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Create dynamic clusters


Overview

When we create a dynamic cluster, the workload of the cluster members is dynamically balanced based on performance information collected from the cluster members. Creating dynamic clusters enables application server virtualization.

Dynamic clusters expand and contract depending on the workload in the environment. Dynamic clusters work with autonomic managers, including the application placement controller and the dynamic workload manager to maximize the use of our computing resources. Dynamic clusters are required for many of the product autonomic functions, including high availability and service policies.

Before creating a dynamic cluster...

If we already have over 40 servers in our core group, we can use the coregroupsplit.py script to split our existing cell into multiple core groups.


Create a dynamic cluster

  1. Create the dynamic cluster.

    In the administrative console, click...

  2. Select the dynamic cluster server type.

    The dynamic cluster server type determines the type of servers that are members of this dynamic cluster. Depending on the type, enter the name of the dynamic cluster on this panel or when we select the membership method.

  3. For some dynamic cluster types, we can select the membership method. The membership method defines how servers join the dynamic cluster as cluster instances.

    Option Description
    Automatically define cluster members with rules We can Automatically define cluster members with rules if we are using servers with complete life-cycle management. With this option, we create a membership policy that defines the nodes on which cluster instances can be placed.
    Manually define cluster members If we are using servers with assisted life-cycle management, we can Manually define cluster members. With this option, we select existing servers to add to the dynamic cluster. The servers that we select must be homogenous: that is, they must be of the same server type, middleware server version, and have the same applications installed.

    To add a new middleware server to an existing dynamic cluster when one or more applications are targeted to the dynamic cluster, install the applications on the middleware server and target the applications to the server before we add the server as member of the dynamic cluster.

  4. Define the dynamic cluster members.

    • If we selected Automatically define cluster members with rules in the previous step, use the subexpression builder to build a membership policy expression for our dynamic cluster. This expression is compared to all the nodes in the cell, selecting any nodes for which the subexpression is true.

      1. By default, the value of the Membership policy field is set to node_nodegroup = 'DefaultNodeGroup', which means that all of the nodes belonging to this node group are members of the new dynamic cluster. To modify the membership policy, click the Subexpression builder link under Edit rule.

      2. From the membership policy Subexpression builder window, modify the initial policy by setting the following options.

        • Define the appropriate value for Logical operator as either AND or OR.
        • Set the expression's operand value, which can be Nodegroup, Node name, Node host name and Node property.
        • Choose the desired expression Operator.
        • Enter the appropriate information in the value field, matching the chosen operand value, for the expression's operation.
        • Click Generate subexpression.
        • Click Append, which modifies the value of the Membership policy field

      3. To see where the new dynamic cluster members will reside, click the Preview membership link.

      4. Click Next.

    • If we selected Manually define cluster members, the action you take depends on what kind of servers are in our dynamic cluster.

      • If the server type is application server, choose an existing static cluster to convert to a dynamic cluster.

      • If the server type is an externally created middleware server with assisted life-cycle management, select servers from the list, and add them to our dynamic cluster. Before we add assisted life-cycle servers, be sure that they are the same type, middleware server version, and have the same set of applications installed.

        Before adding a new middleware server to an existing dynamic cluster when one or more applications are targeted to the dynamic cluster, install the applications on the middleware server and target the applications to the server.

        1. Deploy your unmanaged application to the middleware server.

        2. Define the deployment target for the application. In the administrative console, click...

            Applications > All applications > unmanaged_app_name

          Select the target and click Add.

        3. Click Apply and save our changes.

  5. Select a dynamic cluster server template.

    We can select a dynamic cluster server template only for dynamic clusters that consist of servers with complete life-cycle management. We can choose an existing predefined template, or create our own server templates to use when we create our dynamic cluster. Read about creating server templates.

    If the configuration consists of mixed versions of WAS Network Deployment, specifically the deployment manager is at a higher version than the version of the node, we cannot use a predefined server template to create a dynamic cluster. If we are running a v6.1 node and a v7.0 deployment manager, for example, we can create a static cluster of servers on the node, and then convert the static cluster to a dynamic cluster.

    Deprecated feature: The defaultXD and defaultXDZOS server templates used when creating a dynamic cluster are deprecated. Use the default or defaultZOS server template instead.depfeat

  6. Specify dynamic cluster-specific properties.

    1. Define the minimum number of cluster instances.

      The default minimum number of instances is one instance and the maximum default is no limit on instances. If a minimum value is excessive, performance degradation might occur.

    2. Define the maximum number of cluster instances. The default value has no limit on the number of cluster instances.

    3. Determine whether to enable vertical stacking. When we configure vertical stacking, more than one dynamic cluster instance can start on the same node.

    4. Specify an isolation preference for the dynamic cluster.

  7. Save the changes to the master configuration.

      Finish > Save

  8. Select the mode of operation...

      Servers > Clusters > Dynamic clusters > dynamic_clusters > operational_mode > Set mode

    To use dynamic application placement, click Automatic or Supervised as the mode of operation.

    (ZOS) If we have nodes that run on z/OS systems, use dynamic clusters in supervised or automatic mode. To prevent Intelligent Management from automatically starting a cluster member on a logical partition (LPAR) hosting a dynamic cluster when the LPAR processor is too busy, then we must define the cpuUtilizationThreshold custom property. In this scenario, the product starts the cluster member only if transaction demand requires additional cluster members and the processor utilization on the LPAR is less than the cpuUtilizationThreshold value.

When the dynamic clusters start, at least one instance of each dynamic cluster in the environment becomes available as soon as possible. Multiple instances on the same node can start concurrently if we have multiple processors on the same node. For example, if we have two processors on a node, two instances can start concurrently. The application placement controller continues to start instances evenly across the nodes for all the dynamic clusters until the minimum number of instances for each dynamic cluster is reached.


Specify that exactly two servers are started when the dynamic cluster is running

Click

Click...

...and set the Number of instances value to 2.


Limit the number of started servers to five. Stop servers when no activity occurs

Click...

Set the maximum number of instances by clicking...

...and set the Number of instances value to 5.


Keep at least one instance active. Support an unlimited number of instances to start

Click...


What to do next

Remember: To change the server ports after the server has been created, change the ports on each server instance. We cannot change the ports through the dynamic cluster template. Because multiple servers can be on the same node by configuring vertical stacking, the ports must be unique for each server instance.


Subtopics


Related:

  • Dynamic clusters
  • Dynamic cluster isolation
  • Application lazy start
  • Components of dynamic operations
  • Monitoring and tuning the application placement controller
  • Configure vertical stacking
  • Add assisted lifecycle middleware servers (deprecated)
  • Deploy applications with defined service levels
  • Create and manage reports
  • Create PHP servers and PHP dynamic clusters
  • Deploy unmanaged Web applications
  • Create middleware server templates
  • PlacementControllerProcs.jacl script
  • HmmControllerProcs.jacl script
  • Intelligent Management: static clusters versus dynamic clusters
  • Intelligent Management: administrative roles and privileges
  • coregroupsplit.py script
  • Intelligent Management: application placement custom properties