It is going to depend on the EJB's that you are using.
The ideal is to have Stateless Session Beans that have idempotent methods.
If that is the case then weblogic can failover even in the middle of a
method. If your
methods are not idempotent then weblogic can't safely do this.
For example, if you have a method that updates some state, if the method
dies AFTER that update
then you may not be in a safe enough state for weblogic to just run the
method again on a bean
on another server in the cluster. If you account for that, or you have a
method that doesn't
muck w/ state (maybe it's read only, does some calculation, or whatever)
then you are totally safe.
If you have Stateful Session Beans then you have more to worry about.
WebLogic 6.0 does have
in memory replication, but you should still be wary. Your client code may
want to check
and see if there is an error and recreate the state... e.g. call the
home.create(..) again,
etc.
You do want to make sure that your deployment descriptors note that the home
and bean is clusterable.
Clustering is great... but you still DO have to be wary of things ;)
Dion
-----Original Message-----
From: A mailing list for Enterprise JavaBeans development
[mailto:[EMAIL PROTECTED]]On Behalf Of Dinesh Venkateswaran
Sent: Tuesday, February 13, 2001 10:37 PM
To: [EMAIL PROTECTED]
Subject: Re: Doubt on WebLogic clustering
Thanks for clarifying. Do you mean even the objects dont have to be made
serializable?
Dinesh
Gene Chuang
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Sent by: A Subject: Re: Doubt on
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02/13/01 11:55 PM
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Both load-balancing and failover are the duties of weblogic; you do not
have to make any code alterations... if anything, you may have to switch a
couple of flags on the deployment descriptors, that's all.
Gene
-----Original Message-----
From: A mailing list for Enterprise JavaBeans development
[mailto:[EMAIL PROTECTED]]On Behalf Of Dinesh Venkateswaran
Sent: Tuesday, February 13, 2001 12:56 AM
To: [EMAIL PROTECTED]
Subject: Doubt on WebLogic clustering
Hi,
We have just completed developing a jsp/servlet/ejb application that's
deployed on WebLogic. Now our client has requested for an enhancement to a
clustered environment. I have gone through the examples on clustering that
come alongwith the WebLogic installation.
>From what I have understood, load balancing doesn't require any code
changes as such, and can be achieved by mostly modifying the properties
files, ofcourse, other than making the classes serializable (kindly correct
me if i am wrong). But failover capability seems to be possible only with
substantial code changes, and changes to the database. Hope my
understanding is right. However, I am not able to completely ascertain the
extent of changes required, and hence plan and design for the whole effort
of enhancements.
Can some of you throw light on this? Thanks
Cheers
Dinesh
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