Network Deployment (Distributed operating systems), v8.0 > Applications > Service integration > High availability and workload sharing > Service integration high availability and workload sharing configurations > Policies for service integration > Messaging engine policy assistance
Custom messaging engine policy
The custom messaging engine policy is a messaging engine policy type provided when you use messaging engine policy assistance. It helps you to create and configure messaging engines in a cluster that is a member of a bus when the predefined messaging engine policy types do not meet your needs. We can configure the messaging engine behavior, then the appropriate messaging engine policies are created automatically.
We can create any number of messaging engines for the cluster. For each messaging engine, specify the behavior that you require, such as whether it can fail over and whether it uses preferred servers. The core group policies and match criteria for each messaging engine are automatically created.
Use this policy when the other options of High availability, Scalability, or Scalability with high availability do not provide the messaging engine behavior you require, and you are familiar with creating messaging engines and configuring messaging engine policy settings.
When you select the custom messaging engine policy type, a diagram is displayed that shows the selected cluster and the associated messaging engines, but there are no warnings or advice about the suitability of the configuration.
We can configure the messaging engine policy to set the following:
- Whether the messaging engine can fail over to another server
- Whether the messaging engine can fail back to a server in the preferred servers list
- Whether a messaging engine can run only on a server in the preferred servers list, or can run on any server in the cluster
- The list of preferred servers, where the earlier the server is in the list, the higher the preference for it
When you set the configuration, remember the following points:
- If you select failover and do not create a preferred servers list, the messaging engine can fail over to any other server in the cluster.
- If you select failover and create a preferred servers list, the messaging engine can fail over to the servers in the preferred server list, in the order that they are listed, and then to any other server in the cluster.
- If you select failover, select that the messaging engine can run only on servers in the preferred servers list, and create a preferred servers list, the messaging engine can fail over only to the servers in the preferred server list. We can use this combination of settings to associate a messaging engine with a specific server, by listing only one preferred server. Alternatively, you can use this combination of settings to control how many messaging engines a server can host, by listing a limited number of preferred servers for each messaging engine in the cluster.
It is possible to create a messaging engine for a cluster without using messaging engine policy assistance. However, either use the default core group policy for messaging engines and the default settings, or create the core group policies and settings yourself. Use this procedure if you need a specific configuration and you are familiar with the procedure. Otherwise, use messaging engine policy assistance.
Add a cluster to a bus with a custom configuration