Improve canary deployment description

[xavierbaude]

Description

Currently the canary description is incomplete in the deployment page. I suggest this brief of different progressive solutions.

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[sftim]

Thanks for the PR, but it's as it stands it doesn't improve the documentation. You should carefully check what you want this page to say and make sure that your changes align to that vision.

[sftim]

This is not the same as how the CNCF describe it. RollingUpdate is usually not a canary deployment because RollingUpdate lacks the gradual element where the rate of change is intentionally limited.

See https://glossary.cncf.io/canary-deployment/

[xavierbaude]

I may complete the description of the canary deployment. The gradual deployment can be achieve by using 2 options : .spec.strategy.rollingUpdate.maxUnavailable and .spec.strategy.rollingUpdate.maxSurge and the readiness probe ensure that the pod is ready to get traffic. The gradual element is the number of pod and maybe I can precise that it requires more than one pod.

For me the traffic shift is not the mandatory way to balance user to both version (stable and canary). External tool can bring advanced management rollout like flagger or argo rollout.

What is your opinion?

[lmktfy]

Hi (I was previously @sftim).

My opinion is still that Kubernetes does not default to canary rollouts, and that a rolling update is different from an actual canary rollout.

Canary deployments gradually move traffic, allowing for early aborts if there are problems, whereas RollingUpdate goes as quickly as it can given current constraints.