[wip] [feedback wanted] Do not scrape pods when activator in path

[Alexander-Kita]

Fixes #7324

Proposed Changes

• Pause scraping pods when activator in data path (excess burst capacity < 0)
• Resume when excess burst capacity >= 0

Feedback needed on the following items (more emphasis on the first):

1. In the current implementation, due to Improve SKS handling for unavailable Activator. #13027, in the circumstance that excess burst capacity < 0 AND there are no activator endpoints, then there might be metrics missed since SKS forces "serve" mode. Is there a way to float the status ("proxy" or "serve") to the autoscaler? Or, another way to account for this?

2. Writing unit tests for this situation

3. It appears in the e2e tests it is having trouble scaling to zero. Am I missing a function invokation? I thought the statistics from the activator would be recorded.

Release Note

NONE

[knative-prow]

Hi @Alexander-Kita. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Alexander-Kita
Once this PR has been reviewed and has the lgtm label, please assign skonto for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov]

Codecov Report

❌ Patch coverage is 34.61538% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.98%. Comparing base (090b6ae) to head (ee86a28).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/autoscaler/metrics/collector.go	22.72%	16 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16254      +/-   ##
==========================================
- Coverage   80.05%   79.98%   -0.08%     
==========================================
  Files         215      215              
  Lines       13327    13353      +26     
==========================================
+ Hits        10669    10680      +11     
- Misses       2300     2310      +10     
- Partials      358      363       +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.