Re: thread communication

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Hi Pete

This morning I changed some code. I previously had a Queue<IFileProcessor> which I checked in a thread and called Execute() on each instance as I removed it. I changed this into a simple class which has a SyncRoot which I can Wait and Pulse, and then some code to process the queue.

Now I have 3 queues

Dictionary<EstimatedProcessTime, Queue<IFileProcessor>> Queues;

Previously I did something like this

while (true)
{
bool hasWork;

//These take milliseconds, so we do all of these first
Dequeue(Queues[EstimatedProcessTime.Immediate], out hasWork);
if (hasWork)
continue;

//These take about 1 second, so do these when the Immediate ones are done
Dequeue(Queues[EstimatedProcessTime.Medium], out hasWork);
if (hasWork)
continue;

//These take about 12 seconds, so only do when then others are done
Dequeue(Queues[EstimatedProcessTime.Long], out hasWork);

Thread.Sleep(1000);
}

private void Dequeue(Queue<IFileProcessor> queue, out bool hasWork)
{
IFileProcessor processor = null;
lock(queue)
{
if (queue.Count > 0)
processor = queue.Dequeue();
hasWork = (queue.Count > 0);
}
processor.Execute();
}

The problem with this is that the 12 second process would stop the immediate/medium length processes from executing. I have intended to make this 1 thread per queue for a few days now, so after our discussion I changed it this morning...

public class FileProcessorQueue
{
public readonly object SyncRoot;
readonly Thread Thread;
readonly Queue<IFileProcessor> Queue;

public FileProcessorQueue()
{
SyncRoot = new object();
Queue = new Queue<IFileProcessor>();
Thread = new Thread(new ThreadStart(ProcessQueue));
Thread.Start();
}

public void Enqueue(IFileProcessor processor)
{
lock (SyncRoot)
{
Queue.Enqueue(processor);
Monitor.Pulse(SyncRoot);
}
}

private void ProcessQueue()
{
while (true)
{
IFileProcessor processor = null;
lock (SyncRoot)
{
if (Queue.Count > 0)
processor = Queue.Dequeue();
else
Monitor.Wait(SyncRoot);
}//lock syncroot
if (processor != null)
{
processor.Execute();
if (processor.State == FileProcessState.Ready)
Enqueue(processor);
}
}//while true
}


public void Clear()
{
lock (SyncRoot)
{
Queue.Clear();
}
}
}


Much happier now :-)



--
Pete
====
http://mrpmorris.blogspot.com
http://www.capableobjects.com

.

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