模拟Dubbo的zookeeper一致性Hash发现

public interface HashFunc {
    public Long hash(Object key);
}

public class ConsistentHash<T> {
    /**
     * Hash计算对象，用于自定义hash算法
     */
    HashFunc hashFunc;
    /**
     * 复制的节点个数
     */
    private int numberOfReplicas;
    /**
     * 一致性Hash环
     */
    private SortedMap<Long, T> circle = new TreeMap();

    /**
     * 构造，使用Java默认的Hash算法
     * @param numberOfReplicas 复制的节点个数，增加每个节点的复制节点有利于负载均衡
     * @param nodes            节点对象
     */
    public ConsistentHash(int numberOfReplicas, Collection<T> nodes) {
        this.numberOfReplicas = numberOfReplicas;
        this.hashFunc = new HashFunc() {
            public Long hash(Object key) {
//          return fnv1HashingAlg(key.toString());
                return md5HashingAlg(key.toString());
            }
        };
        //初始化节点
        for (T node : nodes) {
            add(node);
        }
    }

    /**
     * 构造
     * @param hashFunc         hash算法对象
     * @param numberOfReplicas 复制的节点个数，增加每个节点的复制节点有利于负载均衡
     * @param nodes            节点对象
     */
    public ConsistentHash(HashFunc hashFunc, int numberOfReplicas, Collection<T> nodes) {
        this.numberOfReplicas = numberOfReplicas;
        this.hashFunc = hashFunc;
        //初始化节点
        for (T node : nodes) {
            add(node);
        }
    }

    /**
     * 增加节点<br>
     * 每增加一个节点，就会在闭环上增加给定复制节点数<br>
     * 例如复制节点数是2，则每调用此方法一次，增加两个虚拟节点，这两个节点指向同一Node
     * 由于hash算法会调用node的toString方法，故按照toString去重
     *
     * @param node 节点对象
     */
    public void add(T node) {
        for (int i = 0; i < numberOfReplicas; i++) {
            circle.put(hashFunc.hash(node.toString() + i), node);
        }
    }

    /**
     * 移除节点的同时移除相应的虚拟节点
     *
     * @param node 节点对象
     */
    public void remove(T node) {
        for (int i = 0; i < numberOfReplicas; i++) {
            circle.remove(hashFunc.hash(node.toString() + i));
        }
    }

    /**
     * 获得一个最近的顺时针节点
     *
     * @param key 为给定键取Hash，取得顺时针方向上最近的一个虚拟节点对应的实际节点
     * @return 节点对象
     */
    public T get(Object key) {
        if (circle.isEmpty()) {
            return null;
        }
        long hash = hashFunc.hash(key);
        if (!circle.containsKey(hash)) {
            SortedMap<Long, T> tailMap = circle.tailMap(hash); //返回此映射的部分视图，其键大于等于 hash
            hash = tailMap.isEmpty() ? circle.firstKey() : tailMap.firstKey();
        }
        //正好命中
        return circle.get(hash);
    }

    /**
     * 使用MD5算法
     * @param key
     * @return
     */
    private static long md5HashingAlg(String key) {
        MessageDigest md5 = null;
        try {
            md5 = MessageDigest.getInstance("MD5");
            md5.reset();
            md5.update(key.getBytes());
            byte[] bKey = md5.digest();
            long res = ((long) (bKey[3] & 0xFF) << 24) | ((long) (bKey[2] & 0xFF) << 16) | ((long) (bKey[1] & 0xFF) << 8)| (long) (bKey[0] & 0xFF);
            return res;
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return 0l;
    }

    /**
     * 使用FNV1hash算法
     * @param key
     * @return
     */
    private static long fnv1HashingAlg(String key) {
        final int p = 16777619;
        int hash = (int) 2166136261L;
        for (int i = 0; i < key.length(); i++)
            hash = (hash ^ key.charAt(i)) * p;
        hash += hash << 13;
        hash ^= hash >> 7;
        hash += hash << 3;
        hash ^= hash >> 17;
        hash += hash << 5;
        return hash;
    }
}

@Component
public class ClientComsumer implements Watcher {

    //本地缓存服务列表
    private static Map<String, List<String>> servermap;
    @Autowired
    private ZookeeperServer zkServer ;
    private ZooKeeper zk;
    private ConsistentHash consistentHash;
    @Autowired
    Environment env;

    @PostConstruct
    private void init() throws IOException {
        String address = env.getProperty("zookeeper.address");
        this.zk = zkServer.getConnection(address,this);
    }

    private List<String> getNodeList(String serverName) throws KeeperException, InterruptedException, IOException {
        if (servermap == null) {
            servermap = new HashMap<>();
        }
        Stat exists = null;
        try {
            String s = "/guanjian/" + serverName;
            exists = zk.exists(s,this);
        } catch (Exception e) {
        }

        //判断是否存在该服务
        if (exists == null) return null;
        List<String> serverList = servermap.get(serverName);
        if (serverList != null && serverList.size() > 0) {
            //将已存在的serverList放入一致性Hash环
            this.consistentHash = new ConsistentHash(serverList.size(),serverList);
            return serverList;
        }
        List<String> children = zk.getChildren("/guanjian/" + serverName,this);
        List<String> list = new ArrayList<>();
        for (String s : children) {
            byte[] data = zk.getData("/guanjian/" + serverName + "/" + s, this, null);
            String datas = new String(data);
            NodeStat nodeStat = JSONObject.parseObject(datas, NodeStat.class);
            if (!Status.stop.equals(nodeStat.getStatus())) {
                list.add(datas);
            }
        }
        //将list放入一致性Hash环
        this.consistentHash = new ConsistentHash(list.size(),list);
        servermap.put(serverName, list);
        return list;
    }

    public String getServerinfo(String serverName) throws KeeperException, InterruptedException, IOException {
        try {
            List<String> nodeList = getNodeList(serverName);
            if (nodeList == null|| nodeList.size()< 1) {
                return null;
            }
            //这里使用得随机负载策略，如需需要自己可以实现其他得负载策略
            //String snode = nodeList.get((int) (Math.random() * nodeList.size()));
            //从一致性Hash环的第一个服务开始查找
            String snode = (String) this.consistentHash.get(nodeList.get(0));
            NodeStat nodeStat = JSONObject.parseObject(snode, NodeStat.class);
            List<String> children = zk.getChildren("/guanjian/" + serverName,this);
            //随机负载后,将随机取得节点后的状态更新为run
            for (String s : children) {
                byte[] data = zk.getData("/guanjian/" + serverName + "/" + s, this, null);
                String datas = new String(data);
                if (snode.equals(datas)) {
                    nodeStat.setStatus(Status.run);
                    zk.setData("/guanjian/" + serverName + "/" + s,JSONObject.toJSONString(nodeStat).getBytes(),0);
                    break;
                }
            }
            return JSONObject.toJSONString(nodeStat);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    @Override
    public void process(WatchedEvent watchedEvent) {
        //如果服务节点数据发生变化则清空本地缓存
        if (watchedEvent.getType().equals(Event.EventType.NodeChildrenChanged)) {
            servermap = null;
        }
    }
}