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From "James Strachan" <james.strac...@gmail.com>
Subject Re: [Spam: 5.0] Evaluating Embedded ActiveMQ - questions
Date Wed, 07 Mar 2007 08:46:00 GMT
On 3/7/07, rbector <bector.online@gmail.com> wrote:
>
>
> James.Strachan wrote:
> >
> > On 3/6/07, rbector <bector.online@gmail.com> wrote:
> >
> >> I am still trying to understand why this is hard to manage if you are
> >> using
> >> a database.
> >> Cant all the participating applications use the same database ? What
> >> exactly
> >> is
> >> the management overhead there ?
> >
> > Each broker requires its own database. Also if you want high
> > performance, each broker has its own journal files. (For real high
> > performance in version 5.x you'd use the pure file persistence
> > option).
> >
> >
> > That is quite interesting.  I can see each broker requiring its on tables.
> > In our system, we'd probably have 5-8 applications so I think the
> > management is still less of a concern. Performance is definitely a bigger
> > concern
> >
> >> > 2) I would like to have the ability to create topics such that messages
> >> on
> >> > them are never deleted. Essentially, any consumer could attach to the
> >> > topic
> >> > any point in time (even 30 days after the topic was created) and
> >> receive
> >> > older messages (Ideally - it should have the choice to start receiving
> >> > messages from a certain point in time in the past or from a certain
> >> ID).
> >> > The
> >> > idea behind this approach is that consumers are more decoupled. They
> >> could
> >> > process some messages, checkpoint them internally and go away and come
> >> > back
> >> > later.  I would like to try to understand if this is directly or
> >> > indirectly
> >> > supported in ActiveMQ (or other JAVA based messaging systems that
> >> people
> >> > know of)
> >>
> >> Its generally not supported by JMS but we've some extensions you can
> >> use to do this kind of thing...
> >>
> >> http://activemq.apache.org/subscription-recovery-policy.html
> >>
> >>
> >> thanks for pointing that out. I see that description as being quite
> >> sketchy.
> >> I dont know how well it works if there could be *tens of thousands* of
> >> such
> >> messages
> >> enqueued (persistent) while the receiver is gone.
> >
> > BTW I'm not aware of any other MOM which supports retroactive topic
> > subscribers.
> >
> > thanks
> >
> > The feature was mostly written for non-persistent messaging,
> > particularly for things like last image caching or keeping around a
> > buffer so a client could switch brokers without loosing messages etc.
> > There are hooks to plugin in any kind of persistence/query mechanism
> > you wish.
> >
> > Probably a better idea is to tweak the durable topic region for your
> > needs; where every message is always persisted whether there is a
> > subscriber or not and you add retroactive-subscription support to
> > durable topics (which I don't think is implemented yet). Then you can
> > configure when the database cleanup occurs to purge unwanted messages
> > from the database to your exact needs
> >
> > That seems to be the way to go. I've been researching java based message
> > brokers last couple days and I am somewhat disappointed so far (in one of
> > my previous jobs, I was responsible for developing a linux/c/kernel based
> > high performance message broker which provided all of these
> > features/semantics and more) in what I've found. I'd like a
> > high-performance, serverless option to generate, store and deliver events.
> > ActiveMQ is probably the closest thing to what we need. So we may actually
> > go ahead and enhance it for our needs, as you pointed out.

We welcome contributions so please feel free to enhance any part of
ActiveMQ (its been designed to be pluggable so you should be able to
add whatever you need). We'll gladly help point you in the right
direction to add what you need (e.g. adding retroactive subscription
support for topics should be pretty straightforward)

http://activemq.apache.org/contributing.html


-- 

James
-------
http://radio.weblogs.com/0112098/

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