Allow tag names for SqlBagOStuff consistent hashing

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

diff --git a/includes/objectcache/SqlBagOStuff.php b/includes/objectcache/SqlBagOStuff.php
index 3945094..a1394c1 100644 (file)
--- a/includes/objectcache/SqlBagOStuff.php
+++ b/includes/objectcache/SqlBagOStuff.php
@@ -27,10 +27,10 @@
  * @ingroup Cache
  */
 class SqlBagOStuff extends BagOStuff {
-       /** @var array */
+       /** @var array[] (server index => server config) */
        protected $serverInfos;
-       /** @var array */
-       protected $serverNames;
+       /** @var string[] (server index => tag/host name) */
+       protected $serverTags;
        /** @var int */
        protected $numServers;
        /** @var int */
@@ -58,9 +58,12 @@ class SqlBagOStuff extends BagOStuff {
         *   - server:      A server info structure in the format required by each
         *                  element in $wgDBServers.
         *
-        *   - servers:     An array of server info structures describing a set of
-        *                  database servers to distribute keys to. If this is
-        *                  specified, the "server" option will be ignored.
+        *   - servers:     An array of server info structures describing a set of database servers
+        *                  to distribute keys to. If this is specified, the "server" option will be
+        *                  ignored. If string keys are used, then they will be used for consistent
+        *                  hashing *instead* of the host name (from the server config). This is useful
+        *                  when a cluster is replicated to another site (with different host names)
+        *                  but each server has a corresponding replica in the other cluster.
         *
         *   - purgePeriod: The average number of object cache requests in between
         *                  garbage collection operations, where expired entries
@@ -89,11 +92,18 @@ class SqlBagOStuff extends BagOStuff {
        public function __construct( $params ) {
                parent::__construct( $params );
                if ( isset( $params['servers'] ) ) {
-                       $this->serverInfos = $params['servers'];
-                       $this->numServers = count( $this->serverInfos );
-                       $this->serverNames = [];
-                       foreach ( $this->serverInfos as $i => $info ) {
-                               $this->serverNames[$i] = isset( $info['host'] ) ? $info['host'] : "#$i";
+                       $this->serverInfos = [];
+                       $this->serverTags = [];
+                       $this->numServers = count( $params['servers'] );
+                       $index = 0;
+                       foreach ( $params['servers'] as $tag => $info ) {
+                               $this->serverInfos[$index] = $info;
+                               if ( is_string( $tag ) ) {
+                                       $this->serverTags[$index] = $tag;
+                               } else {
+                                       $this->serverTags[$index] = isset( $info['host'] ) ? $info['host'] : "#$index";
+                               }
+                               ++$index;
                        }
                } elseif ( isset( $params['server'] ) ) {
                        $this->serverInfos = [ $params['server'] ];
@@ -180,7 +190,7 @@ class SqlBagOStuff extends BagOStuff {
                        $tableIndex = 0;
                }
                if ( $this->numServers > 1 ) {
-                       $sortedServers = $this->serverNames;
+                       $sortedServers = $this->serverTags;
                        ArrayUtils::consistentHashSort( $sortedServers, $key );
                        reset( $sortedServers );
                        $serverIndex = key( $sortedServers );