[rabbitmq-discuss] Reliable "publishing"

Busoli, Simone Simone.Busoli at ferrari.com
Tue Dec 20 16:19:51 GMT 2011


Indeed, the messages are not lost, but at least lost until the connection eventually goes down and then up once again, which does not necessarily happen frequently and not something you would be doing for the purpose of recovering messages which for some reason haven't been (n)acked, right? Therefore I'm wondering whether a mechanism, perhaps an options of the shovel and federation plugins (every x messages, every x seconds, ...), to process messages which have remain unconfirmed for some time should be introduced.

> -----Original Message-----
> From: rabbitmq-discuss-bounces at lists.rabbitmq.com [mailto:rabbitmq-
> discuss-bounces at lists.rabbitmq.com] On Behalf Of Simon MacMullen
> Sent: martedì 20 dicembre 2011 11:54
> To: Simone Busoli
> Cc: rabbitmq-discuss at lists.rabbitmq.com
> Subject: Re: [rabbitmq-discuss] Reliable "publishing"
> 
> On 16/12/2011 8:05PM, Simone Busoli wrote:
> > On Fri, Dec 16, 2011 at 14:16, Simon MacMullen <simon at rabbitmq.com
> > <mailto:simon at rabbitmq.com>> wrote:
> >
> >     The only reason your client might not receive a (n)ack for any given
> >     message would be if the connection goes down
> >
> >
> > Exactly, which if you're looking for some degree of reliable delivery
> > is something you should take care of as well, right?
> > So what I understand - please correct me if I'm wrong - is that
> > neither Shovel nor Federation are doing anything with unconfirmed
> messages (i.e.
> > no acks/nacks), so theoretically some messages may be "lost" because
> > even if the upstream broker didn't receive an ack for them and will
> > thus store them until they're acked (as the plugin wouldn't send one
> > until it has received confirm from the downstream broker), there is
> > however no one who will issue a recover to the upstream broker to
> > request a requeue of those messages.
> 
> Recover is only one way to get unacked messages requeued - the connection
> going down is another.
> 
> In fact "recover" can really be understood as "pretend this connection went
> down".
> 
> So these messages won't be lost.
> 
> It is however possible for messages to get duplicated in these circumstances
> - for messages where the downstream has confirmed but the shovel /
> federation hasn't yet sent on the corresponding ack when the connection
> dies.
> 
> Cheers, Simon
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> rabbitmq-discuss at lists.rabbitmq.com
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