*_cache_revalidate directives

[Roman Arutyunyan]

Hello,

> On 09 Jul 2015, at 10:59, Alt <nginx-forum at nginx.us> wrote:
> 
> Hello Roman,
> 
> Thanks for the explanation.
> At which moment this revalidation is executed? When there's a new client
> request or is it done automatically when a cache entry is about to expire?

When there’s a client request.
Nginx does not do any background cache updates/revalidations/etc.

> The nginx's cache manager is deleting expiring cache file, so I'm not sure
> to understand how it all works.

Nginx cache manager has nothing to do with cache entry expiration.
In fact, it does 2 things:

 * deletes files which were not accessed for the “inactive” time
 * deletes old files to keep cache within “max_size”

http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_cache_path

--
Roman Arutyunyan