ribbon已經提供了很多負載的策略,如下圖:
這些負載策略通常已經滿足我們的日常業務需求(這些策略的具體介紹,可以點此查看),如特殊需要,我們也需要自定義負載策略。
我的應用場景是:spring cloud zuul做爲用戶請求的入口服務,zuul代理到目標服務的時候,其內部就是通過ribbon的負載策略選出並代理到一個服務實例,這裏我自定義的負載策略實現的功能是“同一個ip下的同一個用戶的所有請求被代理到同一個實例”(如果請求沒有用戶信息,那就相當於ip_hash策略)。
新建一個類IpUserHashRule繼承自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();
//從cookie獲取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);
}
}
關鍵在於ipUserHash方法,其將用戶的ip和用戶標識組合所得的hashcode再與服務實例數量進行模運算從而得到實例有了這個類過後,還需要配置使用這個自定義的負載策略,配置如下:
user.ribbon.NFLoadBalancerRuleClassName=com.bqjr.spring.cloud.zuul.ribbonextend.IpUserHashRule
這個配置的意思是,名叫user服務使用IpUserHashRule這個負載策略(其他服務依然使用默認的負載策略,spring cloud ribbon提供的默認負載策略是這個類com.netflix.loadbalancer.ZoneAvoidanceRule)。醬紫就可以啦。
參考文檔:http://docs.springcloud.cn/user-guide/ribbon/#ribbon-api
推薦文章(Netflix 源碼分析):http://www.idouba.net/sping-cloud-and-netflix/