第 05 周 技术选型 -01 命题作业

public class ConsistentHashBalance {
    public ConsistentHashBalance(int virtualNum) {
        this.virtualNum = virtualNum;
    }
    /**
     * 物理节点
     */
    private List<CacheNode> cacheNodeList = new ArrayList<CacheNode>();
    /**
     * 虚拟节点
     */
    private TreeMap<Integer, CacheNode> virtualNodeMap = new TreeMap<Integer, CacheNode>();
    /**
     * 虚拟节点个数
     */
    private int virtualNum;
    /**
     * 添加节点
     *
     * @param node
     */
    public void addServer(CacheNode node) {
        cacheNodeList.add(node);
        for (int i = 0; i < this.virtualNum; i++) {
            String nodeName = StrUtil.format("{}-VM-{}", node.getIp(), i);
            int hash = this.getHash(nodeName);
            virtualNodeMap.put(hash, node);
        }
    }
    /**
     * 获取节点
     *
     * @param cacheKey
     * @return
     */
    public CacheNode getNode(String cacheKey) {
        int hash = getHash(cacheKey);
        SortedMap<Integer, CacheNode> tailMap = virtualNodeMap.tailMap(hash);
        Integer key = tailMap.isEmpty() ? virtualNodeMap.firstKey() : tailMap.firstKey();
        return virtualNodeMap.get(key);
    }
    /**
     * Hash 算法
     *
     * @param key
     * @return
     */
    private int getHash(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;
        // 如果算出来的值为负数则取其绝对值
        if (hash < 0) {
            hash = Math.abs(hash);
        }
        return hash;
    }
    public List<CacheNode> getCacheNodeList() {
        return cacheNodeList;
    }
    public int getVirtualNum() {
        return virtualNum;
    }
}
public class CacheNode {
    public CacheNode(String ip, int port) {
        this.ip = ip;
        this.port = port;
    }
    private String ip;
    private int port;
    private List<String> data = new ArrayList<String>();
    public String getIp() {
        return ip;
    }
    public void setIp(String ip) {
        this.ip = ip;
    }
    public int getPort() {
        return port;
    }
    public void setPort(int port) {
        this.port = port;
    }
    public List<String> getData() {
        return data;
    }
    public void setData(List<String> data) {
        this.data = data;
    }
}
public class MathUtils {
    /**
     * 求标准差
     *
     * @param x
     * @return
     */
    public static double standardDiviation(int[] x) {
        int m = x.length;
        int sum = 0;
        // 求和
        for (int i = 0; i < m; i++) {
            sum += x[i];
        }
        // 求平均值
        int dAve = sum / m;
        int dVar = 0;
        for (int i = 0; i < m; i++) {
            dVar += (x[i] - dAve) * (x[i] - dAve);
        }
        return Math.sqrt(dVar / m);
    }
}
public class Main {
    public static void main(String[] args) {
        ConsistentHashBalance hashBalance = new ConsistentHashBalance(50);
        //模拟服务器
        for (int i = 1; i <= 10; i++) {
            hashBalance.addServer(new CacheNode("192.168.1." + i, 6379));
        }
        //模拟数据
        for (int i = 0; i < 1000000; i++) {
            String key = IdUtil.objectId();
            CacheNode node = hashBalance.getNode(key);
            node.getData().add(key);
        }
        //计算标准差
        int serverSize = hashBalance.getCacheNodeList().size();
        int[] counters = new int[serverSize];
        List<CacheNode> cacheNodeList = hashBalance.getCacheNodeList();
        for (int i = 0; i < serverSize; i++) {
            counters[i] = cacheNodeList.get(i).getData().size();
        }
        double standardDeviation = MathUtils.standardDiviation(counters);
        System.out.println(StrUtil.format("物理节点 : {}个, 虚拟节点 : {}个, 标准差 : {}", serverSize, hashBalance.getVirtualNum(), standardDeviation));
        //打印服务器情况
        hashBalance.getCacheNodeList().forEach(x -> {
            System.out.println(StrUtil.format("{} : {}", x.getIp(), x.getData().size()));
        });
    }
}