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<?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;
}
}
}
|
