id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
1862	Cache-Control:no-store should remove entry from cache (with proxy_cache_background_update+proxy_cache_use_stale)	Ondřej Nový		"We are using proxy_cache_background_update+proxy_cache_use_stale.

We have backend which sometimes sets Cache-Control to max-age>10, but for same request sometimes to no-cache/no-store. When we cache entry with max-age=10, that entry keeps in cache forever, even if we set no-cache/no-store in late request.

Example nginx conf to simulate same situation:

{{{
events {
    use epoll;
}

http {
    proxy_cache_path /home/debian/test-cache/cache levels=1:2 keys_zone=cache:10m inactive=10m max_size=256m;

    server {
        listen  8080;

        location /in/cache {
            return 200;
            add_header ""Cache-Control"" ""max-age=10"" always;
        }

        location /in/no-cache {
            return 200;
            add_header ""Cache-Control"" ""no-store"" always;
        }

        location / {
            add_header ""X-Cache-Status"" $upstream_cache_status always;
            proxy_cache cache;
            proxy_cache_key ""same"";
            proxy_cache_lock on;
            proxy_cache_background_update on;
            proxy_cache_use_stale updating error timeout;
            proxy_cache_valid any 10s;
            proxy_pass http://localhost:8080/in/;
        }
    }
}


}}}

proxy_cache_key is intentionally same in this example config for all location, because i want to test same cache entry.

Add entry into cache:
{{{
root@mustafar:/home/debian/test-cache# wget -S localhost:8080/cache -O /dev/null 2>&1 | grep X-Cache-Status
  X-Cache-Status: MISS
root@mustafar:/home/debian/test-cache# wget -S localhost:8080/cache -O /dev/null 2>&1 | grep X-Cache-Status
  X-Cache-Status: HIT
root@mustafar:/home/debian/test-cache# wget -S localhost:8080/no-cache -O /dev/null 2>&1 | grep X-Cache-Status
  X-Cache-Status: HIT
}}}

After >10s, entry is not valid, it's STALEd:
{{{
root@mustafar:/home/debian/test-cache# wget -S localhost:8080/no-cache -O /dev/null 2>&1 | grep X-Cache-Status
  X-Cache-Status: STALE
}}}

which is correct. Background task to refresh cache has been started now, because proxy_cache_background_update is on. /in/no-cache location returns Cache-Control: no-store, which should refresh cache entry (in this situation: remove it). But cache entry remains here for ever (until inactive=10m is hit).
"	defect	closed	minor		other	1.16.x	duplicate			"Linux mustafar 4.9.0-8-amd64 #1 SMP Debian 4.9.130-2 (2018-10-27) x86_64 GNU/Linux
"	"nginx version: nginx/1.16.1
built with OpenSSL 1.1.1c  28 May 2019
TLS SNI support enabled
configure arguments: --with-debug --with-cc-opt='-g -O2 -fdebug-prefix-map=/builds/nginx/szn-nginx=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC -Wdate-time -D_FORTIFY_SOURCE=2 -I /builds/nginx/szn-nginx/openssl/.openssl/include -pthread -DNGX_HAVE_CLOCK_MONOTONIC=0' --with-ld-opt='-Wl,-z,relro -Wl,-z,now -fPIC -L /builds/nginx/szn-nginx/openssl/.openssl/lib -pthread' --prefix=/www/nginx --conf-path=/www/nginx/doc/nginx.conf --http-log-path=/www/nginx/log/access.log --error-log-path=/www/nginx/log/error.log --lock-path=/www/nginx/lock/nginx.lock --pid-path=/var/run/nginx.pid --modules-path=/www/nginx/modules --http-client-body-temp-path=/www/nginx/var/lib/body --http-fastcgi-temp-path=/www/nginx/var/lib/fastcgi --http-proxy-temp-path=/www/nginx/var/lib/proxy --http-scgi-temp-path=/www/nginx/var/lib/scgi --http-uwsgi-temp-path=/www/nginx/var/lib/uwsgi --with-debug --with-pcre-jit --with-http_ssl_module --with-http_stub_status_module --with-http_realip_module --with-http_auth_request_module --with-http_v2_module --with-http_dav_module --with-http_slice_module --with-threads --with-http_addition_module --with-http_flv_module --with-http_geoip_module=dynamic --with-http_gunzip_module --with-http_gzip_static_module --with-http_image_filter_module=dynamic --with-http_mp4_module --with-http_perl_module=dynamic --with-http_random_index_module --with-http_secure_link_module --with-http_sub_module --with-http_xslt_module=dynamic --with-mail=dynamic --with-mail_ssl_module --with-stream=dynamic --with-stream_geoip_module=dynamic --with-stream_ssl_module --with-stream_ssl_preread_module"