WebSphere Concepts: Cell, Node, Cluster, Server…

(This paper is from http://itdevworld.wordpress.com/2009/05/03/websphere-concepts-cell-node-cluster-server/. If any question, pls tell me to delete it. )

Quick post… If you are not familiar withWebSphere at first you might get confused with its concepts: cell,deployment manager, node, node agent, cluster, server, …

First of all, lets start with the concept of a Cell:

A Cell is a virtual unit that is built of a Deployment Manager and one or more nodes. I guess a picture will help making things clearer:

 

WebSphere Cell

But still there are a few concepts that need to be explained. The next obvious one is the Deployment Manager.

The Deployment Manageris a process (in fact it is an special WebSphere instance) responsiblefor managing the installation and maintenance of Applications,Connection Pools and other resources related to a J2EE environment. Itis also responsible for centralizing user repositories for applicationand also for WebSphere authentication and authorization.

The Deployment Manager communicates with the Nodes through another special WebSphere process, the Node Agent.

The Node is another virtual unit that is built of a Node Agent and one or more Server instances.

The Node Agentit the process responsible for spawning and killing server processesand also responsible for configuration synchronization between theDeployment Manager and the Node. Extra care must be taken when changingsecurity configurations for the cell, since communication betweenDeployment Manager and Node Agent is ciphered and secured when securityis enabled, Node Agent needs to have configuration fully resynchronizedwhen impacting changes are made to Cell security configuration.

Serversare regular Java process responsible for serving J2EE requests (eg.:serving JSP/JSF pages, serving EJB calls, consuming JMS queues, etc).

And to finish, Clusters are also virtual units that groups Serversso resources added to the Cluster are propagated to every Server thatmakes up the cluster, this will in fact affect usually more than asingle Node instance.

Lets finish this post with another diagram to illustrate all those concepts.

 

WebSphere Concepts