Yii多数据库主从读写分离实例介绍
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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：
<?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 ($this->enableSlave && !empty($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
<?php '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 ) , ) , ) ,
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