nacos客户端一致性hash负载需求实现

public class NacosClient {
    //nacos监听器,处理初始化hash环等逻辑
    private Nodelistener nodelistener;
    //初始化nacosClient,并且监听服务
    public void init() {
        NamingService naming = null;
        try {
            System.out.println(System.getProperty("serveAddr"));
            naming = NamingFactory.createNamingService(System.getProperty("serveAddr"));
            //注册监听器,当集群节点变化的时候调用nodelistener处理节点信息
            naming.subscribe("test", event -> {
                if (event instanceof NamingEvent) {
                    nodelistener.handlerChange((NamingEvent)event);
                }
            });
        } catch (NacosException e) {
            e.printStackTrace();
        }
    }
}

public class Nodelistener {
    private List<Instance> servers;
    //利用treeMap构建hash环
    private volatile SortedMap<Long, Instance> sortedMap = new TreeMap<Long, Instance>();
    //虚拟节点
    private int virtualNodeCount = 100;
    public synchronized void handlerChange(NamingEvent event) {
            List<Instance> servers = new ArrayList<Instance>();
            event.getInstances().stream().filter(instance -> {
                return instance.isEnabled() && instance.isHealthy();
            }).forEach(instance -> servers.add(instance));
            this.onChange(servers);
    }
    //每次集群节点变化时,重新构建hash环
    public void onChange(List<Instance> servers) {
        //只有一个节点的时候这里暂不考虑,读者可以自行处理
        if(servers.size() != 1) {
            SortedMap<Long, Instance> newSortedMap = new TreeMap<Long, Instance>();
            for (int i = 0; i < servers.size(); i ++) {
                for (int j = 0; j < this.virtualNodeCount; j++) {
                    //计算虚拟节点的hash,这里用到的是MurMurHash,网上还有很多其他hash实现,
                    //有兴趣可以自行查阅，具体实现细节就不列出了
                    Long hash = HashUtil.getHash(servers.get(i).getIp() + ":" + 
                                                                     servers.get(i).getPort() + j);
                    //把虚拟节点加入hash环
                    sortedMap.put(hash, servers.get(i));
                }
            }
            sortedMap = newSortedMap;
        }
        this.servers = servers;
    }
    //根据传入的key获取hash环上顺时针到hash环尾部部分所有节点
    public Instance getInstance(String str) {
        Long hash = HashUtil.getHash(str);
        SortedMap<Long, Instance> map = sortedMap.tailMap(hash);
        //这里证明刚好获取的是尾部，所以返回所有的节点，其实是获取第一个节点
        if (map.isEmpty()) {
            map = sortedMap;
        }
        return map.get(map.firsTKEy());
    }
}

public class LoadBalance {
    private Nodelistener nodelistener;
    //只需要简单的从hash环中获取第一个节点
    public Instance doSelect(String key) {
        return nodelistener.getInstance(key);
    }
}

    public void test2() {
        Map<String, Integer> map = new HashMap<String, Integer>();
        Random random = new Random();
        for (int i = 0; i < 10000; i ++) {
            String key = String.valueOf(random.nextLong());
            Instance instance = loadBalance.doSelect(key);
            if(!map.containsKey(instance.getIp())) {
                map.put(instance.getIp(), 0);
            }else {
                map.put(instance.getIp(), map.get(instance.getIp()) + 1);
            }
            System.out.println("test2 count :" + i);
            System.out.printf("select IP is :" + instance.getIp());
        }
        System.out.println(map.toString());
    }

    public void test(String key) throws InterruptedException {
        //这里可以设置重试次数
        for (;;) {
            Instance instance = loadBalance.doSelect(key);
            String addr = instance.getIp() + ":" + instance.getPort();
            //测试请求
            if(post(addr)) {
                //成功逻辑
                .....
                break;
            }else {
                //等待两秒,即可以使文件服务器不同节点之间同步文件，还可以等待更新本地hash环
                Thread.sleep(2000);
                //失败则选取下一个节点
                instance = loadBalance.doSelect(key);
                //此处可以增加重试次数逻辑和如果重试到hash环上最后一个节点则重新获取hash环第一个节点逻辑，
                // 在此就不做论述，读者可以自由发挥
                continue;
            }
        }
    }

    public void onChange(List<Instance> newServers) {
        //单节点时这里暂不考虑
        if(servers.size() != 1 ) {
            //TODO ..
        }
        Map<String, Instance> oldAddrs = 
               this.servers.stream()
                           .collect(Collectors.toMap(Instance::toInetAddr, instance -> instance));
        Map<String, Instance> newAddrs = 
               newServers.stream()
                           .collect(Collectors.toMap(Instance::toInetAddr, instance -> instance));
        //remove
        oldAddrs.forEach((key, value) -> {
            if (!newAddrs.containsKey(key)) {
                for(int j = 0; j < virtualNodeCount; j++) {
                    Long hash = HashUtil.getHash( value.toInetAddr() + "&&VM"+ j);
                    sortedMap.remove(hash);
                }
            }
        });
        //add
        newAddrs.forEach((key, value) -> {
            if (!oldAddrs.containsKey(key)) {
                for(int j = 0; j < virtualNodeCount; j++) {
                    Long hash = HashUtil.getHash(value.toInetAddr() + "&&VM" + j);
                    sortedMap.put(hash, value);
                }
            }
        });
        this.servers = newServers;
    }