Increase File size limitation for /serve

[phaer]

Hello!

/api/v1/cache/{name}/serve/{storehash}/{filepath} is currently limited to 100MB per file.

Increasing this limit would be useful to download nix-built images directly from the cache, even if nix is not (yet) available i.e. in bootstrapping scenarios.

We've discussed this in #cachix:matrix.org in 2022 and iirc the problem back then was that whole nar files needed to be loaded into memory and so larger file would be prohibitively expensive in terms of RAM.

Is this still the case? Is serving larger files a use-case you want to support?

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My use-case at hand is that in nixos-images PRs are built and pushed to cachix already. If the limit was at least 500MB or even 1GB or more, we could just output a cachix serve url for the kexec installer bundles directly. This is compared to downloading the same path on an existing nixos host and mirroring it via HTTP manually.

i.e. (not pinned might be gc'ed)

nixos-anywhere --kexec https://app.cachix.org/api/v1/cache/numtide/serve/i84hj2wbg6lggb0fga4hsfxvj9x2805f/nixos-kexec-installer-x86_64-linux.tar.gz ...

[domenkozar]

Hey @phaer will do :)

The main limitation is that https://github.com/haskell-nix/hnix-store currently doesn't expose the api we need, so we'll have to fix the parser implementation for nars.