Swoole的MySQL连接池实现

在Swoole中实现MySQL连接池可以提高数据库连接的复用率，减少频繁创建和销毁连接所带来的开销。以下是一个简单的Swoole MySQL连接池的实现示例：

首先，确保你已经安装了Swoole扩展和PDO_MySQL扩展（或mysqli，但在这个示例中我们使用PDO）。

<?php

use Swoole\Coroutine as co;
use PDO;
use PDOException;

class SwooleMysqlConnectionPool
{
    private $pool;
    private $config;
    private $maxConnections;
    private $availableConnections = [];
    private $inUseConnections = [];

    public function __construct($config, $maxConnections = 10)
    {
        $this->config = $config;
        $this->maxConnections = $maxConnections;
        $this->pool = new SplQueue();

        // Initialize the pool with available connections
        for ($i = 0; $i < $maxConnections; $i++) {
            $this->pool->enqueue($this->createConnection());
            $this->availableConnections[$i] = true;
        }
    }

    private function createConnection()
    {
        try {
            $dsn = "mysql:host={$this->config['host']};dbname={$this->config['dbname']};charset={$this->config['charset']}";
            $options = [
                PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
                PDO::ATTR_PERSISTENT => false,
                PDO::ATTR_EMULATE_PREPARES => false,
            ];
            return new PDO($dsn, $this->config['username'], $this->config['password'], $options);
        } catch (PDOException $e) {
            throw new Exception("Failed to create MySQL connection: " . $e->getMessage());
        }
    }

    public function getConnection()
    {
        if ($this->pool->isEmpty()) {
            throw new Exception("MySQL connection pool is exhausted");
        }

        $connection = $this->pool->dequeue();
        $this->availableConnections[array_search(true, $this->availableConnections)] = false; // Mark as in use
        unset($this->availableConnections[array_search(true, $this->availableConnections, true)]); // Remove the true value
        $this->inUseConnections[] = $connection;

        return $connection;
    }

    public function releaseConnection($connection)
    {
        if (($key = array_search($connection, $this->inUseConnections)) !== false) {
            unset($this->inUseConnections[$key]);
            $this->pool->enqueue($connection);
            $this->availableConnections[] = true; // Mark as available

            // Optionally, you can add logic here to close and recreate the connection
            // if it has been in use for too long or if an error occurs.
        }
    }

    // Optional: Add methods to handle connection recycling, health checks, etc.

    // Example usage in a Swoole coroutine
    public function queryInCoroutine($sql, $params = [])
    {
        go(function () use ($sql, $params) {
            $connection = $this->getConnection();
            try {
                $stmt = $connection->prepare($sql);
                $stmt->execute($params);
                $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
                $this->releaseConnection($connection);
                co::sleep(1); // Simulate some work
                echo "Query result: " . json_encode($result) . PHP_EOL;
            } catch (PDOException $e) {
                echo "Query failed: " . $e->getMessage() . PHP_EOL;
                // Optionally, handle the connection failure (e.g., remove it from the pool)
            }
        });
    }
}

// Example configuration
$config = [
    'host' => '127.0.0.1',
    'dbname' => 'test',
    'username' => 'root',
    'password' => 'password',
    'charset' => 'utf8mb4',
];

// Create the connection pool
$pool = new SwooleMysqlConnectionPool($config, 5);

// Use the connection pool in a Swoole coroutine (this is just an example, you would typically do this in a Swoole server handler)
$pool->queryInCoroutine("SELECT * FROM your_table WHERE some_column = ?", ['some_value']);

// Note: The queryInCoroutine method is just for demonstration purposes.
// In a real-world application, you would typically handle coroutines and database queries
// within the context of a Swoole server (e.g., Swoole\Http\Server, Swoole\WebSocket\Server).

// Since this is a script and not a Swoole server, the coroutine will not actually run.
// To see the coroutine in action, you need to run this code within a Swoole server environment.

// Remember to start a Swoole server and use the connection pool within the server's event loop.

重要提示：

1. 上面的queryInCoroutine方法只是为了演示如何在协程中使用连接池。在实际应用中，你需要在Swoole服务器（如Swoole\Http\Server或Swoole\WebSocket\Server）的事件循环中处理协程和数据库查询。
2. 由于这是一个脚本而不是Swoole服务器，因此协程实际上不会运行。要看到协程的实际效果，你需要在Swoole服务器环境中运行此代码。
3. 连接池中的连接应该是持久的，但在这个示例中，为了简单起见，我们每次从池中获取连接时都会创建一个新的PDO实例。在实际应用中，你可能需要实现更复杂的连接管理和回收逻辑。
4. 考虑到Swoole的协程特性，你可能还需要处理连接在协程之间的共享问题，以及如何在协程结束时正确关闭连接（尽管在这个简单的示例中我们没有这样做）。

对于生产环境，建议使用更成熟和经过充分测试的MySQL连接池库，或者根据Swoole的文档和社区资源来构建更健壮的连接池实现。