ci: disable stages if only docs changes or .github

[v1v]

What does this PR do?

Faster builds for changes which are not verified/validated by the build system

Why

Smart builds reduce the cost (money and time) for commits which don't need to be validated

Therefore, #2874 could be a good candidate to be done in a few minutes rather than dozens of minutes.

[elasticmachine]

💔 Build Failed

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Build stats

• Start Time: 2022-03-23T13:37:42.388+0000

• Duration: 96 min 58 sec

Test stats 🧪

Test	Results
Failed	0
Passed	4210
Skipped	7
Total	4217

Steps errors

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Test integration: zeek

• Took 65 min 56 sec . View more details here
• Description: eval "$(../../build/elastic-package stack shellinit)" ../../build/elastic-package test -v --report-format xUnit --report-output file --test-coverage

🤖 GitHub comments

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[jsoriano]

Thanks! Added a couple of comments.

[jsoriano]

We want to run mage check if .github/CODEOWNERS change (see #2768). If this is a problem we could extract this to a different target that is always run, though mage check is fast now.

[jsoriano]

Packages have generated content in their README.md files, elastic-package lint or elastic-package check should be executed if doc files are changed, to ensure that the generated content hasn't been unexpectedly modified.

Maybe instead of having the condition here for the whole stage, it could be after the sh that runs elastic-package check below.

[mtojek]

Hi, did we analyze the current costs of running? What we have right now is spawning nodes only for the affected integrations, which I would consider as a required minimum. If we want to optimize it further, I'd like to talk and identify first the most expensive components, instead of sneaking conditions.

[v1v]

setEnvVar('ONLY_DOCS', isGitRegionMatch(patterns: [ '(^docs/.*\\.md|^\\.github/.*)' ], shouldMatchAll: true).toString()) is the approach to skip everything if changes only in .github and docs.

[v1v]

did we analyze the current costs of running?

We have found this particular behaviour in addition to #2878 and also the missing tear down in elastic/elastic-package#701

As a consequence, I looked at the pipeline and raised two different PRs to reduce the number of builds in the CI for changes that potentially are not needed.

[mtojek]

Maybe we should run different pipelines for different elements? Like "docs pipeline", "integrations pipeline", etc.

I agree we don't need to spawn a hundred nodes to check docs, but the last time we changed docs was 9 days ago, 2 months ago, 12 months ago.

[v1v]

To clarify, I didn't use any data in terms of justifying this change is needed, but found out that for some particular PRs won't need to run all the stages as those stages do not test anything for those changes. So, filtering what to run and when could help regardless if it's often changed or not. Even if it's not, there is a chance that accidentally someone could create a few PRs and then cope with all the CI capacity for instance :/

[v1v]

Maybe we should run different pipelines for different elements? Like "docs pipeline", "integrations pipeline", etc.

No strong opinion, even by doing so, it's required to create the filtering. So adding the filtering at the stage level reduces the number of GitHub api calls.