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Multiple threads processing a ConcurrentQueue

Posted on 2010-08-17
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Last Modified: 2013-11-13
Bit of background, we have a sockets server currently supporting around 500 concurrent users, these users are running lots of different actions all at the same time, thus the sockets server is under a lot of stress.

What we're looking at doing is placing each message that is received from the clients into a managed ConcurrentQueue (.NET 4.0). We've successfully put these into the queue and we can dequeue them on a seperate thread, this works up to a point.

What we'd ideally like is for these messages to be processed asynconously by multiple threads at the same time, but we don't want to have these threads waiting in a while loop because the CPU goes through the roof. Ideally we'd like the queue to be observable and for a thread to kick in and process.

To give some perspective, we probably get 10 requests per second so we can't afford for the queue to be blocking.

What direction should we be heading in with this.
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Question by:Type25
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by:SpicyFrog
ID: 33458775
Have you looked into using a thread pool?  Sounds like the ideal application.

http://msdn.microsoft.com/en-us/library/3dasc8as%28VS.80%29.aspx
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SandyAgo earned 500 total points
ID: 33464948
What you need to do is make the Message Queue block using a threading monitor if there are no message on the queue. Here is an example:


public class MsgQueue {

        protected bool blocked = true; // set false when the queue server is running
        protected int limit;
        protected int length;
        protected int maximum;
        protected int failedPutQ1;
        protected int failedPutQ2;
        protected String name;
        protected QueueableObject first;
        protected QueueableObject last;

        public MsgQueue (int limit, String name) {
            if (limit < 500) limit = 500;
	        this.limit = limit;
	        this.name = name;
        }

	        /**
	         * Tests whether there are more messages on this queue. Note that this
	         * method is not synchronized so the caller must be synchronized with all
	         * other users of this queue.
	         * 
	         * @return
	         */
	        public boolean hasMore() {
		        return first != null;
	        }
        	
            /**
             * Return a queued object or wait if none are on the queue. Return null if
             * interrupted.
             */
            [MethodImpl(MethodImplOptions.Synchronized)]
            public QueueableObject getQ() {
                QueueableObject s = null;
                while (s == null) {
                    if (first == null) {
                        Monitor.Wait(this);
                    }
                    s = first;
                    if (s != null) { // s might be null if we got an interrupt
                        s.onQueue = false;
                        first = s.next;
                        length--;
                        if (first == null) {
                            last = null;
                        }
                    }
                } // end while
                return s;
            }

            /**
             * Return a queued object or null if none are on the queue
             */
            [MethodImpl(MethodImplOptions.Synchronized)]
            public QueueableObject getNoWait() {
                QueueableObject s = null;
                s = first;
                if (s != null) {
                    s.onQueue = false;
                    first = s.next;
                    length--;
                    if (first == null) {
                        last = null;
                    }
                }
                return s;
            }

        /**
	        Insert the object onto the end of the queue.  If the queue is blocked
	        or full, return the object.  Otherwise, return null indicating success.
        */
        [MethodImpl(MethodImplOptions.Synchronized)]
        private QueueableObject putQSync (QueueableObject s) {
	        QueueableObject rtn = null;
	        if (s.onQueue) {
                String currentThread = Thread.CurrentThread.Name;
                String detail = "Queue put while still onQueue, id = " + s.ident
                    + ", Queue Len = " + getLength() + ", Queue Max = "
                    + getMaximum() + (blocked ? ", Blocked" : ", Not Blocked")
                    + "\nprevious putting thread: " + s.queuingThread
                    + ", previously put to queue " + s.queueName
                    + "\ncurrent thread: " + currentThread + ", current queue: "
                    + name;
                throw new Exception(detail);
	        }
	        if (blocked) {
		        rtn = s; // indicate couldn't queue Msg
	        }
	        else if (++length > limit) {
                length--;
                rtn = s;
            }
            else {
                if (length > maximum) {
                    maximum = length;
                }
		        if (first == null) {
			        first = last = s;
		        }
		        else {
			        last.next = s;
			        last = s;
		        }
		        s.next = null;
		        s.onQueue = true;
                s.queuingThread = Thread.CurrentThread.Name;
                s.queueName = this.name;
                Monitor.PulseAll(this);
	        }

	        return rtn; // indicate whether QueueableObject successfully queued
        }

        public QueueableObject putQ (QueueableObject s) {
            QueueableObject rtn = putQSync (s);
            if (rtn != null){
               lock (typeof(MsgQueue)) {            
                    failedPutQ1++;
                }
                // try again in 150ms
                try {
                    Thread.Sleep(150);
                } catch (ThreadInterruptedException e) {
                }
                rtn = putQSync (s);
                if (rtn != null){                
                    lock (typeof(MsgQueue)) {                
                        failedPutQ2++;
                    }
                }
                
            }
            return rtn; // indicate whether QueueableObject successfully queued
        }

        /**
         * Put the object onto the queue.  If there is no space, free the object.
         * 
         * @return null
         */
        public QueueableObject putQorFree (QueueableObject s) {
            s = putQ(s);
            if (s != null) {
                s.putFree();
            }
            return null;
        }

        [MethodImpl(MethodImplOptions.Synchronized)]
        public void drain() {
	        QueueableObject s = getNoWait();
	        while (s != null) {
		        s.putFree();
		        s = getNoWait();
	        }
	        failedPutQ1 = 0;
	        failedPutQ2 = 0;
        }

        public void setBlocked(bool newstate) {
            blocked = newstate;
        }

        public void setBlocked(bool newstate, String threadName) {
            blocked = newstate;
        }

        public bool getBlocked() {
            return blocked;
        }

        public int getLength () {
            return length;
        }

        public int getMaximum () {
            return maximum;
        }

        public int getFailedPutQ1() {
            return failedPutQ1;
        }

        public int getFailedPutQ2() {
            return failedPutQ2;
        }

        public void resetStats() {
            maximum = 0;
            failedPutQ1 = 0;
            failedPutQ2 = 0;
        }
    } // end class Queue

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