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From Bruce Snyder <bruce.sny...@gmail.com>
Subject Re: Durable Subscribers
Date Wed, 23 Sep 2009 22:15:42 GMT
On Wed, Sep 23, 2009 at 1:52 PM, Brian Taylor <brian@briantaylor.us> wrote:
>
> Hello,
>
> I need some clarity on Durable Subscriptions. We're using ServiceMix 3.3.1
> with WSN2005 SE 2009.01 for creating Topics in ActiveMQ. Using JConsole, I
> see the Topics being created in ActiveMQ and I believe Durable Subscriptions
> means if messages are sent to these Topics and the Consumers are not
> available, when the Consumers come back on line, their messages will still
> be available for them. The question I have is if the server hosting ActiveMQ
> crashes, on restart, will those Topics be recreated by ActiveMQ and will the
> messages sent to those Topics w/o an available Consumer still be available
> to the Consumer when it becomes active again?

A durable subscription is infinite meaning that the subscription is
registered with the topic to tell ActiveMQ to preserve the
subscription state in the event that the subscriber disconnects. If a
subscriber disconnects, ActiveMQ will hold all messages for that
subscriber until it connects again. Upon reconnection, ActiveMQ will
make all of these messages available to the subscriber.

In the event that the ActiveMQ becomes unavailable, all of the topics
that were previously available with durable subscriptions will be made
available again.

>  I believe there is a feature
> request in ServiceMix for 'Durable Subscriptions' from ActiveMQ but it
> appears this site says it's already supported.

ActiveMQ certainly supports durable subscriptions. So you may be
referring to the type of topics that ServiceMix creates for its
components (durable vs. non-durable). It's been a while since I worked
on ServiceMix, but IIRC, the ServiceMix 3.x JMS flow used non-durable
topics for components as opposed to durable topics.

Bruce
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