Allow analysis arguments to get valueFrom Rollout status

[jessesuen]

Summary

Currently, we can pass arguments to AnalysisTemplates from metadata labels and annotations, e.g.

  strategy:
    canary:
      analysis:
        templates:
        - templateName: args-example
        args:
        - name: region
          valueFrom:
            fieldRef:
              fieldPath: metadata.labels['region']

We should also allow passing arguments to AnalysisTemplates whose value is derived from fields in the rollout status.

Use Cases

As part of #1241, we will be surfacing ALB information under the rollout status. For example:

status:
  alb:
    loadBalancer:
      name: k8s-devdeplo-testdele-b9061572ad
      arn: arn:aws:elasticloadbalancing:us-west-2:1234567891011:loadbalancer/app/k8s-devdeplo-testdele-abcdef1234/3a47c96b75571d0e
    canaryTargetGroup:
      name: k8s-devdeplo-testdele-ab72c5b132
      arn: arn:aws:elasticloadbalancing:us-west-2:1234567891011:targetgroup/k8s-devdeplo-testdele-ab72c5b132/df2957821c1214fc
    stableTargetGroup:
      name: k8s-devdeplo-testdele-8832d6519a
      arn: arn:aws:elasticloadbalancing:us-west-2:1234567891011:targetgroup/k8s-devdeplo-testdele-8832d6519a/df2957821c1214fc 

Once that is available, it would then be useful to pass that information to an AnalysisTemplate, so that argo rollouts could perform CloudWatch queries against the canary targetgroup vs. stable targetgroup, like so:

      analysis:
        templates:
        - templateName: cloud-watch-error-rate
        args:
        - name: env
          valueFrom:
            fieldRef:
              fieldPath: status.alb.canaryTargetGroup.name

---

Message from the maintainers:

Impacted by this bug? Give it a 👍. We prioritize the issues with the most 👍.

[jessesuen]

To make this feature more useful, instead of single field paths, we should support JSON string objects and enhance analysis to allow dot notation referencing when the supplied argument is a json string.

[noam-codefresh]

I am not sure I understand this last comment - do you mean something more complex than the example above? Or just having the ability to reference any field in the status, by using dot notation like status.alb.canaryTargetGroup.name?

I was thinking about using https://github.com/stretchr/objx to extract the value from the rollout instance. Is there any library/way you recommend to do it?

[noam-codefresh]

created PR - #1629

[jessesuen]

Fixed