参考：Java代码实现负载均衡五种算法

概况

轮询法

轮询算法按顺序把每个新的连接请求分配给下一个服务器，最终把所有请求平分给所有的服务器。

• 优点：绝对公平
• 缺点：无法根据服务器性能去分配，无法合理利用服务器资源。

@Configuration
@Slf4j
public class RoundMethod {// 指向该服务的server的指针AtomicInteger index = new AtomicInteger(0);public String roundMethod(Map<String,Integer> serverMap){// 服务名Set<String> set = serverMap.keySet();List<String> list = new ArrayList<>();list.addAll(set);String serverName = "";if(index.get() == list.size()){index.set(0);}int pos = index.getAndIncrement();serverName = list.get(pos);return serverName;}public static void main(String[] args) {RoundMethod roundMethod = new RoundMethod();//模拟eureka注册中心的服务信息列表，key：IP，value：权重Map<String,Integer> map = new ConcurrentHashMap<>();map.put("192.168.13.1",1);map.put("192.168.13.2",1);map.put("192.168.13.3",1);for(int i = 0;i < 10;i++){String s = roundMethod.roundMethod(map);log.info("------------>>>>>>" + s);}}
}

加权轮询法

该算法中，每个机器接受的连接数量是按权重比例分配的。这是对普通轮询算法的改进，比如你可以设定：第三台机器的处理能力是第一台机器的两倍，那么负载均衡器会把两倍的连接数量分配给第3台机器。

@Slf4j
@Configuration
public class RoundWeightMethod {// 指向该服务的server的指针AtomicInteger index = new AtomicInteger(0);public String roundWeightMethod(Map<String,Integer> serverMap){// 服务名Set<String> set = serverMap.keySet();// 放所有的server。可重复，根据权重放List<String> list = new ArrayList<>();Iterator<String> iterator = set.iterator();while(iterator.hasNext()){String serverName = iterator.next();// 取出权重int weight = serverMap.get(serverName);// 放入权重个serverName到list中for(int i = 0;i < weight;i++){list.add(serverName);}}String res = "";if(index.get() == list.size()){index.set(0);}int pos = index.getAndIncrement();res = list.get(pos);return res;}public static void main(String[] args) {RoundWeightMethod roundMethod = new RoundWeightMethod();//模拟eureka注册中心的服务信息列表，key：IP，value：权重Map<String,Integer> map = new ConcurrentHashMap<>();map.put("192.168.13.1",1);map.put("192.168.13.2",1);map.put("192.168.13.3",1);for(int i = 0;i < 10;i++){String s = roundMethod.roundWeightMethod(map);log.info("------------>>>>>>" + s);}}
}

随机法

负载均衡方法随机的把负载分配到各个可用的服务器上，通过随机数生成算法选取一个服务器

@Slf4j
@Configuration
public class RandomMethod {// 指向该服务的server的指针AtomicInteger index = new AtomicInteger(0);public String randomMethod(Map<String,Integer> serverMap){// 服务名Set<String> set = serverMap.keySet();List<String> list = new ArrayList<>();list.addAll(set);String serverName = "";Random random = new Random();int pos = random.nextInt(list.size());serverName = list.get(pos);return serverName;}public static void main(String[] args) {RandomMethod roundMethod = new RandomMethod();//模拟eureka注册中心的服务信息列表，key：IP，value：权重Map<String,Integer> map = new ConcurrentHashMap<>();map.put("192.168.13.1",1);map.put("192.168.13.2",1);map.put("192.168.13.3",1);for(int i = 0;i < 10;i++){String s = roundMethod.randomMethod(map);log.info("------------>>>>>>" + s);}}
}

加权随机法

在随机法的基础上加上权重，权重大的被使用的概率也会增大

@Slf4j
@Configuration
public class RandomWeightMethod {// 指向该服务的server的指针AtomicInteger index = new AtomicInteger(0);public String randomWeightMethod(Map<String,Integer> serverMap){// 服务名Set<String> set = serverMap.keySet();// 放所有的server。可重复，根据权重放List<String> list = new ArrayList<>();Iterator<String> iterator = set.iterator();while(iterator.hasNext()){String serverName = iterator.next();// 取出权重int weight = serverMap.get(serverName);// 放入权重个serverName到list中for(int i = 0;i < weight;i++){list.add(serverName);}}String res = "";Random random = new Random();int pos = random.nextInt(list.size());res = list.get(pos);return res;}public static void main(String[] args) {RandomWeightMethod roundMethod = new RandomWeightMethod();//模拟eureka注册中心的服务信息列表，key：IP，value：权重Map<String,Integer> map = new ConcurrentHashMap<>();map.put("192.168.13.1",1);map.put("192.168.13.2",2);map.put("192.168.13.3",3);for(int i = 0;i < 10;i++){String s = roundMethod.randomWeightMethod(map);log.info("------------>>>>>>" + s);}}
}

IP哈希法

根据客户端的IP进行哈希算法求出请求的机器

@Configuration
public class IpHashMethod {//    1.定义map, key-ip,value-weightstatic Map<String,Integer> ipMap=new HashMap<>();static {ipMap.put("192.168.13.1",1);ipMap.put("192.168.13.2",2);ipMap.put("192.168.13.3",4);}public String ipHash(String clientIP){Map<String,Integer> ipServerMap=new ConcurrentHashMap<>();ipServerMap.putAll(ipMap);//    2.取出来key,放到set中Set<String> ipset=ipServerMap.keySet();//    3.set放到list，要循环list取出ArrayList<String> iplist=new ArrayList<String>();iplist.addAll(ipset);//对ip的hashcode值取余数，每次都一样的int hashCode=clientIP.hashCode();int serverListsize=iplist.size();int pos=hashCode%serverListsize;return iplist.get(pos);}public static void main(String[] args) {IpHashMethod iphash=new IpHashMethod();String servername= iphash.ipHash("192.168.21.2");System.out.println(servername);}
}