[ronef]

Jotting down a few quick thoughts here but we can totally go deep. This is something Michael Brantley started working on a few months ago to test out how to make it super easy to ease and leverage existing Nix & Flox architecture. One of the core differences from my quick perspective is that it specifically leverages the unique way that Flox environments are rendered without performing a nix evaluation, making it safe and optimally performant for the k8s node to realize the packages directly on the node, outside of a container.

[zobzu]

I read this a few times but there's no info.

[Shebanator]

Wrong. If you know nix then you know "leverages the unique way that Flox environments are rendered without performing a nix evaluation" is a very significant statement.

[nixosbestos]

> leverages the unique way that Flox environments are rendered without performing a nix evaluation"

I'm curious! and ignorant! help!

Is that via (centrally?) cached eval? or what? there's only so much room for magic in this arena.

[jeremy_flox]

Yeah, it's essentially cached eval, the key being where/how that eval is stored.

When you create a Flox environment, we evaluate the Nix expressions once and store the concrete result (ie exact store paths) in FloxHub. The k8s node just fetches that pre-rendered manifest and bind-mounts the packages with no evaluation step at pod startup.

It's like the difference between giving the node a recipe to interpret vs. giving it a shopping list of exact items. Faster, safer, and the node doesn't need to know how to cook (evaluate Nix). I don't know, there's a metaphor here somewhere, I'll find it.

Only so much room for magic, for sure, but tons of room for efficiency and optimization.

[jeremy_flox]

Correction: we don't eval when you create environments.

Our catalog continuously pre-evaluates nixpkgs in the background. 'flox install' just selects from pre-evaluated packages -- no eval needed, ever. The k8s node fetches the manifest and mounts the packages.

Eval is done once, centrally, continuously. So... even more pre-val'd, so to speak.