Load balancing and failover of PHP database connections

Load balancing and failover of PHP database connection

Overview:

With the continuous development of Internet business, the database has become an indispensable part of the application system. A missing part. In large-scale application systems, load balancing and failover of database connections are very important to ensure system stability and availability. This article will introduce how to implement load balancing and failover of database connections in PHP, and provide corresponding code examples.

1. Load balancing:

Load balancing refers to evenly distributing database connections to multiple database servers to achieve the purpose of sharing server load. In PHP, you can use connection pooling to achieve load balancing. A connection pool is a buffer that holds database connections. Applications can obtain database connections from the connection pool and put the connections back into the pool after use for use by other applications.

The following is a sample code that uses a connection pool to achieve load balancing:

<?php
class ConnectionPool {
    private static $instance;
    private $connections = array();

    private function __construct() {}

    public static function getInstance() {
        if (!self::$instance) {
            self::$instance = new ConnectionPool();
        }
        return self::$instance;
    }

    public function getConnection() {
        $count = count($this->connections);
        if ($count > 0) {
            $index = rand(0, $count - 1);
            return $this->connections[$index];
        } else {
            // 创建数据库连接
            $connection = new PDO('mysql:host=localhost;dbname=myDB', 'username', 'password');
            array_push($this->connections, $connection);
            return $connection;
        }
    }

    public function releaseConnection($connection) {
        // 将连接放回连接池
        array_push($this->connections, $connection);
    }
}

// 使用连接池获取数据库连接
$pool = ConnectionPool::getInstance();
$connection = $pool->getConnection();

// 执行数据库操作

// 释放数据库连接
$pool->releaseConnection($connection);
?>

In the above code, the ConnectionPool class is an implementation of a connection pool, and the singleton object of the connection pool is obtained through the getInstance method. The getConnection method is used to obtain a database connection from the connection pool. If there is a connection in the connection pool, randomly select one and return it, otherwise create a new connection and return it. The releaseConnection method is used to put the connection back into the connection pool.

2. Failover:

Failover refers to automatically switching to a backup server when the database server fails to ensure system availability. In PHP, database failover can be achieved through heartbeat detection and failover mechanisms.

The following is a simple sample code that demonstrates how to implement database failover:

<?php
try {
    $connection = new PDO('mysql:host=localhost;dbname=myDB', 'username', 'password');
    // 设置超时时间为1秒
    $connection->setAttribute(PDO::ATTR_TIMEOUT, 1);
} catch (PDOException $e) {
    // 连接失败时切换到备用服务器
    $connection = new PDO('mysql:host=backupServer;dbname=myDB', 'username', 'password');
}

// 执行数据库操作
?>

In the above code, try to connect to the main server. If the connection fails, the PDOException exception is captured, and in the exception handling Switch to the backup server in the code.

Summary:

Load balancing and failover are important means to ensure the stability and availability of application systems. In PHP, load balancing and failover of database connections can be achieved through connection pools and failover mechanisms. This article provides code examples, hoping to provide some help to readers in understanding and applying them to actual development.

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