Doctrine 2 Master / Slave connections - doctrine-orm

Question

I'm looking at different ways of settings up Doctrine 2 to use master/slave connections usng MySQL. The set up would be so that there is one master database with multiple slaves. All SELECT statements should come from a random live slave and any UPDATE, INSERT, DELETE statements would always be delegated to the master connection.
Has anyone set up Doctine 2 in this way or have any ideas on how to approach it?

Answer 1

Doctrine2 now has a MasterSlaveConnection in the \Doctrine\DBAL\Connections namespace.
EDIT:
Dont read below unless this piece doesnt work
Dont need an overloader anymore, the dbal configs will take the slaves by itself. e.g.
connections:
default:
driver: %database_driver%
host: %database_host%
dbname: %database_name%
user: %database_user%
password: %database_password%
slaves:
slave1:
host: %database_slave1%
dbname: %database_name%
user: %database_user%
password: %database_password%
If the above doesnt work, try this
Something simple, just put pipes (|) between each host
default:
driver: %database_driver%
host: %database_host%|%database_slave%|%database_slave2%
port: 3306
dbname: %database_name%
user: %database_user%
password: %database_password%
wrapper_class: \Foo\Bar\Symfony\Doctrine\Connections\MasterSlave
<?php
namespace Foo\Bar\Symfony\Doctrine\Connections;
use \Doctrine\DBAL\Connections\MasterSlaveConnection;
use Doctrine\DBAL\Connection,
Doctrine\DBAL\Driver,
Doctrine\DBAL\Configuration,
Doctrine\Common\EventManager,
Doctrine\DBAL\Event\ConnectionEventArgs,
Doctrine\DBAL\Events,
Doctrine\DBAL\Cache\QueryCacheProfile;
class MasterSlave extends MasterSlaveConnection
{
public function __construct(array $params, Driver $driver, Configuration $config = null, EventManager $eventManager = null)
{
$tempParams = array(
'master' => array()
, 'slaves' => array()
, 'driver' => $params['driver']
);
$hosts = explode('|', $params['host']);
unset($params['host']);
foreach($hosts as $num => $host)
{
$params['host'] = $host;
if($num == 0)
{
$tempParams['master'] = $params;
}
else
{
$tempParams['slaves'][] = $params;
}
}
if(!isset($tempParams['master']['driver']))
$tempParams['master']['driver'] = "pdo_mysql";
foreach($tempParams['slaves'] as $k => $slave)
{
if(!isset($slave['driver']))
$tempParams['slaves'][$k]['driver'] = "pdo_mysql";
}
parent::__construct($tempParams, $driver, $config, $eventManager);
}
public function executeQuery($query, array $params = array(), $types = array(), QueryCacheProfile $qcp = null)
{
try
{
return parent::executeQuery($query, $params, $types, $qcp);
}
catch(\Exception $e)
{
$logger = new \Uelib\Core\Logger();
$message = $e->getMessage() . "\nSql: " . $query . "\nParams: \n" . print_r($params, true);
$logger->log($message);
throw $e;
}
}
}

Answer 2

As far as I know there is not built-in support for this in Doctrine 2.
It really seems as if (at least with mysql), this problem is going to be ultimately solved elsewhere. Either in mysql_proxy, or via some very recent work with mysqlnd (the mysql native driver extension for php)
Since neither of those are ready for primetime (though mysql_proxy might be), your only immediate option is, unfortunately, to start looking at the Doctrine DBAL, and extending the built-in classes to handle things smartly -- meaning it might be a good idea to detect if the current request has done any write operations, and then force any subsequent reads to use the master, avoiding any replication-delay-related issues.
Hopefully, we'll see a more formal solution from the Doctrine team in the next 6-12 months. But if you need it now, it's DIY, AFAIK.