MSMQ Receive() method timeout

Question

My original question from a while ago is MSMQ Slow Queue Reading, however I have advanced from that and now think I know the problem a bit more clearer.

My code (well actually part of an open source library I am using) looks like this:

queue.Receive(TimeSpan.FromSeconds(10), MessageQueueTransactionType.Automatic);

Which is using the Messaging.MessageQueue.Receive function and queue is a MessageQueue. The problem is as follows.

The above line of code will be called with the specified timeout (10 seconds). The Receive(...) function is a blocking function, and is supposed to block until a message arrives in the queue at which time it will return. If no message is received before the timeout is hit, it will return at the timeout. If a message is in the queue when the function is called, it will return that message immediately.

However, what is happening is the Receive(...) function is being called, seeing that there is no message in the queue, and hence waiting for a new message to come in. When a new message comes in (before the timeout), it isn't detecting this new message and continues waiting. The timeout is eventually hit, at which point the code continues and calls Receive(...) again, where it picks up the message and processes it.

Now, this problem only occurs after a number of days/weeks. I can make it work normally again by deleting & recreating the queue. It happens on different computers, and different queues. So it seems like something is building up, until some point when it breaks the triggering/notification ability that the Receive(...) function uses.

I've checked a lot of different things, and everything seems normal & isn't different from a queue that is working normally. There is plenty of disk space (13gig free) and RAM (about 350MB free out of 1GB from what I can tell). I have checked registry entries which all appear the same as other queues, and the performance monitor doesn't show anything out of the normal. I have also run the TMQ tool and can't see anything noticably wrong from that.

I am using Windows XP on all the machines and they all have service pack 3 installed. I am not sending a large amount of messages to the queues, at most it would be 1 every 2 seconds but generally a lot less frequent than that. The messages are only small too and nowhere near the 4MB limit.

The only thing I have just noticed is the p0000001.mq and r0000067.mq files in C:\WINDOWS\system32\msmq\storage are both 4,096KB however they are that size on other computers also which are not currently experiencing the problem. The problem does not happen to every queue on the computer at once, as I can recreate 1 problem queue on the computer and the other queues still experience the problem.

I am not very experienced with MSMQ so if you post possible things to check can you please explain how to check them or where I can find more details on what you are talking about.

Currently the situation is:

• ComputerA - 4 queues normal
• ComputerB - 2 queues experiencing problem, 1 queue normal
• ComputerC - 2 queues experiencing problem
• ComputerD - 1 queue normal
• ComputerE - 2 queues normal

So I have a large number of computers/queues to compare and test against.

Answer 1

Any particular reason you aren't using an event handler to listen to the queues? The System.Messaging library allows you to attach a handler to a queue instead of, if I understand what you are doing correctly, looping Receive every 10 seconds. Try something like this:

class MSMQListener
{
    public void StartListening(string queuePath)
    {
        MessageQueue msQueue = new MessageQueue(queuePath);
        msQueue.ReceiveCompleted += QueueMessageReceived;
        msQueue.BeginReceive();
    }

    private void QueueMessageReceived(object source, ReceiveCompletedEventArgs args)
    {
        MessageQueue msQueue = (MessageQueue)source;

        //once a message is received, stop receiving
        Message msMessage = null;
        msMessage = msQueue.EndReceive(args.AsyncResult);

        //do something with the message

        //begin receiving again
        msQueue.BeginReceive();
    }
}

Answer 2

We are also using NServiceBus and had a similar problem inside our network.

Basically MSMQ is using UDP with two-phase commits. After a message is received it has to be acknowledged. Until it is acknowledged it can not be received on the client side as the receive transaction hasn't been finalized.

This was caused by different things in different times for us: - once this was due to the Distributed Transaction Coordinator unable to communicate between machines as firewall misconfiguration - another time we were using cloned virtual machines without sysprep which made internal MSMQ ids non-unique and made it receive a message to one machine and ack to another. Eventually MSMQ figures things out but it takes quite a while.

Hope this helps.

Answer 3

Try this

public Message Receive( TimeSpan timeout, Cursor cursor )

overloaded function.

To get a cursor for a MessageQueue, call the CreateCursor method for that queue.

A Cursor is used with such methods as Peek(TimeSpan, Cursor, PeekAction) and Receive(TimeSpan, Cursor) when you need to read messages that are not at the front of the queue. This includes reading messages synchronously or asynchronously. Cursors do not need to be used to read only the first message in a queue.

When reading messages within a transaction, Message Queuing does not roll back cursor movement if the transaction is aborted. For example, suppose there is a queue with two messages, A1 and A2. If you remove message A1 while in a transaction, Message Queuing moves the cursor to message A2. However, if the transaction is aborted for any reason, message A1 is inserted back into the queue but the cursor remains pointing at message A2.

To close the cursor, call Close.

Answer 4

If you want to use something completely synchronous and without event you can test this method

public object Receive(string path, int millisecondsTimeout)
{
    var mq = new System.Messaging.MessageQueue(path);
    var asyncResult = mq.BeginReceive();
    var handles = new System.Threading.WaitHandle[] { asyncResult.AsyncWaitHandle };
    var index = System.Threading.WaitHandle.WaitAny(handles, millisecondsTimeout);
    if (index == 258) // Timeout
    {
        mq.Close();
        return null;
    }
    var result = mq.EndReceive(asyncResult);
    return result;
}