Hello all,
I have been one of those sitting in the sidelines, just watching the mails.
The clustering project seems a real cool initiative and something I would
love to get involved in at some level.
I am pretty much a novice and I know I have a steep learning curve infront
of me before I become less of a nuisance and more of a help.
But what do I need to do, to get my feet wet? Do I need to readup the J2EE
specification? Any pointers on which of the code modules I should initially
be looking at?
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of marc fleury
Sent: Wednesday, March 07, 2001 8:33 AM
To: JBoss-Dev
Subject: RE: [jBoss-Dev] CL: Clustering, let's get started
Ok, time to be more precise...
Assume a client talking directly to the bean, and load balance SSB. When
THAT is done we will get B2B calls that need DTM. XP methodology. Don't
stop.
We know all that :) YES trivially if you deploy to n nodes, and you do
nothing about "keep beans of an app in one node" and you do B2B, then you
need a DTM.
In clear I specifically want to avoid what mr cook is talking about. 10k
feet "approach" talk. We need this and that oh but first bla bla.. XP!
If DTM is your thing then please work on it since we will need it at the
end. But in terms of approach I want to think of SSB direct clustering :)
marc
|-----Original Message-----
|From: [EMAIL PROTECTED]
|[mailto:[EMAIL PROTECTED]]On Behalf Of Jeremy Boynes
|Sent: Wednesday, March 07, 2001 1:35 AM
|To: [EMAIL PROTECTED]
|Subject: RE: [jBoss-Dev] CL: Clustering, let's get started
|
|
|Tom's question was really about approach rather than solutions and you did
|ask for views... You might choose a "simple" scenario such as pure SSBs
|first, but I tend to agree with Tom that you should consider the core
|building blocks (e.g. DTM, cluster membership, resource location, state
|replication, and many more) whilst doing so as in reality none of the
|scenarios are actually that simple.
|
|
|As for applicability of a DTM, one of the goals of a cluster is location
|transparency (at least to the application). So consider a cluster with two
|nodes, 1 & 2, and two SSBs A & B; SSB A calls a method on SSB B; SSB A is
|deployed to node 1, SSB B to node 2.
|
|So if a client invokes SSB A, it is directed by availability to node 1. SSB
|A calls SSB B and is directed by availability to node 2. You now have more
|than one node involved which requires a distributed transaction.
|
|Now make it more complex, deploy SSB A on both node 1 and node 2 so the
|client could be load balanced to either node. If it goes to node 1 then you
|have a distributed transaction as above whereas if it is directed to node 2
|then the transaction is local to node 2.
|
|Take it further and deploy both beans on both nodes. The client can get
|load-balanced to either node; in theory so could the inter-bean
|call but due
|to the overhead of a remote call + DTM you would prefer it was directed to
|the local machine.
|
|However, suppose SSB B becomes temporarily unavailable on one node for some
|reason; availability would require that the inter-bean call is now directed
|to the surviving node. The determination of which node will service the
|request is dynamic, based on availability, and as a result so is the
|determination of whether the transaction is local or distributed.
|
|If you plan to support scenarios beyond the most basic, you *will* need a
|DTM so design it in early.
|
|Jeremy
|
|-----Original Message-----
|From: [EMAIL PROTECTED]
|[mailto:[EMAIL PROTECTED]]On Behalf Of marc fleury
|Sent: Tuesday, March 06, 2001 7:18 PM
|To: JBoss-Dev
|Subject: RE: [jBoss-Dev] CL: Clustering, let's get started
|
|
|what does a dtm have to do with Stateless session bean load balancing and
|high availability....
|
|?
|
|marc
|
|
