从WCF服务调用基于任务的异步单向回调方法 [英] Calling a task-based asynchronous one way callback method from WCF service

问题描述

我有一个WCF服务，该服务使用回调合同来通知客户端，类似于此

I have a WCF service which uses a callback contract to notify the clients, similar to this

public interface IClientCallback
{
    [OperationContract(IsOneWay = true)]
    void NotifySomething();
}

以及与此类似的服务代码

and the service code calling it similar to this

void NotifySomething()
{
    try
    {
        this.callback.NotifySomething();
    }
    catch (Exception ex)
    {
        // Log the exception and eat it
    }
}

请注意，根据设计，回调通知是可选，即很高兴，但不是必需的.这就是为什么将其标记为OneWay且该实现会吃掉异常的原因.

Note that by design the callback notification is optional, i.e. nice to have, but not required. That's why it's marked as OneWay and the implementation eats exceptions.

由于某些误解，我们认为采用非阻塞性的忘却"方法就足够了.但是当然那不是真的，因此在某些情况下它会阻塞一段时间，这会引起问题，因为它是从内部线程同步块中调用的.因此，我们决定通过如下更改定义来使其异步

Due to some misunderstanding we were thinking that would be enough for having a non blocking fire and forget method. But of course that wasn't true, so under some circumstances it's blocking for a while, which is causing problems because it's called from inside thread synchronized block. So we decided to make it asynchronous by changing the definition as follows

public interface IClientCallback
{
    [OperationContract(IsOneWay = true)]
    Task NotifySomething();
}

我对客户端实现没有问题，我的问题是如何从服务中调用它.这是我想做的事情

I have no problem with client implementation, my question is how to call it from the service. Here is what I'm thinking to do

async void NotifySomething()
{
    try
    {
        await this.callback.NotifySomething();
    }
    catch (AggregateException ex)
    {
        // Unwrap, log the exception(s) and eat it
    }
    catch (Exception ex)
    {
        // Log the exception and eat it
    }
}

现在，既然每个人都说async void不是一个好习惯，那么可以在这里使用它吗?我还有什么其他选择?在WCF服务上下文中执行此操作的推荐方法是什么?

Now, since everyone is saying async void is not a good practice, is it ok to use it here? What other options do I have? What is the recommended way to perform this in the WCF service context?

推荐答案

您编写它的方式非常安全，因为它可以处理异常.您也可以编写一个可重用的扩展方法来做到这一点，这样就无需重复它.

The way you have written it is pretty safe as it handles the exceptions. You could also write a reusable extension method to do that so that you don't need to repeat it.

也许是这样的:

public static class Extensions
{
    public static void FireAndForget(this Task task)
    {
        task.ContinueWith(t => 
        {
            // log exceptions
            t.Exception.Handle((ex) =>
            {
                Console.WriteLine(ex.Message);
                return true;
            });

        }, TaskContinuationOptions.OnlyOnFaulted);
    }
}

public async Task FailingOperation()
{
    await Task.Delay(2000);

    throw new Exception("Error");
}   

void Main()
{
    FailingOperation().FireAndForget();

    Console.ReadLine();
}

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