基于权重的随机负载均衡路由算法

private Map<String,Integer> serverMap = new HashMap<String,Integer>(){{
put("192.168.1.100",1);
put("192.168.1.101",1);
put("192.168.1.102",4);
put("192.168.1.103",1);
put("192.168.1.104",1);
put("192.168.1.105",3);
put("192.168.1.106",1);
put("192.168.1.107",2);
put("192.168.1.108",1);
put("192.168.1.109",1);
put("192.168.1.110",1);
}};

private List<String> servers = new ArrayList<>(serverMap.keySet());

public void weightRandom(){
Set<String> keySet = serverMap.keySet();
List<String> servers = new ArrayList<String>();
for(Iterator<String> it = keySet.iterator();it.hasNext();){
String server = it.next();
int weight = serverMap.get(server);
for(int i=0;i<weight;i++){
servers.add(server);
}
}
String server = null;
Random random = new Random();
int idx = random.nextInt(servers.size());
server = servers.get(idx);
System.out.println(server);
}

public String randomWeight(){
int length = serverMap.size(); // 总个数
int totalWeight = 0; // 总权重
boolean sameWeight = true; // 权重是否都一样
for (int i = 0; i < length; i++) {
int weight = serverMap.get(servers.get(i));
totalWeight += weight; // 累计总权重
if (sameWeight && i > 0
&& weight != serverMap.get(servers.get(i-1))) {
sameWeight = false; // 计算所有权重是否一样
}
}
if (totalWeight > 0 && ! sameWeight) {
// 如果权重不相同且权重大于0则按总权重数随机
int offset = ThreadLocalRandom.current().nextInt(totalWeight);
// 并确定随机值落在哪个片断上
for (int i = 0; i < length; i++) {
offset -= serverMap.get(servers.get(i));
if (offset < 0) {
return servers.get(i);
}
}
}
// 如果权重相同或权重为0则均等随机
return servers.get(ThreadLocalRandom.current().nextInt(length));
}