[CI] Reduce GitHub Actions usage

[kou]

Describe the enhancement requested

See also: https://lists.apache.org/thread/drf0o5kzg1zfmok7gc09k8qz8hh9ymvh

We can use https://infra-reports.apache.org/#ghactions to see statistics.

Component(s)

Continuous Integration

[kou]

https://infra-reports.apache.org/#ghactions&project=arrow&hours=168&limit=15&group=name shows that the "Package Linux" takes most hours (594 hours) in our workflows. Let's optimize the workflow as the first step.

[rok]

This seems like a lot especially after #50047 brought down our run times significantly.

[raulcd]

I see Python is the second most used workflow. I'll investigate whether it can also be reduced. Maybe some of the CI jobs could be moved to nightlies instead of per PR reducing the matrix.

[pitrou]

This seems like a lot especially after #50047 brought down our run times significantly.

That PR only addressed the C++ builds, though, not the Python or packaging builds.

[kou]

We've reduced usages of top 2 workflows ("Package Linux" and "Python").
Let's revisit after a week.

Current numbers at https://infra-reports.apache.org/#ghactions&project=arrow&hours=168&limit=15&group=name :

• Total: 198,402 minutes
• Package Linux: 807h47m
• Python: 464h16m
• C++: 344h56m

[kou]

Current numbers:

• Total: 146,106 minutes (73%)
• Package Linux: 351h39m (43%)
• Python: 258h27m (55%)
• C++: 255h9m (73%)

[pitrou]

It seems the C/GLib/Ruby and R builds still use actions/cache, should we migrate them too?

[pitrou]

Oh, and Integration too.

[pitrou]

Homebrew installs are often very slow (several minutes), can they be sped up with caching?

[kou]

I think that we can speed up Homebrew installs by removing brew update:

arrow/.github/workflows/cpp.yml

Lines 242 to 244 in f349102

	# Workaround for https://github.com/grpc/grpc/issues/41755
	# Remove once the runner ships a newer Homebrew.
	brew update