outlierdetection: add metrics specified in gRFC A91

[davinci26]

Implements gRFC A91: https://github.com/grpc/proposal/blob/master/A91-outlier-detection-metrics.md

Notable implementation detals

• grpc.lb.backend_service is not implemented yet (marked as optional in the gRFC)
• modifies the tests to make sure we can cover all the cases for enforced/unenforced without repeating the test setup.

RELEASE NOTES:

• outlierdetection: add metrics for enforced (grpc.lb.outlier_detection.ejections_enforced) and unenforced (grpc.lb.outlier_detection.ejections_unenforced) outlier ejections.

[codecov]

Codecov Report

❌ Patch coverage is 78.12500% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.81%. Comparing base (8110884) to head (4335462).
⚠️ Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/xds/balancer/outlierdetection/balancer.go	78.12%	5 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8644      +/-   ##
==========================================
+ Coverage   79.45%   81.81%   +2.36%     
==========================================
  Files         415      417       +2     
  Lines       41339    40801     -538     
==========================================
+ Hits        32844    33383     +539     
+ Misses       6621     6045     -576     
+ Partials     1874     1373     -501     

Files with missing lines	Coverage Δ
internal/xds/balancer/outlierdetection/balancer.go	87.63% <78.12%> (-0.08%)	⬇️

... and 40 files with indirect coverage changes

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[easwars]

@davinci26

Thank you for your contribution.

Since PR titles and descriptions become part of our git commit history, please follow these recommendations: https://github.com/grpc/grpc-go/blob/master/CONTRIBUTING.md#pr-descriptions

[easwars]

Haven't reviewed the tests yet.

[easwars]

@davinci26 : Please do not mark comments as resolved. The process that we follow involves the reviewer marking them as resolved. When the author does that, the reviewer will have to click on each of those resolved comments to see what the original comment was and whether it was sufficiently addressed. Thanks for understanding.

[davinci26]

@easwars sorry, habit from a different process. Will keep them open and let the reviewer close them

[easwars]

I'm still looking at the test. Thanks.

[easwars]

LGTM modulo minor nits in the test

[easwars]

Assigning to @mbissa for second set of eyes.

[easwars]

@davinci26 : Thank you for your contribution!

[davinci26]

thank you and I will try to follow with adding the optional label. Do we want to open an issue for that since we are not 100% compliant right now?

[easwars]

thank you and I will try to follow with adding the optional label. Do we want to open an issue for that since we are not 100% compliant right now?

Thank you for offering. We have to wait for #8637 to be merged and I believe @mbissa is going to be out for a little while. We usually wait till we get two approvals on PRs from contributors who are not on the grpc team. And @mbissa is marked as the second reviewer. We might be able to get a different reviewer to approve this and have this merged. So, if that happens, you could just wait for the backend_service PR to get merged and add that optional label in a separate PR. We don't technically need an issue, but feel free to file one if you feel like it.

[arjan-bal]

LGTM, thanks for the contribution!