How can you read the count of an MSMQ on another machine?

Question

My program is successfully using .NET's MessageQueue class to read from an MSMQ. The queue is user configurable, and is sometimes on the local machine, and sometimes on a remote machine. The user can specify the remote machine either by name or IP address, and the queue name (and I'm only using "Private" queues).

I want to display to the user how many messages remain in the Queue, but haven't found a way to do this. The MessageQueue class does not seem to have a Count (or similar) property to give this to me easily.

I've been able to use the PerformanceCounter and PerformanceCounterCategory classes to get the count - but this only seems to work for me on the local machine (although I'm not completely sure I'm using these classes correctly).

My question is how to read the Count (number of messages) from an MSMQ on a remote machine?

Answer 1

I use the following method for message counting (works for both local and remote queues),

        var machineName = "mymachine01";
        var formatName = "FormatName:DIRECT=OS:mymachine01\private$\ftpreceived":
        try
        {
            var msmqManagement = new MSMQ.MSMQManagement();
            msmqManagement.Init(machineName, null, formatName );
            return (uint)msmqManagement.MessageCount;
        }
        catch (COMException ex)
        {
            // If queue is not active or does not exist.
            if (ex.ErrorCode == -1072824316)
            {
                return 0;
            }

            throw;
        }

Note: It returns 0 in the case the queue does not exist or is not active as the MSMQ Managment API considers this the same error.

Note: If the machine name value is null it will look at the queue on the local machine.

Note: If the machinename variable is different from the machinename part of the formatname, it will return a count of messages in the "Outgoing" message queue with the given format name on the machine specified by machinename.

Active means it has 1 or more messages in it, or it has had a message in it within the last N (Not sure how big N is :)) seconds, after that time the queue is considered inactive.

Answer 2

The most reliable solution for getting the count of messages in a local queue is to use the MSMQ APIs using P/Invoke. There's a nice article here: Counting the number of messages in a Message Queue in .NET.

I don't know if it works with remote queues, but I wouldn't rely on it. Generally, the only thing you should do with a remote queue is to send a message. Trying to read messages or properties from a remote queue should be avoided, if possible. "Send remote and read local" will always give you the best performance and avoid all kinds of problems (e.g., what if the remote machine isn't available?)

Answer 3

I am using WMI to get this information. The following is an example of the code that I am using to accomplish this.

            var query = String.Format("select MessagesinQueue from Win32_PerfRawdata_MSMQ_MSMQQueue where name ='{0}'", path.Replace("\\", "\\\\"));
        var selectQuery = new SelectQuery(query);
        using (var searcher = new ManagementObjectSearcher(selectQuery))
        using (var results = searcher.Get())
        {
            foreach (var result in results)
            {
                var messages = result["MessagesinQueue"].ToString();
                return long.Parse(messages);
            }
        }

Answer 4

This may be a solution for you: http://jopinblog.wordpress.com/2008/03/12/counting-messages-in-an-msmq-messagequeue-from-c/

Answer 5

This might be overkill, but you could possibly put a WCF service on the same machine hosting your queue, so you'd be able to retrieve the count using the performance counters in the WCF service and expose that functionality through a method of that service.

Answer 6

I would like to say several things here.

• Before I get to my own answer, I would like to comment John Opncar's solution (in Dr. Wily's Apprentice answer). His code does work on remote machines. I used his code in our project at work to watch the queues on a remote cluster server and it works very well.

• So, if get "RemoteMachineNotAvailable" errors, please check your configurations. Are all machines in the same network or - not to forget - are the queue's security permissions on the remote machine set up to allow others to read them? Do the users/ accounts have sufficient rights to read from other systems?

For example, we had to allow everyone on the clustered queues.

• As far as I know the PerformanceCounters do indeed have problems to read message properties on remote machines. I tried to use them for queues in a Windows Server cluster environment, but was never able to get it working. I did some internet research at that time, but unfortunatelly I do not recall if this is due to security reasons or simply a bug. :-(

• Now to the actual answer. If you do not like the Cursor-Method as described by John Opincar you could also use the MessageQueue.GetAllMessages() or MessageQueue.GetMessageEnumerator methods.

I never tried GetMessageEnumerator, but I can say that I would not recommend GetAllMessages().

We suffered from heavy performance issues when using it every second on a system with several queues that contain several thousands of messages. The method takes a snapshot of all messages in the queue, which can cause heavy loads in memory and network.

The cursor-methodis still somewhat slow. But, at least in our production environment, it feels more snappy than with the GetAllMessages() solution.

If counting the messages in your scenario does not need to be as often as one second and you have less messages to count than we do, then working with GetAllMessages() or GetMessageEnumerator() might be a possible solution for you.

Finally, it always comes down to your own individual needs.