用swoole实现mysql的连接池--摘自https://github.com/153734009/doc/blob/master/php/mysql_pool.php

<?php
	$serv = new swoole_server("0.0.0.0", 9508);
	$serv->set(['worker_num'=>1, 'task_worker_num'=>5]);
	function onReceive($serv, $fd, $from_id, $data)
	{
	$sql = $data;
	$result = $serv->taskwait($sql);
	if($result !== false){
	$serv->send($fd, $result . " ");
	}else{
	$serv->send($fd, "Err:Task timeout ");
	}
	//异步的时候就麻烦了，需要把$fd传递到onFinish，才能send数据到
	//$serv->task($sql);
	}
	/**
	* task保持数据库连接
	* 使用静态变量，因为变量没有释放，所以才能保持连接
	* mysql连接的数量= task_worker_num
	*/
	function onTask($serv, $fd, $from_id, $sql)
	{
	static $conn = null;
	if($conn == null){
	$conn = mysqli_connect('127.0.0.1', 'root', '123456', 'help');
	if(!$conn){
	$conn = null;
	$serv->finish('ERR:'.mysqli_connect_error());
	return;
	}
	}
	$result = $conn->query($sql);
	if(!$result){
	$serv->finish('ERR:'.mysqli_error($conn));
	return;
	}
	$data = $result->fetch_all(MYSQLI_ASSOC);
	$serv->finish('OK:'.serialize($data));
	}
	function onFinish($serv, $task_id, $data)
	{
	// 异步Task时有效
	echo "AsyncTask Finish:Connect.PID=".posix_getpid().PHP_EOL;
	}
	$serv->on('Receive', 'onReceive');
	$serv->on('Task', 'onTask');
	$serv->on('Finish', 'onFinish');
	$serv->start();
	//以下是客户端代码
	//$client = new swoole_client(SWOOLE_SOCK_TCP, SWOOLE_SOCK_SYNC); //同步阻塞
	//$client->connect('172.18.107.194', 9508, 0.5, 0);
	//$client->send("show tables");
	//$data = $client->recv();
	/**
	* 查看mysql连接
	*
	* 1. mysql -uroot -p123456
	* 2. show status;
	* 其中的
	* Threads_connected | 1
	* 就是mysql连接数
	*/