Stabilize cache size on `macOS` runners.

[deemp]

Problem

• Cache size on macOS runners can vary between job runs.
  • First time, a small or zero-size cache is restored.
  • A lot of paths are substituted from remote caches.
  • A lot of paths are accessed.
  • New saved cache is large.
  • Next time, a large cache is restored.
  • Nothing is substituted from remote caches.
  • Not many paths are accessed.
  • New saved cache is small.
  • Next time, a small cache is restored.
  • A lot of paths are substituted from remote caches.
  • Not many paths are accessed.
  • New saved cache is small.
  • See Actions in this repo.
  • Check subsequent macOS jobs.
  • See logs of job steps where this action runs.

Code

Restore

Save

N.B.

Logs are printed when a script finishes.

Example 1

Initial cache size: 39 MB (src)

Installing findutils (src) takes almost a minute.

Mon, 03 Jul 2023 15:06:58 GMT  [START] Installing cross-platform GNU findutils.
Mon, 03 Jul 2023 15:06:58 GMT  
Mon, 03 Jul 2023 15:06:58 GMT  
Mon, 03 Jul 2023 15:06:58 GMT  nix profile install nixpkgs#findutils 2> /Users/runner/work/nix-cache/logs
Mon, 03 Jul 2023 15:06:58 GMT  
Mon, 03 Jul 2023 15:06:58 GMT  cat /Users/runner/work/nix-cache/logs
Mon, 03 Jul 2023 15:07:47 GMT
Mon, 03 Jul 2023 15:07:47 GMT  
Mon, 03 Jul 2023 15:07:47 GMT  
Mon, 03 Jul 2023 15:07:47 GMT  [FINISH] Installing cross-platform GNU findutils.

Final cache size: 112 MB (src)

Example 2

With verbose logs https://github.com/deemp/cache-nix-too/actions/runs/5447637002/jobs/9909864274#step:4:126

Nixos/nix

Now also tracked in https://github.com/NixOS/nix/issues/8641

[deemp]

Another approach is to cache the full store. It's implemented here