cache.nixos.org HTTP 416

[roberth]

Affected service

cache.nixos.org

Describe the issue

The NixOS cache will occasionally report HTTP error 416.

error: unable to download 'https://cache.nixos.org/nar/0kalbqziv0aprssxy5zcv7zcxzwpj62dlyys0lkgr1s81687q9al.nar.xz': HTTP error 416

Possible causes I can think of:

• Range requests are unsupported (and not used most of the time)
• Out of date narinfo has longer length (build impurity, reupload)
• Bugs in fastly/s3

System information

Just encountered this instance from GHA.
(Nix 2.34.7, but this could happen with any client/library that supports download resumption)

[vcunat]

Is this (still) reproducible on some URLs? (I fail to reproduce it now with the one above.)

I suspect that some rough edges in earlier versions of the new queue-runner might've caused this one as well, in addition to e.g. NixOS/hydra#1804

EDIT: though as Mic92 noticed, those would use zstd, not xz

[mweinelt]

https://www.tech-reader.blog/2025/10/error-416-requested-range-not.html is a good read on the topic, as this is likely a response from AWS S3.