Sometimes,command "server" is not easy to manage cluster,this is an useful patch.
CN:
在日常运维时，后端经常需要下线某台服务器，而一台机器上部署的是多个服务，由端口区分，多台机器
镜像，由upstream来负载均衡。这样需要在配置的多个地方进行删除或者修改。这个补丁就是为了简化这种
运维工作的。
examlpe:
upstream app1_cluster{
ip_hash;
server 192.168.20.20:2000;
server 192.168.20.21:2000;
server 192.168.20.22:2000;
...
}
upstream app2_cluster{
ip_hash;
server 192.168.20.20:2001;
server 192.168.20.21:2001;
server 192.168.20.22:2001;
...
}
...
new config:
upstream app_cluster{
server 192.168.20.20;
server 192.168.20.21;
server 192.168.20.22;
...
}
upstream app1_cluster{
ip_hash;
port 2001;
servers app_cluster;
}
upstream app2_cluster{
ip_hash;
port 2002;
servers app_cluster;
}
...