1 files changed, 261 insertions, 0 deletions
diff --git a/includes/db/LBFactory.php b/includes/db/LBFactory.php
new file mode 100644
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+++ b/includes/db/LBFactory.php
@@ -0,0 +1,261 @@
+<?php
+/**
+ * @file
+ * @ingroup Database
+ */
+
+/**
+ * An interface for generating database load balancers
+ * @ingroup Database
+ */
+abstract class LBFactory {
+	static $instance;
+
+	/**
+	 * Get an LBFactory instance
+	 */
+	static function &singleton() {
+		if ( is_null( self::$instance ) ) {
+			global $wgLBFactoryConf;
+			$class = $wgLBFactoryConf['class'];
+			self::$instance = new $class( $wgLBFactoryConf );
+		}
+		return self::$instance;
+	}
+
+	/**
+	 * Shut down, close connections and destroy the cached instance.
+	 * 
+	 */
+	static function destroyInstance() {
+		if ( self::$instance ) {
+			self::$instance->shutdown();
+			self::$instance->forEachLBCallMethod( 'closeAll' );
+			self::$instance = null;
+		}
+	}
+
+	/**
+	 * Construct a factory based on a configuration array (typically from $wgLBFactoryConf)
+	 */
+	abstract function __construct( $conf );
+
+	/**
+	 * Create a new load balancer object. The resulting object will be untracked, 
+	 * not chronology-protected, and the caller is responsible for cleaning it up.
+	 *
+	 * @param string $wiki Wiki ID, or false for the current wiki
+	 * @return LoadBalancer
+	 */
+	abstract function newMainLB( $wiki = false );
+
+	/**
+	 * Get a cached (tracked) load balancer object.
+	 *
+	 * @param string $wiki Wiki ID, or false for the current wiki
+	 * @return LoadBalancer
+	 */
+	abstract function getMainLB( $wiki = false );
+
+	/*
+	 * Create a new load balancer for external storage. The resulting object will be 
+	 * untracked, not chronology-protected, and the caller is responsible for 
+	 * cleaning it up.
+	 *
+	 * @param string $cluster External storage cluster, or false for core
+	 * @param string $wiki Wiki ID, or false for the current wiki
+	 */
+	abstract function newExternalLB( $cluster, $wiki = false );
+
+	/*
+	 * Get a cached (tracked) load balancer for external storage
+	 *
+	 * @param string $cluster External storage cluster, or false for core
+	 * @param string $wiki Wiki ID, or false for the current wiki
+	 */
+	abstract function &getExternalLB( $cluster, $wiki = false );
+
+	/**
+	 * Execute a function for each tracked load balancer
+	 * The callback is called with the load balancer as the first parameter,
+	 * and $params passed as the subsequent parameters.
+	 */
+	abstract function forEachLB( $callback, $params = array() );
+
+	/**
+	 * Prepare all tracked load balancers for shutdown
+	 * STUB
+	 */
+	function shutdown() {}
+
+	/**
+	 * Call a method of each tracked load balancer
+	 */
+	function forEachLBCallMethod( $methodName, $args = array() ) {
+		$this->forEachLB( array( $this, 'callMethod' ), array( $methodName, $args ) );
+	}
+
+	/**
+	 * Private helper for forEachLBCallMethod
+	 */
+	function callMethod( $loadBalancer, $methodName, $args ) {
+		call_user_func_array( array( $loadBalancer, $methodName ), $args );
+	}
+
+	/**
+	 * Commit changes on all master connections
+	 */
+	function commitMasterChanges() {
+		$this->forEachLBCallMethod( 'commitMasterChanges' );
+	}
+}
+
+/**
+ * A simple single-master LBFactory that gets its configuration from the b/c globals
+ */
+class LBFactory_Simple extends LBFactory {
+	var $mainLB;
+	var $extLBs = array();
+
+	# Chronology protector
+	var $chronProt;
+
+	function __construct( $conf ) {
+		$this->chronProt = new ChronologyProtector;
+	}
+
+	function newMainLB( $wiki = false ) {
+		global $wgDBservers, $wgMasterWaitTimeout;
+		if ( $wgDBservers ) {
+			$servers = $wgDBservers;
+		} else {
+			global $wgDBserver, $wgDBuser, $wgDBpassword, $wgDBname, $wgDBtype, $wgDebugDumpSql;
+			$servers = array(array(
+				'host' => $wgDBserver,
+				'user' => $wgDBuser,
+				'password' => $wgDBpassword,
+				'dbname' => $wgDBname,
+				'type' => $wgDBtype,
+				'load' => 1,
+				'flags' => ($wgDebugDumpSql ? DBO_DEBUG : 0) | DBO_DEFAULT
+			));
+		}
+
+		return new LoadBalancer( array(
+			'servers' => $servers, 
+			'masterWaitTimeout' => $wgMasterWaitTimeout 
+		));
+	}
+
+	function getMainLB( $wiki = false ) {
+		if ( !isset( $this->mainLB ) ) {
+			$this->mainLB = $this->newMainLB( $wiki );
+			$this->mainLB->parentInfo( array( 'id' => 'main' ) );
+			$this->chronProt->initLB( $this->mainLB );
+		}
+		return $this->mainLB;
+	}
+
+	function newExternalLB( $cluster, $wiki = false ) {
+		global $wgExternalServers;
+		if ( !isset( $wgExternalServers[$cluster] ) ) {
+			throw new MWException( __METHOD__.": Unknown cluster \"$cluster\"" );
+		}
+		return new LoadBalancer( array(
+			'servers' => $wgExternalServers[$cluster] 
+		));
+	}
+
+	function &getExternalLB( $cluster, $wiki = false ) {
+		if ( !isset( $this->extLBs[$cluster] ) ) {
+			$this->extLBs[$cluster] = $this->newExternalLB( $cluster, $wiki );
+			$this->extLBs[$cluster]->parentInfo( array( 'id' => "ext-$cluster" ) );
+		}
+		return $this->extLBs[$cluster];
+	}
+
+	/**
+	 * Execute a function for each tracked load balancer
+	 * The callback is called with the load balancer as the first parameter,
+	 * and $params passed as the subsequent parameters.
+	 */
+	function forEachLB( $callback, $params = array() ) {
+		if ( isset( $this->mainLB ) ) {
+			call_user_func_array( $callback, array_merge( array( $this->mainLB ), $params ) );
+		}
+		foreach ( $this->extLBs as $lb ) {
+			call_user_func_array( $callback, array_merge( array( $lb ), $params ) );
+		}
+	}
+
+	function shutdown() {
+		if ( $this->mainLB ) {
+			$this->chronProt->shutdownLB( $this->mainLB );
+		}
+		$this->chronProt->shutdown();
+		$this->commitMasterChanges();
+	}
+}
+
+/**
+ * Class for ensuring a consistent ordering of events as seen by the user, despite replication.
+ * Kind of like Hawking's [[Chronology Protection Agency]].
+ */
+class ChronologyProtector {
+	var $startupPos;
+	var $shutdownPos = array();
+
+	/**
+	 * Initialise a LoadBalancer to give it appropriate chronology protection.
+	 *
+	 * @param LoadBalancer $lb
+	 */
+	function initLB( $lb ) {
+		if ( $this->startupPos === null ) {
+			if ( !empty( $_SESSION[__CLASS__] ) ) {
+				$this->startupPos = $_SESSION[__CLASS__];
+			}
+		}
+		if ( !$this->startupPos ) {
+			return;
+		}
+		$masterName = $lb->getServerName( 0 );
+
+		if ( $lb->getServerCount() > 1 && !empty( $this->startupPos[$masterName] ) ) {
+			$info = $lb->parentInfo();
+			$pos = $this->startupPos[$masterName];
+			wfDebug( __METHOD__.": LB " . $info['id'] . " waiting for master pos $pos\n" );
+			$lb->waitFor( $this->startupPos[$masterName] );
+		}
+	}
+
+	/**
+	 * Notify the ChronologyProtector that the LoadBalancer is about to shut
+	 * down. Saves replication positions.
+	 *
+	 * @param LoadBalancer $lb
+	 */
+	function shutdownLB( $lb ) {
+		if ( session_id() != '' && $lb->getServerCount() > 1 ) {
+			$masterName = $lb->getServerName( 0 );
+			if ( !isset( $this->shutdownPos[$masterName] ) ) {
+				$pos = $lb->getMasterPos();
+				$info = $lb->parentInfo();
+				wfDebug( __METHOD__.": LB " . $info['id'] . " has master pos $pos\n" );
+				$this->shutdownPos[$masterName] = $pos;
+			}
+		}
+	}
+
+	/**
+	 * Notify the ChronologyProtector that the LBFactory is done calling shutdownLB() for now.
+	 * May commit chronology data to persistent storage.
+	 */
+	function shutdown() {
+		if ( session_id() != '' && count( $this->shutdownPos ) ) {
+			wfDebug( __METHOD__.": saving master pos for " .
+				count( $this->shutdownPos ) . " master(s)\n" );
+			$_SESSION[__CLASS__] = $this->shutdownPos;
+		}
+	}
+}