JOnAS Terminology

Server or JOnAS instance

A server, or JOnAS instance, is a java process started via the jonas start command, or via the administration tool Java EE.

Several servers may run on the same physical host.

Service

When a server starts, services are started.

A service typically provides system resources to containers.

Most of the components of the JOnAS application server are pre-defined services. However, it is possible and easy for an advanced user to define a new service and to integrate it into JOnAS.

JOnAS services are manageable through JMX.

Container

A container consists of a set of Java classes that implement the Java EE specification.

The role of the container is to provide the facilities for executing Java EE components.

There are three types of containers :

   1. EJB container in which Enterprise JavaBeans are deployed and run

   2. Web container for JSPs and servlets

   3. Client container

Domain

A domain represents an administration perimeter which is under the control of an administration authority.

This perimeter contains management targets like servers and clusters.

If a domain contains several elements, it provides at least one common administration point represented by a master server.

Master server

A master is a JOnAS instance having particular management capabilities within the domain:

• It is aware of the domain's topology
• It allows management and monitoring of all the elements belonging to the domain

Cluster

A cluster is a group of JOnAS servers having common properties within a domain.

It usually allows to run a J2EE application, or a J2EE module, on the cluster members as if they were a single server.

The objective is to achieve applications scalability and high availability.

JOnAS supports several cluster types :

• Clusters for Web level load-balancing
• Clusters for high availability of Web components
• Clusters for EJB level load-balancing
• Clusters for high availability of EJB components
• Clusters for JMS destination scalability and high availability
• Clusters for administration purpose which facilitate management operations like deployment /undeployment.

From the administrator point of view, a cluster represents a single administration target.

Note A particular JOnAS server may belong to zero, one or more clusters.