Yii实现多数据库主从读写分离的方法

本文实例讲述了Yii实现多数据库主从读写分离的方法。分享给大家供大家参考。具体分析如下：

Yii框架数据库多数据库、主从、读写分离 实现,功能描述:

1.实现主从数据库读写分离 主库：写 从库(可多个)：读

2.主数据库无法连接时 可设置从数据库是否 可写

3.所有从数据库无法连接时 可设置主数据库是否 可读

4.如果从数据库连接失败 可设置N秒内不再连接

利用yii扩展实现,代码如下:

<?php

/** 

 * 主数据库 写 从数据库（可多个）读 

 * 实现主从数据库 读写分离 主服务器无法连接 从服务器可切换写功能 

 * 从务器无法连接 主服务器可切换读功 

 * by lmt 

 * */ 

class DbConnectionMan extends CDbConnection { 

    public $timeout = 10; //连接超时时间 

    public $markDeadSeconds = 600; //如果从数据库连接失败 600秒内不再连接  

    //用 cache 作为缓存全局标记 

    public $cacheID = 'cache'; 

 

    /** 

     * @var array $slaves.Slave database connection(Read) config array. 

     * 配置符合 CDbConnection. 

     * @example 

     * 'components'=>array( 

     *   'db'=>array( 

     *    'connectionString'=>'mysql://<master>', 

     *    'slaves'=>array( 

     *     array('connectionString'=>'mysql://<slave01>'), 

     *     array('connectionString'=>'mysql://<slave02>'), 

     *    ) 

     *   ) 

     * ) 

     * */ 

    public $slaves = array(); 

    /** 

     *  

     * 从数据库状态 false 则只用主数据库 

     * @var bool $enableSlave 

     * */ 

    public $enableSlave = true; 

 

    /** 

     * @var slavesWrite 紧急情况主数据库无法连接 切换从服务器（读写）. 

     */ 

    public $slavesWrite = false; 

 

    /** 

     * @var masterRead 紧急情况从主数据库无法连接 切换从住服务器（读写）. 

     */ 

    public $masterRead = false; 

 

    /** 

     * @var _slave 

     */ 

    private $_slave; 

 

    /** 

     * @var _disableWrite 从服务器（只读）. 

     */ 

    private $_disableWrite = true; 

 

    /** 

     * 

     * 重写 createCommand 方法,1.开启从库 2.存在从库 3.当前不处于一个事务中 4.从库读数据 

     * @param string $sql 

     * @return CDbCommand 

     * */ 

    public function createCommand($sql = null) { 

        if ($this->enableSlave && !emptyempty($this->slaves) && is_string($sql) && !$this->getCurrentTransaction() && self::isReadOperation($sql) && ($slave = $this->getSlave()) 

        ) { 

            return $slave->createCommand($sql); 

        } else { 

            if (!$this->masterRead) { 

                if ($this->_disableWrite && !self::isReadOperation($sql)) { 

 

                    throw new CDbException("Master db server is not available now!Disallow write operation on slave server!"); 

                } 

            } 

            return parent::createCommand($sql); 

        } 

    } 

 

    /** 

     * 获得从服务器连接资源 

     * @return CDbConnection 

     * */ 

    public function getSlave() { 

        if (!isset($this->_slave)) { 

            shuffle($this->slaves); 

            foreach ($this->slaves as $slaveConfig) { 

                if ($this->_isDeadServer($slaveConfig['connectionString'])) { 

                    continue; 

                } 

                if (!isset($slaveConfig['class'])) 

                    $slaveConfig['class'] = 'CDbConnection'; 

 

                $slaveConfig['autoConnect'] = false; 

                try { 

                    if ($slave = Yii::createComponent($slaveConfig)) { 

                        Yii::app()->setComponent('dbslave', $slave); 

                        $slave->setAttribute(PDO::ATTR_TIMEOUT, $this->timeout); 

                        $slave->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true); 

                        $slave->setActive(true); 

                        $this->_slave = $slave; 

                        break; 

                    } 

                } catch (Exception $e) { 

                    $this->_markDeadServer($slaveConfig['connectionString']); 

                    Yii::log("Slave database connection failed!ntConnection string:{$slaveConfig['connectionString']}", 'warning'); 

 

                    continue; 

                } 

            } 

 

            if (!isset($this->_slave)) { 

                $this->_slave = null; 

                $this->enableSlave = false; 

            } 

        } 

        return $this->_slave; 

    } 

 

    public function setActive($value) { 

        if ($value != $this->getActive()) { 

            if ($value) { 

                try { 

                    if ($this->_isDeadServer($this->connectionString)) { 

                        throw new CDbException('Master db server is already dead!'); 

                    } 

                    //PDO::ATTR_TIMEOUT must set before pdo instance create 

                    $this->setAttribute(PDO::ATTR_TIMEOUT, $this->timeout); 

                    $this->open(); 

                } catch (Exception $e) { 

                    $this->_markDeadServer($this->connectionString); 

                    $slave = $this->getSlave(); 

                    Yii::log($e->getMessage(), CLogger::LEVEL_ERROR, 'exception.CDbException'); 

                    if ($slave) { 

                        $this->connectionString = $slave->connectionString; 

                        $this->username = $slave->username; 

                        $this->password = $slave->password; 

                        if ($this->slavesWrite) { 

                            $this->_disableWrite = false; 

                        } 

                        $this->open(); 

                    } else { //Slave also unavailable 

                        if ($this->masterRead) { 

                            $this->connectionString = $this->connectionString; 

                            $this->username = $this->username; 

                            $this->password = $this->password; 

                            $this->open(); 

                        } else { 

                            throw new CDbException(Yii::t('yii', 'CDbConnection failed to open the DB connection.'), (int) $e->getCode(), $e->errorInfo); 

                        } 

                    } 

                } 

            } else { 

                $this->close(); 

            } 

        } 

    } 

 

    /** 

     * 检测读操作 sql 语句 

     *  

     * 关键字： SELECT,DECRIBE,SHOW ... 

     * 写操作:UPDATE,INSERT,DELETE ... 

     * */ 

    public static function isReadOperation($sql) { 

        $sql = substr(ltrim($sql), 0, 10); 

        $sql = str_ireplace(array('SELECT', 'SHOW', 'DESCRIBE', 'PRAGMA'), '^O^', $sql); //^O^,magic smile 

        return strpos($sql, '^O^') === 0; 

    } 

 

    /** 

     * 检测从服务器是否被标记 失败. 

     */ 

    private function _isDeadServer($c) { 

        $cache = Yii::app()->{$this->cacheID}; 

        if ($cache && $cache->get('DeadServer::' . $c) == 1) { 

            return true; 

        } 

        return false; 

    } 

 

    /** 

     * 标记失败的slaves. 

     */ 

    private function _markDeadServer($c) { 

        $cache = Yii::app()->{$this->cacheID}; 

        if ($cache) { 

            $cache->set('DeadServer::' . $c, 1, $this->markDeadSeconds); 

        } 

    } 

}

main.php配置:components 数组中,代码如下:

'db'=>array( 

        'class'=>'application.extensions.DbConnectionMan',//扩展路径 

        'connectionString' => 'mysql:host=192.168.1.128;dbname=db_xcpt',//主数据库 写 

        'emulatePrepare' => true, 

        'username' => 'root', 

        'password' => 'root', 

        'charset' => 'utf8', 

        'tablePrefix' => 'xcpt_', //表前缀 

        'enableSlave'=>true,//从数据库启用 

   'urgencyWrite'=>true,//紧急情况 主数据库无法连接 启用从数据库 写功能 

    'masterRead'=>true,//紧急情况 从数据库无法连接 启用主数据库 读功能 

        'slaves'=>array(//从数据库 

            array(   //slave1 

                'connectionString'=>'mysql:host=localhost;dbname=db_xcpt', 

                'emulatePrepare' => true, 

                'username'=>'root', 

                'password'=>'root', 

                'charset' => 'utf8', 

                'tablePrefix' => 'xcpt_', //表前缀 

            ), 

   array(   //slave2 

                'connectionString'=>'mysql:host=localhost;dbname=db_xcpt', 

                'emulatePrepare' => true, 

                'username'=>'root', 

                'password'=>'root', 

                'charset' => 'utf8', 

                'tablePrefix' => 'xcpt_', //表前缀 

            ), 

 

        ), 

),

希望本文所述对大家基于Yii框架的php程序设计有所帮助。