Hello,
This is an interesting article.
I share my idea/opinion, hoping not to be to far from reality...
I think that most of the decisions about which target (i.e. server) an
invocation should be done against, should be made as near as possible from
the cluster (for performance, network throughput, ... reaons) by using, as
said in the article, a kind of router (a "invocation-dispatcher") which
would take the appropriate decisions.
Nevertheless, without using some tricky OS-dependant software or quite
expensive hardware, the router becomes a SPOF (single point of failure). And
we will not be able, in pure Java, to have some kind of IP-shared servers
solution...
Consquently, IMHO, the invocation-dispatcher (i.e. router) should make any
load-balancing/failover decision as long as it is available and when it
dies, the switch to another backup-router should be made by the client. i.e.
The client stub code has the list of all backup routers embedded in its code
and when it receives an invocation failure, it silently tries the other
routers by re-launching the current method invocation. (would it be
possible, on the client side, to have some kind of static information such
that if a router fails, all stub codes will automatically use the new one
without each trying the old one i.e. sharing "the good news" between all
stubs for a same target cluster i.e. target domain)
I think that the invocation-dispatcher solution has the advantage of
allowing to develop quite sophisticated load-balancing/failover algorithms
and to have a single point of decision. Nevertheless, it adds some delay to
the calls. Furthermore, a distributed election algorithm is most probably
necessary in order to insure that only one invocation-router is the master.
This, for example, to be able to determine on which server is a particular
entity bean.
just my 0.002$
Cheers,
Sacha
> -----Message d'origine-----
> De : [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]De la part de Rickard Öberg
> Envoyé : jeudi, 22 février 2001 13:44
> À : jBoss Developer
> Objet : [jBoss-Dev] Article on clustering
>
>
> Hey
>
> You may want to read this:
> http://www.onjava.com/pub/a/onjava/2000/12/15/ejb_clustering.html
>
> regards,
> Rickard
>
> --
> Rickard Öberg
>
> Email: [EMAIL PROTECTED]
>
