index = substr( wfTimestampNow(), 0, 8 );
-		if ( !isset( $data[$index] ) ) {
-			$data[$index] = array();
-		}
-
-		foreach ( self::$instance->mRequestedMessages as $message => $_ ) {
-			if ( !isset( $data[$index][$message] ) ) {
-				$data[$index][$message] = 0;
-			}
-			$data[$index][$message]++;
-		}
-
-		$cache->set( $cachekey, $data );
-		wfProfileOut( __METHOD__ );
-	}
-
-	/**
-	 * @return array
-	 */
-	public function getMostUsedMessages() {
-		wfProfileIn( __METHOD__ );
-		$cachekey = wfMemcKey( 'message-profiling' );
-		$cache = wfGetCache( CACHE_DB );
-		$data = $cache->get( $cachekey );
-		if ( !$data ) {
-			wfProfileOut( __METHOD__ );
-			return array();
-		}
-
-		$list = array();
-
-		foreach( $data as $messages ) {
-			foreach( $messages as $message => $count ) {
-				$key = $message;
-				if ( !isset( $list[$key] ) ) {
-					$list[$key] = 0;
-				}
-				$list[$key] += $count;
-			}
-		}
-
-		$max = max( $list );
-		foreach ( $list as $message => $count ) {
-			if ( $count < intval( $max * self::$mAdaptiveInclusionThreshold ) ) {
-				unset( $list[$message] );
-			}
-		}
-
-		wfProfileOut( __METHOD__ );
-		return array_keys( $list );
-	}
-
 	/**
 	 * Get all message keys stored in the message cache for a given language.
 	 * If $code is the content language code, this will return all message keys
 	 * for which MediaWiki:msgkey exists. If $code is another language code, this
 	 * will ONLY return message keys for which MediaWiki:msgkey/$code exists.
-	 * @param $code string
+	 * @param string $code Language code
 	 * @return array of message keys (strings)
 	 */
 	public function getAllMessageKeys( $code ) {
@@ -1010,9 +1103,12 @@ class MessageCache {
 			// Apparently load() failed
 			return null;
 		}
-		$cache = $this->mCache[$code]; // Copy the cache
-		unset( $cache['VERSION'] ); // Remove the VERSION key
-		$cache = array_diff( $cache, array( '!NONEXISTENT' ) ); // Remove any !NONEXISTENT keys
+		// Remove administrative keys
+		$cache = $this->mCache[$code];
+		unset( $cache['VERSION'] );
+		unset( $cache['EXPIRY'] );
+		// Remove any !NONEXISTENT keys
+		$cache = array_diff( $cache, array( '!NONEXISTENT' ) );
 		// Keys may appear with a capital first letter. lcfirst them.
 		return array_map( array( $wgContLang, 'lcfirst' ), array_keys( $cache ) );
 	}
diff --git a/includes/cache/ProcessCacheLRU.php b/includes/cache/ProcessCacheLRU.php
index f215ebd8..76c76f37 100644
--- a/includes/cache/ProcessCacheLRU.php
+++ b/includes/cache/ProcessCacheLRU.php
@@ -28,6 +28,8 @@
 class ProcessCacheLRU {
 	/** @var Array */
 	protected $cache = array(); // (key => prop => value)
+	/** @var Array */
+	protected $cacheTimes = array(); // (key => prop => UNIX timestamp)
 
 	protected $maxCacheKeys; // integer; max entries
 
@@ -44,7 +46,7 @@ class ProcessCacheLRU {
 
 	/**
 	 * Set a property field for a cache entry.
-	 * This will prune the cache if it gets too large.
+	 * This will prune the cache if it gets too large based on LRU.
 	 * If the item is already set, it will be pushed to the top of the cache.
 	 *
 	 * @param $key string
@@ -57,9 +59,12 @@ class ProcessCacheLRU {
 			$this->ping( $key ); // push to top
 		} elseif ( count( $this->cache ) >= $this->maxCacheKeys ) {
 			reset( $this->cache );
-			unset( $this->cache[key( $this->cache )] );
+			$evictKey = key( $this->cache );
+			unset( $this->cache[$evictKey] );
+			unset( $this->cacheTimes[$evictKey] );
 		}
 		$this->cache[$key][$prop] = $value;
+		$this->cacheTimes[$key][$prop] = time();
 	}
 
 	/**
@@ -67,10 +72,14 @@ class ProcessCacheLRU {
 	 *
 	 * @param $key string
 	 * @param $prop string
+	 * @param $maxAge integer Ignore items older than this many seconds (since 1.21)
 	 * @return bool
 	 */
-	public function has( $key, $prop ) {
-		return isset( $this->cache[$key][$prop] );
+	public function has( $key, $prop, $maxAge = 0 ) {
+		if ( isset( $this->cache[$key][$prop] ) ) {
+			return ( $maxAge <= 0 || ( time() - $this->cacheTimes[$key][$prop] ) <= $maxAge );
+		}
+		return false;
 	}
 
 	/**
@@ -100,9 +109,11 @@ class ProcessCacheLRU {
 	public function clear( $keys = null ) {
 		if ( $keys === null ) {
 			$this->cache = array();
+			$this->cacheTimes = array();
 		} else {
 			foreach ( (array)$keys as $key ) {
 				unset( $this->cache[$key] );
+				unset( $this->cacheTimes[$key] );
 			}
 		}
 	}
diff --git a/includes/cache/ResourceFileCache.php b/includes/cache/ResourceFileCache.php
index 61f1e8c3..2ad7b853 100644
--- a/includes/cache/ResourceFileCache.php
+++ b/includes/cache/ResourceFileCache.php
@@ -29,7 +29,7 @@
 class ResourceFileCache extends FileCacheBase {
 	protected $mCacheWorthy;
 
-	/* @TODO: configurable? */
+	/* @todo configurable? */
 	const MISS_THRESHOLD = 360; // 6/min * 60 min
 
 	/**
diff --git a/includes/cache/SquidUpdate.php b/includes/cache/SquidUpdate.php
index 423e3884..71afeba9 100644
--- a/includes/cache/SquidUpdate.php
+++ b/includes/cache/SquidUpdate.php
@@ -26,32 +26,42 @@
  * @ingroup Cache
  */
 class SquidUpdate {
-	var $urlArr, $mMaxTitles;
 
 	/**
-	 * @param $urlArr array
-	 * @param $maxTitles bool|int
+	 * Collection of URLs to purge.
+	 * @var array
 	 */
-	function __construct( $urlArr = array(), $maxTitles = false ) {
+	protected $urlArr;
+
+	/**
+	 * @param array $urlArr Collection of URLs to purge
+	 * @param bool|int $maxTitles Maximum number of unique URLs to purge
+	 */
+	public function __construct( $urlArr = array(), $maxTitles = false ) {
 		global $wgMaxSquidPurgeTitles;
 		if ( $maxTitles === false ) {
-			$this->mMaxTitles = $wgMaxSquidPurgeTitles;
-		} else {
-			$this->mMaxTitles = $maxTitles;
+			$maxTitles = $wgMaxSquidPurgeTitles;
 		}
-		$urlArr = array_unique( $urlArr ); // Remove duplicates
-		if ( count( $urlArr ) > $this->mMaxTitles ) {
-			$urlArr = array_slice( $urlArr, 0, $this->mMaxTitles );
+
+		// Remove duplicate URLs from list
+		$urlArr = array_unique( $urlArr );
+		if ( count( $urlArr ) > $maxTitles ) {
+			// Truncate to desired maximum URL count
+			$urlArr = array_slice( $urlArr, 0, $maxTitles );
 		}
 		$this->urlArr = $urlArr;
 	}
 
 	/**
-	 * @param $title Title
+	 * Create a SquidUpdate from the given Title object.
 	 *
+	 * The resulting SquidUpdate will purge the given Title's URLs as well as
+	 * the pages that link to it. Capped at $wgMaxSquidPurgeTitles total URLs.
+	 *
+	 * @param Title $title
 	 * @return SquidUpdate
 	 */
-	static function newFromLinksTo( &$title ) {
+	public static function newFromLinksTo( Title $title ) {
 		global $wgMaxSquidPurgeTitles;
 		wfProfileIn( __METHOD__ );
 
@@ -61,13 +71,13 @@ class SquidUpdate {
 			array( 'page_namespace', 'page_title' ),
 			array(
 				'pl_namespace' => $title->getNamespace(),
-				'pl_title'     => $title->getDBkey(),
+				'pl_title' => $title->getDBkey(),
 				'pl_from=page_id' ),
 			__METHOD__ );
 		$blurlArr = $title->getSquidURLs();
-		if ( $dbr->numRows( $res ) <= $wgMaxSquidPurgeTitles ) {
+		if ( $res->numRows() <= $wgMaxSquidPurgeTitles ) {
 			foreach ( $res as $BL ) {
-				$tobj = Title::makeTitle( $BL->page_namespace, $BL->page_title ) ;
+				$tobj = Title::makeTitle( $BL->page_namespace, $BL->page_title );
 				$blurlArr[] = $tobj->getInternalURL();
 			}
 		}
@@ -79,12 +89,11 @@ class SquidUpdate {
 	/**
 	 * Create a SquidUpdate from an array of Title objects, or a TitleArray object
 	 *
-	 * @param $titles array
-	 * @param $urlArr array
-	 *
+	 * @param array $titles
+	 * @param array $urlArr
 	 * @return SquidUpdate
 	 */
-	static function newFromTitles( $titles, $urlArr = array() ) {
+	public static function newFromTitles( $titles, $urlArr = array() ) {
 		global $wgMaxSquidPurgeTitles;
 		$i = 0;
 		foreach ( $titles as $title ) {
@@ -97,20 +106,19 @@ class SquidUpdate {
 	}
 
 	/**
-	 * @param $title Title
-	 *
+	 * @param Title $title
 	 * @return SquidUpdate
 	 */
-	static function newSimplePurge( &$title ) {
+	public static function newSimplePurge( Title $title ) {
 		$urlArr = $title->getSquidURLs();
 		return new SquidUpdate( $urlArr );
 	}
 
 	/**
-	 * Purges the list of URLs passed to the constructor
+	 * Purges the list of URLs passed to the constructor.
 	 */
-	function doUpdate() {
-		SquidUpdate::purge( $this->urlArr );
+	public function doUpdate() {
+		self::purge( $this->urlArr );
 	}
 
 	/**
@@ -119,25 +127,30 @@ class SquidUpdate {
 	 * (example: $urlArr[] = 'http://my.host/something')
 	 * XXX report broken Squids per mail or log
 	 *
-	 * @param $urlArr array
-	 * @return void
+	 * @param array $urlArr List of full URLs to purge
 	 */
-	static function purge( $urlArr ) {
-		global $wgSquidServers, $wgHTCPMulticastRouting;
+	public static function purge( $urlArr ) {
+		global $wgSquidServers, $wgHTCPRouting;
 
-		if( !$urlArr ) {
+		if ( !$urlArr ) {
 			return;
 		}
 
-		if ( $wgHTCPMulticastRouting ) {
-			SquidUpdate::HTCPPurge( $urlArr );
+		wfDebugLog( 'squid', __METHOD__ . ': ' . implode( ' ', $urlArr ) . "\n" );
+
+		if ( $wgHTCPRouting ) {
+			self::HTCPPurge( $urlArr );
 		}
 
 		wfProfileIn( __METHOD__ );
 
-		$urlArr = array_unique( $urlArr ); // Remove duplicates
-		$maxSocketsPerSquid = 8; //  socket cap per Squid
-		$urlsPerSocket = 400; // 400 seems to be a good tradeoff, opening a socket takes a while
+		// Remove duplicate URLs
+		$urlArr = array_unique( $urlArr );
+		// Maximum number of parallel connections per squid
+		$maxSocketsPerSquid = 8;
+		// Number of requests to send per socket
+		// 400 seems to be a good tradeoff, opening a socket takes a while
+		$urlsPerSocket = 400;
 		$socketsPerSquid = ceil( count( $urlArr ) / $urlsPerSocket );
 		if ( $socketsPerSquid > $maxSocketsPerSquid ) {
 			$socketsPerSquid = $maxSocketsPerSquid;
@@ -160,17 +173,20 @@ class SquidUpdate {
 	}
 
 	/**
+	 * Send Hyper Text Caching Protocol (HTCP) CLR requests.
+	 *
 	 * @throws MWException
-	 * @param $urlArr array
+	 * @param array $urlArr Collection of URLs to purge
 	 */
-	static function HTCPPurge( $urlArr ) {
-		global $wgHTCPMulticastRouting, $wgHTCPMulticastTTL;
+	public static function HTCPPurge( $urlArr ) {
+		global $wgHTCPRouting, $wgHTCPMulticastTTL;
 		wfProfileIn( __METHOD__ );
 
-		$htcpOpCLR = 4; // HTCP CLR
+		// HTCP CLR operation
+		$htcpOpCLR = 4;
 
 		// @todo FIXME: PHP doesn't support these socket constants (include/linux/in.h)
-		if( !defined( "IPPROTO_IP" ) ) {
+		if ( !defined( "IPPROTO_IP" ) ) {
 			define( "IPPROTO_IP", 0 );
 			define( "IP_MULTICAST_LOOP", 34 );
 			define( "IP_MULTICAST_TTL", 33 );
@@ -178,55 +194,73 @@ class SquidUpdate {
 
 		// pfsockopen doesn't work because we need set_sock_opt
 		$conn = socket_create( AF_INET, SOCK_DGRAM, SOL_UDP );
-		if ( $conn ) {
-			// Set socket options
-			socket_set_option( $conn, IPPROTO_IP, IP_MULTICAST_LOOP, 0 );
-			if ( $wgHTCPMulticastTTL != 1 )
-				socket_set_option( $conn, IPPROTO_IP, IP_MULTICAST_TTL,
-					$wgHTCPMulticastTTL );
-
-			$urlArr = array_unique( $urlArr ); // Remove duplicates
-			foreach ( $urlArr as $url ) {
-				if( !is_string( $url ) ) {
-					throw new MWException( 'Bad purge URL' );
-				}
-				$url = SquidUpdate::expand( $url );
-				$conf = self::getRuleForURL( $url, $wgHTCPMulticastRouting );
-				if ( !$conf ) {
-					wfDebug( "No HTCP rule configured for URL $url , skipping\n" );
-					continue;
-				}
-				if ( !isset( $conf['host'] ) || !isset( $conf['port'] ) ) {
+		if ( ! $conn ) {
+			$errstr = socket_strerror( socket_last_error() );
+			wfDebugLog( 'squid', __METHOD__ .
+				": Error opening UDP socket: $errstr\n" );
+			wfProfileOut( __METHOD__ );
+			return;
+		}
+
+		// Set socket options
+		socket_set_option( $conn, IPPROTO_IP, IP_MULTICAST_LOOP, 0 );
+		if ( $wgHTCPMulticastTTL != 1 ) {
+			// Set multicast time to live (hop count) option on socket
+			socket_set_option( $conn, IPPROTO_IP, IP_MULTICAST_TTL,
+				$wgHTCPMulticastTTL );
+		}
+
+		// Remove duplicate URLs from collection
+		$urlArr = array_unique( $urlArr );
+		foreach ( $urlArr as $url ) {
+			if ( !is_string( $url ) ) {
+				wfProfileOut( __METHOD__ );
+				throw new MWException( 'Bad purge URL' );
+			}
+			$url = self::expand( $url );
+			$conf = self::getRuleForURL( $url, $wgHTCPRouting );
+			if ( !$conf ) {
+				wfDebugLog( 'squid', __METHOD__ .
+					"No HTCP rule configured for URL {$url} , skipping\n" );
+				continue;
+			}
+
+			if ( isset( $conf['host'] ) && isset( $conf['port'] ) ) {
+				// Normalize single entries
+				$conf = array( $conf );
+			}
+			foreach ( $conf as $subconf ) {
+				if ( !isset( $subconf['host'] ) || !isset( $subconf['port'] ) ) {
+					wfProfileOut( __METHOD__ );
 					throw new MWException( "Invalid HTCP rule for URL $url\n" );
 				}
+			}
 
-				// Construct a minimal HTCP request diagram
-				// as per RFC 2756
-				// Opcode 'CLR', no response desired, no auth
-				$htcpTransID = rand();
+			// Construct a minimal HTCP request diagram
+			// as per RFC 2756
+			// Opcode 'CLR', no response desired, no auth
+			$htcpTransID = rand();
 
-				$htcpSpecifier = pack( 'na4na*na8n',
-					4, 'HEAD', strlen( $url ), $url,
-					8, 'HTTP/1.0', 0 );
+			$htcpSpecifier = pack( 'na4na*na8n',
+				4, 'HEAD', strlen( $url ), $url,
+				8, 'HTTP/1.0', 0 );
 
-				$htcpDataLen = 8 + 2 + strlen( $htcpSpecifier );
-				$htcpLen = 4 + $htcpDataLen + 2;
+			$htcpDataLen = 8 + 2 + strlen( $htcpSpecifier );
+			$htcpLen = 4 + $htcpDataLen + 2;
 
-				// Note! Squid gets the bit order of the first
-				// word wrong, wrt the RFC. Apparently no other
-				// implementation exists, so adapt to Squid
-				$htcpPacket = pack( 'nxxnCxNxxa*n',
-					$htcpLen, $htcpDataLen, $htcpOpCLR,
-					$htcpTransID, $htcpSpecifier, 2);
+			// Note! Squid gets the bit order of the first
+			// word wrong, wrt the RFC. Apparently no other
+			// implementation exists, so adapt to Squid
+			$htcpPacket = pack( 'nxxnCxNxxa*n',
+				$htcpLen, $htcpDataLen, $htcpOpCLR,
+				$htcpTransID, $htcpSpecifier, 2 );
 
-				// Send out
-				wfDebug( "Purging URL $url via HTCP\n" );
+			wfDebugLog( 'squid', __METHOD__ .
+				"Purging URL $url via HTCP\n" );
+			foreach ( $conf as $subconf ) {
 				socket_sendto( $conn, $htcpPacket, $htcpLen, 0,
-					$conf['host'], $conf['port'] );
+					$subconf['host'], $subconf['port'] );
 			}
-		} else {
-			$errstr = socket_strerror( socket_last_error() );
-			wfDebug( __METHOD__ . "(): Error opening UDP socket: $errstr\n" );
 		}
 		wfProfileOut( __METHOD__ );
 	}
@@ -242,21 +276,20 @@ class SquidUpdate {
 	 *
 	 * Client functions should not need to call this.
 	 *
-	 * @param $url string
-	 *
+	 * @param string $url
 	 * @return string
 	 */
-	static function expand( $url ) {
+	public static function expand( $url ) {
 		return wfExpandUrl( $url, PROTO_INTERNAL );
 	}
-	
+
 	/**
 	 * Find the HTCP routing rule to use for a given URL.
-	 * @param $url string URL to match
-	 * @param $rules array Array of rules, see $wgHTCPMulticastRouting for format and behavior
+	 * @param string $url URL to match
+	 * @param array $rules Array of rules, see $wgHTCPRouting for format and behavior
 	 * @return mixed Element of $rules that matched, or false if nothing matched
 	 */
-	static function getRuleForURL( $url, $rules ) {
+	private static function getRuleForURL( $url, $rules ) {
 		foreach ( $rules as $regex => $routing ) {
 			if ( $regex === '' || preg_match( $regex, $url ) ) {
 				return $routing;
@@ -264,5 +297,4 @@ class SquidUpdate {
 		}
 		return false;
 	}
-	
 }
diff --git a/includes/cache/UserCache.php b/includes/cache/UserCache.php
index 6ec23669..6085f586 100644
--- a/includes/cache/UserCache.php
+++ b/includes/cache/UserCache.php
@@ -45,7 +45,7 @@ class UserCache {
 	 * Get a property of a user based on their user ID
 	 *
 	 * @param $userId integer User ID
-	 * @param $prop string User property
+	 * @param string $prop User property
 	 * @return mixed The property or false if the user does not exist
 	 */
 	public function getProp( $userId, $prop ) {
@@ -59,10 +59,21 @@ class UserCache {
 	}
 
 	/**
+	 * Get the name of a user or return $ip if the user ID is 0
+	 *
+	 * @param integer $userId
+	 * @param string $ip
+	 * @since 1.22
+	 */
+	public function getUserName( $userId, $ip ) {
+		return $userId > 0 ? $this->getProp( $userId, 'name' ) : $ip;
+	}
+
+	/**
 	 * Preloads user names for given list of users.
-	 * @param $userIds Array List of user IDs
-	 * @param $options Array Option flags; include 'userpage' and 'usertalk'
-	 * @param $caller String: the calling method
+	 * @param array $userIds List of user IDs
+	 * @param array $options Option flags; include 'userpage' and 'usertalk'
+	 * @param string $caller the calling method
 	 */
 	public function doQuery( array $userIds, $options = array(), $caller = '' ) {
 		wfProfileIn( __METHOD__ );
@@ -70,6 +81,8 @@ class UserCache {
 		$usersToCheck = array();
 		$usersToQuery = array();
 
+		$userIds = array_unique( $userIds );
+
 		foreach ( $userIds as $userId ) {
 			$userId = (int)$userId;
 			if ( $userId <= 0 ) {
@@ -124,8 +137,8 @@ class UserCache {
 	 * Check if a cache type is in $options and was not loaded for this user
 	 *
 	 * @param $uid integer user ID
-	 * @param $type string Cache type
-	 * @param $options Array Requested cache types
+	 * @param string $type Cache type
+	 * @param array $options Requested cache types
 	 * @return bool
 	 */
 	protected function queryNeeded( $uid, $type, array $options ) {