Create clusters

Use this task to create clusters, which are sets of application servers that are managed together and participate in workload management.

 

Overview

You can manage application servers collectively using a cluster. Use the Server cluster collection to view and manage the cluster.

 

Procedure

  1. Enter basic cluster information.

    1. In the administrative console, click Servers > Clusters > New.

    2. Create a name for the cluster.

    3. To enable or disable node-scoped routing optimization, select Prefer local. The default is enabled, which indicates that, if possible, Enterprise JavaBeans (EJB) requests are routed to the client node. If you enable this feature, performance is improved because client requests are sent to local enterprise beans.

    4. To create a replication domain for this cluster, select Create a replication domain for this cluster. Use replication domains to transfer data, objects, or events for session manager, dynamic cache, or stateful session beans among the application servers in a cluster. Create a separate replication domain to use with each component that acts as a consumer of the replication. For example, one can configure one replication domain to use with a session manager and another domain to use with dynamic cache. The replication domain name that is created is identical to the cluster name. See Replicating data across application servers in a cluster for more information.

    5. Choose whether to create an empty cluster or to create a cluster based on an existing server.

      To create an empty cluster, select Do not include an existing server in this cluster.

      To create a cluster based on an existing server, choose Select an existing server to add to this cluster and select the server you want to add. The server you add becomes a template for any additional cluster members that you add to the cluster. Be sure that the template is configured correctly before adding more cluster members that are based on this template. Note that this is the only time you are able to add an existing server to the cluster. After you create the first cluster member, one cannot add other existing application servers to the cluster. Be careful when adding an existing server because the only way to remove an application server from a cluster is to delete the application server. Consider using the existing server as a template for the cluster members but not as a cluster member. Keeping the original application server out of the cluster allows you to reuse the template to rebuild the configuration.

    6. If you chose to add an existing server, specify the server weight. The weight value controls the amount of work that is directed to the application server. If the weight value for this server is greater than the weight values assigned to other servers in the cluster, then the server receives a larger share of the workload. The weight value represents a relative proportion of the workload that is assigned to a particular application server. The value can range from 0 to 20.

  2. Create cluster members.

    Note: With WebSphere Application Server v6, one can upgrade a portion of the nodes in a cell, while leaving others at the older release level. This means that, for a period of time, you might be managing servers that are at the current release and servers that are running the newer release in the same cell. Note that in this mixed environment, there are some restrictions on what one can do with clusters and cluster members:

    • You cannot create a cluster member using a server running on WAS V5.x.

    • You cannot add a member that is running WAS Version 5.x to any cluster.

    • You can add a new WAS v6 cluster member to a mixed cluster only if the cluster already contains a WebSphere Application Server v6 member that was upgraded from WebSphere Application Server V5.x. All new cluster members must be running WebSphere Application Server v6.

    For each new cluster member, perform the following actions:

    1. Type the name of a new application server (cluster member) to add to the cluster.

    2. Select the node on which the server resides.

    3. Specify the server weight. The weight value controls the amount of work directed to the application server. If the weight value for the server is greater than the weight values assigned to other servers in the cluster, then the server receives a larger share of the workload. The value can range from 0 to 20.

    4. Make sure that Generate Unique HTTP Port is selected.

    5. Specify the server template. You can choose the default application server template or an existing application server template. All the application servers you add after the first application server use the same template.

    6. Click Apply to finish the cluster member. You can add more cluster members. All cluster members you add are based on the same server template.

  3. View the summary. View a summary of the changes and then click Finish. Your cluster is created.

  4. Define a virtual host with a unique port number. See Configuring virtual hosts for more information.

    1. In the administrative console, click Environment > Virtual Hosts > default_host > Host Aliases.

    2. Click New and, on the settings page for a virtual host that displays, specify an administrative name for the virtual host.

    3. Under Additional Properties, click Host Aliases and define a unique port number for the virtual host.

  5. Save your configuration. As part of saving the change to the configuration, one can select Synchronize changes with Nodes before clicking Save on the Save page.

  6. Before one can start the cluster, the configuration needs to be synchronized to the nodes. If you selected Synchronize changes with Nodes when saving your configuration in the previous step, one can ignore this step. If you are running automatic synchronization, wait until synchronization runs. Or, run manual synchronization to get the configuration files moved to the nodes. Click System administration > Nodes and, on the Nodes page, select the node and click Synchronize or Full resynchronize. The Nodes page displays status indicating whether the node is synchronized.

  7. To further configure a cluster, click Servers > Clusters. To view the settings for the cluster, click on the cluster Name. Note that unless you have clicked Save and saved your administrative configuration, you only see the Configuration and Local Topology tabs; to see the Runtime tab save your administrative configuration. Also, ensure that changes are synchronized to the nodes (step 7).

 

What to do next

You can create cluster members or start the cluster. See Balancing workloads with clusters for more information about cluster configuration options.

Use scripting to automate the task of creating clusters. See Creating clusters using scripting for more information.

 

See also


Creating a cluster : Basic cluster settings
Creating a cluster : Basic cluster member settings
Creating a cluster : Summary settings
Server cluster collection

 

Related Tasks


Balancing workloads with clusters

 



 

 

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