How to deploy Ruby and Node app on Heroku using Docker - Part 1

TL;DR

We needed to deploy a ruby+node application as a docker image on Heroku, but I didn’t use Heroku cli to build it. This document is about how we did the development, test, build, tag and deployment of a docker image on a Heroku application according to the best practices.

I will split this article into some parts. In this “Part 1” I will explain in details how I delivered the first version of a Dockerfile, without Multistage build, to create the docker image and Docker compose file to bring up the whole development environment.

Attention

If you copy and paste some codes shown here without reading the context, it may not work properly on your environment.

I will present the code, tell the story behind this phase and show how I improved it after seeing the problem.

Setup

To reproduce this article, you need to install these tools:

The environments

We have three environments:

Dockerization for developers first

I started this job providing docker environment to developers and getting feedbacks.

Here is my Dockerfile to developers:

FROM ruby:2.5.1 as builder

RUN curl -sL https://deb.nodesource.com/setup_8.x | bash - &&\
    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

RUN apt-get update \
    && apt-get install -y locales \
                        graphviz \
                        imagemagick \
                        postgresql-client-9.6 \
                        yarn \
                        nodejs \
    && echo "en_US.UTF-8 UTF-8" > /etc/locale.gen && /usr/sbin/locale-gen &&\
    rm -rf /var/lib/apt/lists/*

ENV GEM_HOME /gems/vendor
ENV GEM_SPEC_CACHE /gems/specs
ENV BUNDLE_APP_CONFIG /gems/vendor
ENV BUNDLE_PATH /gems/vendor
ENV BUNDLE_BIN /gems/vendor/bin
ENV PATH /app/bin:/gems/vendor/bin:$PATH
ARG RAILS_ENV
ENV RAILS_ENV=$RAILS_ENV

ENV APP_ROOT /app

WORKDIR $APP_ROOT/

RUN mkdir -p /gems

RUN groupadd -r app \
    && groupmod -g 1000 app \
    && useradd -g app -ms /bin/bash app \
    && chown app $APP_ROOT \ 
    && chown app /gems

USER app

COPY Gemfile.lock $APP_ROOT/
COPY Gemfile $APP_ROOT/
COPY package-lock.json $APP_ROOT/
COPY package.json $APP_ROOT/

RUN bundle install
RUN yarn install

EXPOSE 3000

CMD ["bundle","exec","rails","server","-b","0.0.0.0"]

This Dockerfile is responsible for setting up everything that we needed to start the development job.

We didn’t need to copy the code to docker context on the docker image creation phase. We mounted the source code inside the container on runtime:

docker build -t ruby_node_app:0.1 .
docker run -it --build-arg RAILS_ENV=development -v $PWD:/app ruby_node_app:0.1

The RAILS_ENV variable was used to change the gem installation behavior — some gems we didn’t need to install in production.

Dockefile, explained

We used this first section to set up the basis of this dev environment:

FROM ruby:2.5.1 as builder

RUN curl -sL https://deb.nodesource.com/setup_8.x | bash - &&\
    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

RUN apt-get update \
    && apt-get install -y locales \
                        graphviz \
                        imagemagick \
                        postgresql-client-9.6 \
                        yarn \
                        nodejs \
    && echo "en_US.UTF-8 UTF-8" > /etc/locale.gen && /usr/sbin/locale-gen &&\
    rm -rf /var/lib/apt/lists/*

We needed to use a specific folder of gems. We mounted this folder on runtime. It was a dev requirement to troubleshoot gem usage:

ENV GEM_HOME /gems/vendor
ENV GEM_SPEC_CACHE /gems/specs
ENV BUNDLE_APP_CONFIG /gems/vendor
ENV BUNDLE_PATH /gems/vendor
ENV BUNDLE_BIN /gems/vendor/bin

We needed to specify the app folder and create the app user to use root instead:

ENV APP_ROOT /app

WORKDIR $APP_ROOT/

RUN mkdir -p /gems

RUN groupadd -r app \
    && groupmod -g 1000 app \
    && useradd -g app -ms /bin/bash app \
    && chown app $APP_ROOT \ 
    && chown app /gems

USER app

We needed to install all ruby and node requirements:

COPY Gemfile.lock $APP_ROOT/
COPY Gemfile $APP_ROOT/
COPY package-lock.json $APP_ROOT/
COPY package.json $APP_ROOT/

RUN bundle install
RUN yarn install

In the end, we needed to specify the exposed port and default command:

EXPOSE 3000

CMD ["bundle","exec","rails","server","-b","0.0.0.0"]

Adding docker-compose

We needed to use some external resources (i.e., DB), to that, Docker-compose was used on this setup.

version: '3.4'
services:
  onboarding_app:
    working_dir: /app
    build:
      context: .
      args:
        RAILS_ENV: development
    env_file:
      - ./.env
    volumes:
      - .:/app
      - ./tmp/gems:/gems
      - onboarding_app_home:/home/app/
      - .irbrc:/home/app/.irbrc
    ports:
      - 3010:3000
    depends_on:
      - mailcatcher
      - postgres
      - redis
  mailcatcher:
    image: schickling/mailcatcher
    ports:
      - 1080:1080
  postgres:
    image: postgres:9.6-alpine
    ports:
      - 5432:5432
    volumes:
      - postgres:/var/lib/postgresql/data
  redis:
    image: redis:4.0.6-alpine
    volumes:
      - redis:/data
volumes:
  gems_2_5_1:
  postgres:
  redis:
  onboarding_app_home:

Run this command to bring up this environment:

docker-compose up --build

Docker-compose file, explained

We needed to send the RAILS_ENV argument to build process of docker image. This RAILS_ENV variable was used to install all the gems related to development environment:

build:
      context: .
      args:
        RAILS_ENV: development

We needed to inform the environment variable to be used on docker container execution:

    env_file:
      - ./.env

We mounted some folders to help coding and troubleshooting. I will explain one by one.

First, we needed to mount the source code:

    volumes:
      - .:/app

We needed to mount the folder used inside the docker image to add gems. This mounted folder is necessary to troubleshoot gem usage:

      - ./tmp/gems:/gems

We needed to persist some config of app user so that we mounted the home folder of app user and .irbrc file too:

      - onboarding_app_home:/home/app/
      - .irbrc:/home/app/.irbrc

To finish this service, we needed to publish the port used to connect on the application and inform which services it depends on:

    ports:
      - 3010:3000
    depends_on:
      - mailcatcher
      - postgres
      - redis

These services are being used to provide external resources to app service:

mailcatcher:
    image: schickling/mailcatcher
    ports:
      - 1080:1080
  postgres:
    image: postgres:9.6-alpine
    ports:
      - 5432:5432
    volumes:
      - postgres:/var/lib/postgresql/data
  redis:
    image: redis:4.0.6-alpine
    volumes:
      - redis:/data

Here we added the volumes used inside this docker-compose file:

volumes:
  gems_2_5_1:
  postgres:
  redis:
  onboarding_app_home:

To be continued…

Thanks

My co-workers at Paycertify who helped me giving me feedbacks and options to fix the problems, I need to say a special thanks to Rafael Affonso who enabled me to correct some mistakes about my English.


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