proxy_cache_background_update after cache expiry

[IgorR]

thank you Maxim, 

the resourse was saved to cache but was quickly expiring in the browser
causing a Cache-Control: no-cache header to be sent.

Sending something like 

Cache-Control:
public,max-age=15,s-maxage=240;must-revalidate,stale-while-revalidate=240

together with Last-Modified/ETag from the upstream server seem to be getting
me where I want.

Thanks for pointing me in the right direction.


@jeanpaul: I didn't have the chance to check your idea since taking a closer
look at the headers really helped moving forward.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,273417,273439#msg-273439