Hello! On Fri, Oct 15, 2021 at 12:14:38PM +0200, Jiří Setnička wrote:
> Hello! > > Thanks for your reply. I didn't realize the implications arising from > the RFC mentioned. > > >> In ngx_http_upstream_test_next(...) in revalidate part there is firstly > >> cache time from upstream 304 response saved to temporal variable (valid > >> = r->cache->valid_sec) and then request is reinited and > >> r->cache->valid_sec is set according to headers in the cached file. > >> Problem is when value == 0 (no caching info from upstream) and there is > >> an absolute time in the cached file headers. > >> > >> This patch should fix this behavior - time computed from cached file is > >> used only when it is in the future otherwise, time calculated by > >> ngx_http_file_cache_valid(...) is used. > > As long as Expires is in the past, r->cache->valid_sec is not set > > and remains 0, see ngx_http_upstream_process_expires(). As such, > > suggested patch is a nop as long as standard Expires and > > Cache-Control headers are used: nginx will ignore Expires from the > > original response automatically, and will use proxy_cache_valid > > instead. > > As you mentioned below, I deal with the X-Accel-Expires header. I didn't > explicitly check ngx_http_upstream_process_expires() and I thought that > the behavior is similar as X-Accel-Expires, sorry for that. > > > Are you trying to address X-Accel-Expires with an absolute time in > > the past? Note that it is known to be specifically used to > > achieve the "revalidate on each request" behaviour, and the > > suggested change will break this. (Also, changing the > > X-Accel-Expires behaviour is better to be done in > > ngx_http_upstream_process_accel_expires(), rather than indirectly, > > in 304 response handling code.) > > Ok I will look into implementation in > ngx_http_upstream_process_accel_expires(). > > Is "revalidate on each request" behaviour intended as the right one, or > it is considered as a hack because there is no other way to do > "revalidate on each request"? I did not find it in any documentation, > only in some email threads and tickets [1]. > > Would you be interested in the updated patch or should I patch it only > locally for my own usecase? I don't think that X-Accel-Expires behaviour should be changed: while not really documented[*], it is known to be used as it is now, and currently there are no other ways to request revalidation on each request. [*] The only X-Accel-Expires documentation I'm aware of is in the original mod_accel docs (http://sysoev.ru/mod_accel/readme.html), and it only accepted relative time at that time. -- Maxim Dounin http://mdounin.ru/ _______________________________________________ nginx-devel mailing list nginx-devel@nginx.org http://mailman.nginx.org/mailman/listinfo/nginx-devel
