If you want to know how many nodes there are in the current cluster partition, all you have to do is to ask HAPartition for the node list. HAPartition represents your cluster partition, and it contains all the information you need to know about your cluster and the nodes: their host names, IPs, position in the cluster view.

Lets assume you have a service bean that extends from HASingletonSupport. HASingletonSupport in its turn extends from HAServiceMBeanSupport.

HAServiceMBeanSupport is the one who gives you access to HAPartition object.

The code to request for HAPartition object and node list that you see below , you can put somewhere in your service bean:

HAPartition partition = getPartition();ClusterNode[] nodes = partition.getClusterNodes();System.out.println(nodes.length);

Another way, is to do practically the same, but to request from a HAPartition a current view of your cluster:

HAPartition partition = getPartition();Vector v = partition.getCurrentView();System.out.println(partition.getCurrentView().size());for (Object o : v) {
System.out.println(o.toString());}

The view, which is a Vector contains information about node sockets. When printed, it will return to you a String representation of node ip port: xxx.xxx.xxx.xxx:port. Also by printing size of the Vector, you will get number of nodes in the cluster.

Important note:

I noticed there is some delay happening from the time when node leaves the cluster to the time when HAPartition returns updated view. In another words - after node has left the cluster and topology change occurred, the HAPartition may return to you an old view still containing the dead node. So be careful.

Thats it.