BEA WebLogic Server Administration Kit (Prentice Hall PTR Advanced Web Development)

Configuration of the clusters is done from the Clusters tab in the left pane of the Administration console. (See Figure 6-1.)

Figure 6-1. Configuring Socket Readers in WLS 6.x

General

In this tab you set the basic attributes of the cluster.

Name

The collective name of the elements of the cluster.

Cluster Address

The IP address(es) shared by servers in the cluster. As with the individual servers, this must be a static IP address, not one obtained via DHCP.

Default Load Algorithm

The system used to route requests among the nodes in the cluster.

Service Age Threshold

A value used in the load-calculation algorithm. It specifies the number of seconds by which two services must differ in age before one is considered older than the other.

To record your changes to the data values on this screen and put them into effect, click the Apply button.

Multicast

Servers in a cluster must be on the same subnet. The information in this tab is used to define the properties of the TCP/IP connection that they use to communicate among themselves .

Multicast Address

The multicast IP address which the servers use to broadcast messages to one another.

Multicast Send Delay

The number of milliseconds servers will wait before sending messages. This value exists to fix a problem whereby servers sent messages too fast and overflowed the buffer of their host OS.

Multicast TTL

Multicast Time To Live. This is sort of an expiration date, given in milliseconds, for multicast broadcasts. The larger the network on which your cluster lives, the larger the value in this field. It is recommended, however, that you build your clusters on a LAN, which means that the Multicast TTL should be set to a value of 1.

On WebLogic versions 7 and above, you can also set the following properties:

Port

IP Port used for multicast communication

Multicast Buffer Size

Size of the buffer used for multicast communication

\Servers

This tab is used to define the membership of a cluster. The arrow interface is pretty intuitive; to add a server to the cluster, highlight it from the collection of servers on the left side of the right pane and click the right arrow. To remove it from a cluster, highlight a server in the cluster and click the left arrow.

Monitoring

This tab is display-only with two sets of values:

Number of servers configured for this cluster

Number of servers participating in this cluster.

For any situation other than a server being down for maintenance, the two values should be the same. If not, you have a problem.

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