Nginx实现负载均衡

config
http {

    upstream backend {
        server 127.0.0.1;
        server 127.0.0.2;
    }
 
    server {
        listen 80;
        server_name www.example.com;

        location / {
            proxy_pass http://backend;
        }
    }
}

upstream 使用域名

以下使用会出现 502 bad gateway 错误

config
http {

    upstream backend {
        server a.example.com;
        server b.example.com;
    }

    server {
        listen 80;
        server_name www.example.com;

        location / {
            proxy_pass http://backend;
        }
    }
}

正确使用

config
http {

    upstream backend {
        server localhost:8081;
        server localhost:8082;
    }

    server {
      listen 8081;
      location / {
          proxy_set_header HOST a.example.com;
          proxy_pass       http://a.example.com;
      }
    }

    server {
      listen 8082;
      location / {
          proxy_set_header HOST b.example.com;
          proxy_pass       http://b.example.com;
      }
    }
 
    server {
        listen 80;
        server_name www.example.com;

        location / {
            proxy_pass http://backend;
        }
    }
}

DNS 修改

出现[emerg] host not found in upstream “a.example.com” 错误

尝试ping下域名

ping a.example.com

如果提示ping: unknown host a.example.com，则应该是dns解析域名失败，检查/etc/resolv.conf,发现没有配置域名服务器，增加域名服务器

nameserver 8.8.8.8
nameserver 8.8.4.4