1 Reply Latest reply on Jan 11, 2013 3:26 PM by René van Wijk

    How does Replication Group in Cluster work ?


      I have 4 servers (MS1,MS2,MS3,MS4) in a cluster and the cluster address has the IP addresses of these 4 servers.

      While MS1,MS2 are on MachineA MS3,MS4 are on MachineB

      Below is what i need

      Table 1.1
      *[Primary Server - Secondary Server]* for HTTP sessions.

      MS1 - MS4
      MS2 - MS3
      MS3 - MS1
      MS4 - MS2

      I gave the below settings in the Replication Group:

      MS1 - TeamB
      MS2 - TeamC
      MS3 - TeamA
      MS4 - TeamD

      I gave the below settings in the Preferred Secondary Group:

      MS1 - TeamD
      MS2 - TeamA
      MS3 - TeamB
      MS4 - TeamC

      Below is how I test:

      I have a session based application which has System.out on each JSP / Servlet and I can thus determine the primary server that gets the request. After login in the application I shutdown the primary server expecting the seconday server as mention above to continue processing the client request.

      But it does not happen as expected in Table 1.1 above i.e for MS1(Primary) i am expecting MS4 to process the client request but MS2 or MS3 out files show that they are processing the client request post shutting down MS1.

      I have mentioned the below in weblogic.xml


      But it is not working as expected. Is there a flaw in my understanding or in the product. Please clarify.

      Edited by: Mohtashim Shaikh on Jan 8, 2013 5:58 AM
        • 1. Re: How does Replication Group in Cluster work ?
          René van Wijk
          http://docs.oracle.com/cd/E23943_01/web.1111/e13709/failover.htm (see the 'using replication groups' section)

          By default, WebLogic Server attempts to create session state replicas on a different machine than the one that hosts the primary session state. You can further control where secondary states are placed using replication groups. A replication group is a preferred list of clustered servers to be used for storing session state replicas.

          Using the WebLogic Server Administration Console, you can define unique machine names that will host individual server instances. These machine names can be associated with new WebLogic Server instances to identify where the servers reside in your system.

          Machine names are generally used to indicate servers that run on the same machine. For example, you would assign the same machine name to all server instances that run on the same machine, or the same server hardware.

          If you do not run multiple WebLogic Server instances on a single machine, you do not need to specify WebLogic Server machine names. Servers without a machine name are treated as though they reside on separate machines. For detailed instructions on setting machine names, see Configure Machine Names.

          When you configure a clustered server instance, you can assign the server to a replication group, and a preferred secondary replication group for hosting replicas of the primary HTTP session states created on the server.

          When a client attaches to a server in the cluster and creates a primary session state, the server hosting the primary state ranks other servers in the cluster to determine which server should host the secondary. Server ranks are assigned using a combination of the server's location (whether or not it resides on the same machine as the primary server) and its participation in the primary server's preferred replication group.