Rails in Kubernetes not picking up environment variables provided by configmap - ruby-on-rails

Question

I have a simple .env file with content like this
APP_PORT=5000
I add the values of that file with Kustomize. When I apply my Rails app, it crashes because it cannot find the environment vars:
I also tried to place a puts ENV['APP_PORT'] in application.rb but that one is nil
Rails Version & environment: 6.1.4.1 - development
! Unable to load application: KeyError: key not found: "APP_PORT"
Did you mean? "APP_HOME"
bundler: failed to load command: puma (/app/vendor/bundle/ruby/2.7.0/bin/puma)
KeyError: key not found: "APP_PORT"
Did you mean? "APP_HOME"
/app/config/environments/development.rb:2:in `fetch'
/app/config/environments/dev
when I change my image to image: nginx then the env vars are not there:
env
KUBERNETES_SERVICE_PORT_HTTPS=443
ELASTICSEARCH_PORT_9200_TCP_PORT=9200
KUBERNETES_SERVICE_PORT=443
ELASTICSEARCH_PORT_9200_TCP_ADDR=10.103.1.6
ELASTICSEARCH_SERVICE_HOST=10.103.1.6
HOSTNAME=myapp-backend-api-56b44c7445-h9g5m
ELASTICSEARCH_PORT=tcp://10.103.1.6:9200
PWD=/
ELASTICSEARCH_PORT_9200_TCP=tcp://10.103.1.6:9200
PKG_RELEASE=1~buster
HOME=/root
KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443
ELASTICSEARCH_SERVICE_PORT_9200=9200
NJS_VERSION=0.6.2
TERM=xterm
SHLVL=1
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
KUBERNETES_SERVICE_HOST=10.96.0.1
KUBERNETES_PORT=tcp://10.96.0.1:443
KUBERNETES_PORT_443_TCP_PORT=443
ELASTICSEARCH_SERVICE_PORT=9200
ELASTICSEARCH_PORT_9200_TCP_PROTO=tcp
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
NGINX_VERSION=1.21.3
_=/usr/bin/env
This is my current state:
kustomization.yml
kind: Kustomization
configMapGenerator:
- name: backend-api-configmap
files:
- .env
bases:
- ../../base
patchesStrategicMerge:
- api-deployment.yml
api-deployment.yml
apiVersion: apps/v1
kind: Deployment
spec:
template:
spec:
containers:
- image: nginx
imagePullPolicy: Never #imagePullPolicy: Never: the image is assumed to exist locally. No attempt is made to pull the image. envFrom:
- configMapRef:
name: backend-api-configma
That is the describe pod:
❯ k describe pod xxx-backend-api-56774c796d-s2zkd
Name: xxx-backend-api-56774c796d-s2zkd
Namespace: default
Annotations: <none>
Status: Running
IP: 172.17.0.6
IPs:
IP: 172.17.0.6
Controlled By: ReplicaSet/xxx-backend-api-56774c796d
Containers:
xxx-backend-api:
Container ID: docker://5ee3112b0805271ebe4b32d7d8e5d1b267d8bf4e220f990c085638f7b975c41f
Image: xxx-backend-api:latest
Image ID: docker://sha256:55d96a68267d80f19e91aa0b4d1ffb11525e9ede054fcbb6e6ec74356c6a3c7d
Port: 5000/TCP
Ready: False
Restart Count: 3
Environment Variables from:
backend-api-configmap-99fbkbc4c9 ConfigMap Optional: false
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-w5czc (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
kube-api-access-w5czc:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 55s default-scheduler Successfully assigned default/xxx-backend-api-56774c796d-s2zkd to minikube
Normal Pulled 8s (x4 over 54s) kubelet Container image "xxx-backend-api:latest" already present on machine
Normal Created 8s (x4 over 54s) kubelet Created container xxx-backend-api
Normal Started 8s (x4 over 54s) kubelet Started container xxx-backend-api
Warning BackOff 4s (x4 over 48s) kubelet Back-off restarting failed container
and that is the describe configmap
❯ k describe configmaps backend-api-configmap-99fbkbc4c9
Name: backend-api-configmap-99fbkbc4c9
Namespace: default
Labels: <none>
Annotations: <none>
Data
====
.env:
----
RAILS_MAX_THREADS=5
APPLICATION_URL=localhost:8000/backend
FRONTEND_URL=localhost:8000
APP_PORT=3000
BinaryData
====
Events: <none>

Answer 1

I got it:
Instead of using files: in my configMapGenerator I had to use envs: like so:
configMapGenerator:
- name: backend-api-configmap
envs:
- .env