异步日志记录抛出一个NullReferenceException [英] Async logging throwing a NullReferenceException
问题描述
我想以异步方式记录一个MVC 4控制器动作针对.NET 4.0使用AsyncTargetingPack内部的一些信息到SQL Server。我会直接跳到.NET 4.5,但我的应用程序住在Azure和<一href="http://www.mygreatwindowsazureidea.com/forums/34192-windows-azure-feature-voting/suggestions/2598170-iis8-and-asp-net-4-5-support-in-azure-platform">we're还在等待更新 ...
I am trying to asynchronously log some information to SQL Server inside of an MVC 4 controller action targeting .NET 4.0 using the AsyncTargetingPack. I would jump straight to .NET 4.5 but my app lives in Azure and we're still waiting for the update...
这code按预期工作(一排被写入我的数据库抛出没有例外):
This code works as expected (a row is written to my database with no exceptions thrown):
public class SystemActionLogger : ISystemActionLogger
{
private readonly ActionBlock<Tuple<SystemAction, object>> actionBlock;
public SystemActionLogger(ISystemActionLogEntryRepository repository)
{
actionBlock = new ActionBlock<Tuple<SystemAction, object>>(
entry => TaskEx.Run(async () =>
{
string data = await JsonConvert.SerializeObjectAsync(entry.Item2);
await repository.PersistAsync(new SystemActionLogEntry(entry.Item1, data));
}));
}
public void Log(SystemAction systemAction, object data)
{
actionBlock.Post(new Tuple<SystemAction, object>(systemAction, data));
}
}
这code抛出一个NullReferenceException:
And this code throws a NullReferenceException:
public class SystemActionLogger : ISystemActionLogger
{
private readonly ActionBlock<Tuple<SystemAction, object>> actionBlock;
public SystemActionLogger(ISystemActionLogEntryRepository repository)
{
actionBlock = new ActionBlock<Tuple<SystemAction, object>>(async entry =>
{
string data = await JsonConvert.SerializeObjectAsync(entry.Item2);
await repository.PersistAsync(new SystemActionLogEntry(entry.Item1, data));
});
}
public void Log(SystemAction systemAction, object data)
{
actionBlock.Post(new Tuple<SystemAction, object>(systemAction, data));
}
}
的NullReferenceException:对象未设置为一个对象的实例
NullReferenceException: "Object reference not set to an instance of an object."
Server stack trace:
at System.Web.ThreadContext.AssociateWithCurrentThread(Boolean setImpersonationContext)
at System.Web.HttpApplication.OnThreadEnterPrivate(Boolean setImpersonationContext)
at System.Web.LegacyAspNetSynchronizationContext.CallCallbackPossiblyUnderLock(SendOrPostCallback callback, Object state)
at System.Web.LegacyAspNetSynchronizationContext.CallCallback(SendOrPostCallback callback, Object state)
at System.Runtime.CompilerServices.TaskAwaiter.<>c__DisplayClassa.<OnCompletedInternal>b__0(Task param0)
Exception rethrown at [0]:
at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>b__1(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
我不可见性的例外,因为它是所有外部code。我不明白为什么code中的第二块失败。这是code我原来写的。
I have no visibility into the exception as it is all external code. I don't understand why the second block of code fails. This is the code I originally wrote.
我究竟做错了什么?
推荐答案
我只是有一个非常类似的问题(从AssociateWithCurrentThread使用日志记录任务时NullReference)。
I was just having a very similar issue (NullReference from AssociateWithCurrentThread when using a logging task).
我遇到的问题是,原来的动作并没有等待完成测井任务,所以当日志完成,并试图重新加入原来的线程nullReference被抛出,因为原来的线程终止。
The issue I was having was that the original action did not await the completion of the logging task, so when the log finishes and tries to rejoin the original thread a nullReference is thrown because the original thread has terminated.
这是解决了,我要确保请求控制器等待记录功能。
This was solved for me by making sure that the request controller awaited the logging function.
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