Selecting Members for Task Execution
As previously mentioned, it is possible to indicate where in the Hazelcast cluster the Runnable or Callable is executed. Usually, you will execute these in the cluster based on the location of a key, set of keys, or you will just allow Hazelcast to select a member.
If you want more control over where your code runs, use the MemberSelector interface. For example, you may want certain tasks to run only on certain members, or you may wish to implement some form of custom load balancing regime. The MemberSelector is an interface that you can implement and then provide to the IExecutorService when you submit or execute.
The select(Member) method is called for every available member in the cluster. Implement this method to decide if the member is going to be used or not.
In a simple example shown below, we select the cluster members based on the presence of an attribute.
public class MyMemberSelector implements MemberSelector {
public boolean select(Member member) {
return Boolean.TRUE.equals(member.getAttribute("my.special.executor"));
}
}
You can use MemberSelector instances provided via com.hazelcast.cluster.memberselector.MemberSelectors class. For example, you can select a lite member for running a task using com.hazelcast.cluster.memberselector.MemberSelectors#LITE_MEMBER_SELECTOR.