tree c2b839f6caf8157484d18d7f3e76eca9062f8eaf
parent 66bac42eeac50dd5316c1f3e3b74e490f64e6c13
author Roman Arutyunyan <arut@nginx.com> 1596018484 +0300
committer Roman Arutyunyan <arut@nginx.com> 1596018484 +0300

Cache: ignore stale-if-error for 4xx and 5xx codes.

Previously the stale-if-error extension of the Cache-Control upstream header
triggered the return of a stale response for all error conditions that can be
specified in the proxy_cache_use_stale directive.  The list of these errors
includes both network/timeout/format errors, as well as some HTTP codes like
503, 504, 403, 429 etc.  The latter prevented a cache entry from being updated
by a response with any of these HTTP codes during the stale-if-error period.

Now stale-if-error only works for network/timeout/format errors and ignores
the upstream HTTP code.  The return of a stale response for certain HTTP codes
is still possible using the proxy_cache_use_stale directive.

This change also applies to the stale-while-revalidate extension of the
Cache-Control header, which triggers stale-if-error if it is missing.

Reported at
http://mailman.nginx.org/pipermail/nginx/2020-July/059723.html.