ribbon已经提供了很多负载的策略,如下图:
这些负载策略通常已经满足我们的日常业务需求(这些策略的具体介绍,可以点此查看),如特殊需要,我们也需要自定义负载策略。
我的应用场景是:spring cloud zuul做为用户请求的入口服务,zuul代理到目标服务的时候,其内部就是通过ribbon的负载策略选出并代理到一个服务实例,这里我自定义的负载策略实现的功能是“同一个ip下的同一个用户的所有请求被代理到同一个实例”(如果请求没有用户信息,那就相当于ip_hash策略)。
新建一个类IpUserHashRule继承自com.netflix.loadbalancer.AbstractLoadBalancerRule:
public class IpUserHashRule extends AbstractLoadBalancerRule {
private static Logger log = LoggerFactory.getLogger(IpUserHashRule.class);
public Server choose(ILoadBalancer lb, Object key) {
if (lb == null) {
log.warn("no load balancer");
return null;
}
Server server = null;
int count = 0;
while (server == null && count++ < 10) {
List<Server> reachableServers = lb.getReachableServers();
List<Server> allServers = lb.getAllServers();
int upCount = reachableServers.size();
int serverCount = allServers.size();
if ((upCount == 0) || (serverCount == 0)) {
log.warn("No up servers available from load balancer: " + lb);
return null;
}
int nextServerIndex = ipUserHash(serverCount);
server = allServers.get(nextServerIndex);
if (server == null) {
/* Transient. */
Thread.yield();
continue;
}
if (server.isAlive() && (server.isReadyToServe())) {
return (server);
}
// Next.
server = null;
}
if (count >= 10) {
log.warn("No available alive servers after 10 tries from load balancer: "
+ lb);
}
return server;
}
private int ipUserHash(int serverCount) {
String userTicket = getTicketFromCookie();
String userIp = getRemoteAddr();
try {
userIp = InetAddress.getLocalHost().getHostAddress();
} catch (UnknownHostException e) {
}
int userHashCode = Math.abs((userIp+userTicket).hashCode());
return userHashCode%serverCount;
}
private String getRemoteAddr() {
RequestContext ctx = RequestContext.getCurrentContext();
HttpServletRequest request = ctx.getRequest();
String remoteAddr = "0.0.0.0";
if (request.getHeader("X-FORWARDED-FOR") != null) {
remoteAddr = request.getHeader("X-FORWARDED-FOR");
} else {
remoteAddr = request.getRemoteAddr();
}
return remoteAddr;
}
private String getTicketFromCookie() {
String ticket = "";
RequestContext ctx = RequestContext.getCurrentContext();
HttpServletRequest request = ctx.getRequest();
//从cookie获取ticket
Cookie cookie = CookieUtil.getCookieByName(request,CookieUtil.COOKIE_TICKET_NAME);
if (cookie!=null) {
ticket = cookie.getValue()!=null?cookie.getValue():"";
}
return ticket;
}
@Override
public Server choose(Object key) {
return choose(getLoadBalancer(), key);
}
@Override
public void initWithNiwsConfig(IClientConfig clientConfig) {
// TODO Auto-generated method stub
}
public static void main(String[] args) {
String ticket = "";
String localIp = "127.0.0.1";
System.out.println(Math.abs((ticket+localIp).hashCode())%5);
}
}
关键在于ipUserHash方法,其将用户的ip和用户标识组合所得的hashcode再与服务实例数量进行模运算从而得到实例
有了这个类过后,还需要配置使用这个自定义的负载策略,配置如下:
user.ribbon.NFLoadBalancerRuleClassName=com.bqjr.spring.cloud.zuul.ribbonextend.IpUserHashRule
这个配置的意思是,名叫user服务使用IpUserHashRule这个负载策略(其他服务依然使用默认的负载策略,spring cloud ribbon提供的默认负载策略是这个类com.netflix.loadbalancer.ZoneAvoidanceRule)。
酱紫就可以啦。
参考文档:http://docs.springcloud.cn/user-guide/ribbon/#ribbon-api
推荐文章(Netflix 源码分析):http://www.idouba.net/sping-cloud-and-netflix/