5 Replies Latest reply on Feb 17, 2009 11:34 AM by sadat khan

    clustering achieved ?

    sadat khan Newbie

      I have an apache web server in front of some jboss server instances ( running on different m/cs )... i have configured mod_jk to route requests to the app servers... in this respect i have some queries : -
      when the server instances on the different nodes are started , they automatically detect each other... also requests are routed from one to another as in if i shutdown an instance after a request has gone to it, the request is served by another instance...

      1. ) can i then claim to have achieved clustering amongst the servers ? or have i missed something... i.e. do i need to do changes in some configuration files or something like that ?

      2.) is there a concept of vertical clustering in jboss like in websphere or 2 instances of jboss on the same m/c are completely independent ?

      thanks

        • 1. Re: clustering achieved ?
          sadat khan Newbie

          in continuation of the above architecture what i have now done is separate one m/c from a cluster by changing its PartitionName in cluster-service.xml.... the server logs show appropriate messages indicating the remaining members of the cluster... however failover is still occurring amongst the severs not in cluster... how is that possible ?

          • 2. Re: clustering achieved ?
            Brian Stansberry Master

            Apache knows nothing about how you've organized the backend servers beyond what you configure in workers.properties. In workers.properties when you set up a load balancer worker you list the regular workers it should balance requests across. You need to limit that list to the workers that you want to receive requests.

            • 3. Re: clustering achieved ?
              sadat khan Newbie

              exactly... apache will not care about how the app servers are arranged... you mean to say that just because the app servers are given in the workers.properties file and load balanced , failover will occur in case one of the constituents goes down ?? why will apache care about the failover part ?
              shouldnt that be the headache of the app servers ?

              • 4. Re: clustering achieved ?
                Brian Stansberry Master

                The load balancer (Apache) is what handles failover. The request comes into apache and it decides how to handle it. If it sees the request's session is associated with a backend server that is no longer available, Apache picks a different server (i.e. fails over). If it passes the request through to a backend server and the request fails with a recoverable problem (e.g. ConnectException connecting to the backend server), it tries a different backend server (i.e. fails over).

                • 5. Re: clustering achieved ?
                  sadat khan Newbie

                  oh... now i get it... but consider the following situation... say i have 2 app servers load balanced by an apache server... after a request has gone to AS1 suppose it goes down... now my question is how does apache know whether AS1 has gone down and route the request to AS2 ( this will not be a case of ConnectException )... i mean this is exactly what i too have observed but i would like to know the reason of the behaviour...
                  does apache keep a track of the requests ?