Front-end/back-end cluster question

Question

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Answer 1

Patrick Power wrote:
          > Thanx for your reply Prasad. I was surprised none of the Bea engineers
          > wished to touch this one. What do you suppose is up with that? Either
          > they are too busy, or possibly my question is too dumb.
          >
          I am from BEA so its not that we are not responding ;).
          >
          > Back to the issue: Yes, we will NES bridge/proxy into servlet front-end
          > cluster, potentially with Directors on the very front of the topology for
          > balancing. Your diagram as such:
          >
          > <Netscape/IIS/Apache/WLS FRONT END> ----- <CLUSTER OF WEBLOGIC SERVER
          > > SERVING SERVLETS> --- <CLUSTER OF WEBLOGIC SERVERS SERVING EJB>
          >
          > 1) Does <Netscape/IIS/Apache/WLS FRONT END> mean NES with proxy shared lib,
          > with a WLS service definition into cluster in obj.conf? I assume yes.
          Yes.
          >
          > 2) I would assume that <CLUSTER OF WEBLOGIC SERVERS SERVING SERVLETS> would
          > need the WLS HttpClusterServlet to the <CLUSTER OF WEBLOGIC SERVERS SERVING
          > EJB> all the way in the back.
          No. I was splitting presentation logic (namely servlets and jsp) and business
          logic (ejb) into two layers. Again you don't have to split it into two. You can
          colocate them both together. You could use NES or IIS or Apache or WLS. You
          don't need HttpClusterServlet.
          Lets get this straight.
          1. You need our proxy plugin for failover and to load balance the request that
          are going to presentation logic.
          2. From presentation logic layer, when you talk to backend business logic
          providers (like ejb cluster), if you use stateless session beans we provide
          failover and load balancing. In future we will support clustered stateful
          session beans as well. Therefore you don't need load balancer here.
          3. HttpClusterServlet should run only in front of presentation logic cluster and
          also it supports http only.
          Hope this helps.
          - Prasad
          > The NES proxy would only proxy into the f/e
          > cluster, right? You're not suggesting an external proxy of some type, are
          > you? The HttpClusterServlet is for WLS cluster-to-cluster proxies.
          > 3) A load balancer between the wls f/e and wls b/e clusters? That doesn't
          > seem applicable here. Once again, it should be HttpClusterServlet for WLS
          > cluster-to-cluster proxies.
          > 4) "use two or three proxy servers to avoid single point of failure."
          > Hmmm, once again - are we talking the WLS HttpClusterServlet proxy? Well,
          > that's the inital question: Can I have more than one HttpClusterServlet
          > proxy in the front-end cluster, proxying to the back-end cluster?
          > Otherwise, internally from this WLS architecture perspective, it is a single
          > point of failure.
          >
          > An example: 10 instances in f/e cluster. can more than one of these
          > instances have the WLS HttpClusterServlet proxy to the b/e cluster? Or, are
          > there instances of WLS HttpClusterServlet proxy in all 10 f/e cluster
          > instances?
          >
          > Cheers, Pat
          >
          > Prasad Peddada <[email protected]> wrote in message
          > news:[email protected]...
          > >
          > >
          > > Patrick Power wrote:
          > >
          > > > I know that this topic was addressed to some degree here in an earlier
          > > > posting, but I still have a question regarding the architecture
          > > > design:
          > > >
          > > > If configuring a front-end cluster for servlets/sessions and a
          > > > back-end cluster for remote services -- you route requests to the
          > > > back-end using the WLS proxy servlet. ok, got that part.
          > >
          > > Not quite. The typical scenario is
          > >
          > > <Netscape/IIS/Apache/WLS FRONT END> ----- <CLUSTER OF WEBLOGIC SERVER
          > > SERVING SERVLETS> --- <CLUSTER OF WEBLOGIC SERVERS SERVING EJB>
          > >
          > > You don't proxy and serve servlets from the same server.
          > >
          > > >
          > > > The question: Is there a single instance of the wls proxy servlet in
          > > > the front-end cluster? Or, is it on every instance in the front-end
          > > > cluster? What is the failover mechanism, in the case of a single
          > > > instance of proxy servlet in the f-e cluster failing?
          > >
          > > To prevent that you need to use some kind of h/w or software load
          > > balancer and then use two or three proxy servers to avoid single point
          > > of failure.
          > >
          > > > Is it a single point of failure between the 2 clusters?
          > > >
          > > > Thanx in advance for your help.
          > > >
          > > > BTW, I think Wei, Kumar and the other Bea folks cruising this group
          > > > have been doing a bang-up job of providing badly-needed detail on this
          > > > subject area - material this largely absent from the documentation.
          > > > Good job.
          > > >
          > > >
          > >
          > > --
          > > Cheers
          > >
          > > - Prasad
          > >
          > >