本文章來給各位同學介紹一篇關於Yii多數據庫主從讀寫分離實例，希望此文章對各位同學會有所幫助哦。
Yii框架數據庫多數據庫、主從、讀寫分離 實現
功能描述：
1.實現主從數據庫讀寫分離 主庫：寫 從庫(可多個)：讀
2.主數據庫無法連接時 可設置從數據庫是否 可寫
3.所有從數據庫無法連接時 可設置主數據庫是否 可讀
4.如果從數據庫連接失敗 可設置N秒內不再連接
利用yii擴展實現：
代碼如下 復制代碼<?php
/**
* 主數據庫 寫 從數據庫（可多個）讀
* 實現主從數據庫 讀寫分離 主服務器無法連接 從服務器可切換寫功能
* 從務器無法連接 主服務器可切換讀功
* by lmt
* */
class DbConnectionMan extends CDbConnection {
public $timeout = 10; //連接超時時間
public $markDeadSeconds = 600; //如果從數據庫連接失敗 600秒內不再連接
//用 cache 作為緩存全局標記
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();
/**
*
* 從數據庫狀態 false 則只用主數據庫
* @var bool $enableSlave
* */
public $enableSlave = true;
/**
* @var slavesWrite 緊急情況主數據庫無法連接 切換從服務器（讀寫）.
*/
public $slavesWrite = false;
/**
* @var masterRead 緊急情況從主數據庫無法連接 切換從住服務器（讀寫）.
*/
public $masterRead = false;
/**
* @var _slave
*/
private $_slave;
/**
* @var _disableWrite 從服務器（只讀）.
*/
private $_disableWrite = true;
/**
*
* 重寫 createCommand 方法,1.開啟從庫 2.存在從庫 3.當前不處於一個事務中 4.從庫讀數據
* @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);
}
}
/**
* 獲得從服務器連接資源
* @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 {
$this->close();
}
}
}
/**
* 檢測讀操作 sql 語句
*
* 關鍵字： SELECT,DECRIBE,SHOW ...
* 寫操作:UPDATE,INSERT,DELETE ...
* */
public static function isReadOperation($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;
}
/**
* 檢測從服務器是否被標記 失敗.
*/
private function _isDeadServer($c) {
$cache = Yii::app()->{$this->cacheID};
if ($cache && $cache->get('DeadServer::' . $c) == 1) {
return true;
}
return false;
}
/**
* 標記失敗的slaves.
*/
private function _markDeadServer($c) {
$cache = Yii::app()->{$this->cacheID};
if ($cache) {
$cache->set('DeadServer::' . $c, 1, $this->markDeadSeconds);
}
}
}
main.php配置：components 數組中
代碼如下 復制代碼'db'=>array(
'class'=>'application.extensions.DbConnectionMan',//擴展路徑
'connectionString' => 'mysql:host=192.168.1.128;dbname=db_xcpt',//主數據庫 寫
'emulatePrepare' => true,
'username' => 'root',
'password' => 'root',
'charset' => 'utf8',
'tablePrefix' => 'xcpt_', //表前綴
'enableSlave'=>true,//從數據庫啟用
'urgencyWrite'=>true,//緊急情況 主數據庫無法連接 啟用從數據庫 寫功能
'masterRead'=>true,//緊急情況 從數據庫無法連接 啟用主數據庫 讀功能
'slaves'=>array(//從數據庫
array( //slave1
'connectionString'=>'mysql:host=localhost;dbname=db_xcpt',
'emulatePrepare' => true,
'username'=>'root',
'password'=>'root',
'charset' => 'utf8',
'tablePrefix' => 'xcpt_', //表前綴
),
array( //slave2
'connectionString'=>'mysql:host=localhost;dbname=db_xcpt',
'emulatePrepare' => true,
'username'=>'root',
'password'=>'root',
'charset' => 'utf8',
'tablePrefix' => 'xcpt_', //表前綴
),
),
),
