Make canary-only configuration for skipper-ingress possible

[RomanZavodskikh]

When "skipper_ingress_canary_enabled" and "skipper_ingress_test_single_pod" are both "true"

[szuecs]

@RomanZavodskikh that looks super complex. Why not something like a custom bool config item?
Another way could be also if max_replica set to 0 then delete hpa, but I guess a bool would be simple and cover what we need.

[RomanZavodskikh]

Yes, I tried this idea, and I agree the configuration becomes much simpler. However, what if "skipper_ingress_canary_enabled" is set to "exclusive" in some important production cluster? Such accidential configuration will make all traffic go through single skipper-ingress pod.
I have considered such a scenario and added additional safety net.

[szuecs]

@RomanZavodskikh you can also damage it by setting max replica to 1...

[RomanZavodskikh]

Okay, I see, we cannot take so much responsibility here. Reverted to the most simple option.

[szuecs]

Looks much better now!

[AlexanderYastrebov]

I think you can add replicas: 0 to the deployment conditionally - HPA does not scale deployment that has zero replicas

[AlexanderYastrebov]

I also do not like that we change boolean (note _enabled suffix) config into multivalue but alternative is another config item which might be even worse.

[RomanZavodskikh]

👍

[szuecs]

👍

[AlexanderYastrebov]

Hm, I think it would be cleaner to do

{{ if eq .Cluster.ConfigItems.skipper_ingress_test_single_pod "true" }}
{{ template "skipper-ingress" dict
  "name" "skipper-ingress"
  "internal_version" $internal_version
  "replicas": 0
  "Cluster" .Cluster
  "Values" .Values
}}
{{ else }}
{{ template "skipper-ingress" dict
  "name" "skipper-ingress"
  "internal_version" $internal_version
  "Cluster" .Cluster
  "Values" .Values
}}
{{ end }}

[AlexanderYastrebov]

Also skipper_ingress_test_single_pod implies test and single, but it is single canary pod which in the future might become several pods.
Maybe it should be just skipper_ingress_replicas that is empty by default:

{{ if ne .Cluster.ConfigItems.skipper_ingress_replicas "" }}
{{ template "skipper-ingress" dict
  "name" "skipper-ingress"
  "internal_version" $internal_version
  "replicas": .Cluster.ConfigItems.skipper_ingress_replicas
  "Cluster" .Cluster
  "Values" .Values
}}
{{ else }}
{{ template "skipper-ingress" dict
  "name" "skipper-ingress"
  "internal_version" $internal_version
  "Cluster" .Cluster
  "Values" .Values
}}
{{ end }}