Should I use configMap for every environment variable? - kubernetes

Question

I am using helm right now. My project is like that:
values.yaml:
environmentVariables:
KEY1: VALUE1
KEY2: VALUE2
configmap.yaml:
apiVersion: v1
kind: ConfigMap
metadata:
name: {{ template "myproject.fullname" . }}
data:
{{- range $k, $v := .Values.environmentVariables }}
{{ $k }}: {{ $v | quote }}
{{- end }}
deployment.yaml:
apiVersion: apps/v1
kind: Deployment
metadata:
name: {{ template "myproject.fullname" . }}
spec:
template:
spec:
containers:
- name: {{ .Chart.Name }}
image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
imagePullPolicy: {{ .Values.image.pullPolicy }}
env:
{{- range $k, $v := .Values.environmentVariables }}
- name: {{ $k }}
valueFrom:
configMapKeyRef:
name: {{ template "myproject.fullname" $ }}
key: {{ $k }}
{{- end }}
...
But right now, I'm really confused. Am I really need this configmap? Is there any benefit to use configmap for environment variables?

Answer 1

Aside from the points about separation of config from pods, one advantage of a ConfigMap is it lets you make the values of the variables accessible to other Pods or apps that are not necessarily part of your chart.
It does add a little extra complexity though and there can be a large element of preference about when to use a ConfigMap. Since your ConfigMap keys are the names of the environment variables you could simplify your Deployment a little by using 'envFrom'

Answer 2

It would work even if you don't use a configmap, but it has some advantages:
You can update the values at runtime, without updating a deployment. Which means you might not need to restart your application (pods). If you don't use a config map, everytime you update the value, your application (or pod) will be recreated.
Separation of concerns, i.e. deployment configuration and external values separated

Answer 3

I feel like this is largely a matter of taste; but I've generally been avoiding ConfigMaps for cases like these.
env:
{{- range $k, $v := .Values.environmentVariables }}
- name: {{ quote $k }}
value: {{ quote $v }}
{{- end }}
You generally want a single source of truth and Helm can be that: you don't want to be in a situation where someone has edited a ConfigMap outside of Helm and a redeployment breaks local changes. So there's not a lot of value in a ConfigMap being "more editable" than a Deployment spec.
In principle (as #Hazim notes) you can update a ConfigMap contents without restarting a container, but that intrinsically can't update environment variables in running containers, and restarting containers is so routine that doing it once shouldn't matter much.