You can add a cluster as a member of a bus and use messaging
engine policy assistance and a predefined messaging engine policy
that provides high availability, scalability, or scalability with
high availability. Messaging engine policy assistance helps you to
create and configure the messaging engines in a cluster to provide
the required messaging engine behavior.
About this task
The following predefined messaging engine policies are
available:
- High availability. Use the high availability policy when you want
to ensure that there is always a messaging engine running in that
cluster, so that messages are always transmitted.
The high availability
messaging engine policy creates a single messaging engine for the
cluster. The messaging engine is configured to fail over to any of
the other servers in the cluster. The order in which the servers are
used for failover depends on their order in the preferred servers
list. The earlier the server in the preferred servers list, the stronger
the preference for that server. The messaging engine does not fail
back, that is, if a more preferred server becomes available again,
the messaging engine does not move back to that server.
- Scalability. Use the scalability policy for a system where you
want to add more servers to a cluster and maintain the performance.
The
scalability messaging engine policy creates a single messaging engine
for each server in the cluster. Each messaging engine can run only
on the server that it is assigned to, and it cannot fail over to another
server. If a server fails, the messaging engine that is running on
it also fails, and is not available until the server recovers. You
can add new servers to the cluster without affecting existing messaging
engines in the cluster.
- Scalability with high availability. Use the scalability with high
availability policy for a system where you want to add more servers
to a cluster and maintain the performance, but you also want to ensure
that messaging is always available.
The scalability with high availability
messaging engine policy creates a single messaging engine for each
server in the cluster. Each messaging engine can fail over to one
other specified server in the cluster. Each server can host up to
two messaging engines, such that there is an ordered circular relationship
between the servers. Each messaging engine can fail back, that is,
if a messaging engine fails over to another server, and then the original
server becomes available again, the messaging engine automatically
moves back to that server.
If you are working in a mixed-version cell, a service integration bus running in this version of the product can only include WebSphere® Application Server Version 6 bus members that are running in the following versions of the product:
- 6.0.2 (Fix Pack 23 or later)
- 6.1.0 (Fix Pack 13 or later)
If security is enabled, and the bus has mixed-version bus members, the bus members establish trust by using an inter-engine authentication alias. If you add a server cluster as a bus member at WebSphere Application Server Version 6, and it is the first bus member at this level, you must select or create an authentication alias during this task. This action sets the inter-engine authentication alias.
Procedure
- In the navigation pane, click .
- Click Add to start the Add a
new bus member wizard.
- In the first pane, select Cluster,
and, from the drop-down list, select the cluster that you want to
make a member of the bus.
- In the Messaging engine policy assistance settings pane,
ensure that the Enable messaging engine policy assistance check
box is selected. Select one of the following options, depending on
the messaging engine policy that you require:
- High availability
- Scalability
- Scalability with high availability
If the value of the "Is further configuration required" column
for the selected messaging engine policy is No, continue with the
procedure. Otherwise, examine the messages displayed and decide whether
to go back and change the cluster configuration, or to continue.
A diagram of the selected cluster and the eventual outcome
of the selected messaging engine policy is displayed.
- Select the type of message store that you have already
defined.
- In the Configure messaging engines pane, for each messaging
engine listed, click the messaging engine name and enter details for
its message store.
- If you use a file store, specify the directory paths for the
log files, the permanent file store, and the temporary file store.
Do not use the default path, and ensure that you use a unique path
for each messaging engine.
- If you use a data store, specify the JNDI name of the data
source that provides access to the database that holds the data store.
- If security is enabled, and adding this cluster bus member
creates a mixed-version bus, the wizard prompts for an authentication
alias. Do one of the following:
- Select an existing authentication alias.
- Create a new authentication alias. Specify a unique alias
name and password.
This action sets the inter-engine authentication alias.
- When the Add a new bus member wizard is finished, save
your changes to the master configuration.
Results
You have created a cluster bus member.
- For the high availability messaging engine policy, there is a
single messaging engine, named cluster_name.nnn-bus_name,
which can fail over to any of the servers in the cluster.
- For the scalability messaging engine policy, there is one messaging
engine for each server in the cluster, named cluster_name.nnn-bus_name.
Each messaging engine in the cluster is restricted to running on one
server.
- For the scalability with high availability messaging engine policy,
there is one messaging engine for each application server in the cluster,
named cluster_name.nnn-bus_name.
Each messaging engine in the cluster can fail over to one other specified
server in the cluster, and can fail back to its preferred server if
that server becomes available again.
For each messaging engine, there is a core group policy named
messaging_engine_name-
numberPolicy.
This core group policy is configured with the behavior you chose for
the messaging engine policy, and is associated with the messaging
engine through its match criteria.