[rabbitmq-discuss] How to handle full exchange history delivery

Wed Jun 1 15:58:39 BST 2011

Maybe I wasn't being clear: 

I've already written a custom exchange that stores every message it receives in Riak (http://wiki.basho.com/). I'm going to be talking about it next week at Erlang Factory in London, as a matter of fact. :) 

https://github.com/jbrisbin/riak-exchange 

When I was writing it, I thought it would be really easy to, when a new queue is bound to this exchange, go fetch all the messages in that bucket and send them to the queue. 

Since I'm using Riak, the messages themselves are not all stored in memory. 

Thanks! 

Jon Brisbin 
http//jbrisbin.com 

----- Original Message -----

> From: "Simone Busoli" <Simone.Busoli at ferrari.com>
> To: rabbitmq-discuss at lists.rabbitmq.com
> Sent: Wednesday, June 1, 2011 8:43:58 AM
> Subject: Re: [rabbitmq-discuss] How to handle full exchange history
> delivery

> That’s what I thought as well, although I’m thinking about a couple
> of issues about it:

> · Lack of knowledge about Erlang, which is the language I’d have to
> use to build a custom exchange, I guess
> · Amount of memory it would require to store the entire history in
> memory. It needn’t be in memory actually, but I’m not sure what
> would be the recommended way if the storage has to be carried out by
> exchange itself. Mnesia perhaps, would it make sense?

> _______________________________________________________ ________
> Simone Busoli
> Direzione risorse umane e segreteria generale – Sistemi informativi
> gestione sportiva
> Collaboratore
> Ferrari S.p.A. Via Ascari 55/57, 41053, Maranello (MO); Italy
> T (+39) 0536-949.850
> E simone.busoli at ferrari.com www.ferrari.com

> From: Jon Brisbin [mailto:jon at jbrisbin.com]
> Sent: Wednesday, June 01, 2011 3:38 PM
> To: Busoli, Simone
> Cc: rabbitmq-discuss at lists.rabbitmq.com
> Subject: Re: [rabbitmq-discuss] How to handle full exchange history
> delivery

> I've been seriously considering adding this functionality to the
> Riak-backed custom exchange. It was something I thought I would add
> first time through but didn't.

> You'd have to use a custom exchange. Not sure if that's an issue in
> your scenario or not.

> Thanks!

> Jon Brisbin
> http//jbrisbin.com

> ----- Original Message -----

> > From: "Simone Busoli" <Simone.Busoli at ferrari.com>
> 
> > To: rabbitmq-discuss at lists.rabbitmq.com
> 
> > Sent: Wednesday, June 1, 2011 5:52:24 AM
> 
> > Subject: [rabbitmq-discuss] How to handle full exchange history
> > delivery
> 

> > Hi,
> 

> > I am trying to achieve a scenario in which messages are published
> > from some data source into a RabbitMQ exchange and clients should
> > be
> > able to receive the full history of messages flown through that
> > exchange, regardless of the exact moment in time when they connect.
> 

> > I’ve been thinking to solve it by setting up a proxy which
> > subscribes
> > to the exchange where messages are published using its own queue,
> > keeps an internal storage of the messages and accepts requests from
> > clients.
> 
> > When a request from a client arrives it just replays the full
> > message
> > history to the client by publishing the messages to the client
> > queue
> > (supplied in the ReplyTo field), then binds the client queue to the
> > messages exchange, so that the client from this moment onwards
> > starts receiving the “live” messages, and is pretty much unaware of
> > what’s happened; it simply just receives the whole history.
> 

> > Now I am under the impression that there’s a fundamental flaw in
> > this
> > reasoning, since the proxy cannot know when the message history has
> > completed and he can switch the client to the live stream, because
> > while it is replaying historical messages to the client other live
> > messages might be arriving on the proxy’s queue, thus getting into
> > an endless loop.
> 

> > I’m probably missing something obvious, any advice about how others
> > would approach this scenario is appreciated.
> 

> > Simone
> 
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