Re: How to ensure reliability of publish/subscribe against occassional network hiccup?

[pragmaticjdev <am...@gmail.com>]

I would like to revive this email thread since I have a exact similar use
case for which I am planning to use activemq - to keep the java objects in
sync between multiple nodes. This thread discusses a couple of approaches -
transacted session (does this refer to transactions?) or acknowledgements
(AUTO_ACKNOWLEDGE or CLIENT_ACKNOWLEDGE). There is no conclusion on this
discussion though, hence I wanted to bring it back up to get expert
opinions. Kindly suggest. Thanks!



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Re: How to ensure reliability of publish/subscribe against occassional network hiccup?

[Tim Bain <tb...@alumni.duke.edu>]

On Mon, Apr 16, 2018 at 6:08 AM, pragmaticjdev <am...@gmail.com> wrote:

> I would like to revive this email thread since I have a exact similar use
> case for which I am planning to use activemq - to keep the java objects in
> sync between multiple nodes. This thread discusses a couple of approaches -
> transacted session (does this refer to transactions?)



Yes, this refers to transactions, either JMS transactions or XA
transactions. A transaction allows you to roll back the work that you've
done if some portion of the transaction fails. JMS transactions cover only
interactions with the ActiveMQ broker (acking and publishing messages),
whereas XA transactions can cover interactions with RDBMSes as well.
http://activemq.apache.org/how-do-transactions-work.html has some
additional details.



> or acknowledgements
> (AUTO_ACKNOWLEDGE or CLIENT_ACKNOWLEDGE).



Using some form of explicit acknowledgement (CLIENT_ACKNOWLEDGE,
INDIVIDUAL_ACKNOWLEDGE) instead of AUTO_ACKNOWLEDGE allows you to avoid
acknowledging the message until you've actually consumed it, but doesn't
allow you to roll back other operations if something fails.



> There is no conclusion on this
> discussion though, hence I wanted to bring it back up to get expert
> opinions. Kindly suggest. Thanks!
>


I suspect that there is no conclusion in part because different options are
best for different situations.
http://activemq.apache.org/should-i-use-transactions.html recommends using
transactions over explicit acknowledgement, but both can work depending on
your needs, so it really comes down to what your needs are. If you need to
roll back database transactions, use XA transactions. If you need the
ability to roll back one or more JMS operation if another JMS operation
fails but you don't need the ability to roll back database transactions,
use JMS transactions to avoid the overhead of XA transactions. If you just
need to ensure that messages are delivered at least once but don't need the
ability to roll back any processing if an error occurs, use explicit
acknowledgement.

Tim