CODEWITHSUNDEEP
c#.netmultithreadingeventsdelegates
Yauvaraj Rimal
Yauvaraj Rimal

Reputation: 630

Event is not triggered when number of threads is large

I am having trouble with multi-threading and event delegate in C#. If anyone could help me solve this problem, that would be great. The problem is with multiple threads and events. In a single thread or up to 10 threads, custom event is triggered properly and works fine. However, when I increase the number of threads to 15 or 20, event are not triggered at all. Here is sample piece of code:

LegacyMemberStream memberStream=new LegacyMemberStream();
memberStream.OpenStream();
legacyMemberStrm = (LegacyMemberStream)memberStream;                
legacyMemberStrm.ThreadErrorOccur += OnParserThreadInterrupt;

Here is code for OnParserThreadInterrupt():

  private void OnParserThreadInterrupt(Object Sender, ThreadErrorEventArgs args)
        {
            // Exception logging is done here
        }

And, the part of LegacyMemberStream.OpenStream() method is: 

parserThreads[i].OnThreadError = HandleThreadError;
parserThreads[i].StartThread();

This method simply initializes number of threads requested and assigns event for each thread when exception occur and finally starts threads.

And, HandleThreadError method in LegacyMemberStream is : 

 public void HandleThreadError(Exception exception, string threadName)
        {

            lock (SyncObject)
            {
                Console.WriteLine("From parser thread");
                for (int i = 0; i < parserThreads.Length; i++)
                {
                    if (parserThreads[i].Name.Equals(threadName))
                    {
                        parserThreads[i].StopThread();                        
                        break;
                    }
                }

                int threadFailureErrorCode = -1111;
                OnThreadFailure(new ThreadErrorEventArgs(threadFailureErrorCode, true,exception));

               somethingQueue.StopQueuing();
            }
        }

LegacyMemberStream.OnThreadFailure:

protected virtual void OnThreadFailure(ThreadErrorEventArgs e)
        {            
            lock (_locker)
            {
                var threaderrorOccur = ThreadErrorOccur;
             //   Console.WriteLine("Exception occurred");
                if (threaderrorOccur != null)
                {
                    ThreadErrorOccur(this, e);
                }
            }
        }

For any number of threads, HandleThreadError() method is called from OnThreadError event.

What I have discovered so far from debugging is that, OnParserThreadInterrupt() method is not being invoked when number of threads are greater than 15 (or sometimes 20). However, for same input and same scenario, OnParserThreadInterrupt() event is triggered when number of threads is lesser. I can't understand why event is not being triggered when number of threads are increased.

Upvotes: 0

Views: 55

Answers (1)

Rami Yampolsky
Rami Yampolsky

Reputation: 475

Basing on this code that you have shared, the only reason that seems to be possible is that the error happens before you submit the event handler. so just change order of the first lines to be:

LegacyMemberStream memberStream=new LegacyMemberStream();
legacyMemberStrm = (LegacyMemberStream)memberStream;                
legacyMemberStrm.ThreadErrorOccur += OnParserThreadInterrupt;
memberStream.OpenStream();

If the context switch was before you got the chance to submit the event handler then this function:

protected virtual void OnThreadFailure(ThreadErrorEventArgs e)
        {            
            lock (_locker)
            {
                var threaderrorOccur = ThreadErrorOccur;
             //   Console.WriteLine("Exception occurred");
                if (threaderrorOccur != null)
                {
                    ThreadErrorOccur(this, e);
                }
            }
        }

skipped the call to ThreadErrorOccur because the if statement is false.

Why is that related to number of threads? I think it is matter of probability. Maybe creating many threads consumes enought time so the main thread context switched, then the threads run (also context switched between them), get errors... and all of that happens before the main thread, whci creates them had the chance to do the line that subscribes the ThreadErrorOccur event Hope it solves your issue.

Upvotes: 2

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