private boolean isActive() {
    State localState = state.get();
    return (localState != State.LATENT && localState != State.CLOSED);
  }
We would have used the curator ephemeral node with some extra logic but it doesn't handle
the EXISTS condition, which is crucial here; so we c/p parts of Curator and add our logic.
llap-client/src/java/org/apache/hadoop/hive/llap/registry/impl/SlotZnode.java