OutOfMemory Exception C# When working with threads

Question

I have a service that needs to run forever in order to monitor one server. In order to do so I have 5 tasks that need to be done by the service (5 at the moment, there are going to be hundreds).

I created a threadpool with maximum 5 threads. There is a queue that the threads use in order to get the task, then each thread processes the task and then enqueues it again. The queue contains objects with 5 small attributes.

After the service runs for a while I get an OutOfMemoryException, at the line where I execute this:

ThreadPool.QueueUserWorkItem(currentJob.ProcessJob, (object)timeToWwait);

The timeToWwait is an int and I don't use it anymore.

The context is like this:

        ThreadPool.SetMinThreads(0, 0);
        ThreadPool.SetMaxThreads(5, 5);
        while (true)
        {
            bool processJob = false;
            bool checkedFrontEnd = false;
            _qLock.EnterWriteLock();
            try
            {
                if (_jobQueue.Count > 0)
                {
                    currentJob = _jobQueue.Dequeue();
                    // currentJob.IsActive = true;
                    // processJob = true;
                }
            }
            finally
            {
                _qLock.ExitWriteLock();
            }
            ThreadPool.QueueUserWorkItem(currentJob.ProcessJob, (object)timeToWwait);
            //currentJob.ProcessJob((object)timeToWwait);


            _qLock.EnterWriteLock();
            try
            {
                _jobQueue.Enqueue(currentJob);
            }
            finally
            {
                _qLock.ExitWriteLock();
            }

Do you have any suggestions please?

Please refer to the FAQ regarding including signatures in your question and tags in your title. I've fixed it twice but the 2 rep I would get from it isn't worth doing it again. — M.Babcock
– M.Babcock, Commented Dec 30, 2011 at 4:47

voutmaster · Accepted Answer · 2011-12-30 04:58:35Z

2

Your problem is that you're enqueuing the currentJob instance before your background task has had a chance to complete. You'll want to do something like this instead:

        ThreadPool.QueueUserWorkItem((state) =>
                                         { 
                                             currentJob.ProcessJob();
                                             _qLock.EnterWriteLock();
                                             try
                                             {
                                                 _jobQueue.Enqueue(currentJob);
                                             }
                                             finally
                                             {
                                                 _qLock.ExitWriteLock();
                                             } 

                                         }
            );

answered Dec 30, 2011 at 4:58

voutmaster

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1 Comment

Ryan Papke Over a year ago

Thank you so much for helping me. This is indeed solving my problem and thanks for your suggestion. I will use this approach. I was just thinking at a new design and your answer came out to be very helpful.

mikey · Accepted Answer · 2011-12-30 04:56:18Z

1

It looks like you may want to enqueue the job again (to the jobQueue) only after it has been completed by the thread working on it. Imagine there is only 1 thread in the pool and 1 job in the jobQueue, if the job is long running, your code would execute ThreadPool.QueueUserWorkItem many times on the same job. Also I think you'd only want to execute ThreadPool.QueueUserWorkItem if there was a job in the jobQueue (from the code above it looks like it would run regardless). Thanks for the interesting question.

answered Dec 30, 2011 at 4:56

mikey

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1 Comment

Ryan Papke Over a year ago

Thank you for your interest in my problem. You are right. This is really solving my problem... finally. Very helpful.

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