chore(cache.tvl.su): Raise cache priority to 50 r/3525

The priority of binary caches is decided by the remotes in Nix (???),
and by default nix-serve (which is *very* slow) has a lower priority
than cache.nixos.org (which means that it will be preferred over the
faster cache for paths that exist on both).

To avoid this, override the hardcoded (????) priority by serving the
nix-cache-info response directly from nginx instead.

Change-Id: I15a2d6618386d16edaf69f1c9257a36bd72132d2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4823
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: grfn <grfn@gws.fyi>

1 files changed, 5 insertions, 0 deletions

diff --git a/ops/modules/www/cache.tvl.su.nix b/ops/modules/www/cache.tvl.su.nix
index 633178b5ccec..99bc008cd6a5 100644
--- a/ops/modules/www/cache.tvl.su.nix
+++ b/ops/modules/www/cache.tvl.su.nix
@@ -17,6 +17,11 @@
           alias /run/agenix/nix-cache-pub;
         }
 
+        location = /nix-cache-info {
+          add_header Content-Type text/plain;
+          return 200 "StoreDir: /nix/store\nWantMassQuery: 1\nPriority: 50\n";
+        }
+
         location / {
           proxy_pass http://localhost:${toString config.services.nix-serve.port};
         }