boolean setFailedToSendGuaranteed() {
    synchronized (actualState) {
      assert actualState.sending != -1;
      actualState.sending = -1;
      // It's ok to skip a failed message if the target has changed back to the old value.
      return (actualState.sent == actualState.target);
    }
  }
The actual state of the guaranteed task, and the update state, for the session.
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/WmTezSession.java