@Monitor(name=PREFIX + "InstanceCount", type = DataSourceType.GAUGE)    
    public int getInstanceCount() {
        return loadBalancerStats.getInstanceCount(zone);
    }
Class that stores Statistics per Zone (where Zone is typically a Amazon
Availability Zone)

@author awang

@param <T>
ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/ZoneStats.java