Bad Gateway in Rails app with Kubernetes setup - kubernetes

Question

I try to setup a Rails app within a Kubernetes Cluster (which is created with k3d on my local machine.
k3d cluster create --api-port 6550 -p "8081:80#loadbalancer" --agents 2
kubectl create deployment nginx --image=nginx
kubectl create service clusterip nginx --tcp=80:80
# apiVersion: networking.k8s.io/v1beta1 # for k3s < v1.19
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: nginx
annotations:
ingress.kubernetes.io/ssl-redirect: "false"
spec:
rules:
- http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: nginx
port:
number: 80
I can get an Ingress running which correctly exposes a running Nginx Deployment ("Welcome to nginx!")
(I took this example from here: https://k3d.io/usage/guides/exposing_services/
So I know my setup is working (with nginx).
Now, I simpy wanna point that ingress to my Rails app, but I always get an "Bad Gateway". (I also tried to point to my other services (elasticsearch, kibana, pgadminer) but I always get a "Bad gateway".
I can see my Rails app running at (http://localhost:62333/)
last lines of my Dockerfile:
EXPOSE 3001:3001
CMD rm -f tmp/pids/server.pid && bundle exec rails s -b 0.0.0.0 -p 3001
Why is my API has the "bad gateway" but Nginx not?
Does it have something to do with my selectors and labels which are created by kompose convert?
This is my complete Rails-API Deployment:
kubectl apply -f api-deployment.yml -f api.service.yml -f ingress.yml
api-deployment.yml
apiVersion: apps/v1
kind: Deployment
metadata:
annotations:
kompose.cmd: kompose convert -c --file metashop-backend/docker-compose.yml --file metashop-backend/docker-compose.override.yml
kompose.version: 1.22.0 (HEAD)
creationTimestamp: null
labels:
io.kompose.service: api
name: api
spec:
replicas: 1
selector:
matchLabels:
io.kompose.service: api
strategy:
type: Recreate
template:
metadata:
annotations:
kompose.cmd: kompose convert -c --file metashop-backend/docker-compose.yml --file metashop-backend/docker-compose.override.yml
kompose.version: 1.22.0 (HEAD)
creationTimestamp: null
labels:
io.kompose.network/metashop-net: 'true'
io.kompose.service: api
spec:
containers:
- env:
- name: APPLICATION_URL
valueFrom:
configMapKeyRef:
key: APPLICATION_URL
name: env
- name: DEBUG
value: 'true'
- name: ELASTICSEARCH_URL
valueFrom:
configMapKeyRef:
key: ELASTICSEARCH_URL
name: env
image: metashop-backend-api:DockerfileJeanKlaas
name: api
ports:
- containerPort: 3001
resources: {}
# volumeMounts:
# - mountPath: /usr/src/app
# name: api-claim0
# restartPolicy: Always
# volumes:
# - name: api-claim0
# persistentVolumeClaim:
# claimName: api-claim0
status: {}
api-service.yml
apiVersion: v1
kind: Service
metadata:
annotations:
kompose.cmd: kompose convert -c --file metashop-backend/docker-compose.yml --file metashop-backend/docker-compose.override.yml
kompose.version: 1.22.0 (HEAD)
creationTimestamp: null
labels:
app: api
io.kompose.service: api
name: api
spec:
type: ClusterIP
ports:
- name: '3001'
protocol: TCP
port: 3001
targetPort: 3001
selector:
io.kompose.service: api
status:
loadBalancer: {}
ingress.yml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: api
annotations:
ingress.kubernetes.io/ssl-redirect: "false"
spec:
rules:
- http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: api
port:
number: 3001
configmap.yml
apiVersion: v1
data:
APPLICATION_URL: localhost:3001
ELASTICSEARCH_URL: elasticsearch
RAILS_ENV: development
RAILS_MAX_THREADS: '5'
kind: ConfigMap
metadata:
creationTimestamp: null
labels:
io.kompose.service: api-env
name: env
I hope I didn't miss anything.
thank you in advance
EDIT: added endpoint, requested in comment:
kind: endpoint
kind: Endpoints
apiVersion: v1
metadata:
name: api
namespace: default
labels:
app: api
io.kompose.service: api
selfLink: /api/v1/namespaces/default/endpoints/api
subsets:
- addresses:
- ip: 10.42.1.105
nodeName: k3d-metashop-cluster-server-0
targetRef:
kind: Pod
namespace: default
apiVersion: v1
ports:
- name: '3001'
port: 3001
protocol: TCP

Answer 1

The problem was within the Dockerfile:
I had not defined ENV RAILS_LOG_TO_STDOUT true, so I was not able to see any errors in the pod logs.
After I added ENV RAILS_LOG_TO_STDOUT true I saw errors like database xxxx does not exist