public void addStateChangeListener(
      StateChangeListener<FragmentInstanceState> stateChangeListener) {
    instanceState.addStateChangeListener(stateChangeListener);
  }
Listener is always notified asynchronously using a dedicated notification thread pool so, care
should be taken to avoid leaking {@code this} when adding a listener in a constructor.
Additionally, it is possible notifications are observed out of order due to the asynchronous
execution.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/fragment/FragmentInstanceStateMachine.java