Question

Any help with this one greatly appreciated…

I have a WPF application, and I am trying to leverage the Enterprise Library (v5) logging capability to capture certain events. The application is all .Net 4.0.

I have several long running processes, and am using the Task Parallel Library to multithread where necessary. I use the Task.Factory.StartNew syntax, and have several continuations to control flow.

The chain of events finishes with a call to a method I run back on the UI thread, allowing me to udpate various UI components and the like. Wtihin this method I am also trying to write to my log… and the application simply hangs.

To summarise:

1) I have a static ‘logging’ class to allow me to resolve an instance of the Logger with the usual method:

public static void LogThis(string message)
{    
LogWriter logWriter = EnterpriseLibraryContainer.Current.GetInstance<LogWriter>();
logWriter.Write(message, "My Default Logging Category");
}

2) I have a Task Factory call which kicks off my long running work:

...
var longProcess = Task.Factory.StartNew(() => ThisMethodTakesAWhile(variable));
...

3) This task finishes, via continuation, with a call to my ‘wrap things up’ method:

... 
// longProcess is the task coming out of the Factory call in point 2.
// We use the Current Sync Context to allow us to come back to the UI thread.
longProcess.ContinueWith(ant => WrapThingsUp(ant.Result), CancellationToken.None, TaskContinuationOptions.NotOnFaulted, TaskScheduler.FromCurrentSynchronizationContext());
...

4) My ‘wrap things up’ method attempts to log:

private void WrapThingsUp(string resultOfLongProcess)
{
//This call locks the applicaiton.
LogThis("Just to let you know I've finished that long task");
// I never get here!
}

My Logging is configured to target a rolling flat file, in a local folder. Any calls from the UI thread work without issue. It seems to ONLY be the calls from out of the TPL that lock.

I have read articles about not being able to write to a single file simultaneously from multiple source (which I am not trying to do, I’m ensuring in point 4 above that nothing else is trying to log).

I have also seen the article here about thread safety, and I wonder if that is related.

EDIT: I’ve also tried calling the log write explicitly as discussed here, which is pinged in the StackOverflow article here.

EDIT: I’m convinced this is to do with the UI / Dispatcher, as right clicking rapidly on the applications task bar item ‘wakes’ it up.

If I can add any more detail, please let me know.

Answer 1

First off, use a static constructor to init your static logger, and use a static field to communicate with it.
you are wasting a lot of overhead using the factory constntly (it checks the config file every time you log something).

that being said,

I created a simple TPL example that just sleeps for random amounts of time (between 8 and 10 min) before returning to the UI, it sends updates via AsyncOperationManager, to the UI and everything works.

I could not repeat your issue. can you elaborate more ?

using EL 5.0