Cool. I haven't really the first idea where to start on it, but I do have
time now, so I'll start looking into DTMs.. anyone else out there looking?
Tom
On Wed, 7 Mar 2001, marc fleury wrote:
> 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
> |
> |
>
>
>
--
"If you mess with something for long enough it will break." - Schmidt
