在Windows服务中处理MSMQ消息

Question

I have a windows service for processing the MSMQ messages. It relies on the following logic

· There is a timer in the windows service. Every ten minute it will execute the method named “ProcessMessages”.

· Inside this method, it first creates a list of existing messageIds by calling GetAllMessages method of the queue.

· For each messageId, it receives the message (using ReceiveById) and stores it into a file

Is there a better way to achieve the message processing?

Reference: http://www.switchonthecode.com/tutorials/creating-a-simple-windows-service-in-csharp

Note: The following code does not give the desired result when I made it as a service; however there is no error in event viewer (I am not doing any explicit logging). It was working fine when it was a simple console app. How to correct it? [Now it is working when I changed the accoun to "User" as shwon in the comments below]

My actaul requirement is to process all messages at fixed time slots – say at 10 AM and 11 AM only (on each day). What is the best approach to do this?

namespace ConsoleSwitchApp
{
    class Program : ServiceBase
    {
        private static Timer scheduleTimer = null;
        static MessageQueue helpRequestQueue = null;
        static System.Messaging.XmlMessageFormatter stringFormatter = null;

        static void Main(string[] args)
        {
            ServiceBase.Run(new Program());
        }

        public Program()
        {
            this.ServiceName = "LijosService6";

            //Queue initialize
            helpRequestQueue = new MessageQueue(@".\Private$\MyPrivateQueue", false);
            stringFormatter = new System.Messaging.XmlMessageFormatter(new string[] { "System.String" });

            //Set Message Filters
            MessagePropertyFilter filter = new MessagePropertyFilter();
            filter.ClearAll();
            filter.Body = true;
            filter.Label = true;
            filter.Priority = true;
            filter.Id = true;
            helpRequestQueue.MessageReadPropertyFilter = filter;

            //Start a timer
            scheduleTimer = new Timer();
            scheduleTimer.Enabled = true;
            scheduleTimer.Interval = 120000;//2 mins
            scheduleTimer.AutoReset = true;
            scheduleTimer.Start();
            scheduleTimer.Elapsed += new ElapsedEventHandler(scheduleTimer_Elapsed);
        }

        protected static void scheduleTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            ProcessMessages();
        }

        private static void ProcessMessages()
        {
            string messageString = "1";

            //Message Processing
            List<string> messageIdList = GetAllMessageId();
            foreach (string messageId in messageIdList)
            {
                System.Messaging.Message messages = helpRequestQueue.ReceiveById(messageId);
                //Store the message into database

                messages.Formatter = stringFormatter;
                string messageBody = System.Convert.ToString(messages.Body);

                if (String.IsNullOrEmpty(messageString))
                {
                    messageString = messageBody;
                }
                else
                {
                    messageString = messageString + "___________" + messageBody;
                }
            }

            //Write File
            string lines = DateTime.Now.ToString();
            lines = lines.Replace("/", "-");
            lines = lines.Replace(":", "_");
            System.IO.StreamWriter file = new System.IO.StreamWriter("c:\\test" + lines + ".txt");
            file.WriteLine(messageString);
            file.Close();
        }

        private static List<string> GetAllMessageId()
        {
            List<string> messageIdList = new List<string>();

            DataTable messageTable = new DataTable();
            messageTable.Columns.Add("Label");
            messageTable.Columns.Add("Body");

            //Get All Messages
            System.Messaging.Message[] messages = helpRequestQueue.GetAllMessages();
            for (int index = 0; index < messages.Length; index++)
            {
                string messageId = (System.Convert.ToString(messages[index].Id));
                messageIdList.Add(messageId);

                messages[index].Formatter = stringFormatter;
                messageTable.Rows.Add(new string[] { messages[index].Label, messages[index].Body.ToString() });
            }

            return messageIdList;
        }


        protected override void OnStart(string[] args)
        {
            base.OnStart(args);
        }

        protected override void OnStop()
        {
            base.OnStop();
        }
    }
}

namespace ConsoleSwitchApp
{
    [RunInstaller(true)]
    public class MyWindowsServiceInstaller : Installer
    {
        public MyWindowsServiceInstaller()
        {
            var processInstaller = new ServiceProcessInstaller();
            var serviceInstaller = new ServiceInstaller();

            //set the privileges
            processInstaller.Account = ServiceAccount.LocalSystem;
            serviceInstaller.DisplayName = "LijosService6";
            serviceInstaller.StartType = ServiceStartMode.Manual;

            //must be the same as what was set in Program's constructor

           serviceInstaller.ServiceName = "LijosService6";

            this.Installers.Add(processInstaller);
            this.Installers.Add(serviceInstaller);
        }
    }
}

Answer 1

A nice alternative to using a timer is to use the MessageQueue.BeginReceive method and do work in the ReceiveCompleted event. This way your code will wait until there is a message in the queue and then immediately process the message, then check for the next message.

A short stub (a complete example in the linked MSDN article.)

private void Start()
{
    MessageQueue myQueue = new MessageQueue(".\\myQueue");

    myQueue.ReceiveCompleted += 
        new ReceiveCompletedEventHandler(MyReceiveCompleted);

    myQueue.BeginReceive();
}

private static void MyReceiveCompleted(Object source, 
    ReceiveCompletedEventArgs asyncResult)
{
    try
    {
        MessageQueue mq = (MessageQueue)source;
        Message m = mq.EndReceive(asyncResult.AsyncResult);

        // TODO: Process the m message here

        // Restart the asynchronous receive operation.
        mq.BeginReceive();
    }
    catch(MessageQueueException)
    {
        // Handle sources of MessageQueueException.
    }

    return; 
}

Answer 2

Why not to subscribe to ReceiveCompleted event? Another option, if both sender and subscriber is .Net projects you are working on, use WCF over MSMQ .