@Override
    public int compareTo(Delayed o) {
      AMNodeInfo other = (AMNodeInfo)o;
      if (this.nextHeartbeatTime > other.nextHeartbeatTime) {
        return 1;
      } else if (this.nextHeartbeatTime < other.nextHeartbeatTime) {
        return -1;
      } else {
        return 0;
      }
    }
@return A snapshot of the tasks running at this daemon from this AM.
Doesn't have to be consistent between multiple tasks; whether some task makes it into
a given heartbeat when it's about to be started/about to finish is a timing issue anyway.
llap-server/src/java/org/apache/hadoop/hive/llap/daemon/impl/AMReporter.java