PHP ZF2 Mysql has gone away - php

Question

Hi I have a php daemon that handle request from rabbitmq
After a day, it can no longer execute due to error MySQL has gone away.
PHP Warning: PDOStatement::execute(): MySQL server has gone away in /var/www/daemon/www/vendor/zendframework/zendframework/library/Zend/Db/Adapter/Driver/Pdo/Statement.php on line 239
PHP Warning: PDOStatement::execute(): Error reading result set\'s header in /var/www/daemon/www/vendor/zendframework/zendframework/library/Zend/Db/Adapter/Driver/Pdo/Statement.php on line 239
I didn't use doctrine, instead I send my \Zend\Db\Adapter\Adapter to a db wrapper class with below function.
public static function executeScalar($statement, $parameters, \Zend\Db\Adapter\Adapter $dbAdapter)
{
$dbResult = new DbResult();
if (! $statement) {
$dbResult->addError('No statement given');
return $dbResult;
}
$stmt = $dbAdapter->createStatement();
$stmt->prepare($statement);
foreach ($parameters as $key => &$param) {
$stmt->getResource()->bindParam($key + 1, $param[0], $param[1]);
}
try {
$result = $stmt->execute();
$dbResult->setResult($result);
} catch (\Zend\Db\Adapter\ExceptionInterface $e) {
$dbResult->addError('DB Error');
$message = $e->getPrevious() ? $e->getPrevious()->getMessage() : $e->getMessage();
$dbResult->addError($message);
} catch (\Zend\Db\Adapter\Exception $e) {
$dbResult->addError('DB Error');
$dbResult->addError($e->getMessage());
} catch (\PDOException $e) {
$dbResult->addError('DB Error');
$dbResult->addError($e->getMessage());
} catch (\Exception $e) {
$dbResult->addError('DB Error');
$dbResult->addError($e->getMessage());
}
$stmt->getResource()->closeCursor();
return $dbResult;
}
DbResult is my own db result wrapper class it mainly check whether it return empty, what's the error, how many rows, etc.
Here is my database.local.php configuration
return array(
'service_manager' => array(
'factories' => array(
'mysql' => function ($sm)
{
return new Zend\Db\Adapter\Adapter(array(
'driver' => 'PdoMysql',
'hostname' => 'localhost',
'database' => 'daemon',
'username' => 'daemon',
'password' => 'password',
'driver_options' => array(
\PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES \'UTF8\'',
\PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,
\PDO::ATTR_EMULATE_PREPARES => true,
\PDO::MYSQL_ATTR_LOCAL_INFILE => true
)
));
},
)
)
)
So everytime I want to execute a sql I do this inside controller or any other class ( Just an example )
$service = $this->getServiceLocator();
$dbAdapter = $service->get('mysql');
$get = \Db\Database::executeScalar('SELECT * FROM mytable WHERE id <= ?', array(10), $dbAdapter);
It seems I cannot catch the warning, and is there a way to force reconnect or perhaps I just do a disconnect after each request ?
Will this works, to handle the error ?
On every new request I do this
$dbAdapter->getDriver()->getConnection()->connect();
At the end of request I do this
$dbAdapter->getDriver()->getConnection()->disconnect();

Answer 1

Yes, I check the persistent connection option, but I also not fond of it.
I find the problem, it cause by mysql server close idle connection after 'wait timeout'. when mysql closing the idle connection, PDO will not receive any event so the next time you initiate a query it will return Mysql has gone away error.
For http request this is acceptable since after the server response the request it will stop/exit php execution which close all connection to database.
For daemon/service this is not acceptable since most of the time it waiting for client request (idle). My solution is to close the connection everytime it finish handling client request. e.g :
while (true) {
//listen to rabbitmq queue
//...
//do something base on client request from rabbitmq queue
//...
//close the connection whether it use database or not
//connection will be reconnected when we call $service->get('mysql');
$service = $this->getServiceLocator();
$dbAdapter = $service->get('mysql');
$dbAdapter->getDriver()->getConnection()->disconnect();
}

Answer 2

You can create a persistent connection to your database but be warned that creating a persistent connection should not be the first solution to look for. Be sure to do some research on the subject before trying it. You can find some documentation here :
http://php.net/manual/en/pdo.connections.php#example-954
On the other hand, you should look for the queries sent so the reason of the gone away message is not caused by the mysql server recieving a packet too large (ex: inserting a large blob). Because if it is, the connection will still close unexpectedly.