架构师训练营第五周作业

import java.util.TreeMap;import java.util.Map;import java.util.Random;import java.lang.Math;
public class ConsistentHash {
    private int virtual_node_count = 150;    private TreeMap<Integer, String> hash_ring = new TreeMap<Integer, String>();    private TreeMap<String, Integer> server_hit_map = new TreeMap<String, Integer>();        public ConsistentHash() {    }    public ConsistentHash(int virtualNodCount) {        if (virtualNodCount > 0) {            virtual_node_count = virtualNodCount;        }    }
    public void addServerNode(String server_node_ip) {        //invalid        if (server_node_ip == null || server_node_ip.isEmpty()){            return;        }
        //already in the map        if (server_hit_map.containsKey(server_node_ip)) {            return;        }
        Random rom = new Random(1);        int nCurrentSize = hash_ring.size();        int nNewSize = nCurrentSize + virtual_node_count;        while (hash_ring.size() < nNewSize) {            int value = rom.nextInt();            if (!hash_ring.containsKey(value)) {                hash_ring.put(value, server_node_ip);            }        }    }
    public String queryServerNodeByKey(String key) {        if (key == null || hash_ring.isEmpty()) {            return null;        }
        Map.Entry<Integer, String> entry = hash_ring.ceilingEntry(key.hashCode());        if (entry == null) {            entry = hash_ring.firstEntry();        }
        String server = entry.getValue();        if (server_hit_map.containsKey(server)) {            Integer value = server_hit_map.get(server);            server_hit_map.put(server, value+1);        }        else {            server_hit_map.put(server, 1);        }
        return server;    }
    public void outPutStatistics() {        int totalQuery = 0;        double standardDeviation = 0.0;        double variance = 0;
        for (Map.Entry<String, Integer> entry : server_hit_map.entrySet() ) {            totalQuery += entry.getValue();        }
        double average = 1.0/(double)server_hit_map.size();
        System.out.println("Total " + totalQuery + " queries.");        for (Map.Entry<String, Integer> entry : server_hit_map.entrySet() ) {            System.out.println("Server " + entry.getKey() + " hit: " + entry.getValue() + "; percentage: " + 100 * entry.getValue()/(double)totalQuery + "%");            double dif = entry.getValue()/(double)totalQuery - average;            variance += dif * dif;        }        variance = variance / server_hit_map.size();        standardDeviation = Math.sqrt(variance);        System.out.println("Standard deviation of probability distribution is: " + standardDeviation);
    }
    public static void main(String[] args) {        ConsistentHash ch = new ConsistentHash(200);        //add 10 sever node.        ch.addServerNode("192.168.1.1");        ch.addServerNode("192.168.1.12");        ch.addServerNode("192.168.1.23");        ch.addServerNode("192.168.1.44");        ch.addServerNode("192.168.1.25");        ch.addServerNode("192.168.1.76");        ch.addServerNode("192.168.1.27");        ch.addServerNode("192.168.1.98");        ch.addServerNode("192.168.1.49");        ch.addServerNode("192.168.1.20");
        int caseSize = 1000000;        Random rom = new Random(1);        for(int i = 0; i < caseSize; ++i) {            String c = new String("case_value_" + rom.nextInt());            ch.queryServerNodeByKey(c);        }        ch.outPutStatistics();    }}
OutPut:Total 1000000 queries.Server 192.168.1.1 hit: 103978; percentage: 10.3978%Server 192.168.1.12 hit: 112146; percentage: 11.2146%Server 192.168.1.20 hit: 106206; percentage: 10.6206%Server 192.168.1.23 hit: 101144; percentage: 10.1144%Server 192.168.1.25 hit: 100779; percentage: 10.0779%Server 192.168.1.27 hit: 89479; percentage: 8.9479%Server 192.168.1.44 hit: 96215; percentage: 9.6215%Server 192.168.1.49 hit: 101727; percentage: 10.1727%Server 192.168.1.76 hit: 85643; percentage: 8.5643%Server 192.168.1.98 hit: 102683; percentage: 10.2683%Standard deviation of probability distribution is: 0.0073831019632672