private void notifyServerStatusChangeListener(final Collection<Server> changedServers) {
        if (changedServers != null && !changedServers.isEmpty() && !serverStatusListeners.isEmpty()) {
            for (ServerStatusChangeListener listener : serverStatusListeners) {
                try {
                    listener.serverStatusChanged(changedServers);
                } catch (Exception e) {
                    logger.error("LoadBalancer [{}]: Error invoking server status change listener", name, e);
                }
            }
        }
    }
Class that contains the mechanism to "ping" all the instances

@author stonse
ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer/BaseLoadBalancer.java