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ProxySQL

Configure ProxySQL for MySQL

ProxySQL runs between your application and a linked MySQL add-on. It keeps backend connections available for reuse while your application connects locally through a Unix domain socket. This is useful for applications that do not already maintain an efficient connection pool.

ProxySQL is available in every runtime except Docker, where processes and services are managed by the container image.

Enable ProxySQL

Link a MySQL add-on to the application, then enable ProxySQL:

clever env set CC_ENABLE_MYSQL_PROXYSQL true

The platform starts one ProxySQL process on each application instance and injects CC_MYSQL_PROXYSQL_SOCKET_PATH with the local socket path. Your application must keep using the linked add-on credentials from MYSQL_ADDON_USER, MYSQL_ADDON_PASSWORD and MYSQL_ADDON_DB, but use this socket instead of MYSQL_ADDON_HOST and MYSQL_ADDON_PORT.

TLS is enabled between ProxySQL and MySQL by default. You can configure the maximum number of backend connections per application instance with CC_MYSQL_PROXYSQL_MAX_CONNECTIONS, which defaults to 10. See the environment variables reference for all available options.

Connect your application

PHP with PDO

Pass the socket through the unix_socket parameter of the PDO MySQL DSN:

<?php

$dsn = sprintf(
    'mysql:unix_socket=%s;dbname=%s;charset=utf8mb4',
    getenv('CC_MYSQL_PROXYSQL_SOCKET_PATH'),
    getenv('MYSQL_ADDON_DB')
);

$connection = new PDO(
    $dsn,
    getenv('MYSQL_ADDON_USER'),
    getenv('MYSQL_ADDON_PASSWORD'),
    [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]
);

Node.js with mysql2

Set socketPath when creating a connection or pool with mysql2:

import mysql from "mysql2/promise";

const pool = mysql.createPool({
  socketPath: process.env.CC_MYSQL_PROXYSQL_SOCKET_PATH,
  user: process.env.MYSQL_ADDON_USER,
  password: process.env.MYSQL_ADDON_PASSWORD,
  database: process.env.MYSQL_ADDON_DB,
});

WordPress

Use the socket in wp-config.php:

define('DB_HOST', 'localhost:' . getenv('CC_MYSQL_PROXYSQL_SOCKET_PATH'));

Size the connection pool

Each running instance owns its ProxySQL process. During a rolling deployment, old and new instances can run simultaneously, so the maximum number of backend connections can temporarily reach:

2 × maximum running instances × CC_MYSQL_PROXYSQL_MAX_CONNECTIONS

Keep this result below the MySQL plan’s connection limit and reserve capacity for administration or other clients. For example, an application scaling to four instances with CC_MYSQL_PROXYSQL_MAX_CONNECTIONS=15 can temporarily open up to 120 backend connections during a deployment.

Monitor ProxySQL

ProxySQL exports connection, query and error metrics for each application instance. Use the Metrics overview to inspect them in the Console and create alerts for your application.

Learn more

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