Automatically scale down Deployment after migrating to Rollout

[carlossg]

Summary

When using Rollout with workloadRef it could be expected that the workload (Deployment) is scaled down as the Rollout is scaled up, or at the end after successful rollout

Use Cases

During migration of 10s-1000s of Deployments to Rollouts

After talking to several maintainers during ArgoCon this could be a new field under spec.workloadRef, maybe something like

spec:
  workloadRef:
    apiVersion: apps/v1
    kind: Deployment
    name: "acme"
    scaleDown: "never|onsuccess|progressively"

• never: do not downscale
• onsuccess: after successful rollout
• progressively: as rollout is scaled up deployment is scaled down. If rollout fails then deployment is scaled back up to original replicas (I think this may be interesting for very large replica numbers, but maybe too early to say)

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Message from the maintainers:

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[zachaller]

I think this could make sense as long as the default behavior maintains backwards compatibility, which if scaleDown: nil or "" equates to never

[github-actions]

This issue is stale because it has been open 60 days with no activity.