PHP协程初体验
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PHP协程初体验
By warezhou 2014.11.24
上次通过C扩展为PHP添加coroutine尝试失败之后，由于短期内啃下Zend可能性几乎为零，只能打语言原生能力的主意了。Google之后发现，PHP5.5引入了Generator和Coroutine新特性，于是才有了本文的诞生。
背景阅读
《当C/C++后台开发遇上Coroutine》
http://blog.csdn.net/cszhouwei/article/details/14230529
《一次失败的PHP扩展开发之旅》
http://blog.csdn.net/cszhouwei/article/details/41290673
预备知识
Generator
function my_range($start, $end, $step = 1) { for ($i = $start; $i <= $end; $i += $step) { yield $i; }}foreach (my_range(1, 1000) as $num) { echo $num, "\n";}/* * 1 * 2 * ... * 1000 */图 1 基于generator的range()实现
$range = my_range(1, 1000);var_dump($range);/* * object(Generator)#1 (0) { * } */var_dump($range instanceof Iterator);/* * bool(true) */图 2 my_range()的实现推测
由于接触PHP时日尚浅，并未深入语言实现细节，所以只能根据现象进行猜测，以下是我的一些个人理解：
- 包含yield关键字的函数比较特殊，返回值是一个Generator对象，此时函数内语句尚未真正执行
- Generator对象是Iterator接口实例，可以通过rewind()、current()、next()、valid()系列接口进行操纵
- Generator可以视为一种“可中断”的函数，而yield构成了一系列的“中断点”
- Generator类似于车间生产的流水线，每次需要用产品的时候才从那里取一个，然后这个流水线就停在那里等待下一次取操作
Coroutine
细心的读者可能已经发现，截至目前，其实Generator已经实现了Coroutine的关键特性：中断执行、恢复执行。按照《当C/C++后台开发遇上Coroutine》的思路，借助“全局变量”一类语言设施进行信息传递，实现异步Server应该足够了。
其实相对于swapcontext族函数，Generator已经前进了一大步，具备了“返回数据”的能力，如果同时具备“发送数据”的能力，就再也不必通过那些蹩脚的手法绕路而行了。在PHP里面，通过Generator的send()接口（注意：不再是next()接口），可以完成“发送数据”的任务，从而实现了真正的“双向通信”。
function gen() { $ret = (yield 'yield1'); echo "[gen]", $ret, "\n"; $ret = (yield 'yield2'); echo "[gen]", $ret, "\n";}$gen = gen();$ret = $gen->current();echo "[main]", $ret, "\n";$ret = $gen->send("send1");echo "[main]", $ret, "\n";$ret = $gen->send("send2");echo "[main]", $ret, "\n";/* * [main]yield1 * [gen]send1 * [main]yield2 * [gen]send2 * [main] */图 3 Coroutine双向通信示例
作为C/C++系码农，发现“可重入”、“双向通信”能力之后，貌似没有更多奢求了，不过PHP还是比较慷慨，继续添加了Exception机制，“错误处理”机制得到进一步完善。
function gen() { $ret = (yield 'yield1'); echo "[gen]", $ret, "\n"; try { $ret = (yield 'yield2'); echo "[gen]", $ret, "\n"; } catch (Exception $ex) { echo "[gen][Exception]", $ex->getMessage(), "\n"; } echo "[gen]finish\n";}$gen = gen();$ret = $gen->current();echo "[main]", $ret, "\n";$ret = $gen->send("send1");echo "[main]", $ret, "\n";$ret = $gen->throw(new Exception("Test"));echo "[main]", $ret, "\n";/* * [main]yield1 * [gen]send1 * [main]yield2 * [gen][Exception]Test * [gen]finish * [main] */图 4 Coroutine错误处理示例
实战演习
前面简单介绍了相关的语言设施，那么具体到实际项目中，到底应该如何运用呢？让我们继续《一次失败的PHP扩展开发之旅》描述的场景，借助上述特性实现那个美好的愿望：以同步方式书写异步代码！
第一版初稿
<?phpclass AsyncServer { protected $handler; protected $socket; protected $tasks = []; public function __construct($handler) { $this->handler = $handler; $this->socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); if(!$this->socket) { die(socket_strerror(socket_last_error())."\n"); } if (!socket_set_nonblock($this->socket)) { die(socket_strerror(socket_last_error())."\n"); } if(!socket_bind($this->socket, "0.0.0.0", 1234)) { die(socket_strerror(socket_last_error())."\n"); } } public function Run() { while (true) { $reads = array($this->socket); foreach ($this->tasks as list($socket)) { $reads[] = $socket; } $writes = NULL; $excepts= NULL; if (!socket_select($reads, $writes, $excepts, 0, 1000)) { continue; } foreach ($reads as $one) { $len = socket_recvfrom($one, $data, 65535, 0, $ip, $port); if (!$len) { //echo "socket_recvfrom fail.\n"; continue; } if ($one == $this->socket) { //echo "[Run]request recvfrom succ. data=$data ip=$ip port=$port\n"; $handler = $this->handler; $coroutine = $handler($one, $data, $len, $ip, $port); $task = $coroutine->current(); //echo "[Run]AsyncTask recv. data=$task->data ip=$task->ip port=$task->port timeout=$task->timeout\n"; $socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); if(!$socket) { //echo socket_strerror(socket_last_error())."\n"; $coroutine->throw(new Exception(socket_strerror(socket_last_error()), socket_last_error())); continue; } if (!socket_set_nonblock($socket)) { //echo socket_strerror(socket_last_error())."\n"; $coroutine->throw(new Exception(socket_strerror(socket_last_error()), socket_last_error())); continue; } socket_sendto($socket, $task->data, $task->len, 0, $task->ip, $task->port); $this->tasks[$socket] = [$socket, $coroutine]; } else { //echo "[Run]response recvfrom succ. data=$data ip=$ip port=$port\n"; if (!isset($this->tasks[$one])) { //echo "no async_task found.\n"; } else { list($socket, $coroutine) = $this->tasks[$one]; unset($this->tasks[$one]); socket_close($socket); $coroutine->send(array($data, $len)); } } } } }}class AsyncTask { public $data; public $len; public $ip; public $port; public $timeout; public function __construct($data, $len, $ip, $port, $timeout) { $this->data = $data; $this->len = $len; $this->ip = $ip; $this->port = $port; $this->timeout = $timeout; }}function RequestHandler($socket, $req_buf, $req_len, $ip, $port) { //echo "[RequestHandler] before yield AsyncTask. REQ=$req_buf\n"; list($rsp_buf, $rsp_len) = (yield new AsyncTask($req_buf, $req_len, "127.0.0.1", 2345, 1000)); //echo "[RequestHandler] after yield AsyncTask. RSP=$rsp_buf\n"; socket_sendto($socket, $rsp_buf, $rsp_len, 0, $ip, $port);}$server = new AsyncServer(RequestHandler);$server->Run();?>代码解读：
- 为了便于说明问题，这里所有底层通讯基于UDP，省略了TCP的connect等繁琐细节
- AsyncServer为底层框架类，封装了网络通讯细节以及协程切换细节，通过socket进行coroutine绑定
- RequestHandler为业务处理函数，通过yield new AsyncTask()实现异步网络交互
第二版完善
第一版遗留问题：
- 异步网络交互的timeout未实现，仅预留了接口参数
- yield new AsyncTask()调用方式不够自然，略感别扭
<?phpclass AsyncServer { protected $handler; protected $socket; protected $tasks = []; protected $timers = []; public function __construct(callable $handler) { $this->handler = $handler; $this->socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); if(!$this->socket) { die(socket_strerror(socket_last_error())."\n"); } if (!socket_set_nonblock($this->socket)) { die(socket_strerror(socket_last_error())."\n"); } if(!socket_bind($this->socket, "0.0.0.0", 1234)) { die(socket_strerror(socket_last_error())."\n"); } } public function Run() { while (true) { $now = microtime(true) * 1000; foreach ($this->timers as $time => $sockets) { if ($time > $now) break; foreach ($sockets as $one) { list($socket, $coroutine) = $this->tasks[$one]; unset($this->tasks[$one]); socket_close($socket); $coroutine->throw(new Exception("Timeout")); } unset($this->timers[$time]); } $reads = array($this->socket); foreach ($this->tasks as list($socket)) { $reads[] = $socket; } $writes = NULL; $excepts= NULL; if (!socket_select($reads, $writes, $excepts, 0, 1000)) { continue; } foreach ($reads as $one) { $len = socket_recvfrom($one, $data, 65535, 0, $ip, $port); if (!$len) { //echo "socket_recvfrom fail.\n"; continue; } if ($one == $this->socket) { //echo "[Run]request recvfrom succ. data=$data ip=$ip port=$port\n"; $handler = $this->handler; $coroutine = $handler($one, $data, $len, $ip, $port); if (!$coroutine) { //echo "[Run]everything is done.\n"; continue; } $task = $coroutine->current(); //echo "[Run]AsyncTask recv. data=$task->data ip=$task->ip port=$task->port timeout=$task->timeout\n"; $socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); if(!$socket) { //echo socket_strerror(socket_last_error())."\n"; $coroutine->throw(new Exception(socket_strerror(socket_last_error()), socket_last_error())); continue; } if (!socket_set_nonblock($socket)) { //echo socket_strerror(socket_last_error())."\n"; $coroutine->throw(new Exception(socket_strerror(socket_last_error()), socket_last_error())); continue; } socket_sendto($socket, $task->data, $task->len, 0, $task->ip, $task->port); $deadline = $now + $task->timeout; $this->tasks[$socket] = [$socket, $coroutine, $deadline]; $this->timers[$deadline][$socket] = $socket; } else { //echo "[Run]response recvfrom succ. data=$data ip=$ip port=$port\n"; list($socket, $coroutine, $deadline) = $this->tasks[$one]; unset($this->tasks[$one]); unset($this->timers[$deadline][$one]); socket_close($socket); $coroutine->send(array($data, $len)); } } } }}class AsyncTask { public $data; public $len; public $ip; public $port; public $timeout; public function __construct($data, $len, $ip, $port, $timeout) { $this->data = $data; $this->len = $len; $this->ip = $ip; $this->port = $port; $this->timeout = $timeout; }}function AsyncSendRecv($req_buf, $req_len, $ip, $port, $timeout) { return new AsyncTask($req_buf, $req_len, $ip, $port, $timeout);}function RequestHandler($socket, $req_buf, $req_len, $ip, $port) { //echo "[RequestHandler] before yield AsyncTask. REQ=$req_buf\n"; try { list($rsp_buf, $rsp_len) = (yield AsyncSendRecv($req_buf, $req_len, "127.0.0.1", 2345, 3000)); } catch (Exception $ex) { $rsp_buf = $ex->getMessage(); $rsp_len = strlen($rsp_buf); //echo "[Exception]$rsp_buf\n"; } //echo "[RequestHandler] after yield AsyncTask. RSP=$rsp_buf\n"; socket_sendto($socket, $rsp_buf, $rsp_len, 0, $ip, $port);}$server = new AsyncServer(RequestHandler);$server->Run();?>代码解读：
- 借助PHP内置array能力，实现简单的“超时管理”，以毫秒为精度作为时间分片
- 封装AsyncSendRecv接口，调用形如yield AsyncSendRecv()，更加自然
- 添加Exception作为错误处理机制，添加ret_code亦可，仅为展示之用
性能测试
测试环境
测试数据
100Byte/REQ1000Byte/REQasync_svr_v1.php16000/s15000/sasync_svr_v2.php11000/s10000/s展望未来
- 有兴趣的PHPer可以基于该思路进行底层框架封装，对于常见阻塞操作进行封装，比如：connect、send、recv、sleep ...
- 本人接触PHP时日尚浅，很多用法非最优，高手可有针对性优化，性能应该可以继续提高
- 目前基于socket进行coroutine绑定，如果基于TCP通信，每次connect/close，开销过大，需要考虑实现连接池
- python等语言也有类似的语言设施，有兴趣的读者可以自行研究
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