Dynamic cluster is the new Intelligent Management feature, which enables WebSphere 8.5 to dynamically stop, start and allocate resource as and when, required for an application running on a dynamic cluster. Dynamic cluster works in two modes: Add operation & Remove operation.
Add operation- in Add operation, it add resources when all servers in a dynamic cluster are started and demand is still not satisfied. This is possible through automatic actions, which you have defined under the Add operation.
Remove operation- in Remove operation, it stops the servers when demand is very minimal or if running resources are not required to serve the requests. This operation will never shutdown below the number of minimum active server instance configured in Remove operation.
Operational Mode
Operation Mode is the method that interacts with the dynamic operation environment. This has three modes: Manual, Supervised & Automatic.
Manual- it’s similar to the normal application server environment with static cluster. Manual operation mode is as good as WebSphere application server traditional cluster.
Supervised- provides information and recommendation for actions that WebSphere administrator can approve or deny.
Automatic- the intelligent management takes action automatically. Dynamic operations environment handles add/remove operation and provisioning.
Creating Dynamic Cluster
Login into Deployment Manager Console
Go to Servers >> Clusters >> Dynamic clusters
Select Operational mode as Automatic and click on New
Select Server type as WebSphere application server and click on Next
Leave default method – Automatically define cluster members with rules
Provide Dynamic cluster name – First Dynamic Cluster and click on Next
You can select multiple Node Group if you have, in this course we have only one Node group as Default Group. Leave default setting and click on Next
Select dynamic cluster template as default and click on Next
Specify dynamic cluster specific properties are the one you configure how dynamic cluster should behave. We will leave the default settings as following and click on Next.
Keep one instance started at all times – dynamic cluster will be always active with one instance. By configuring this we ensure there is no application outage.
Do not limit thee number of instances that can start- dynamic cluster will start all instances in defined node as demand increases. By configuring this we ensure all resources are utilized when demand is high.
No isolation requirements- as we have only one Node Group we can continue with no isolation requirements.
Review the configuration summary and click on Finish to create Dynamic Cluster
Save the configuration and synchronize changes with nodes. Once done, you can see newly created Dynamic cluster is listed.
You can also see dynamic cluster member is created under Application servers and started one instance as we have selected to keep one instance started all times.
Now in this dynamic cluster setup, one instance will be always running. However, as demand increase other cluster instance also will be started.
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