env-echo

A docker container that echos back environment variables.

The primary use case is to print back configuration to a frontend application that does not support runtime configuration via env (looking at you next.js). The process takes a prefix for env and prints back all env variables that start with it.

The response is served according to Accept header, plaintext and json are the only types supported.

Important

The default prefix is CONFIG_, don't deploy this container with empty prefix because it will print the entire environment including any secrets that are present.

Example

Within k8s environment, the envFrom configuration field supports an optional prefix which can be used to automatically prefix all variables coming from a particular config map, example below:

# Config map, note no need for prefix since we load the envFrom with a prefix
apiVersion: v1
kind: ConfigMap
metadata:
  name: ui-config
data:
  GRAPHQL_URL: "example.com/graphql"
---
# Define deployment, load config map
apiVersion: apps/v1
kind: Deployment
metadata:
  name: &name ui
spec:
  replicas: 1
  selector:
    matchLabels:
      app: *name
  template:
    metadata:
      labels:
        app: *name
    spec:
      containers:
      - name: *name
        image: docker.io/your-org/your-image:latest
        imagePullPolicy: Always
        ports:
        - containerPort: 3000
        resources:
          requests:
            cpu: 0m
            memory: 0Mi
          limits:
            cpu: 1000m
            memory: 3Gi
      - name: ui-env
        image: quay.io/road/env-echo:latest
        imagePullPolicy: Always
        envFrom:
          - configMapRef:
                name: ui-config
            prefix: CONFIG_
        ports:
          - containerPort: 8080
        resources:
          requests:
            cpu: 0m
            memory: 0Mi
          limits:
            cpu: 200m
            memory: 500Mi
---
# Define service for both
apiVersion: v1
kind: Service
metadata:
  labels:
    name: ui
  name: ui
spec:
  selector:
    app: ui
  ports:
    - protocol: TCP
      port: 3000
      name: ui
    - protocol: TCP
      port: 8080
      name: ui-env
---
# Define ingress with path mapping, example with Traefik
apiVersion: traefik.io/v1alpha1
kind: IngressRoute
metadata:
  name: ui
spec:
  entryPoints:
    - web
  routes:
    - kind: Rule
      match: Host(`example.com`) && PathPrefix(`/.env`)
      services:
        - name: ui
          port: 8080
    - kind: Rule
      match: Host(`example.com`)
      services:
        - name: ui
          port: 3000