Enhance Coroutine::cancel() to throw an exception after canceling an IO operation

[tw2066]

目前执行cancel只会中断当前io操作, 程序还是会往下执行

use \Swoole\Coroutine;

\Swoole\Coroutine::set(['hook_flags' => SWOOLE_HOOK_ALL]);
\Swoole\Coroutine\run(function () {
    $cid = Coroutine::create(function () {
        for($i = 0; $i < 5; $i++) {
            $bool = Coroutine::sleep(1.0);
            var_dump($bool);
            print_r('$bool:'.$bool . '  '.$i);
            echo PHP_EOL;

        }
    });
    sleep(3);


    $bool = Swoole\Coroutine::cancel($cid);
    var_dump('cancel:'.$bool);

    sleep(5);
});

希望
增加 第2个参数(isThrow ),是否触发报错

当传入true时, cancel遇到io时,底层触发报错
终止当前协程; 达到类似kill的功能

Swoole\Coroutine::cancel($cid,bool isThrow = false): bool

---

use \Swoole\Coroutine;

\Swoole\Coroutine::set(['hook_flags' => SWOOLE_HOOK_ALL]);
\Swoole\Coroutine\run(function () {
    $cid = Coroutine::create(function () {
        for($i = 0; $i < 5; $i++) {
            $bool = Coroutine::sleep(1.0);
            // swoole 底层支持
            if ($bool === false){
                throw new Exception('coroutine cancel');
            }
            var_dump($bool);
            print_r('$bool:'.$bool . '  '.$i);
            echo PHP_EOL;
        }
    });
    sleep(3);


    $bool = Swoole\Coroutine::cancel($cid);
    var_dump('cancel:'.$bool);

    sleep(5);
});

控制台

bool(true)
$bool:1  0
bool(true)
$bool:1  1
PHP Fatal error:  Uncaught Exception: coroutine cancel in /home/test.php:10
Stack trace:
#0 [internal function]: {closure}()
#1 {main}
  thrown in /home/test.php on line 10

[NathanFreeman]

这个要想想怎么做，因为Swoole\Coroutine::cancel的执行逻辑在C++那一层，要抛出异常的话需要在PHP Zend VM层

[fakharksa]

@tw2066 If i am able to understand the issue correctly, then how about putting a try-catch around IO ?

// Inside Coroutine/create
try {
 $bool = Coroutine::sleep(1.0);
}
catch (Throwable $th) {
              // .... do nothing OR use continue() or do something based on conditions / requirement
             //OR 
            $chan->push($bool);  // A channel used in coroutine to output the value of $bool
}

The couroutine may take $isThrow, by setting $isThrow as true or false, as below:

$cid = Coroutine::create(function () use ($isThrow) { ... } (or as global $isThrow; $isThrow = true; )

... which you can consider in the catch part of the coroutine. (I have not tested it so it is just an idea)

[tw2066]

@fakharksa This approach is invasive to the code. Business logic may involve extensive I/O operations, and adapting all of them to this logic would be impractical. Such work would require enormous effort, and third-party packages cannot be modified to fit this logic

[edwjusti]

I was very disappointed when I realized that Swoole didn't provide a proper cancellation mechanism. It's something that I assumed would be supported out of the box given that we have a throw method for the stackless generators and stackful fibers as well. I hope this method can be included in Swoole at some point, this would bring Swoole closer to other PHP async libraries such as React and AMP.