void setIsIrrelevantForWm(String killReason) {
    if (killReason == null) {
      throw new AssertionError("Cannot reset the kill reason " + this.killReason);
    }
    this.killReason = killReason;
  }
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