WebLogic: Cluster Adress option
Published on: Author: Michel Schildmeijer Category: OracleAlthough I haven’t had time lately to do some blogposting, I’d like to pick it up from here with short articles from which I hope you will learn some about the features of Oracle Fusion Middleware areas with special focus on WebLogic.
One of the things I often encounter is that there is a misconception about something called the ‘Cluster Address Option’ within a WebLogic Domain Configuration. So, what is it? Every time you configure a WebLogic Cluster, you can set several configurations for your cluster to facilitate the high availability of an application. One of those is the Cluster Address Option, which you find on the General Tab of you Cluster:
Format is : <mshost1:port>,<mshost2:port>, etc… Each entry corresponds to a Managed Server and port that received the request.
This is a static list for applications (EJB’s) to choose from. When not filled in, WebLogic generates in each request dynamically an adress.
My best practise is to fill in it in when you have an Oracle Service Bus cluster. The OSB configuration, but also the reportingprovider rely to the underlying entity and stateless beans to generate a hostname as part of a request URL for processing messages.
Another option is to fill in one Virtual hostname, that points to all available managed servers in the cluster, but be aware that in this case all managed servers should be set to the same listenport. If the request was received by a Managed Server, the listen address and port combinations in the cluster address reflect the ListenAddress and ListenPort values from the associated ServerMBean and/or SSLMBean instances.
The default number of the NumberOfServersInClusterAddress attribute on the ClusterMBean is 3. You can modify this value on the Environments—>Clusters—>ClusterName->Configuration->General
If there are fewer Managed Servers available in the cluster than the value of NumberOfServersInClusterAddress, the dynamically generated cluster address contains all available for each of the running Managed Servers.
If there are more Managed Servers available in the cluster than the value set in, WebLogic Server does a random select of the available managed servers in this value.
