MQQueueManager message pooling

Question

I've used in the past RabbitMq as MessageQueue and it was really simple to have an event fired when a message has been received.

I've looked at the .NET sources provided with IBM installer but I've found a not good way to handle it. Looking at the sample SimpleSubscribe it does such a thing to pool

// getting messages continuously
for (int i = 1; i <= numberOfMsgs; i++)
{
    // creating a message object
    message = new MQMessage();

    try
    {
        topic.Get(message);
        Console.WriteLine("Message " + i + " got = " + message.ReadString(message.MessageLength));
        message.ClearMessage();
    }
    catch (MQException mqe)
    {
        if (mqe.ReasonCode == 2033)
        {
            ++time;
            --i;
            Console.WriteLine("No message available");
            Thread.Sleep(1000);
            //waiting for 10sec
            if (time > 10)
            {
                Console.WriteLine("Timeout : No message available");
                break;
            }
            continue;
        }
        else
        {
            Console.WriteLine("MQException caught: {0} - {1}", mqe.ReasonCode, mqe.Message);
        }
    }
}

where the number of numberOfMsgs is an integer passed as an argument. If I pass -1 it probably will pool at the infinite but I think it's not a good approach. This leads me to pool the queue at a specific interval then probably will spin a thread at 100% I don't put a Thread.Sleep Does anyone have a better approach?

Answer 1

You should use "MQGET with Wait" option rather than use polling. The MQGET call will wait for a message to arrive and return immediately when it receives a message otherwise it will wait for "x" milliseconds.

Here is a simple working C# MQ program:

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using IBM.WMQ;

/// <summary> Program Name
/// MQTest62
///
/// Description
/// This C# class will connect to a remote queue manager
/// and get messages from a queue using a managed .NET environment.
///
/// Sample Command Line Parameters
/// -h 127.0.0.1 -p 1415 -c TEST.CHL -m MQWT1 -q TEST.Q1 -u tester -x mypwd
/// </summary>
/// <author>  Roger Lacroix
/// </author>
namespace MQTest62
{
   public class MQTest62
   {
      private Hashtable inParms = null;
      private Hashtable qMgrProp = null;
      private System.String qManager;
      private System.String inputQName;

      /*
      * The constructor
      */
      public MQTest62()
          : base()
      {
      }

      /// <summary> Make sure the required parameters are present.</summary>
      /// <returns> true/false
      /// </returns>
      private bool allParamsPresent()
      {
         bool b = inParms.ContainsKey("-h") && inParms.ContainsKey("-p") &&
                  inParms.ContainsKey("-c") && inParms.ContainsKey("-m") &&
                  inParms.ContainsKey("-q");
         if (b)
         {
            try
            {
               System.Int32.Parse((System.String)inParms["-p"]);
            }
            catch (System.FormatException e)
            {
               b = false;
            }
         }

         return b;
      }

      /// <summary> Extract the command-line parameters and initialize the MQ variables.</summary>
      /// <param name="args">
      /// </param>
      /// <throws>  IllegalArgumentException </throws>
      private void init(System.String[] args)
      {
         inParms = System.Collections.Hashtable.Synchronized(new System.Collections.Hashtable(14));
         if (args.Length > 0 && (args.Length % 2) == 0)
         {
            for (int i = 0; i < args.Length; i += 2)
            {
               inParms[args[i]] = args[i + 1];
            }
         }
         else
         {
            throw new System.ArgumentException();
         }

         if (allParamsPresent())
         {
            qManager = ((System.String)inParms["-m"]);
            inputQName = ((System.String)inParms["-q"]);

            qMgrProp = new Hashtable();
            qMgrProp.Add(MQC.TRANSPORT_PROPERTY, MQC.TRANSPORT_MQSERIES_MANAGED);

            qMgrProp.Add(MQC.HOST_NAME_PROPERTY, ((System.String)inParms["-h"]));
            qMgrProp.Add(MQC.CHANNEL_PROPERTY, ((System.String)inParms["-c"]));

            try
            {
               qMgrProp.Add(MQC.PORT_PROPERTY, System.Int32.Parse((System.String)inParms["-p"]));
            }
            catch (System.FormatException e)
            {
               qMgrProp.Add(MQC.PORT_PROPERTY, 1414);
            }

            if (inParms.ContainsKey("-u"))
               qMgrProp.Add(MQC.USER_ID_PROPERTY, ((System.String)inParms["-u"]));

            if (inParms.ContainsKey("-x"))
               qMgrProp.Add(MQC.PASSWORD_PROPERTY, ((System.String)inParms["-x"]));

            System.Console.Out.WriteLine("MQTest62:");
            Console.WriteLine("  QMgrName ='{0}'", qManager);
            Console.WriteLine("  Output QName ='{0}'", inputQName);

            System.Console.Out.WriteLine("QMgr Property values:");
            foreach (DictionaryEntry de in qMgrProp)
            {
               Console.WriteLine("  {0} = '{1}'", de.Key, de.Value);
            }
         }
         else
         {
            throw new System.ArgumentException();
         }
      }

      /// <summary> Connect, open queue, read (browse) a message, close queue and disconnect. </summary>
      ///
      private void testReceive()
      {
         MQQueueManager qMgr = null;
         MQQueue inQ = null;
         int openOptions = MQC.MQOO_INPUT_AS_Q_DEF + MQC.MQOO_FAIL_IF_QUIESCING;

         try
         {
            qMgr = new MQQueueManager(qManager, qMgrProp);
            System.Console.Out.WriteLine("MQTest62 successfully connected to " + qManager);

            inQ = qMgr.AccessQueue(inputQName, openOptions);
            System.Console.Out.WriteLine("MQTest62 successfully opened " + inputQName);

            testLoop(inQ);

         }
         catch (MQException mqex)
         {
            System.Console.Out.WriteLine("MQTest62 cc=" + mqex.CompletionCode + " : rc=" + mqex.ReasonCode);
         }
         catch (System.IO.IOException ioex)
         {
            System.Console.Out.WriteLine("MQTest62 ioex=" + ioex);
         }
         finally
         {
            try
            {
               if (inQ != null)
                  inQ.Close();
               System.Console.Out.WriteLine("MQTest62 closed: " + inputQName);
            }
            catch (MQException mqex)
            {
               System.Console.Out.WriteLine("MQTest62 cc=" + mqex.CompletionCode + " : rc=" + mqex.ReasonCode);
            }

            try
            {
               if (qMgr != null)
                  qMgr.Disconnect();
               System.Console.Out.WriteLine("MQTest62 disconnected from " + qManager);
            }
            catch (MQException mqex)
            {
               System.Console.Out.WriteLine("MQTest62 cc=" + mqex.CompletionCode + " : rc=" + mqex.ReasonCode);
            }
         }
      }

      private void testLoop(MQQueue inQ)
      {
         bool flag = true;
         MQGetMessageOptions gmo = new MQGetMessageOptions();
         gmo.Options |= MQC.MQGMO_WAIT | MQC.MQGMO_FAIL_IF_QUIESCING;
         gmo.WaitInterval = 2500;  // 2.5 seconds wait time or use MQC.MQEI_UNLIMITED to wait forever
         MQMessage msg = null;

         while (flag)
         {
            try
            {
               msg = new MQMessage();
               inQ.Get(msg, gmo);
               System.Console.Out.WriteLine("Message Data: " + msg.ReadString(msg.MessageLength));
            }
            catch (MQException mqex)
            {
               System.Console.Out.WriteLine("MQTest62 CC=" + mqex.CompletionCode + " : RC=" + mqex.ReasonCode);
               if (mqex.Reason == MQC.MQRC_NO_MSG_AVAILABLE)
               {
                  // no meesage - life is good - loop again
               }
               else
               {
                  flag = false;  // severe error - time to exit
               }
            }
            catch (System.IO.IOException ioex)
            {
               System.Console.Out.WriteLine("MQTest62 ioex=" + ioex);
            }
         }
      }

      /// <summary> main line</summary>
      /// <param name="args">
      /// </param>
      //        [STAThread]
      public static void Main(System.String[] args)
      {
         MQTest62 write = new MQTest62();

         try
         {
            write.init(args);
            write.testReceive();
         }
         catch (System.ArgumentException e)
         {
            System.Console.Out.WriteLine("Usage: MQTest62 -h host -p port -c channel -m QueueManagerName -q QueueName [-u userID] [-x passwd]");
            System.Environment.Exit(1);
         }
         catch (MQException e)
         {
            System.Console.Out.WriteLine(e);
            System.Environment.Exit(1);
         }

         System.Environment.Exit(0);
      }
   }
}