Yii 数据库重连告别General error: 2006 MySQL server has gone away

General error: 2006 MySQL server has gone away

• 错误原因
• 制造错误
• 解决办法
• 最新办法

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错误原因

Mysql has gone away

1. MySQL 服务宕了
2. mysql连接超时 show global variables like ‘%timeout’;
3. mysql请求链接进程被主动kill show global status like ‘com_kill’;
4. Your SQL statement was too large. show global variables like ‘max_allowed_packet’;

制造错误

造一个表

-- ----------------------------
-- Table structure for t_biubiu
-- ----------------------------
DROP TABLE IF EXISTS `t_biubiu`;
CREATE TABLE `t_biubiu` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `value` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

然后造一个程序

public function actionInsert(){
        Biubiu::model()->findAll();
        $result = Yii::app()->db->createCommand("show global variables like '%timeout'")->queryAll();
        self::show_vars($result);
        for($index = 1 ;$index< 10;$index++){
            $model_ = new Biubiu();
            $model_->value = "insert".$index;
            if($index == 8){
                sleep(31);
            }
            $model_->save();
        }
        $model = new Biubiu();
        $model->value = "insert4";
        $model->save();
     }

设置你的MYSQL的wait_timeout = 30，interactive_timeout也要设置，否则不生效

执行的时候就会抛异常：

exception 'CDbException' with message 'CDbCommand failed to execute the SQL statement: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away. The SQL statement executed was: INSERT INTO `t_biubiu` (`value`) VALUES (:yp0). Bound with :yp0='insert8'' in E:\phpWorks\framework\db\CDbCommand.php:362

sleep有效果了。

大部分情况就是超时导致的，尤其是脚本执行时间太长

解决办法

如果运维不同意　改变wait_timeout的值：

方法	做法
1	wait_timeout改大一些，并不能一劳永逸
2	代码中遇到超时重连
3	检查是不是Mysql连接过多，并发太高，忘记释放连接

解决方法推荐

例如，读写分离的 JDbConnection。在调用save delete方法的时候执行ensureActive() 。注意 @，否则异常发生的时候PHP ERROR直接挂掉。

<?php
/**
 * JDbConnection(Database Connection Manager) class is a manager of database connections.
 *
 * for the purpose of database read/write splitting.
 * It override the createCommand method,
 * detect the sql statement to decide which connection will be used.
 * Default it use the master connection.
 *
 */
class JDbConnection extends CDbConnection
{
    /**
     * @var array $slaves.Slave database connection(Read) config array.
     * The array value's format is the same as CDbConnection.
     * <code>
     * 'components'=>array(
     * 'db'=>array(
     * 'class' => 'JDbConnection',
     * 'connectionString'=>'MySQL://<master>',
     * 'slaves'=>array(
     * array('connectionString'=>'mysql://<slave01>'),
     * array('connectionString'=>'mysql://<slave02>'),
     * )
     * )
     * )
     * </code>
     */
    public $slaves = array();
    /**
     * Whether enable the slave database connection.
     * Defaut is true.Set this property to false for the purpose of only use the master database.
     *
     * @var bool $enableSlave
     */
    public $enableSlave = true;
    /**
     * @var CDbConnection
     */
    private $_slave;
    /**
     * Creates a CDbCommand object for excuting sql statement.
     * It will detect the sql statement's behavior.
     * While the sql is a simple read operation.
     * It will use a slave database connection to contruct a CDbCommand object.
     * Default it use current connection(master database).
     *
     * @override
     * @param string $sql
     * @return CDbCommand
     */
    public function createCommand($query = null)
    {
        if ($this->enableSlave && !$this->getCurrentTransaction() && self::isReadOperation($query)) {
            return $this->getSlave()->createCommand($query);
        } else {
            return parent::createCommand($query);
        }
    }
    /**
     * Construct a slave connection CDbConnection for read operation.
     *
     * @return CDbConnection
     */
    public function getSlave()
    {
        if (!isset($this->_slave)) {
            foreach ($this->slaves as $slaveConfig) {
                if (!isset($slaveConfig['class']))
                    $slaveConfig['class'] = 'CDbConnection';
                try {
                    if ($slave = Yii::createComponent($slaveConfig)) {
                        Yii::app()->setComponent('dbslave', $slave);
                        $this->_slave = $slave;
                        break;
                    }
                } catch (Exception $e) {
                    Yii::log('Create slave database connection failed!', 'warn');
                    continue;
                }
            }
            if (!$this->_slave) {
                $this->_slave = clone $this;
                $this->_slave->enableSlave = false;
            }
        }
        return $this->_slave;
    }
    /**
     * Detect whether the sql statement is just a simple read operation.
     * Read Operation means this sql will not change any thing ang aspect of the database.
     * Such as SELECT,DECRIBE,SHOW etc.
     * On the other hand:UPDATE,INSERT,DELETE is write operation.
     *
     * @return bool
     */
    public function isReadOperation($sql)
    {
        return !!preg_match('/^\s*(SELECT|SHOW|DESCRIBE|PRAGMA)/i', $sql);
    }
    /**
     * 确保数据库连接有效
     *
     * @params bool $isSlaveping主库还是从库
     * @return void
     */
    public function ensureActive($isSlave = true)
    {
            if ($this->getActive()) {
                try {
                    @$this->getPdoInstance()->query('SELECT 1');
                } catch (PDOException $e) {
                    $this->setActive(false);
                    $this->setActive(true);
                }
            }
    }
}

调用示例：

 Yii::app()->db->ensureActive();

另外一种方法

执行SQL之前执行：

Yii::$app->db->createCommand('SET SESSION wait_timeout = 28800;')->execute();

最新办法

避免每次多请求了一次数据库。只有在遇到问题时进入异常处理，重试的时候Yii会自动进行重连[不确定]。

public static function retry($params, $call){
    for($retry = 0; $retry < 3;$retry++){
        try{
            if($params instanceof CModel){
                return $params->$call();
            }
        }catch(CDbException $e){
            if (!(strpos($e, "error: 2006") && !strpos($e, "error: 2013"))) {
                throw new Exception($e->getMessage(), 520);
            }
        }
    }
    return false;
}

2017年4月9日 更新

最近发现，公司所用的yii framework1.1的框架，和官方下载的不太一样。

下载最新框架，测试代码如下，我将mysql设置为wait_timeout=30, interactive_timeout=30

class DbTestCommand extends CConsoleCommand {
    public function actionInsert(){
        $sql = "insert into adv_pro ( `name` , `int_value`) values ('insert', 100)";
        Yii::app()->localdb->createCommand($sql)->execute();
        sleep(31);
        $sql = "insert into adv_pro ( `name` , `int_value`) values ('insert', 200)";
        Yii::app()->localdb->createCommand($sql)->execute();
    }
}

结果就出现了：

PHP Error[2]: PDOStatement::execute(): MySQL server has gone away
    in file D:\work_project\framework\db\CDbCommand.php at line 336
#0 D:\work_project\framework\db\CDbCommand.php(336): PDOStatement->execute()
#1 D:\work_project\task\protected\commands\DbTestCommand.php(19): CDbCommand->execute()
#2 unknown(0): DbTestCommand->actionInsert()

再加上@符号抑制错误

@Yii::app()->localdb->createCommand($sql)->execute();

结果异常就抛出来了：

exception 'CDbException' with message 'CDbCommand failed to execute the SQL statement: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away. The SQL statement executed was: insert into adv_pro ( `name` , `int_value`) values ('insert', 200)' in D:\work_project\framework\db\CDbCommand.php:363
Stack trace:
#0 D:\work_project\task\protected\commands\DbTestCommand.php(19): CDbCommand->execute()

那么可以把框架的db/CDbCommand.php内的execute方法改一下，改成：

if($params===array())
    @$this->_statement->execute();
else
    @$this->_statement->execute($params);

这样就能捕获到这个异常了。

那么据此，可以为CDbCommand.php增加一个方法：

public function sqlDbExecute($params=array()){
    $e = new Exception("sqlDbExecute failed three times", 10001);
    for ($count=0;$count<3;$count++){
        try {
            $result = $this->execute($params);
            return $result;
        } catch (Exception $e) {
               Yii::log('Error in sqlDbExecute SQL: '.$this->getText(),CLogger::LEVEL_ERROR,'system.db.CDbCommand');
            $this->_connection->setActive(true);
            //If not found 2006 then throw up
            if (!strpos($e, "error: 2006")) {
                   throw new Exception($e,10001);
            }
        }
    }
    throw new Exception($e,10001);
}