我需要一些時間資料來優化 nginx。但是我找不到$connection_time變數的含義。
官方檔案解釋（http://nginx.org/en/docs/http/ngx_http_core_module.html#var_connection_time）：
connection_time
connection time in seconds with a milliseconds resolution (1.19.10)
在訪問日志中，我只知道$connection_time總是大于$request_time.
uj5u.com熱心網友回復：
$connection_time 是 http 請求使用的 TCP 連接的存活時間。
HTTP keep-alive和 HTTP/2 允許單個 TCP 連接發送和接收多個 HTTP 請求/回應。所以$connection_time應該總是大于$request_time;
我們可以用下面的nginx組態檔來證明
http {
...
log_format testlog '[$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 $date_gmt;
add_header Cache-Control 'no-store, no-cache, must-revalidate, proxy-revalidate, max-age=0';
if_modified_since off;
etag off;
# disable keep alive
location /keep-alive-off/ {
keepalive_timeout 0;
}
# enable keep alive
location /keep-alive-on/ {
keepalive_timeout 300s;
}
}
訪問日志
[12/Oct/2021:06:38:03 0000] "GET /keep-alive-off/test.pdf HTTP/1.1" connection_time= 0.212 request_time= 0.210
[12/Oct/2021:06:38:05 0000] "GET /keep-alive-off/test.pdf HTTP/1.1" connection_time= 0.252 request_time= 0.253
[12/Oct/2021:06:38:06 0000] "GET /keep-alive-off/test.pdf HTTP/1.1" connection_time= 0.200 request_time= 0.203
[12/Oct/2021:06:38:11 0000] "GET /keep-alive-on/test.pdf HTTP/1.1" connection_time= 0.240 request_time= 0.239
[12/Oct/2021:06:38:14 0000] "GET /keep-alive-on/test.pdf HTTP/1.1" connection_time= 3.268 request_time= 0.185
[12/Oct/2021:06:38:17 0000] "GET /keep-alive-on/test.pdf HTTP/1.1" connection_time= 6.177 request_time= 0.168
我們可以看到，如果關閉HTTP keep-alive以禁止 TCP 連接重用，$request_time將始終等于$connection_time
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