如何取消协程中的阻止代码 [英] How to cancel the blocking code in the coroutines

问题描述

我具有以下代码结构:

 @Throws(InterruptedException::class)
 fun method() {
     // do some blocking operations like Thread.sleep(...)
 }
 var job = launch {
     method()
 }
 job.cancelAndJoin()

method由外部库提供，我无法控制其行为.执行可能会花费很多时间，因此在某些情况下，应通过超时将其取消.

The method is provided by the external library and I can't control its behaviour. It can take a lot of time for execution, so in some cases it should be canceled by timeout.

我可以使用kotlin协程库提供的withTimeout函数，但是由于协程的设计，它无法取消带有阻塞的代码.有解决方法吗?

I can use the withTimeout function provided by the kotlin coroutines library, but it can't cancel a code with blockings due to the coroutines design. It there some workaround to do it?

推荐答案

主要思想是将协程外上下文线程池与可以在旧样式中中断的自然线程一起使用，并从协程订阅取消事件执行.当事件被invokeOnCancellation捕获时，我们可以中断当前线程.

The main idea is to use the out of coroutines context thread pool with narutal threads that can be interrupted in the old style and subscribe on the cancellation event from the coroutines execution. When the event is catched by invokeOnCancellation, we can interrupt the current thread.

实现:

val externalThreadPool = Executors.newCachedThreadPool()
suspend fun <T> withTimeoutOrInterrupt(timeMillis: Long, block: () -> T) {
    withTimeout(timeMillis) {
        suspendCancellableCoroutine<Unit> { cont ->
            val future = externalThreadPool.submit {
                try {
                    block()
                    cont.resumeWith(Result.success(Unit))
                } catch (e: InterruptedException) {
                    cont.resumeWithException(CancellationException())
                } catch (e: Throwable) {
                    cont.resumeWithException(e);
                }
            }
            cont.invokeOnCancellation {
                future.cancel(true)
            }
        }
    }
}

它具有与通常的withTimeout类似的行为，但它还支持运行带有阻塞的代码.

It provides the similar behaviour like usual withTimeout, but it additionally supports running a code with blockings.

注意:仅当您知道内部代码使用阻塞并且可以正确处理抛出的InterruptedException时，才应调用它.在大多数情况下，首选withTimeout功能.

Note: It should be called only when you know, that the inner code use blockings and can correctly process a throwed InterruptedException. In most cases the withTimeout function is prefered.

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