$connection_time 在 nginx 中是什么意思？

Question

我需要一些时间数据来优化nginx。但是我找不到$connection_time变量的含义。

官方文档说明(http://nginx.org/en/docs/http/ngx_http_core_module.html#var_connection_time):

connection_time 

    connection time in seconds with a milliseconds resolution (1.19.10)

在访问日志中，我只知道$connection_time总是大于$request_time。

Answer 1

$connection_time 是 http 请求使用的 TCP 连接的存活时间。

HTTP keep-alive 和 HTTP/2 允许单个 TCP 连接发送和接收多个 HTTP requests/responses。所以 $connection_time 应该总是大于 $request_time;

我们可以使用以下 nginx 配置文件来证明它

http {
  ...
  log_format testlog '[$time_local] "$request" connection_time= $connection_time request_time= $request_time';
}


server {
    listen       80;
    server_name  localhost;

    root   /www;

    location / {
        index  index.html index.htm;
    }

    access_log /var/log/nginx/test.access.log testlog;
    error_log /var/log/nginx/test.error.log;

    # disable cache
    expires -1;
    add_header Last-Modified $date_gmt;
    add_header Cache-Control 'no-store, no-cache, must-revalidate, proxy-revalidate, max-age=0';
    if_modified_since off;
    etag off;

    # disable keep alive
    location /keep-alive-off/ {
        keepalive_timeout 0;
    }

    # enable keep alive
    location /keep-alive-on/ {
        keepalive_timeout 300s;
    }

}

access.log

[12/Oct/2021:06:38:03 +0000] "GET /keep-alive-off/test.pdf HTTP/1.1" connection_time= 0.212 request_time= 0.210
[12/Oct/2021:06:38:05 +0000] "GET /keep-alive-off/test.pdf HTTP/1.1" connection_time= 0.252 request_time= 0.253
[12/Oct/2021:06:38:06 +0000] "GET /keep-alive-off/test.pdf HTTP/1.1" connection_time= 0.200 request_time= 0.203
[12/Oct/2021:06:38:11 +0000] "GET /keep-alive-on/test.pdf HTTP/1.1" connection_time= 0.240 request_time= 0.239
[12/Oct/2021:06:38:14 +0000] "GET /keep-alive-on/test.pdf HTTP/1.1" connection_time= 3.268 request_time= 0.185
[12/Oct/2021:06:38:17 +0000] "GET /keep-alive-on/test.pdf HTTP/1.1" connection_time= 6.177 request_time= 0.168

我们可以看到，如果关闭 HTTP keep-alive 以禁止 TCP 连接重用，$request_time 将始终等于 $connection_time

$connection_time 在 nginx 中是什么意思？

What does $connection_time mean in nginx?

nginx

nginx-config