Feature to Support for Nginx Ingress Canary

[bzon]

It would be good if Flagger can support Workloads that depends on Nginx Ingress Controller's Canary annotations.

Basing on the architecture diagram of Flagger, the VirtualService “adjust weight” seems like possible to be also implemented to an Ingress Object that uses Nginx Ingress Controller Class.

[stefanprodan]

Flagger generates and owns the VirtualService and the ClusterIP services, but for an Ingress object I don't see how would this work without pulling into the Canary CRD the whole Ingress spec.

[stefanprodan]

One option would be to introduce an ingressRef in the Canary CRD that would work similar to the HPA ref. Flagger would use an existing ingress to create the canary clone and adjust the weight for progressive delivery or the header/cookie for A/B testing.

[stefanprodan]

Nginx doesn't report metrics for canaries kubernetes/ingress-nginx#4026 so Flagger can't have built-in checks for HTTP errors or latency. The apps must be instrumented and custom metrics checks must be used.