架构师训练营第五周作业

public class ConsistencyHash {
    private TreeMap<Long, NodeDefine> nodes;         // 虚拟节点
    private List<NodeDefine>          shards;        // 真实机器节点
    private final int                 NODE_NUM = 150; // 每个机器节点关联的虚拟节点个数
    public ConsistencyHash(List<NodeDefine> shards) {        super();        this.shards = shards;        init();    }
    private void init() { // 初始化一致性hash环        nodes = new TreeMap<Long, NodeDefine>();        for (int i = 0; i != shards.size(); ++i) { // 每个真实机器节点都需要关联虚拟节点            final NodeDefine shardInfo = shards.get(i);
            for (int n = 0; n < NODE_NUM; n++)                // 一个真实机器节点关联NODE_NUM个虚拟节点                nodes.put(hash("SHARD-" + i + "-NODE-" + n), shardInfo);
        }    }
    public NodeDefine getShardInfo(String key) {        SortedMap<Long, NodeDefine> tail = nodes.tailMap(hash(key)); // 沿环的顺时针找到一个虚拟节点        if (tail.size() == 0) {            return nodes.get(nodes.firstKey());        }        return tail.get(tail.firstKey()); // 返回该虚拟节点对应的真实机器节点的信息    } }

 public static void main(String[] args) {        List<NodeDefine> shards = new ArrayList<>();        for (int i=1;i<=10;i++){            NodeDefine nodeDefine1 = new NodeDefine("node"+i);            shards.add(nodeDefine1);        }
        for (int i=50;i<200;i+=10){            calSD(shards,i);        }
    }
    private static void calSD(List<NodeDefine> shards, int virNum) {        ConsistencyHash hashGeneroTools = new ConsistencyHash(shards,virNum);
        NodeDefine nodeDefine = hashGeneroTools.getShardInfo("test003");
        Map<NodeDefine,Integer> hits = new HashMap<>();
        for (int i=0;i<10000000;i++){            nodeDefine = hashGeneroTools.getShardInfo("test"+i);            if (i%100000 ==0) {                //System.out.println(nodeDefine);            }
            hits.put(nodeDefine, hits.get(nodeDefine)==null?1:hits.get(nodeDefine)+1);        }

        Integer[] nums = hits.values().toArray(new Integer[0]);        double sd = calculateSD(nums);
        System.out.println(virNum +"->" +sd);    }

    public static double calculateSD(Integer numArray[])    {        double sum = 0.0, standardDeviation = 0.0;        int length = numArray.length;
        for(double num : numArray) {            sum += num;        }
        double avg = sum/length;
        for(double num: numArray) {            standardDeviation += Math.pow(num - avg, 2);        }
        return Math.sqrt(standardDeviation/length-1);    }

方差：50->16118.15430500651460->16659.85493334200570->11781.38368783565280->7230.94148780087990->7634.385829914545100->7226.703660729419110->5370.755775493799120->8509.62398699261130->5219.742733123922140->5433.480541973073150->5587.672436261333160->4252.703399015737170->3883.7512021240495180->4519.301848737258190->5608.920876603627