Challenges with setting namespace when using generators

[howardjohn]

Describe your problem

I am trying to write a generator function. Basically it inserts some data into a configmap, nothing too fancy.

My Kptfile looks like:

pipeline:
  mutators:
    - image: my-generator
      configMap:
        data: "..."
   - image: gcr.io/kpt-fn/set-namespace:v0.1
     configMap:
       namespace: grafana

My function generates a new config, and inserts it into the list of items with merging:

	rl.Items = append(rl.Items, yaml.NewRNode(&node))
	rl.Items, err = filters.MergeFilter{}.Filter(rl.Items)

The problem is that the generator doesn't add a namespace, but then it later is added. This means that the second run of the pipeline ends up appending the config again - so we end up with 2x copies.

Possible solutions:

• Generator functions should not include namespace on merge key. This seems prone to failure in cases of multiple namespaces handled by one Kptfile
• Generator functions should always explicit set the namespace. This requires all generators to take a namespace param, and all usages to set it as well - a lot of churn and duplication.
• When configMap is used, set the namespace equal to that of the Kptfile namespace. Bonus points if set-namespace also uses this. Then, the whole Kptfile could look like:

apiVersion: kpt.dev/v1
kind: Kptfile
metadata:
  name: grafana
  namespace: grafana
pipeline:
  mutators:
    - image: my-generator
      configMap:
        data: "..."
   - image: gcr.io/kpt-fn/set-namespace:v0.1
     configMap: {}

To get the namespace that should be used, functions can use rl.FunctionConfig.GetNamespace()

• if set-namespaces generates a duplicate resource, it could filter one of them out. This feels like the wrong solution - especially if it picks the wrong copy.