[zeromq-dev] Requirements for reliability

Apps, John john.apps at hp.com
Wed Apr 7 10:47:13 CEST 2010

Before this goes much further, may I ask what is meant by 'reliability' in this context?
I have entered a brief note in the 0MQ blog saying that the JMS spec would be a good place to start in my mind as we would all be on the same page (pun intended).

Yes, the JMS spec contains more than is required, at least for an initial version, but it does have some good terms and is well understood, I think.

In that context: if we take Martin's "...reliable request/reply on top of TCP transport" comment, what does this mean to the client and the server? (Front-end and back-end if you prefer.)

Reliable to me means that no message may be lost -and if it is, the fact has to be recognized and reported-, no message may be delivered more than once if so desired, messages may be batched into transactions, meaning either all messages in the batch are delivered, or none.

If this is not what is meant, then please help me with a definition of what is being asked!

Cheers, John
-- John.Apps at hp.com | +491718691813 | http://twitter.com/johnapps --

-----Original Message-----
From: zeromq-dev-bounces at lists.zeromq.org [mailto:zeromq-dev-bounces at lists.zeromq.org] On Behalf Of Martin Sustrik
Sent: Wednesday, April 07, 2010 10:03
To: Pieter Hintjens
Cc: zeromq-dev at lists.zeromq.org
Subject: Re: [zeromq-dev] Requirements for reliability

Martin Sustrik wrote:
> Pieter Hintjens wrote:
>> Martin,
>> If we try to implement reliability for pub-sub on top of 0MQ, that
>> means knowing all subscribers for a socket.  Is this information
>> available to applications?
> No. It's not.

Btw, I believe that trying to solve the reliability in a general manner 
is an infeasible task. At least at the present moment.

Let's rather focus on a very specific use case: reliable request/reply 
on top of TCP transport. Once we have that we can think of whether it's 
possible to make it more general.

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