GNU bug report logs - #37207
nginx serving files from the store returns Last-Modified = Epoch

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From: Ludovic Courtès <ludo <at> gnu.org>
To: Tobias Geerinckx-Rice <me <at> tobias.gr>
Cc: 37207 <at> debbugs.gnu.org
Subject: bug#37207: guix.gnu.org Last Modified at epoch
Date: Thu, 26 Sep 2019 10:39:45 +0200

Hi Tobias,

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

> Turning these off will of course prevent all caching.  I don't know if
> that would add measurable load to guix.gnu.org (it would be more
> problematic if we used a CDN, but it might still make a difference).
>
> Nix does something both interesting and icky — as always: patch[0]
> nginx to look up the realpath() instead, so clients can still cache
> using If-None-Match.

> [0]: https://github.com/NixOS/nixpkgs/pull/48337

(See
<https://raw.githubusercontent.com/NixOS/nixpkgs/9bc23f31d29138f09db6af52708a9b8b64deec64/pkgs/servers/http/nginx/nix-etag-1.15.4.patch>.)

I had overlooked this patch but it looks like the right approach
overall.  Calling ‘realpath’ each time seems a bit expensive as it
creates an ‘lstat’ storm, but I can’t think of a better solution.

I also found this post whose main interest is in showing how to write a
plugin to generate custom etags:

  https://mikewest.org/2008/11/generating-etags-for-static-content-using-nginx/

Thoughts?

Ludo’.

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