Deploy Rails on Docker to heroku

Practice deploying to heroku

If you build a Rails application on a Dcoker container and use Circleci to do automatic deployment at once Now that I've entered the labyrinth, I'm going to return to the origin. (2nd)

My environment

Ruby : 2.6.6 rails : git : 2.23.0 heroku-cli : 7.42.13 darwin-x64 node-v12.16.2 Docker : 19.03.12

Development environment is MySQL I will try to build a production environment with a pattern called PostgreSQL.

Prepare a Rails application on your Docker

First, create a directory to create the application, and prepare various necessary items with the touch command there.


$ touch {Dockerfile,docker-compose.yml,Gemfile,Gemfile.lock,}


FROM ruby:2.6

RUN curl -sS | apt-key add - \
    && echo "deb stable main" | tee /etc/apt/sources.list.d/yarn.list \
    && apt-get update -qq \
    && apt-get install -y nodejs yarn \
    && mkdir /heroku_app
WORKDIR /heroku_app

COPY Gemfile //Gemfile
COPY Gemfile.lock /heroku_app/Gemfile.lock
RUN bundle install
COPY . /heroku_app

COPY /usr/bin/
RUN chmod +x /usr/bin/

CMD ["rails", "server", "-b", ""]


version: '3'
    image: mysql:8.0
      MYSQL_ROOT_PASSWORD: password
      - '3306:3306'
    command: --default-authentication-plugin=mysql_native_password
      - mysql-data:/var/lib/mysql:cached
    build: .
    command: bash -c "rm -f tmp/pids/ && bundle exec rails s -p 3006 -b ''"
      - .:/heroku_app
      - "3006:3000"
      - db
    stdin_open: true
    tty: true
    command: bundle exec rails server -b
    driver: local


source ''
rails ‘6.0.3’

set -e
# Remove a potentially pre-existing for Rails.
rm -f /heroku_app/tmp/pids/
# Then exec the container's main process (what's set as CMD in the Dockerfile).
exec "$@"

If you can prepare the above 5 points, execute the following command to create a Rails application.


$docker-compose run web rails new . --force --no-deps --database=mysql

At the same time, make a textual content.

$ docker-compose run web rails g scaffold blog title:string body:text
$ docker-compose run web rails db:migrate
$ docker-compose up -d

スクリーンショット 2020-09-09 0.00.04.png

Ready to deploy to heroku

Next, prepare postgreSQL for your production environment before deploying your Rails app to heroku. --config / database.yml settings --Add pg to Gemfile --Settings in config / environments / deviropment.rb

config / database.yml settings


  <<: *default
  adapter: postgresql
  encoding: unicode
  pool: 5

Gemfile settings

Prepare the gem file for the production environment. Add pg to the production group. Also, move MySQL into `group: development,: test do` so that it will be treated as a development environment.


group :production do
  gem 'pg', '~> 0.19.0'

Settings in config / environments / deviropment.rb

It is peculiar to Rails6, but it seems that it has protection from DNS detachment binding attacks, You need to put in the host.


config.hosts << ""

I referred to the following article.

After editing, build.


docker-compose build
$docker-compose run web rails db:create
$docker-compose up -d

After that, type a command and deploy to Runrun and heroku.

$ docker-compose down #If you do not drop it once, an error may occur.
$ heroku login
$heroku create app name or blank
$ heroku container:login
$ heroku container:push web
$ heroku adding:create heroku-postgresql:hobby-dev
$ heroku container:release web
$ heroku open

スクリーンショット 2020-09-09 10.44.50.png

the end!

I omitted it, but an error occurred when deploying to heroku. In that case, I typed $ heroku logs --tail etc. on the terminal to check the error and solve it. Even if you refer to a successful article, an error may occur due to differences in the environment, so I thought it was important to get into the habit of checking each time for understanding.

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