Bringing foreign connection logic into the core. Committing for test on server.

diff --git a/includes/DefaultSettings.php b/includes/DefaultSettings.php
index 690d9c2..98b94d4 100644 (file)
--- a/includes/DefaultSettings.php
+++ b/includes/DefaultSettings.php
@@ -592,6 +592,14 @@ $wgDBmysql5                        = false;
  */
 $wgLocalDatabases   = array();
 
+/**
+ * A map of database name (key) to connection index (value), describing the 
+ * master database server for each database. The connection index is an 
+ * index into the $wgDBservers array. If a database is not listed here, the
+ * default load balancing settings will be used.
+ */
+$wgAlternateMaster = array();
+
 /**
  * Object cache settings
  * See Defines.php for types

diff --git a/includes/LoadBalancer.php b/includes/LoadBalancer.php
index d3d072e..b9fda22 100644 (file)
--- a/includes/LoadBalancer.php
+++ b/includes/LoadBalancer.php
@@ -240,6 +240,53 @@ class LoadBalancer {
                return $i;
        }
 
+       /**
+        * Get a connection to a foreign DB. Will use the following types of 
+        * connection in order of precedence:
+        *    * The alternate master, if there is one and DB_MASTER is given
+        *    * The query group
+        *    * The alternate master, if there is one
+        *    * The default writer, if DB_MASTER was specified
+        *    * The default reader. 
+        * 
+        * Connection error will *not* lead to progression down this list. Selection
+        * of a group depends only on configuration.
+        *
+        * @param string $dbName The database name
+        * @param mixed $group The query group, or DB_MASTER for the foreign master
+        * @return Database object with the database selected
+        */
+       function getForeignConnection( $dbName, $group = false ) {
+               global $wgAlternateMaster;
+
+               // Try cache
+               if ( isset( $this->mForeignConnections[$dbName][$group] ) ) {
+                       return $this->mForeignConnections[$dbName][$group];
+               }
+
+               // Try the precedence list described in the function description
+               if ( $group === DB_MASTER && isset( $wgAlternateMaster[$dbName] ) ) {
+                       $index = $this->mServers[$wgAlternateMaster[$dbName]];
+               } if ( $group && $group !== DB_MASTER ) {
+                       $index = $this->getGroupIndex( $group );
+               } elseif ( isset( $wgAlternateMaster[$dbName] ) ) {
+                       $index = $this->mServers[$wgAlternateMaster[$dbName]];
+               } elseif ( $group === DB_MASTER ) {
+                       $index = $this->getWriterIndex();
+               } else {
+                       $index = $this->getReaderIndex();
+               }
+
+               if ( $index === false || !isset( $this->mServers[$index] ) ) {
+                       throw new MWException( "No configured server available for foreign connection to $dbName" );
+               }
+
+               $dbInfo = $this->mServers[$index];
+               $dbc = $this->reallyOpenConnection( $dbInfo, $dbName );
+               $this->mForeignConnections[$dbName][$group] = $dbc;
+               return $dbc;
+       }
+
        /**
         * Set the master wait position
         * If a DB_SLAVE connection has been opened already, waits
@@ -415,12 +462,15 @@ class LoadBalancer {
         * Really opens a connection
         * @access private
         */
-       function reallyOpenConnection( &$server ) {
+       function reallyOpenConnection( &$server, $overrideDBname = false ) {
                if( !is_array( $server ) ) {
                        throw new MWException( 'You must update your load-balancing configuration. See DefaultSettings.php entry for $wgDBservers.' );
                }
 
                extract( $server );
+               if ( $overrideDBname ) {
+                       $dbname = $overrideDBname;
+               }
                # Get class for this database type
                $class = 'Database' . ucfirst( $type );