Granny's Programming Pearls
"inside of every large program is a small program struggling to get out"
JavaRanch.com/granny.jsp
The moose likes EJB and other Java EE Technologies and the fly likes Clustered Servers Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login


Win a copy of Spring in Action this week in the Spring forum!
JavaRanch » Java Forums » Java » EJB and other Java EE Technologies
Bookmark "Clustered Servers" Watch "Clustered Servers" New topic
Author

Clustered Servers

Seetesh Hindlekar
Ranch Hand

Joined: Feb 13, 2004
Posts: 244
Hi all,

Cld anyone explain how a clustering can help in the following scenario?

Table xxx in database has 4 columns column 1..4

The jsp page displayed on the screen has 4 text fields : textfield1..4 mapped to table xxx.

There is a button which add additional fields say textfield5..10 and which are not mapped to table xxx.

Requirement : the information entered in textfield5..10 has to be captured and stored.

How is this done and how Clustering will play an important role in storing of data not associated to the table?

Rgds,

Seetesh
Paul Sturrock
Bartender

Joined: Apr 14, 2004
Posts: 10336


how Clustering will play an important role in storing of data not associated to the table

Whether an application is deployed accross clustered servers or not has no effect one way or the other in your example.


JavaRanch FAQ HowToAskQuestionsOnJavaRanch
Vicky Mohan
Ranch Hand

Joined: Oct 14, 2004
Posts: 130
well, i am not sure what your issue is. just because your environment is going to be clustered, does not change anything here.
Stan James
(instanceof Sidekick)
Ranch Hand

Joined: Jan 29, 2003
Posts: 8791
Clustering gives you multiple copies of your application across multiple physical machines or LPARs or JVMs or whatever. Done well, the app is "horizontally scalable" meaning you can add more boxes to get more capacity (assuming you have no bottlenecks in another shared resource like a network gateway or database.) The app is also redundant, so if one copy of the app goes down, some kind of load balancer can divert all work to the remaining copies. You may take a performance hit but keep on serving customers. There are also challenges. If you keep any state in memory - including HTTP sessions - you may want to replicate it across all the copies of your app somehow. You have to be able to stop and start, add or remove copies without confusing the load balancer. All great fun!

Any of that shed light on your original question?


A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi
Seetesh Hindlekar
Ranch Hand

Joined: Feb 13, 2004
Posts: 244
Hi all,

Clustering is a group of servers that service the clients, but the client is unaware of presence of multiple servers he feels that he is interacting with a single server. Once you deploy an application in clustered environment, you can increase number of servers depending upon the increasing number of clients. Clustering gives good scalability when the number of clients increase and also gives high availability. Some of the major EJB vendors support clustering. For example if you deploy a cluster aware EJB application in three servers and if the first server is overloaded, clients are routed automatically to the next server depending upon the load balancing algorithms. And also clients are routed to the other server if the first server dies, in this situation client state is passed to the other server to handle from that point ( this is called as fail over). When you deploy your application on a single server and don't have future anticipation of increase in number of clients then do not use clustering because cluster aware EJBeans have overheads involved.
You need to configure vendor specific deployment descriptor file(or other vendor specific manner) in order to get cluster aware EJB application. When you configure for clustering, EJB Container/Server generates cluster aware EJBeans. Look at vendor specific documentation for details on clustering. So use clustering to get high scalability and fail over.

I am aware of Clustered servers but need to know if a clustered environment could be used for the scenario mentioned in my original post.

Rgds,

Seetesh
 
 
subject: Clustered Servers