[rabbitmq-discuss] ordering semantics

Fri Apr 30 20:54:36 BST 2010

Hi,

I'm trying to get a handle on ordering semantics on the topic exchange.

Assume there are two publishers, each on their own channel.  Publishers produce a stream of messages.  So:

Publisher A produces A1, A2, A3 (in that order) Publisher B produces B1, B2, B3 (in that order)

There is a single subscriber on a queue that all the messages produced by both publishers are targeted to.

Questions:

1. Messages A1, A2, A3 are received in that order.  Messages B1, B2, B3 are received in that order.  Correct?

2. Messages from A can be interleaved from B as in: A1, A2, B1, B2, B3, A3.  (Still subject to the constraint from question 1 above) Correct?

3. In the event of a failure of a node in a cluster, messages may be lost, but do they still obey the strict ordering, even though messages may travel a different route in the cluster?

4. I'm assuming that the ordering semantics guaranteed per-channel, correct?

5.Can a subscriber determine a unique ID of the actual sender (i.e., can a subscriber know if a message was sent by A or B)?

Thanks,

Jim

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