PHP数据库连接的高可用性和容错处理技术

<?php
class DatabaseConnectionPool {
    private static $instance;
    private $connections = [];

    private function __construct() {}

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

    public function getConnection($config) {
        $hash = md5(serialize($config));
        if (!isset($this->connections[$hash])) {
            $this->connections[$hash] = new PDO($config['dsn'], $config['username'], $config['password']);
        }
        return $this->connections[$hash];
    }
}

// 使用连接池获取数据库连接
$config = [
    'dsn' => 'mysql:host=localhost;dbname=test',
    'username' => 'root',
    'password' => 'password',
];
$connectionPool = DatabaseConnectionPool::getInstance();
$connection = $connectionPool->getConnection($config);

// 执行数据库查询操作
$stmt = $connection->prepare('SELECT * FROM users');
$stmt->execute();
$results = $stmt->fetchAll(PDO::FETCH_ASSOC);

// 输出查询结果
foreach ($results as $result) {
    echo $result['name'] . ': ' . $result['email'] . PHP_EOL;
}
?>

<?php
class DatabaseConnection {
    private $config;
    private $connection;

    public function __construct($config) {
        $this->config = $config;
        $this->connect();
    }

    private function connect() {
        try {
            $this->connection = new PDO($this->config['dsn'], $this->config['username'], $this->config['password']);
        } catch (PDOException $e) {
            // 连接失败，等待一段时间后继续尝试连接
            sleep(5);
            $this->connect();
        }
    }

    public function query($sql) {
        try {
            return $this->connection->query($sql);
        } catch (PDOException $e) {
            // 查询失败，重新连接数据库
            $this->connect();
            return $this->query($sql);
        }
    }
}

// 创建数据库连接
$config = [
    'dsn' => 'mysql:host=localhost;dbname=test',
    'username' => 'root',
    'password' => 'password',
];
$connection = new DatabaseConnection($config);

// 执行数据库查询操作
$stmt = $connection->query('SELECT * FROM users');
$results = $stmt->fetchAll(PDO::FETCH_ASSOC);

// 输出查询结果
foreach ($results as $result) {
    echo $result['name'] . ': ' . $result['email'] . PHP_EOL;
}
?>