Use this task to create clusters, which are sets of application
servers that are managed together and participate in workload management.
Why and when to perform this task
You can manage application servers collectively using a cluster.
Use the
Server cluster collection to
view and manage the cluster.
Steps for this task
- Enter basic cluster information.
- In the administrative console, click Servers > Clusters >
New.
- Create a name for the cluster.
- 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.
- 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, you 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.
- 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, you 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 if you need to rebuild the configuration.
- 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.
- Create cluster members.
Note: With
WebSphere Application Server Version 6.0, you 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 you can do with clusters and cluster members:
- You cannot create a cluster member using a server running on WebSphere
Application Server Version 5.x.
- You cannot add a member that is running WebSphere Application Server Version
5.x to any cluster.
- You can add a new WebSphere Application Server Version 6.0 cluster member
to a mixed cluster only if the cluster already contains a WebSphere Application
Server Version 6.0 member that was upgraded from WebSphere Application Server
Version 5.x. All new cluster members must be running WebSphere Application
Server Version 6.0.
For each new cluster member, perform the following actions:
- Type the name of a new application server (cluster member) to
add to the cluster.
- Select the node on which the server resides.
- 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.
- Make sure that Generate Unique HTTP Port is selected.
- 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.
- 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.
- View the summary. View a summary of the changes
and then click Finish. Your cluster is created.
- Define a virtual host with a unique port number. See Configuring virtual hosts for more information.
- In the administrative console, click Environment > Virtual
Hosts > default_host > Host Aliases.
- Click New and, on the settings page for a virtual host
that displays, specify an administrative name for the virtual host.
- Under Additional Properties, click Host Aliases and
define a unique port number for the virtual host.
- Save your configuration. As part of saving the change to the configuration,
you can select Synchronize changes with Nodes before clicking Save
on the Save page.
- Before you 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, you 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.
- 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 you must save your administrative configuration.
Also, ensure that changes are synchronized to the nodes (step 7).