1 files changed, 29 insertions, 9 deletions

diff --git a/includes/objectcache/ObjectCacheSessionHandler.php b/includes/objectcache/ObjectCacheSessionHandler.php
index cdf8da1e..789f1e3b 100644
--- a/includes/objectcache/ObjectCacheSessionHandler.php
+++ b/includes/objectcache/ObjectCacheSessionHandler.php
@@ -28,6 +28,9 @@
  * @ingroup Cache
  */
 class ObjectCacheSessionHandler {
+	/** @var array Map of (session ID => SHA-1 of the data) */
+	protected static $hashCache = array();
+
 	/**
 	 * Install a session handler for the current web request
 	 */
@@ -49,10 +52,11 @@ class ObjectCacheSessionHandler {
 
 	/**
 	 * Get the cache storage object to use for session storage
-	 * @return ObjectCache
+	 * @return BagOStuff
 	 */
-	static function getCache() {
+	protected static function getCache() {
 		global $wgSessionCacheType;
+
 		return ObjectCache::getInstance( $wgSessionCacheType );
 	}
 
@@ -62,11 +66,19 @@ class ObjectCacheSessionHandler {
 	 * @param string $id Session id
 	 * @return string Cache key
 	 */
-	static function getKey( $id ) {
+	protected static function getKey( $id ) {
 		return wfMemcKey( 'session', $id );
 	}
 
 	/**
+	 * @param mixed $data
+	 * @return string
+	 */
+	protected static function getHash( $data ) {
+		return sha1( serialize( $data ) );
+	}
+
+	/**
 	 * Callback when opening a session.
 	 *
 	 * @param string $save_path Path used to store session files, unused
@@ -95,22 +107,29 @@ class ObjectCacheSessionHandler {
 	 */
 	static function read( $id ) {
 		$data = self::getCache()->get( self::getKey( $id ) );
-		if ( $data === false ) {
-			return '';
-		}
-		return $data;
+
+		self::$hashCache = array( $id => self::getHash( $data ) );
+
+		return ( $data === false ) ? '' : $data;
 	}
 
 	/**
 	 * Callback when writing session data.
 	 *
 	 * @param string $id Session id
-	 * @param mixed $data Session data
+	 * @param string $data Session data
 	 * @return bool Success
 	 */
 	static function write( $id, $data ) {
 		global $wgObjectCacheSessionExpiry;
-		self::getCache()->set( self::getKey( $id ), $data, $wgObjectCacheSessionExpiry );
+
+		// Only issue a write if anything changed (PHP 5.6 already does this)
+		if ( !isset( self::$hashCache[$id] )
+			|| self::getHash( $data ) !== self::$hashCache[$id]
+		) {
+			self::getCache()->set( self::getKey( $id ), $data, $wgObjectCacheSessionExpiry );
+		}
+
 		return true;
 	}
 
@@ -122,6 +141,7 @@ class ObjectCacheSessionHandler {
 	 */
 	static function destroy( $id ) {
 		self::getCache()->delete( self::getKey( $id ) );
+
 		return true;
 	}