How to create a singleton deployment in EAP7

Solution Verified - Updated

Environment

  • Red Hat JBoss Enterprise Application Platform (EAP)
    • 7.x

Issue

  • Is the HA Singleton deployment shown in this article supported in EAP7?
  • what is the purpose of the META-INF/singleton-deployment.xml
  • How can I deploy my application as a HA-Singleton in a cluster, I need to have this deployed only at one node

Resolution

Applications which are marked as singleton-deployment in EAP7 are started only from one node in a cluster.
It is possible to add simple election policies within the configuration, see the EAP 7 developer guide

Note:

Applications marked with singleton-deployment are started on multiple nodes if

  • the cluster can't be established because of configuration or network issues
  • a non HA configuration (standalone.xml (default), standalone-full.xml or domain profile "default" or "full") is used.

application deployed as WAR or JAR

The singleton-deployment.xml or jboss-all.xml must be included in the /META-INF folder at the top-level of the archive.

If maven WAR plugin is used the file can be placed in **/src/main/webapp/META-INF to add it.

application deployed as EAR

If an application is deployed as an EAR file either the singleton-deployment.xml or jboss-all.xml must be located at the top level META-INF folder of the ear. Any occurrence in sub-deployments are ignored!

Important
If a non-cluster configuration is used the singleton-deployment.xml will be ignored and the application will be deployed successfully.
The jboss-all.xml will fail with a parser error "Unexpected element '{urn:jboss:1.0}singleton-deployment'". This is because the singleton subsystem is not available by default in non HA configurations. The recommendation is to use the singleton-deployment.xml descriptor if it is necessary to deploy in both environments.

Related articles

  • If invocation of EJB applications deployed as HASingleton with automatic client side is needed with 7.0 or 7.1.BETA see this solution
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