PHP 데이터베이스 연결의 로드 밸런싱 및 장애 조치

<?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);
?>

<?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
?>