gistfile1.php

<?php
namespace Jarlssen\Doctrine2\DBAL;

use Doctrine\DBAL\Connection,
    Doctrine\DBAL\Driver,
    Doctrine\ORM\Configuration,
    Doctrine\Common\EventManager,
    Doctrine\DBAL\Events;

class MasterSlaveConnection extends Connection
{
    /**
     * Master connection
     *
     * @var Doctrine\DBAL\Driver\Connection
     */
    protected $_masterConn;

    /**
     * Slave connection
     *
     * @var Doctrine\DBAL\Driver\Connection
     */
    protected $_slaveConn;

    public function __construct(
        array $params,
        Driver $driver,
        Configuration $config = null,
        EventManager $eventManager = null
    )
    {
        if (!isset($params['slaves']) or !isset($params['master'])) {
            throw new \InvalidArgumentsException('master or slaves configuration missing');
        }

        $params['master']['driver'] = $params['driver'];
        foreach ($params['slaves'] as &$slave) {
            $slave['driver'] = $params['driver'];
        }

        parent::__construct($params, $driver, $config, $eventManager);
    }

    public function connect($connectionName = 'slave')
    {
        $forceMasterAsSlave = false;

        if ($this->getTransactionNestingLevel() > 0) {
            $connectionName = 'master';
            $forceMasterAsSlave = true;
        }

        $connectionProperty = '_' . $connectionName . 'Conn';
        if ($this->{$connectionProperty}) {
            if ($forceMasterAsSlave) {
                $this->_slaveConn = $this->_conn = $this->_masterConn;
            } else {
                $this->_conn = $this->{$connectionProperty};
            }
            return false;
        }

        if ($connectionName === 'master') {
            /** Set master and slave connection to master to avoid invalid reads */
            $this->_masterConn = $this->_slaveConn = $this->_conn = $this->_connectTo($connectionName);
        } else {
            $this->_slaveConn = $this->_conn = $this->_connectTo($connectionName);
        }

        if ($this->_eventManager->hasListeners(Events::postConnect)) {
            $eventArgs = new Event\ConnectionEventArgs($this);
            $this->_eventManager->dispatchEvent(Events::postConnect, $eventArgs);
        }

        return true;
    }

    protected function _connectTo($connectionName)
    {
        $params = $this->getParams();

        $driverOptions = isset($params['driverOptions']) ? $params['driverOptions'] : array();

        $connectionParams = $this->_chooseConnectionConfiguration($connectionName, $params);

        $user = isset($connectionParams['user']) ? $connectionParams['user'] : null;
        $password = isset($connectionParams['password']) ? $connectionParams['password'] : null;

        return $this->_driver->connect($connectionParams, $user, $password, $driverOptions);
    }

    protected function _chooseConnectionConfiguration($connectionName, $params)
    {
        if ($connectionName === 'master') {
            return $params['master'];
        }

        return $params['slaves'][array_rand($params['slaves'])];
    }

    public function executeUpdate($query, array $params = array(), array $types = array())
    {
        $this->connect('master');
        return parent::executeUpdate($query, $params, $types);
    }

    public function beginTransaction()
    {
        $this->connect('master');
        return parent::beginTransaction();
    }

    public function commit()
    {
        $this->connect('master');
        return parent::commit();
    }

    public function rollback()
    {
        $this->connect('master');
        return parent::rollback();
    }

    public function delete($tableName, array $identifier)
    {
        $this->connect('master');
        return parent::delete($tableName, $identifier);
    }

    public function update($tableName, array $data, array $identifier)
    {
        $this->connect('master');
        return parent::update($tableName, $data, $identifier);
    }

    public function insert($tableName, array $data)
    {
        $this->connect('master');
        return parent::insert($tableName, $data);
    }

    public function exec($statement)
    {
        $this->connect('master');
        return parent::exec($statement);
    }

    public function getWrappedConnection()
    {
        $this->connect('master');

        return $this->_conn;
    }
}