一致性hash算法

场景一：普通hash算法

public static void main(String[] args) {
        //定义客户端IP
        String[] clients = new String[]{"172.12.0.1","172.18.1.1","168.21.2.01"};
        //定义服务器数量
        int serverCount = 3;
        //hash(ip)%node_count=index
        //根据index锁定应该路由到的tomcat服务器
        for(String client:clients){
            int hash = Math.abs(client.hashCode());//取IP的hash绝对值
            int index = hash%serverCount;
            System.out.println("客户端：" + client + " 被路由到服务器编号为：" + index);
        }
    }

场景二：一致性hash算法，hash闭环

public static void main(String[] args) {
        //初始化：把服务器节点IP的哈希值映射到哈希环上
        //定义服务器IP
        String[] tomcatServers = new String[]{"130.12.0.1","160.18.12.1","168.35.11.8","150.2.12.6"};
        SortedMap<Integer,String> hashServerMap = new TreeMap<>();

        for(String tomcatServer:tomcatServers){
            //求出每个IP的hash值，对应到hash环上，存储hash值与ip的对应关系
            int serverHash = Math.abs(tomcatServer.hashCode());
            //存储hash值与ip的对应关系
            hashServerMap.put(serverHash,tomcatServer);
        }

        //针对客户端IP求出hash值
        String[] clients = new String[]{"172.12.0.1","172.18.1.1","168.21.2.01"};
        for(String client:clients){
            int clientHash = Math.abs(client.hashCode());
            //根据客户端ip的哈希值去找出哪一个服务器节点能够处理
            SortedMap<Integer, String> integerStringSortedMap = hashServerMap.tailMap(clientHash);
            if(integerStringSortedMap.isEmpty()){
                //取哈希环上的顺时针第一台服务器
                Integer firstKey = hashServerMap.firstKey();
                System.out.println("===========>>>客户端：" + client + " 被路由到服务器：" + hashServerMap.get(firstKey));
            }else{
                Integer firstKey = integerStringSortedMap.firstKey();
                System.out.println("===========>>>客户端：" + client + " 被路由到服务器：" + hashServerMap.get(firstKey));
            }
        }
    }

场景三：一致性hash算法，虚拟节点

public static void main(String[] args) {
        //初始化：把服务器节点IP的哈希值映射到哈希环上
        //定义服务器IP
        String[] tomcatServers = new String[]{"130.12.0.1","160.18.12.1","168.35.11.8","150.2.12.6"};
        SortedMap<Integer,String> hashServerMap = new TreeMap<>();

        //定义针对每个真是服务器虚拟出来的几个节点
        int virtaulCount = 3;

        for(String tomcatServer:tomcatServers){
            //求出每个IP的hash值，对应到hash环上，存储hash值与ip的对应关系
            int serverHash = Math.abs(tomcatServer.hashCode());
            //存储hash值与ip的对应关系
            hashServerMap.put(serverHash,tomcatServer);
            //针对虚拟节点
            for (int i = 0; i < virtaulCount; i++) {
                int virtaulHash = Math.abs((tomcatServer + "#" + i).hashCode());
                hashServerMap.put(virtaulHash,"---由虚拟节点" + i + "映射过来的请求：" + tomcatServer);
            }
        }

        //针对客户端IP求出hash值
        String[] clients = new String[]{"172.12.0.1","172.18.1.1","168.21.2.01"};
        for(String client:clients){
            int clientHash = Math.abs(client.hashCode());
            //根据客户端ip的哈希值去找出哪一个服务器节点能够处理
            SortedMap<Integer, String> integerStringSortedMap = hashServerMap.tailMap(clientHash);
            if(integerStringSortedMap.isEmpty()){
                //取哈希环上的顺时针第一台服务器
                Integer firstKey = hashServerMap.firstKey();
                System.out.println("===========>>>客户端：" + client + " 被路由到服务器：" + hashServerMap.get(firstKey));
            }else{
                Integer firstKey = integerStringSortedMap.firstKey();
                System.out.println("===========>>>客户端：" + client + " 被路由到服务器：" + hashServerMap.get(firstKey));
            }
        }
    }