CODEWITHSUNDEEP
.nettransactionsmsmqordered-delivery
Ron Klein
Ron Klein

Reputation: 9440

What is the proper configuration so that messages are sent once, in-order, in MSMQ?

Here's the scenario:

2 Machines: "Machine A" and "Machine B".

Let's sat that their corresponding IP addresses are 192.168.0.100 (for A) and 192.168.0.200 (for B). Both machines have MSMQ installed on them, on Windows Server 2008.

Machine A

Has the following queue configured: private$\aaa, transactional.

Has a single consumer for that queue, which wraps every Read action in an MSMQ transaction, and reads only from the "current" message (that is, no cursor operations are used).

Machine B

Has a single application that sends messages to FormatName:direct=os:192.168.0.100\private$\aaa. Each Send message is wrapped in an MSMQ transaction, with (code in C#):
TimeToReachQueue = Message.InfiniteTimeout
and
TimeToBeReceived = Message.InfiniteTimeout

And... the question

Under this scenario and configuration of private$\aaa, are the messages sent from B to A:

  1. Delivered once? I mean, do I have to make sure in the consumer application on machine A that the "current" message is actually "new" (that is, was not processed before)? Or does the MSMQ itself take care for that matter? I know it sounds a bit silly, since it's a queue, right?! But I couldn't find a concrete reference claiming that the messages are in order. I've seen such a claim, but not from Microsoft official resource.
  2. In-order? I mean, is it possible that a message M1 cannot be sent from B to A, because of network problems, and then, perhaps, the network is back to normal, and the following message, M2, is successfully sent to machine A?

Thanks a lot!

Upvotes: 1

Views: 136

Answers (1)

Chris Wenham
Chris Wenham

Reputation: 24017

  1. Delivered Once is guaranteed, but keep in mind that you have a transactional queue, so if message processing fails the first time, then it'll be delivered again until it either succeeds or gets moved to a poisoned message queue. Therefore "Delivered Once" is only guaranteed within that context, and if the other resources you manipulate are also transactional and participate in the distributed transaction then you should be safe.

  2. Messages are "sent together, in the order they were sent, or not at all". See MSMQ Tips

Upvotes: 3

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