private void updateSessionAllocationWithEvent(WmTezSession session, double allocation) {
      WmEvent event = null;
      WmContext ctx = session.getWmContext();
      if (ctx != null && session.hasClusterFraction()
          && !DoubleMath.fuzzyEquals(session.getClusterFraction(), allocation, 0.0001f)) {
        event = new WmEvent(EventType.UPDATE);
      }
      session.setClusterFraction(allocation);
      if (event != null) {
        event.endEvent(session);
      }
    }
State of a single pool.
Unless otherwise specified, the members are only modified by the master thread.
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/WorkloadManager.java