public ID getTarget() {
    return target;
  }
A member of the cluster sends a HeartbeatRequestMessage to another member if it suspects
that member is gone. A member receiving one of these messages should respond with a
HeartbeatMessage having the same requestId as this message.
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/messages/HeartbeatRequestMessage.java