GlassFish Clustering

februari 2nd, 2009
Yenlo
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Clustering is one of the strongest points in GlassFish and is very easy to configure.

Clusters in a application server improves reliability and scalability.
A cluster has a Domain Admin Server (DAS) and one or more nodeagents, on the nodeagents can be unlimited instances.

The DAS is a central point of the administration and manages the configuration of the cluster.
The DAS can be managed in a lot of different ways; admin console, command line, IDE like Netbeans or Eclipse or with the Sun provisioning server.

The Nodeagent is a lightweight instance of the AS. On every server there is one nodeagent present.The nodeagent manages the lifecycle of the instances. This means the nodeagent creates, starts, stops and deletes instances.
Also of the instance dies the nodeagent will restart it.

We now know what all the components are within a cluster.
The communication between the DAS and the NA goes true JMX and HTTP.

But how does the communcation between the DAS and NA Works?
The DAS communicats with the nodeagents when a configuration changes and when it checks if the NA is still online.

The NA communicates with the DAS when its created or when it starts to synchronize itself or the instances it manages.

A cluster is very simple to install:

In the admin console the cluster support can be enabled with only 2 clicks.
When the GlassFIsh AS is in cluster mode, it’s possible to create a nodeagent with the command line. This can be realized with the command asadmin create-node-agent.
After this the nodeagent is started with the asadmin start-node-agent command.
In the admin console instances can be made on all the nodeagents connected to the DAS. Also the load balance on the instances can be configured here.

At this point the cluster is running!

A cluster is installed within 10 minutes, this is proven bij J. Clingan in his screencast. In this screencast he downloaded Glassfish, installed the cluster and tested the cluster.
http://blogs.Sun.com/jclingan/entry/GlassFish_clustering_in_under_10