修改nginx配置如下，reload生效，/usr/local/nginx/sbin/nginx -s reload

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '

                      '$status $body_bytes_sent "$http_referer" '

                      '"$http_user_agent" "$http_x_forwarded_for "|$request_time|$upstream_response_time'; 

    access_log  logs/access.log  main;

配置说明：

(1)request_time

官网描述：request processing time in seconds with a milliseconds resolution; time elapsed between the first bytes were read from the client and the log write after the last bytes were sent to the client 。

 

指的就是从接受用户请求的第一个字节到发送完响应数据的时间，即包括接收请求数据时间、程序响应时间、输出

响应数据时间。

 

(2)upstream_response_time

官网描述：keeps times of responses obtained from upstream servers; times are kept in seconds with a milliseconds resolution. Several response times are separated by commas and colons like addresses in the $upstream_addr variable

 

是指从Nginx向后端（php-cgi)建立连接开始到接受完数据然后关闭连接为止的时间。

 

从上面的描述可以看出，$request_time肯定比$upstream_response_time值大，特别是使用POST方式传递参数时，因为Nginx会把request body缓存住，接受完毕后才会把数据一起发给后端。所以如果用户网络较差，或者传递数据较大时，$request_time会比$upstream_response_time大很多。