Symfony 3.4出现“2006 MySQL server has gone away”错误求助

Let's tackle this frustrating issue where your Symfony 3.4 app throws a "MySQL server has gone away" error after being idle, then works fine again for a while. This typically happens because Doctrine holds onto a database connection that MySQL has already closed due to inactivity—even with your high wait_timeout setting, there are a few key fixes to implement:

1. Enable Doctrine Auto-Reconnect & Connection Pinging #

First, update your Doctrine DBAL configuration in app/config/config.yml to tell Doctrine to automatically check and reestablish broken connections:

doctrine:
    dbal:
        default_connection: default
        connections:
            default:
                # Keep your existing database config (driver, host, dbname, user, password)
                auto_reconnect: true
                options:
                    !php/const PDO::ATTR_PING: true

• auto_reconnect tells Doctrine to attempt reconnection if it detects a dead connection.
• PDO::ATTR_PING makes PDO check if the connection is alive before executing any query—if it's dead, it'll reconnect automatically.

2. Verify interactive_timeout in MySQL #

You've set wait_timeout to 328800 seconds, but MySQL also has an interactive_timeout setting that affects connections from interactive clients. While PHP usually uses non-interactive connections, it's worth checking if this value is lower than wait_timeout:
Run these commands in your MySQL console:

SHOW VARIABLES LIKE 'interactive_timeout';

If the value is less than 328800, update it to match your wait_timeout and restart MySQL:

SET GLOBAL interactive_timeout = 328800;

Don't forget to add this to your MySQL config file (like my.cnf or my.ini) to make the change permanent.

3. Configure Doctrine Connection Pool Idle Timeout #

Symfony 3.4's Doctrine integration lets you set an idle timeout for the connection pool, which ensures idle connections are recycled before MySQL can drop them:
Add this to your Doctrine DBAL config:

doctrine:
    dbal:
        connections:
            default:
                # Existing config
                pool:
                    min_connections: 1
                    max_connections: 10
                    idle_timeout: 300 # 5 minutes—adjust based on your app's idle periods

This setting tells the pool to close any connection that's been idle for 300 seconds, so the next request will get a fresh connection instead of a dead one.

4. Fallback: Manual Reconnection in Code #

As a safety net, you can catch the specific exception and manually reconnect in your controllers or services:

use Doctrine\DBAL\Driver\PDOException;
use Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException;

// Inside your controller method or service
try {
    // Your database operation (e.g., fetching entities, running queries)
    $entities = $this->getDoctrine()->getRepository(YourEntity::class)->findAll();
} catch (PDOException $e) {
    if (strpos($e->getMessage(), 'MySQL server has gone away') !== false) {
        // Close the dead connection and reconnect
        $connection = $this->getDoctrine()->getConnection();
        $connection->close();
        $connection->connect();

        // Retry your database operation once
        $entities = $this->getDoctrine()->getRepository(YourEntity::class)->findAll();
    } else {
        // Re-throw other PDO exceptions as a service unavailable error
        throw new ServiceUnavailableHttpException(null, $e->getMessage(), $e);
    }
}

Quick Notes for Your Environment #

Since you're using PHP 5.6 and MySQL 5.6, make sure your Doctrine DBAL version is compatible with Symfony 3.4—stick to versions ~2.5 or ~2.6 (check your composer.json to confirm). Older versions might have bugs with connection handling that these fixes address.

内容的提问来源于stack exchange，提问作者Sameh Serag