bug#26201: No notification of cache misses when downloading substitutes

[ludo@gnu.org (Ludovic Courtès)]

Hey Tobias,

Tobias Geerinckx-Rice <me@tobias.gr> skribis:

> On 21/03/17 17:43, Ludovic Courtès wrote:
>> I think there’s room for improvement in our nginx config at
>> <https://git.savannah.gnu.org/cgit/guix/maintenance.git/tree/hydra/nginx/mirror.conf>.
>> 
>> For instance, I just discovered ‘proxy_cache_lock’ while looking at
>> <http://nginx.org/en/docs/http/ngx_http_proxy_module.html>; looks useful
>> in reducing load on hydra.gnu.org.  Surely there are other ways to tweak
>> caching.
>
> Indeed! For reference, here's my cache configuration.
>
> That's right. Now you can all¹ steal some criminally overpriced Belgian
> bandwidth!

Heheh.  :-)

>       limit_except GET {        deny all; }
>       proxy_pass                SUPER_SEKRIT_BACKEND;
>
>       # https://www.nginx.com/blog/nginx-caching-guide
>       add_header                X-Cache-Status $upstream_cache_status;
>
>       proxy_cache               default;
>       # We allow only GET requests, so don't waste key space:
>       proxy_cache_key           "$request_uri";
>       proxy_cache_lock          on;
>       proxy_cache_lock_timeout  3h; #yolo
>       proxy_cache_use_stale     error timeout
>                                 http_500 http_502 http_503 http_504;

I didn’t fully understand the docs for the last 3 directives here.  For
instance, what happens when 10 clients do GET /nar/xyz-texlive?  Do the
9 unlucky clients wait for 3 hours and then get 404?

Anyway, thanks for sharing your tips.  :-)

> Entirely off-topic, but this 'tude is a part of what drew me to Guix in
> the first place. So, like, thanks, in general :-)

:-)

Ludo’.