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From "James Strachan" <james.strac...@gmail.com>
Subject Re: Recovery Policies should apply between broker restart
Date Tue, 25 Jul 2006 04:48:50 GMT
BTW I've moved this over to the dev list.

You could have a single durable subscription that was used by a new
'PersistentLastImageRecoveryPolicy' implementation. Then each message
received by the policy is used to update the cache - but you only
acknowledge the previous message.

e.g.

Receive M1, update the cache.
Receive M2, update the cache then acknowledge M1.
*broker dies*
Restart durable subscriber for policy
Receive M2, update the cache
Receive M3, update the cache and acknowledge M2
...

Another option could be to try just write a LastImageRecoveryPolicy
store where you maybe use Kaha to keep a persistent image of the cache
on disk. The former is maybe the simplest to write, the latter is
probably more efficient but would require you to delve into the Kaha
codebase


On 7/24/06, himmeric <himmeric@vnet.ibm.com> wrote:
>
> I discussed this a while back on IRC with Hiram and a few others.
>
> Basically I need to have Subscription Recovery Policies work between broker
> restarts for non durable subscribers and NON_PERSISTENT messages on topics.
> So the use case would looks something like this:
>
> topic://FOO.X is configured with LastImageRecoveryPolicy
>
> Msg 1 published on topic://FOO.X
> Consumer A joins and receives Msg 1 (since he is consumer.retroactive=true)
> Broker stops and restarts
> Consumer B joins before additional messages published to topic://FOO.X
> Consumer B receives Msg 1 on topic://FOO.X
>
> I'm not sure the best way to achieve this.  I played with having a durable
> root consumer that would only acknowlege() messages if they weren't found in
> the recovery policy.  Then the recovery process would be for this durable
> consumer to replay messages to the recovery policy on a restart.  Obviously
> this is quite a hack and I didn't get it working because I don't think I
> actually had the Topic's real RecoveryPolicy object (appears the
> PolicyEntry.getSubscriptionRecoveryPolicy() returned a copy).
>
> I think we need to make sure if a message is referenced by a recovery policy
> it needs to be persisted even if it's not persistent.  And then second
> replay these messages somehow on restart.
>
> I'd actually be happy if I could get this working with just the
> LastImageRecoveryPolicy as it's the only one I'm using at this point.  But a
> more generic solution would be good too.
>
> Thoughts?
> --
> View this message in context: http://www.nabble.com/Recovery-Policies-should-apply-between-broker-restart-tf1994690.html#a5474786
> Sent from the ActiveMQ - User forum at Nabble.com.
>
>


-- 

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

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