fix: check isScalingEvent only on stable and newRS

[zachaller]

This bug can cause rollouts to get stuck in a tight loop of thinking it's constantly in a scaling event. Argo rollouts does not ever update the /desired-replicas annotation on ReplicaSets that are not stable or desired (newRs) there can be races where a ReplicaSet will get marked as old with a value in /desired-replicas that dose not match spec.replicas on the rollout this could either be due to a scaling event right after that rs gets moved to old or a code path that does not update the rs before marking it as old.

This change makes this loop not possible because we will not check all replicasets but instead only check stable and newRs which are the only ones we scale on scaling events.

Example state of issue below: We have an old replicaset that does not match spec.replicas of the rollout this causes isScalingEvent to get into a loop.

Rollout:

apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
spec:
  replicas: 10

Desired/Canary

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  annotations:
    rollout.argoproj.io/desired-replicas: '10'

Old

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  annotations:
    rollout.argoproj.io/desired-replicas: '9'

Stable

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  annotations:
    rollout.argoproj.io/desired-replicas: '10'

[github-actions]

Published E2E Test Results

  4 files    4 suites   3h 18m 19s ⏱️
113 tests 101 ✅  7 💤 5 ❌
458 runs  424 ✅ 28 💤 6 ❌

For more details on these failures, see this check.

Results for commit 0e92e32.

♻️ This comment has been updated with latest results.

[github-actions]

Published Unit Test Results

2 276 tests   2 276 ✅  2m 59s ⏱️
  128 suites      0 💤
    1 files        0 ❌

Results for commit 0e92e32.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.85%. Comparing base (50300e5) to head (0e92e32).
Report is 11 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3883      +/-   ##
==========================================
- Coverage   83.88%   83.85%   -0.04%     
==========================================
  Files         163      163              
  Lines       18564    18564              
==========================================
- Hits        15573    15567       -6     
- Misses       2119     2122       +3     
- Partials      872      875       +3     

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[leoluz]

please check my comment

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[leoluz]

LGTM