public void addSubscribedCounters(final Set<String> moreCounters) {
    if (subscribedCounters == null) {
      subscribedCounters = new HashSet<>();
    }
    subscribedCounters.addAll(moreCounters);
  }
Some context information that are required for rule evaluation.
ql/src/java/org/apache/hadoop/hive/ql/wm/WmContext.java