Strict message ordering can be achieved
when deploying
message driven bean applications to the WebSphere® MQ messaging provider for WebSphere Application Server when no special facilities
have been coded into the application to handle messages arriving out
of order by using the strict message ordering facility of the WebSphere Application Server default messaging provider.
The following assumptions have been made in this
scenario:
- The message-driven bean (MDB) application is transactional.
- The back-out threshold (BOTHRESH) on theWebSphere MQ queue has been set to 0.
Configuration for ordered delivery
Important
information about this configuration
- This deployment
option combines the message ordering capabilities
of WebSphere MQ (which include when
sending over a channel) with the additional messages ordering facilities
provided by the default messaging provider for WebSphere Application Server (which
prevent out of order delivery in transaction recovery scenarios).
- This deployment option is complex as it requires planning, and
runtime administration, of a bus topology in addition to a WebSphere MQ topology.
- It also
adds internal complexity as messages are converted automatically
between the low level WebSphere MQ and
default messaging provider formats as they travel over the WebSphere MQ link.
Circumstances in which messages can arrive out of
order
There are no circumstances in which this deployment
is expected to cause messages to be delivered out of order.
Considerations for clustered deployment
- Ordered
delivery from the bus destination to the MDB is enforced
automatically in a clustered environment when the Strict
message ordering option is selected for the destination.
- The main consideration for a clustered environment is establishing
high availability of the WebSphere MQ link
between the queue manager and the bus. For more information about
the options available for ensuring that the connection to a failover WebSphere Application Server gateway messaging
engine is reinstated, see .