Fix memory leaks in expired matchers

[dsimansk]

Changes

• Fix memory leak in metrics' expired matchers

Memory leaks observed in @maschmid long running soak tests:

After pruning expired inexact matchers, the code checked len(s) (the exact matchers map) instead of len(ms) (the inexact matchers map), and then deleted from i.exact instead of i.inexact. This meant empty inexact matcher entries were never cleaned up, causing a memory leak for every label-selector-based tracker reference.

When removing inexact matchers for a deleted object, the code called delete(i.exact, ref) instead of delete(i.inexact, ref), so empty inexact entries accumulated indefinitely and could also incorrectly remove unrelated exact entries.

Release Note

Fix memory leak in metrics' expired matchers

PTAL, it's a follow-up to other memory leak in networking hanging idle connections.

/cc @dprotaso

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dsimansk

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.85%. Comparing base (71f6ad6) to head (d194ed4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3358   +/-   ##
=======================================
  Coverage   74.85%   74.85%           
=======================================
  Files         189      189           
  Lines        8347     8347           
=======================================
  Hits         6248     6248           
  Misses       1854     1854           
  Partials      245      245           

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[dsimansk]

/cc @maschmid @linkvt

[linkvt]

/lgtm
/hold in case Dave should also take a look, feel free to unhold

[dprotaso]

I don't generally like the tests accessing the internals - but I see the style is just complementing what's already there so I don't want to gate the PR on that

/hold cancel

[dsimansk]

/cherry-pick release-1.22
/cherry-pick release-1.21

[knative-prow-robot]

@dsimansk: new pull request created: #3359

Details

In response to this:

/cherry-pick release-1.22
/cherry-pick release-1.21

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[knative-prow-robot]

@dsimansk: new pull request created: #3360

Details

In response to this:

/cherry-pick release-1.22
/cherry-pick release-1.21

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.