@Override
  public void addStatListener(StatListener observer, StatResource observedResource,
      Stat observedStat) {
    AddStatListenerResponse resp = (AddStatListenerResponse) sendAndWait(
        AddStatListenerRequest.create(observedResource, observedStat));
    int listenerId = resp.getListenerId();
    synchronized (statListenersLock) {
      statListeners.put(listenerId, observer);
    }
  }
Adds a <code>StatListener</code> that is notified when a statistic in a given statistics
instance changes value.

@param observer The listener to be notified
@param observedResource The statistics instance to be observed
@param observedStat The statistic to be observed

@see AddStatListenerRequest
geode-core/src/main/java/org/apache/geode/internal/admin/remote/RemoteGemFireVM.java