Java中的权重算法(如Dubbo的负载均衡权重)详解

 /**
  * <h3>根据权重获取对应服务，传入服务：权重map</h3>
  *
  * @param map 服务：权重map
  * @return java.lang.String
  * @author Hubers 
  * @date 2021/6/15 16:16
  **/
 public static String getServerByWeight(Map<String, Integer> map) {
        if (map.isEmpty()){
            return null;
        }
        Integer total = 0;
        // 计算所有权重，如100+200+300=600
        for (Integer value : map.values()) {
            total += value;
        }
        Random random = new Random();
        // 在权重范围内随机，600以内随机
        int nextInt = random.nextInt(total);
        // 遍历所有服务提供者provide的ip地址
        for (String ip : map.keySet()) {
            // 取出权重值
            Integer weight = map.get(ip);
            // 权重在范围内，则返回对应ip
            if (nextInt < weight) {
                return ip;
            }
            // 否则减去权重，继续下一次循环，匹配对应的ip
            nextInt -= weight;
        }
        return null;
    }
public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<>();
        map.put("192.168.1.1", 10);
        map.put("192.168.1.2", 10);
        map.put("192.168.1.3", 10);
        map.put("192.168.1.4", 10);
        for (int i = 0; i < 10; i++) {
            String weight = getServerByWeight(map);
            if (Objects.isNull(weight)) {
                throw new RuntimeException("无可用服务");
            }
            System.out.println(weight);
        }
    }