public Map<String, String> getAgentIdNameMap() {
        // Stream is not recommended
        final Map<String, String> map = new LinkedHashMap<>();
        for (ServerGroup serverGroup : this.serverGroupList) {
            for (ServerInstance serverInstance : serverGroup.getInstanceList()) {
                // NPE
                map.put(serverInstance.getName(), serverInstance.getAgentName());
            }
        }
        return map;
    }
@author emeroad
@author netspider
@author minwoo.jung
@author HyunGil Jeong
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/nodes/ServerGroupList.java