Cache NAR files for upto a year

[arianvp]

NAR files are immutable. There is no harm in caching them for longer than the default 24 hours. It might save us on bandwidth cost to S3 and lower costs?

[mweinelt]

Does this only apply for successful (HTTP 200) responses?

[arianvp]

Because the is-404 condition has priority = 0 I would expect it to take precedence. But to be honest I'm not very familiar with Fastly and VCL

We could perhaps add an explicit

cache_setting {
  name  = "cache-404"
  cache_condition = "is-404"
  ttl  = 86400 # 1 day
}

to be 100% sure?

[mweinelt]

What I'm worried about is that someone could abuse the negative cache and block new build results, so limiting the duration on 404 responses sounds good to me.

[arianvp]

What I'm worried about is that someone could abuse the negative cache and block new build results, so limiting the duration on 404 responses sounds good to me.

So I think this is already the behaviour due to this rule

https://github.com/NixOS/infra/blob/main/terraform/cache.tf#L233-L240

But we can add the explicit cache_setting to be sure.

[arianvp]

Okay this should now deploy the changes to staging environment as opposed to applying immediately.

Would love to apply this pairing together with someone

[jfly]

Could you add comment(s) to tge relevant part of this file explaining what we've learned about the is-404 codepath?

[arianvp]

Yes will do

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/2025-s3-sponsorship-more-resources-for-a-sustainable-nix/67019/1