MembershipListener

The MembershipListener interface is similar to the MessageListener interface above: every time a new view, a suspicion message, or a block event is received, the corresponding method of the class implementing MembershipListener will be called.

    public interface MembershipListener {    
        public void viewAccepted(View new_view);
        public void suspect(Object suspected_mbr);
        public void block();
    }

Oftentimes the only method containing any functionality will be viewAccepted() which notifies the receiver that a new member has joined the group or that an existing member has left or crashed. The suspect() callback is invoked by JavaGroups whenever a member if suspected of having crashed, but not yet excluded^3.1. The block method is called whenever the member needs to stop sending messages. When the next view is received (viewAccepted()), the member can resume sending messages. If a member does not comply, the message(s) sent between a block() and a matching viewAccepted() callback will probably be delivered in the next view. The block() callback is only needed by the Virtual Synchrony suite of protocols (FLUSH protocol)^3.2, otherwise it will never be invoked.