workflows/doctor: use ephemeral runners

[carlocab]

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This workflow hasn't been set up to run on our ephemeral runners. Let's
fix that.

[BrewTestBot]

Review period will end on 2022-11-25 at 06:17:22 UTC.

[BrewTestBot]

Review period skipped due to critical label.

[Bo98]

I've enabled this repo in the GitHub App settings, so should work now.

[carlocab]

Running on ephemeral is really slow. Our bare metal runners can complete the brew doctor workflow in 12s. The ephemeral runners take between three and seven minutes. 13-arm64 takes three and a half minutes. See https://github.com/Homebrew/brew/actions/runs/3538204547.

I wonder why they're so much slower.

[Bo98]

Some of it will be updating homebrew-core being slow (ephemeral will have an older copy while non-ephemeral will be near up-to-date from the last run) and needing to run brew install-bundler-gems on an older install (which we could cache).

Cleanup slowness on Monterey still needs further investigation.

[MikeMcQuaid]

Some of it will be updating homebrew-core being slow (ephemeral will have an older copy while non-ephemeral will be near up-to-date from the last run)

Perhaps we could avoid doing this at all for Homebrew/brew usage?

needing to run brew install-bundler-gems on an older install (which we could cache).

actions/cache feels like a good call. also: why do we need these gems for brew doctor?

Cleanup slowness on Monterey still needs further investigation.

Is this pre-cleanup?

[Bo98]

why do we need these gems for brew doctor?

We don't really but it's a fixed part of --only-setup.

Is this pre-cleanup?

Yes (--only-cleanup-before). We could skip it, but I'm a bit concerned something that should be doing little to nothing is taking 3 minutes so this feels like something's wrong that's indicating something to fix in the base image.

[MikeMcQuaid]

We don't really but it's a fixed part of --only-setup.

Gotcha. Could definitely remove or move to another --only where these gems are actually needed.

We could skip it, but I'm a bit concerned something that should be doing little to nothing is taking 3 minutes so this feels like something's wrong that's indicating something to fix in the base image.

Agreed 👍🏻.

IMO we should do the bare minimum to only cleanup the stuff brew doctor complains about that. Could experiment with faster ways of doing this e.g. renaming /usr/local/include to /usr/local/include.old instead of moving to /tmp.

[carlocab]

We don't really but it's a fixed part of --only-setup.

Gotcha. Could definitely remove or move to another --only where these gems are actually needed.

How much of the setup do we need? (Or the cleanup steps, for that matter?) I'm wondering if we can cut those all out and run setup-homebrew and then call brew doctor.

[Bo98]

IMO we should do the bare minimum to only cleanup the stuff brew doctor complains about that. Could experiment with faster ways of doing this e.g. renaming /usr/local/include to /usr/local/include.old instead of moving to /tmp.

The self-hosted images should already be set up that the cleanup required is zero.

How much of the setup do we need?

Should be zero I think.

[carlocab]

So, maybe something like this then?

diff --git a/.github/workflows/doctor.yml b/.github/workflows/doctor.yml
index 50409557e..0335cda25 100644
--- a/.github/workflows/doctor.yml
+++ b/.github/workflows/doctor.yml
@@ -32,8 +32,9 @@ jobs:
         uses: Homebrew/actions/setup-homebrew@master
 
       - run: brew test-bot --only-cleanup-before
+        if: ! contains(matrix.runner, github.run_id)
 
-      - run: brew test-bot --only-setup
+      - run: brew doctor
 
       - run: brew test-bot --only-cleanup-after
-        if: always()
+        if: always() && ! contains(matrix.runner, github.run_id)

Not sure if some of those should be wrapped in ${{ }}. I assume not.