Question

Does NServicebus make sure messages are drawn down from a queue in a particular order like FIFO or LIFO?

Thx

Answer 1

NServiceBus doesn’t guarantee that messages will be processed in order (as far as im aware). Even if you ran a single thread, you can’t guarantee that message 2 doesn’t arrive before message 1.

I did a quick google search and also found:

http://mikaelkoskinen.net/post/NServiceBus-In-order-message-processing.aspx

Which seems to test the scenario, but came to the conclusion:

Conclusion

NServiceBus doesn’t handle messages
in-order. It’s up to the developer to
make sure that the relevant messages
are handler in the right order. The
easiest way to do this is to send
messages as batches from the client.

Also if a message fails for some reason, it will be thrown to the back of the queue, and processed out of order from the previous related messages.