如何在头文件中显示nginx缓存文件的年龄-Howtodisplaytheageofannginxcachedfileinheaders

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The nginx documentation is quite exhaustive — there's no variable with the direct relative age of the cached file.

nginx文档非常详尽——没有任何变量与缓存文件的直接相对年龄有关。

The best way would be to use the $upstream_http_ variable class to get the absolute age of the resource by picking up its Date header through $upsteam_http_date.

最好的方法是使用$upstream_http_变量类，通过$upsteam_http_date获取其日期头，从而获得资源的绝对年龄。

add_header X-Cache-Date $upstream_http_date;

For the semantic meaning of the Date header field in HTTP/1.1, refer to rfc7231#section-7.1.1.2, which describes it as the time of the HTTP response generation, so, basically, this should accomplish exactly what you want (especially if the backend runs with the same timecounter).

对于HTTP/1.1中的日期头字段的语义含义，请参考rfc7231# section7.1.1.2，它将它描述为HTTP响应生成的时间，因此，基本上，这应该完全实现您想要的(特别是如果后端运行时使用相同的timecounter)。

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I spent some time attempting to solve this with the Nginx Perl module, which does not seem to have access to $upstream_http_NAME headers that would allow you to successfully calculate the current time from a timestamp header that your proxied application created during render time.

我花了一些时间尝试使用Nginx Perl模块来解决这个问题，该模块似乎无法访问$upstream_http_NAME头文件，这些头文件可以让您成功地从您的经过代理的应用程序在呈现期间创建的时间戳头中计算当前时间。

Alternatively, you could use a different caching layer architecture like Varnish Cache, which does indeed provide the Age HTTP response header:

或者，您可以使用不同的缓存层架构，如Varnish缓存，它确实提供了Age HTTP响应头:

http://book.varnish-software.com/3.0/HTTP.html#age

http://book.varnish-software.com/3.0/HTTP.html年龄