如何捕获第三方库中未等待的任务引发的异常？

Question

我有一个依赖于第三方库 EasyRedisMQ 的 Windows 服务（使用 Topshelf）。不幸的是，我刚刚在其中一个库方法中发现了以下代码：

    public async Task InitializeAsync()
    {
        if (SubscriberInfo == null) throw new NullReferenceException("SubscriberInfo is required.");
        if (string.IsNullOrWhiteSpace(SubscriberInfo.SubscriberId)) throw new NullReferenceException("SubscriberId is required");
        if (string.IsNullOrWhiteSpace(SubscriberInfo.ExchangeName)) throw new NullReferenceException("ExchangeName is required");
        if (string.IsNullOrWhiteSpace(SubscriberInfo.QueueName)) throw new NullReferenceException("QueueName is required");
        if (OnMessageAsync == null) throw new NullReferenceException("OnMessageAsync is required");

        await _cacheClient.SubscribeAsync<string>(SubscriberInfo.ExchangeName, DoWorkAsync);

        DoWorkAsync("").FireAndForget();
    }

这里 DoWorkAsync 返回一个任务，但正如 FireAndForget 所指出的，不幸的是，这没有等待。实际上，FireAndForget 是一个具有空主体的方法（唯一的目的是明确地表明该任务不处于等待状态）。 查看完整源代码here。

问题是DoWorkAsync偶尔会抛出异常，导致服务崩溃：

{
  "Depth": 0,
  "ClassName": "StackExchange.Redis.RedisConnectionException",
  "Message": "SocketFailure on RPOP",
  "Source": "mscorlib",
  "StackTraceString": "   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at StackExchange.Redis.Extensions.Core.StackExchangeRedisCacheClient.<ListGetFromRightAsync>d__67`1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at EasyRedisMQ.Models.Subscriber`1.<GetNextMessageAsync>d__12.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at EasyRedisMQ.Models.Subscriber`1.<DoWorkAsync>d__13.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at StackExchange.Redis.Extensions.Core.StackExchangeRedisCacheClient.<>c__DisplayClass59_0`1.<<SubscribeAsync>b__0>d.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<>c.<ThrowAsync>b__6_1(Object state)\r\n   at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object state)\r\n   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)\r\n   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)\r\n   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()\r\n   at System.Threading.ThreadPoolWorkQueue.Dispatch()\r\n   at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()",
...
}

我非常想捕捉异常（因为它实际上是无害的，只需重试操作）。但是，在阅读了this StackOverflow question 并尝试了 AppDomain.CurrentDomain.FirstChanceException 之后，我并没有寄予厚望。 FirstChanceException 的问题在于它发生在 Tophelf 的

之外

HostFactory.Run(hostConfigurator => { ... }

方法，我在其中引用了服务（业务逻辑所在的位置）：

hostConfigurator.Service<IConsumer>(serviceConfigurator =>
{
    serviceConfigurator.ConstructUsing(() => IocContainer.IocContainer.Instance.Resolve<IConsumer>());
    serviceConfigurator.WhenStarted(consumer => { /* Here I have control */ });
    ...
}

有人对如何处理这种情况有任何想法吗？

Answer 1

订阅TaskScheduler的event：

TaskScheduler.UnobservedTaskException += TaskScheduler_UnobservedTaskException;
//...

private void TaskScheduler_UnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
{
    e.SetObserved();
}