How To Send in a MSMQ Single-Message Transaction (179016)

SUMMARY

As part of its internal transaction support, Microsoft Message Queue Server (MSMQ) provides specific functionality to handle cases where an MSMQ application wants to send only a single message in a single transaction. One reason to do this is to ensure exactly-once delivery, without needing to coordinate with other activities into a single transaction.

The benefits of using this functionality are:

Speed, compared to using an external transaction coordinator.
Simplified application code.
Delivery that is assured to occur exactly once.

The software development kit (SDK) provides examples of doing this as an explicit internal transaction. This article provides examples of how to perform the send as an implicit internal transaction, because there are no examples of this in the SDK online Help.

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The following code sample illustrates sending a single-message transaction using the ActiveX methods:

   Dim qinfo As New MSMQQueueInfo
   Dim q As MSMQQueue
   Dim m As New MSMQMessage

   qinfo.PathName = "MachineName\TransactionalQueueName"
   Set q = qinfo.Open(MQ_SEND_ACCESS, MQ_DENY_NONE)
   m.Send q, MQ_SINGLE_MESSAGE
   q.Close

Using C API, set the pTransaction parameter to MQ_SINGLE_MESSAGE. The following code uses the "Sending Messages Using an Internal Transaction" example from the SDK; it demonstrates an explicit internal transactional send and modifies it for the implicit semantics:

   void TransactSend(QUEUEHANDLE h, MQMSGPROPS * pMsgProps)
   {
      HRESULT hr;
      printf ("\nStarting transaction...\n\n");
      ////////////////////////////////////// 
      // Call MQSendMessage to send a transactional message to
      // the destination queue.
      ////////////////////////////////////// 
      hr = MQSendMessage(h,                  // Handle to dest queue
                        &amp;msgprops,           // Pointer to MQMSGPROPS
                        MQ_SINGLE_MESSAGE);  // Implicit internal
                                             // transactional message.
      if (FAILED(hr))
      {
      printf("\nFailed in MQSendMessage(). hresult- %lxh\n", (DWORD) hr) ;
      }
      else
      {
          printf ("Committing the transaction...   ");
      }
     }

How To Send in a MSMQ Single-Message Transaction (179016)

SUMMARY

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