MessageCache: derive the hash from the cache contents

Follow-up for I020617d, where I got this wrong. It is probable that multiple
application servers will try to build a local cache at the same time, in which
case they will cause the cache key to thrash. It is necessary that two
application servers building a local cache from the database generate the same
hash for a given set of messages.

Change-Id: Ieeefc2094a83be9401c466bec859c1588ddfbcdf

diff --git a/includes/cache/MessageCache.php b/includes/cache/MessageCache.php
index 304c4f2..3f60d8c 100644 (file)
--- a/includes/cache/MessageCache.php
+++ b/includes/cache/MessageCache.php
@@ -530,7 +530,8 @@ class MessageCache {
                }
 
                $cache['VERSION'] = MSG_CACHE_VERSION;
-               $cache['HASH'] = wfRandomString( 8 );
+               ksort( $cache );
+               $cache['HASH'] = md5( serialize( $cache ) );
                $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );
 
                return $cache;