Should the Nix CI do caching

[andreasabel]

@peterbecich You added a Nix CI:

hackage-server/.github/workflows/nix-shell.yml

Lines 16 to 18 in 2d4f3f7

	- uses: cachix/install-nix-action@v16
	with:
	nix_path: nixpkgs=channel:nixos-21.11

Does this cache between builds?

If not, would caching be possible, maybe along the lines of:
https://github.com/cachix/install-nix-action#how-do-i-add-a-binary-cache

I am asking because the Nix workflow takes at least 17min each time, whereas Haskell CI can get down to <10min (probably thanks to caching).
(Haskell CI takes long when it cannot restore from the cache, see e.g.: https://github.com/haskell/hackage-server/runs/6437475007?check_suite_focus=true#step:16:23)

[peterbecich]

Good idea, working on it

It doesn't seem to produce an improvement to use https://github.com/cachix/install-nix-action#how-do-i-add-a-binary-cache

It would be an improvement to have actions/cache@v3.0.2 working and cache /nix/store in Github; I'm trying to make this work: cachix/install-nix-action#56 (comment)

The current errors are:

...
/usr/bin/tar: ../../../../../nix/store/01dww3kbj952cbbacnwbpzc4y3qr7clc-glibc-2.34-115-bin/sbin: 
Cannot create symlink to ‘bin’: File exists
/usr/bin/tar: ../../../../../nix/store/01dww3kbj952cbbacnwbpzc4y3qr7clc-glibc-2.34-115-bin/bin/xtrace: 
Cannot open: File exists
/usr/bin/tar: ../../../../../nix/store/01dww3kbj952cbbacnwbpzc4y3qr7clc-glibc-2.34-115-bin/bin/zic: 
Cannot open: File exists
/usr/bin/tar: ../../../../../nix/store/01dww3kbj952cbbacnwbpzc4y3qr7clc-glibc-2.34-115-bin/bin/getent: 
Cannot open: File exists
/usr/bin/tar: ../../../../../nix/store/01dww3kbj952cbbacnwbpzc4y3qr7clc-glibc-2.34-115-bin/bin/ldd: 
Cannot open: File exists
...

https://github.com/peterbecich/hackage-server/runs/6567988004?check_suite_focus=true

[peterbecich]

As far as I can tell, the Cachix GitHub Action (https://github.com/cachix/install-nix-action) is designed to only cache on Cachix, and is not compatible with https://github.com/actions/cache

Can we set up a free Cachix account for hackage-server (https://www.cachix.org/pricing)? If you set secrets.CACHIX_SIGNING_KEY and secrets.CACHIX_AUTH_TOKEN in GitHub, then I should be able to implement this https://nix.dev/tutorials/continuous-integration-github-actions#setting-up-github-actions

[andreasabel]

Can we set up a free Cachix account for hackage-server (cachix.org/pricing)?

I suppose yes. The conditions are:

Users have a free 5 GB limit for open source projects.

[peterbecich]

Should be enough. i.i.r.c. the GitHub caching action indicated this needs less than three GB. (It progressed far enough to inform me of that, but nonetheless could not successfully use the cache.)

[andreasabel]

I created a personal account on cachix.org, but when I created organization hackage-server, I am told that this isn't free (except for a 14 day trial).
Maybe it makes sense for you @peterbecich to set up the account there, since you will (supposedly) maintain the nix CI? If you need more rights on hackage-server to set up the connection, @gbaz is your man.

[andreasabel]

Does this work yet? I see cachix cache jumping into action, but the build time is still 20min: https://github.com/haskell/hackage-server/runs/6777589545?check_suite_focus=true

[peterbecich]

Apparently it is not working yet, I'll try a few more things: #1086

[domenkozar]

Note that I've granted hackage-server organization 50GB free plan, let me know if that's enough!

[peterbecich]

Thank you @domenkozar , I think 50GB is more than enough