运维系列Nginx：负载均衡策略

1、轮询（默认策略，nginx自带策略）
http {
    upstream my_load_balance {
        server 192.168.1.12:80;
        server 192.168.1.13:80;
    }
  
    server {
        listen 81;
        server_name www.laowubiji.com;
  
        location / {
            proxy_pass http://my_load_balance;
            proxy_set_header Host $proxy_host;
        }
    }
}

2、weight（权重，nginx自带策略）
http {
    upstream my_load_balance {
        server 192.168.1.12:80 weight=7;
        server 192.168.1.13:80 weight=2;
    }
  
    server {
        listen 81;
        server_name www.laowubiji.com;
  
        location / {
            proxy_pass http://my_load_balance;
            proxy_set_header Host $proxy_host;
        }
    }
}

3、ip_hash（依据ip分配，nginx自带策略）
http {
    upstream my_load_balance {
        ip_hash;
        server 192.168.1.12:80;
        server 192.168.1.13:80;
    }
  
    server {
        listen 81;
        server_name www.laowubiji.com;
  
        location / {
            proxy_pass http://my_load_balance;
            proxy_set_header Host $proxy_host;
        }
    }
}

4、least_conn（最少连接，nginx自带策略）:把请求转发给连接数较少的后端服务器。
http {
    upstream my_load_balance {
        #把请求转发给连接数比较少的服务器
        least_conn;
        server 192.168.1.12:80;
        server 192.168.1.13:80;
    }
  
    server {
        listen 81;
        server_name www.laowubiji.com;
  
        location / {
            proxy_pass http://my_load_balance;
            proxy_set_header Host $proxy_host;
        }
    }
}   

5、fair（第三方）:按照服务器端的响应时间来分配请求，响应时间短的优先分配。
http {
    upstream my_load_balance {
        fair;
        server 192.168.1.12:80;
        server 192.168.1.13:80;
    }
  
    server {
        listen 81;
        server_name www.laowubiji.com;
  
        location / {
            proxy_pass http://my_load_balance;
            proxy_set_header Host $proxy_host;
        }
    }
}  

6、url_hash（第三方）:该策略按访问url的hash结果来分配请求，使每个url定向到同一个后端服务器，需要配合缓存用
http {
    upstream my_load_balance {
        hash $request_uri;
        server 192.168.1.12:80;
        server 192.168.1.13:80;
    }
  
    server {
        listen 81;
        server_name www.laowubiji.com;
  
        location / {
            proxy_pass http://my_load_balance;
            proxy_set_header Host $proxy_host;
        }
    }
}