[rabbitmq-discuss] Message timeouts

[Alex Grönholm]

11.12.2011 14:14, Alex Grönholm kirjoitti:
> Sorry for taking this long to respond. I've been otherwise engaged and 
> forgot about this conversation.
> Thank you for your replies.
>
>     If you don't want the server queue requests to be 'lost' then
>     don't allow the
>     queues to expire!
>
>     On the other hand your clients apparently wait forever.  Is there
>     a reason I
>     don't understand why the server queues expire but the clients
>     don't have a
>     timeout for the responses?
>
> If the upgrade of the server software fails and the developers do 
> nothing, the queue expires eventually so that stale requests are 
> dropped and the clients will start getting proper error messages 
> informing them of this condition.
> This is not the ideal solution of course (per-message TTL and return 
> notification would be).
>
>     You want requests to either be processed or (reliably) not
>     processed.  You
>     never want the clients to be in any doubt about whether the
>     request was
>     processed or not.  So you wait forever in the client.  However,
>     requests that
>     get discarded never return so the client doesn't know.  So you
>     want expiry to
>     trigger replies to the clients.  (Per-queue message TTLs also
>     don't return.)
>
>
>  Sounds about right.
>
>     Let's see -- how would we do this without a dead-letter mechanism?
>
Now that the dead-letter mechanism is part of the server, I don't still 
don't see how this could be done. The dead lettered RPC commands would 
still have to be processed somewhere.
>
>      Well, apart
>     from making the server transactional, it might be useful to have
>     an 'offline'
>     server that can take over any server's queue when it fails and
>     either deal with
>     the requests [by issuing an 'offline' response?] or arrange for
>     the server to
>     be restarted (and/or upgraded).
>
>
> This seems fairly complicated. I'll have to look into transactions to 
> see if they will help in my case.

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