Error with Job in Kubernestes(How to deploy rails app with Kubernentes?)

1/15/2020

I made my project with rails + mysql + vue.js + webpacker.

Then I made Dockerfile and docker-compose.yml, so i can run it in localhost.

Now I want to deploy them with K8s, but I have a problem with Job in K8s. Actually this is my first time to work with K8s, so if there is something missing or something wrong, please let me know what i need to do. Here's my Dockerfile and ymls.

ps. khjoo19/line-manager:v1 is my docker image uploaded to docker hub.

Dockerfile

FROM ruby:2.5.5
ENV LANG C.UTF-8
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs && \
    curl -sL https://deb.nodesource.com/setup_7.x | bash - && \
    apt-get install nodejs

RUN apt-get update && apt-get install -y curl apt-transport-https wget && \
    curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - && \
    echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list && \
    apt-get update && apt-get install -y yarn && \
    gem install bundler

WORKDIR /tmp
COPY Gemfile Gemfile
COPY Gemfile.lock Gemfile.lock
RUN bundle install

COPY entrypoint.sh /usr/bin/
RUN chmod +x /usr/bin/entrypoint.sh
ENTRYPOINT [ "entrypoint.sh" ]

ENV APP_HOME /line_manager
RUN mkdir -p $APP_HOME
WORKDIR $APP_HOME
COPY . /line_manager
RUN yarn upgrade

docker-compose.yml

version: '3'
services:
  db:
    image: mysql:5.7
    environment:
      DB_USER: root
      DB_ROOT_PASSWORD: password
      DB_PASSWORD: password
      DB_HOST: db

  webpacker:
    build: .
    command: bundle exec bin/webpack-dev-server
    volumes:
      - .:/line_manager
    ports:
      - "8080:8080"

  web:
    build: .
    command: /bin/sh -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    volumes:
      - .:/line_manager
    environment:
      DB_USER: root
      DB_ROOT_PASSWORD: password
      DB_PASSWORD: password
      DB_HOST: db
      RAILS_ENV: development
    ports:
      - "3000:3000"
    depends_on:
      - db
      - webpacker
    tty: true
    stdin_open: true

mysql.yml (K8s)

apiVersion: v1
kind: Service
metadata:
  namespace: line-manager
  name: db
  labels:
    app: web
spec:
  selector:
    app: web
  clusterIP: None
  ports:
    - port: 3306
---
kind: PersistentVolume
apiVersion: v1
metadata:
  namespace: line-manager
  name: db-pv
  labels:
    app: web
spec:
  capacity:
    storage: 20Gi
  accessModes:
  - ReadWriteOnce
  storageClassName: standard
  hostPath:
    path: "/tmp/mysql"
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  namespace: line-manager
  name: db-pvc
  labels:
    app: web
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
  storageClassName: standard
---
apiVersion: apps/v1
kind: Deployment
metadata:
  namespace: line-manager
  name: db
  labels:
    app: web
spec:
  selector:
    matchLabels:
      app: web
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: mysql
        image: mysql:5.7.17
        envFrom:
        - configMapRef:
            name: rails-config
        ports:
        - containerPort: 3306
          name: db
        volumeMounts:
        - name: db-pv
          mountPath: /var/lib/mysql
      volumes:
      - name: db-pv
        persistentVolumeClaim:
          claimName: db-pvc

rails-config.yaml(K8s)

apiVersion: v1
kind: ConfigMap
metadata:
  namespace: line-manager
  name: rails-config
data:
  RAILS_ENV: 'development'
  DB_HOST: 'db'
  DB_USER: 'root'
  DB_ROOT_PASSWORD: 'password'
  DB_PASSWORD: 'password'

rails-job.yaml(K8s)

apiVersion: batch/v1
kind: Job
metadata:
  namespace: line-manager
  name: web-job
  labels:
    app: web
spec:
  template:
    metadata:
      namespace: line-manager
      name: web-job
      labels:
        app: web
    spec:
      containers:
      - name: web-job
        image: khjoo19/line-manager:v1
        imagePullPolicy: Always
        command: ["/bin/sh"]
        args: ["-c", "bundle exec rake db:create && bundle exec rake db:migrate"]
        envFrom:
        - configMapRef:
            name: rails-config
      restartPolicy: Never
-- Realpro
docker
kubernetes
mysql
ruby-on-rails

1 Answer

1/15/2020

I applied your deployments and first I saw was mysql database crashing. After checking logs with kubectl logs -n line-manager <db-pod-name> I saw this:

error: database is uninitialized and password option is not specified 
  You need to specify one of MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD and MYSQL_RANDOM_ROOT_PASSWORD

So I added MYSQL_ROOT_PASSWORD: 'password' to rails-config configmap and it started working.

Then I deployed web-job job and saw it was also crashing so I checked the logs:

...
Mysql2::Error: No database selected
...

In the container khjoo19/line-manager:v1 in ./config/database.yml file I have found this line: database: <%= ENV['DB_DATABASE'] %> which suggests the code is trying to load DB name from DB_DATABASE environment variable which wasn't being set anywhere so I added this env variable to rails-config:

apiVersion: v1
kind: ConfigMap
metadata:
  namespace: line-manager
  name: rails-config
data:
  ...
  DB_DATABASE: 'database'

and then it worked and job completed successfully.

Let me know if it helped.

-- HelloWorld
Source: StackOverflow