In general it is not necessary to create more than one
WS-Notification service in each service integration bus, however there
are some cases where it is useful to do so.
If you have multiple service integration buses defined in a cell
and you want to provide WS-Notification access to messaging resources
defined on each of the buses, then you need to define a WS-Notification
service on each of the buses. This configuration of one WS-Notification
service on each service integration bus that needs WS-Notification
access is the recommended approach. It ensures that applications connected
to different WS-Notification services cannot pass information to each
other, or cause interference.
You might choose to define multiple WS-Notification services on
a single bus in order to segregate groups of client applications into
disjoint sets, for example to meet one of the requirements listed
below. However you should use this pattern with care, because there
are significant implications to making this choice - in particular
associated with the WS-Notification topic namespaces that are defined
on the WS-Notification service. For more information about topic namespace
patterns see Options for associating a permanent topic namespace with a bus topic space.
- Segregation of applications using different namespaces.
You can use distinct topic namespace URIs (and equally, different
service integration bus topic spaces) in the two WS-Notification services
to segregate the applications that use each service. For more information,
see 1 to 1 association between a service integration bus topic space and a topic namespace URI. Note that segregation in this way can also
be achieved using a single WS-Notification service.
- Enforced segregation of applications using the same namespace.
The key advantage of defining multiple WS-Notification services on
a single bus comes from the ability to partition a collection of applications
that are written to use the same topic namespace into two (or more)
distinct groups that do not interact at all. This allows the applications
connected to the first WS-Notification service to operate completely
isolated from those connected to the second WS-Notification service,
even though they are using the same topic namespace, and quite probably
the same set of topics. For more information, see many to 1 association between a service integration bus topic space and a topic namespace URI
- Alternative JAX-RPC handler lists and outbound security settings.
These properties are specified for each WS-Notification service, rather
than for each outbound port. If you need alternative options for these
properties then you should create a separate WS-Notification service
on the same bus for each alternative outbound configuration.