Use consistent hashing for SqlBagOStuff servers

[lhc/web/wiklou.git] / includes / objectcache / SqlBagOStuff.php

diff --git a/includes/objectcache/SqlBagOStuff.php b/includes/objectcache/SqlBagOStuff.php
index 653fb15..eccfe00 100644 (file)
--- a/includes/objectcache/SqlBagOStuff.php
+++ b/includes/objectcache/SqlBagOStuff.php
@@ -33,6 +33,7 @@ class SqlBagOStuff extends BagOStuff {
        var $lb;
 
        var $serverInfos;
+       var $serverNames;
        var $numServers;
        var $conns;
        var $lastExpireAll = 0;
@@ -75,6 +76,10 @@ class SqlBagOStuff extends BagOStuff {
                if ( isset( $params['servers'] ) ) {
                        $this->serverInfos = $params['servers'];
                        $this->numServers = count( $this->serverInfos );
+                       $this->serverNames = array();
+                       foreach ( $this->serverInfos as $i => $info ) {
+                               $this->serverNames[$i] = isset( $info['host'] ) ? $info['host'] : "#$i";
+                       }
                } elseif ( isset( $params['server'] ) ) {
                        $this->serverInfos = array( $params['server'] );
                        $this->numServers = count( $this->serverInfos );
@@ -154,16 +159,21 @@ class SqlBagOStuff extends BagOStuff {
         * @return Array: server index and table name
         */
        protected function getTableByKey( $key ) {
-               $numTables = $this->shards * $this->numServers ;
-               if ( $numTables > 1 ) {
-                       $hash = ( hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff ) % $numTables;
+               if ( $this->shards > 1 ) {
+                       $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
                        $tableIndex = $hash % $this->shards;
-                       $serverIndex = intval( round( ( $hash - $tableIndex ) / $this->shards ) );
-                       $tableName = $this->getTableNameByShard( $tableIndex );
-                       return array( $serverIndex, $tableName );
                } else {
-                       return array( 0, $this->tableName );
+                       $tableIndex = 0;
+               }
+               if ( $this->numServers > 1 ) {
+                       $sortedServers = $this->serverNames;
+                       ArrayUtils::consistentHashSort( $sortedServers, $key );
+                       reset( $sortedServers );
+                       $serverIndex = key( $sortedServers );
+               } else {
+                       $serverIndex = 0;
                }
+               return array( $serverIndex, $this->getTableNameByShard( $tableIndex ) );
        }
 
        /**