Helm template syntax when using subcharts? - kubernetes-helm

Question

I asked Use one Helm chart for ALL microservices? and now I'm trying to implement the answer I accepted, i.e., using sub charts. (Note: If there's a better answer for that post, please put it in that post, not here.)
Per the answer I accepted, I have the following directory structure
my-deployment-repo/
|- base-microservice/
|- templates/
|- deployment.yml
|- service.yml
|- Chart.yaml
|- values.yaml
|- myapp/
|- Chart.yaml
|- values.yaml
base-microservice/values.yaml file has
image:
name: ""
version: ""
repository: 01234567890.dkr.ecr.us-east-1.amazonaws.com
pullPolicy: IfNotPresent
# Overrides the image tag whose default is the chart appVersion.
tag: ""
service:
type: NodePort
port: 5000
# More key/value pairs defined
myapp/Chart.yaml has
apiVersion: v2
name: myapp
description: A Helm chart for Kubernetes
...
dependencies:
- alias: my-microservice-1
name: base-microservice
version: "0.1.0"
repository: file://../base-microservice
- alias: my-microservice-2
name: base-microservice
version: "0.1.0"
repository: file://../base-microservice
myapp/values.yaml simply has this because I want myapp to use ALL the values in base-microservice/values.yaml except for the values I provide here.
my-microservice-1:
image:
name: foo
version: 1.2.3
my-microservice-2:
image:
name: bar
version: 4.5.6
So now when I do a...
$ helm update ./myapp
$ helm install myapp myapp/
...I want to be able to get, for example, the deployment for the alias microservice-1
apiVersion: apps/v1
kind: Deployment
...
spec:
...
template:
...
spec:
...
containers:
- name: foo # image name for microservice-1 alias
# These are from the different values.yaml files
# <repository from base-microservice>/<image name from myapp>:v<ersion from myapp>
image: 01234567890.dkr.ecr.us-east-1.amazonaws.com/foo:1.2.3
IOW, what should the base-microserivce/templates/deployment.yaml syntax be to...
spec.template.spec.containers.name: {{ what should be here to produce "foo" }} and
spec.template.spec.containers.image: {{ what should be here to produce "01234567890.dkr.ecr.us-east-1.amazonaws.com/foo:1.2.3" }}
I hope that makes sense. TIA!

Answer 1

When the template file is eventually rendered, .Values will be a subset specific to this subchart. So in your template code, just use .Values the same way you would if it were a standalone chart.
containers:
- name: foo {{-/* not templated */}}
image: {{ with .Values.image }}{{ .repository }}/{{ .name }}:{{ .version }}{{ end }}
I've intentionally chosen to not template name in this example. A container name is only useful in a couple of very specific contexts (to review kubectl logs in a multi-container Pod, for example) and IME it's much easier to set it to a fixed name than to try to template it. You could use {{ .Values.image.name }} here as well if you wanted to.