I'm trying to get my dokerized Rails app to run on Kubernetes hosted at GCP.

kubectl apply -f k8s/webshop.yml
kubectl get pods
NAME                      READY     STATUS             RESTARTS   AGE
shop-lcvxc   2/3       CrashLoopBackOff   23         1h

So far so good, but the app will not start. Investigating further reveals that it has tried to start Rails (Puma) twice. Any idea why this happens?

Logs

$ kubectl logs shop-lcvxc -c webshop

=> Booting Puma
=> Rails 5.2.0 application starting in development
=> Run `rails server -h` for more startup options
initialize PushNotifications
Puma starting in single mode...
* Version 3.11.4 (ruby 2.4.4-p296), codename: Love Song
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://0.0.0.0:3001
Exiting
/usr/local/bundle/gems/puma-3.11.4/lib/puma/binder.rb:270:in `initialize': 
Address already in use - bind(2) for "0.0.0.0" port 3001 (Errno::EADDRINUSE)

$ kubectl logs shop-lcvxc -c app

=> Booting Puma
=> Rails 5.2.0 application starting in development
=> Run `rails server -h` for more startup options
initialize PushNotifications
Puma starting in single mode...
* Version 3.11.4 (ruby 2.4.4-p296), codename: Love Song
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://0.0.0.0:3001
Use Ctrl-C to stop

k8s/webshop.yml

  1 # from https://cloud.google.com/sql/docs/postgres/connect-kubernetes-engine
  2 apiVersion: extensions/v1beta1
  3 kind: Deployment
  4 metadata:
  5   name: webshop
  6   labels:
  7     app: webshop
  8
  9 spec:
 10   template:
 11     metadata:
 12       labels:
 13         app: webshop
 14     spec:
 15       containers:
 16         - name: app
 17           image: eu.gcr.io/company/webshop:latest
 18           ports:
 19             - containerPort: 3000
 20           # The following environment variables will contain the database host,
 21           # user and password to connect to the PostgreSQL instance.
 22           env:
 23             - name: POSTGRES_HOST
 24               value: 127.0.0.1:5432
 25             - name: POSTGRES_DB
 26               value: webshop-staging
 27             # [START cloudsql_secrets]
 28             - name: POSTGRES_USER
 29               valueFrom:
 30                 secretKeyRef:
 31                   name: cloudsql-db-credentials
 32                   key: username
 33             - name: POSTGRES_PASSWORD
 34               valueFrom:
 35                 secretKeyRef:
 36                   name: cloudsql-db-credentials
 37                   key: password
 38             # [END cloudsql_secrets]
 39
 40         # [START proxy_container]
 41         - name: cloudsql-proxy
 42           image: gcr.io/cloudsql-docker/gce-proxy:1.11
 43           command: ["/cloud_sql_proxy",
 44                     "-instances=company:europe-west1:staging=tcp:5432",
 45                     "-credential_file=/secrets/cloudsql/credentials.json"]
 46           volumeMounts:
 47             - name: cloudsql-instance-credentials
 48               mountPath: /secrets/cloudsql
 49               readOnly: true
 50         # [END proxy_container]
 51       # [START volumes]
 52       volumes:
 53         - name: cloudsql-instance-credentials
 54           secret:
 55             secretName: cloudsql-instance-credentials
 56       # [END volumes]
 57

Dockerfile

FROM XX.dkr.ecr.eu-west-1.amazonaws.com/webshop-bundled:1.3

COPY Gemfile* /app/
COPY . /app/

WORKDIR /app

CMD ["/usr/local/bundle/bin/rails", "s", "-b", "0.0.0.0", "-p", "3001"]

^ That image is from this image:

Dockerfile-bundled

FROM ruby:2.4-slim-jessie

RUN apt-get update
RUN apt-get install -y libpq-dev libgmp-dev libxml2-dev libxslt-dev
RUN apt-get install -y build-essential patch ruby-dev zlib1g-dev liblzma-dev

COPY Gemfile* /app/
WORKDIR /app
RUN bundle install

✗ kubectl describe pod shop-lcvxc

Name:           webapp-5845b768f7-tflbv
Namespace:      default
Node:           gke-my-fam-default-pool-12d29bdf-c9t0/10.166.0.3
Start Time:     Fri, 06 Jul 2018 08:18:16 +0200
Labels:         pod-template-hash=1401632493
                run=webapp
Annotations:    kubernetes.io/limit-ranger=LimitRanger plugin set: cpu request for container webapp
Status:         Running
IP:             10.4.0.6
Controlled By:  ReplicaSet/webapp-5845b768f7
Containers:
  webapp:
    Container ID:   docker://889fbc56fc28
    Image:          eu.gcr.io/acme-my-fam/webapp:latest
    Image ID:       docker-pullable://eu.gcr.io/acme-my-fam/webapp@sha256:nnnn
    Port:           8080/TCP
    State:          Running
      Started:      Fri, 06 Jul 2018 08:18:43 +0200
    Ready:          True
    Restart Count:  0
    Requests:
      cpu:        100m
    Environment:  <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-bs796 (ro)
Conditions:
  Type           Status
  Initialized    True
  Ready          True
  PodScheduled   True
Volumes:
  default-token-bs796:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-bs796
    Optional:    false
QoS Class:       Burstable
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason                 Age   From                                                 Message
  ----    ------                 ----  ----                                                 -------
  Normal  Scheduled              10m   default-scheduler                                    Successfully assigned webapp-5845b768f7-tflbv to gke-my-fam-default-pool-12d29bdf-c9t0
  Normal  SuccessfulMountVolume  10m   kubelet, gke-my-fam-default-pool-12d29bdf-c9t0  MountVolume.SetUp succeeded for volume "default-token-bs796"
  Normal  Pulling                10m   kubelet, gke-my-fam-default-pool-12d29bdf-c9t0  pulling image "eu.gcr.io/acme-my-fam/webapp:latest"
  Normal  Pulled                 10m   kubelet, gke-my-fam-default-pool-12d29bdf-c9t0  Successfully pulled image "eu.gcr.io/acme-my-fam/webapp:latest"
  Normal  Created                10m   kubelet, gke-my-fam-default-pool-12d29bdf-c9t0  Created container
  Normal  Started                10m   kubelet, gke-my-fam-default-pool-12d29bdf-c9t0  Started container