public boolean hasServerInstance() {
        for (ServerGroup serverGroup : this.serverGroupList) {
            if (!serverGroup.getInstanceList().isEmpty()) {
                return true;
            }
        }
        return false;
    }
@author emeroad
@author netspider
@author minwoo.jung
@author HyunGil Jeong
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/nodes/ServerGroupList.java