fix: retarget blue-green preview service before scaling up preview replicaset

[jessesuen]

Resolves #1151

This change implements the following behavior when creating the preview service and changing selectors.

1. create preview replicaset with size 0
2. retarget preview service to replicaset hash
3. scale up the preview replicaset

Previously we would create the preview replicaset with the desired size (without the separate create and scale steps). This will allow all pods of the preview to be considered for readiness gate injection by the AWS LoadBalancer controller

Signed-off-by: Jesse Suen jesse_suen@intuit.com

[huikang]

@jessesuen , could you update the timeline in the b/g rollout doc: https://github.com/argoproj/argo-rollouts/blob/master/docs/features/bluegreen.md#previewservice? I think this change obsoletes some of the description. Thanks.

[jessesuen]

Sure I'll update that as well. Thank you for the feedback.

[codecov]

Codecov Report

Merging #1368 (f0f1497) into master (2620490) will decrease coverage by 0.02%.
The diff coverage is 66.66%.

❗ Current head f0f1497 differs from pull request most recent head 5a90436. Consider uploading reports for the commit 5a90436 to get more accurate results

@@            Coverage Diff             @@
##           master    #1368      +/-   ##
==========================================
- Coverage   81.22%   81.19%   -0.03%     
==========================================
  Files         108      108              
  Lines        9916     9911       -5     
==========================================
- Hits         8054     8047       -7     
- Misses       1309     1310       +1     
- Partials      553      554       +1     

Impacted Files	Coverage Δ
utils/conditions/conditions.go	78.94% <ø> (ø)
rollout/bluegreen.go	70.91% <33.33%> (ø)
rollout/sync.go	76.63% <100.00%> (+0.16%)	⬆️
rollout/canary.go	76.41% <0.00%> (-2.06%)	⬇️

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[khhirani]

LGTM

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
2.0% Duplication