[英]How to catch exception thrown by a task that's not awaited in a third party library?
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 指出的那样,不幸的是没有等待。 实际上,FireAndForget 是一个具有空主体的方法(唯一的目的是明确表示不等待任务)。 在这里查看完整的源代码。
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()",
...
}
我非常想捕获异常(因为它实际上是无害的,只需重试操作即可)。 但是,在阅读了这个 StackOverflow 问题并尝试了 AppDomain.CurrentDomain.FirstChanceException 之后,我并不抱太大希望。 FirstChanceException 的问题在于它发生在 Tophelf 的外部
HostFactory.Run(hostConfigurator => { ... }
方法,其中我引用了服务(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 */ });
...
}
有没有人对如何处理这种情况有任何想法?
订阅 TaskScheduler 的事件:
TaskScheduler.UnobservedTaskException += TaskScheduler_UnobservedTaskException;
//...
private void TaskScheduler_UnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
{
e.SetObserved();
}
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