Introduction

We were developing using rails in the local environment, but in consideration of future deployment, we decided to manage the environment in a container with Docker. It took a long time for the first time, so I will leave it as a memorandum. I hope it will be helpful for those who need to build a similar environment.

Goals for building an environment

I want to containerize the local environment and make it easy when building the production environment.
I want to make the Docker image as light as possible in consideration of efficiency.
I want to reduce the startup time by making bundle and yarn modules persistent.
DB used sqlite, so I want to make it Mysql.

Built environment

Container configuration

db
web
webpacker ← for running webpack_dev_server

version

ruby 2.7.2
Rails 6.0.3
Mysql 8.0.22

List

Only the parts changed this time are listed. The root directory is the root directory of the rails app.

.
├── config
│   ├── database.yml    #update
│   └── webpacker.yml   #update
├── docker
│   └── rails
│       └── Dockerfile  #Create New
├── docker-compose.yml  #Create New
├── .env                #Create New
└── Gemfile             #update

Dockerfile

`Dockerfile`


#Alpine is used for weight reduction.
FROM ruby:2.7.2-alpine3.12

ENV TZ="Asia/Tokyo" \
    LANG="C.UTF-8" \
    APP_ROOT="/app" \
    ENTRYKIT_VERSION="0.4.0"

WORKDIR $APP_ROOT

#Introduction of ENTRY KIT
RUN wget https://github.com/progrium/entrykit/releases/download/v${ENTRYKIT_VERSION}/entrykit_${ENTRYKIT_VERSION}_Linux_x86_64.tgz \
    && tar -xvzf entrykit_${ENTRYKIT_VERSION}_Linux_x86_64.tgz \
    && rm entrykit_${ENTRYKIT_VERSION}_Linux_x86_64.tgz \
    && mv entrykit /bin/entrykit \
    && chmod +x /bin/entrykit \
    && entrykit --symlink

RUN apk update \
&&  apk add --no-cache \
    alpine-sdk \
    bash \
    build-base \
	mysql-client \
    mysql-dev \
    nodejs \
    tzdata \
    yarn

COPY . $APP_ROOT

ENTRYPOINT [ \
  "prehook", "bundle install -j4 --quiet", "--", \
  "prehook", "yarn install --check-files --ignore-optional", "--"]

Image weight reduction

Alpine is used to reduce the weight of the image for the efficiency of future work. The capacity has been reduced from about 1.6GB to about 400MB.

By using a multi-stage build and installing nodejs separately, it seems that the image can be further reduced in weight. I was able to reduce the weight to some extent, so this time I decided to stop.

Introduction of ENTRY KIT

I am using ENTRY KIT to execute yarn install and bundle install when the container is started. In the articles I examined, most of them were executed in the Dockerfile, but due to the following problems, I forgot this time.

If you need to add gem etc., you need to start over from the container build.
When the container is down, the installed gem etc. are not retained.

Therefore, it is configured to solve the above problem by executing it when the container is started and making the module persistent.

docker-compose.yml

`docker-compose.yml`


version: '3'

services:
  db:
    image: mysql:8.0.22
    command: mysqld --character-set-server=utf8 --collation-server=utf8_unicode_ci
    ports: 
      - '3306:3306'
    volumes:
      - db_data:/var/lib/mysql
    environment:
      MYSQL_DATABASE: ${DATABASE}
      MYSQL_ROOT_PASSWORD: ${ROOTPASS}
      MYSQL_USER: ${USERNAME}
      MYSQL_PASSWORD: ${USERPASS}

  web: &app_base
    build:
      context: .
      dockerfile: ./docker/rails/Dockerfile
    command: bash -c "rm -f tmp/pids/server.pid && bundle exec rails s -p 3000 -b 0.0.0.0"
    depends_on:
      - db
    ports:
      - "3000:3000"
    volumes:
      - .:/app
      - gem_modules:/vendor/bundle
      - node_modules:/node_modules
    tty: true            #binding.For pry execution
    stdin_open: true     #binding.For pry execution
    environment:
      WEBPACKER_DEV_SERVER_HOST: webpacker    #webpack_dev_Specify the container for server execution
      BUNDLE_APP_CONFIG: ./.bundle
      NODE_ENV: development
      RAILS_ENV: development

  webpacker:             #webpack_dev_container for server execution
    <<: *app_base
    command: bash -c "bundle exec bin/webpack-dev-server"
    depends_on:
      - web
    ports:
      - '3035:3035'
    tty: false           #binding.Change to false because pry is unnecessary
    stdin_open: false    #binding.Change to false because pry is unnecessary
    environment:
      BUNDLE_APP_CONFIG: ./.bundle
      WEBPACKER_DEV_SERVER_HOST: 0.0.0.0
      NODE_ENV: development
      RAILS_ENV: development

volumes:
  db_data:
  gem_modules:
  node_modules:

I wanted to keep the DB user information in a separate file, so I made it into a variable and described it in .env.
Even if the container is brought down, the data of DB and module is made persistent so that it will not be lost.

database.yml

`database.yml`


 default: &default
-  adapter: sqlite3
+  adapter: mysql2
+  username: app
+  password: password
+  host: db    #Specify the service name

 development:
   <<: *default
-  database: db/development.sqlite3
+  database: mysql_development

webpacker.yml

`webpacker.yml`


 default: &default
   dev_server:
-    host: localhost
+    host: webpack    #Specify the service name

Gemfile

`Gemfile`


-gem 'sqlite3', '~> 1.4'
+gem 'mysql2', '0.5.3'

.env

`.env`


DATABASE=mysql_development
USERNAME=app
USERPASS=password
ROOTPASS=password

Questions / things that could not be resolved

First container startup error (stack Error: getaddrinfo EAI_AGAIN nodejs.org)

An error may occur during yarn install when the container is started for the first time. As a result of investigation, it seems that the cause is that the name cannot be resolved by DNS.

I tried changing the DNS on the host side, which seems to be the solution, and specifying the DNS in docker-compose.yml, but it did not solve. The error did not occur at the second startup, and there was an article that the solution was to restart the container, so leave it as it is.

error /app/node_modules/node-sass: Command failed.
web_1        | Exit code: 1
web_1        | Command: node scripts/build.js
web_1        | Arguments: 
web_1        | Directory: /app/node_modules/node-sass
web_1        | Output:
web_1        | Building: /usr/bin/node /app/node_modules/node-gyp/bin/node-gyp.js rebuild --verbose --libsass_ext= --libsass_cflags= --libsass_ldflags= --libsass_library=
web_1        | gyp info it worked if it ends with ok
web_1        | gyp verb cli [
web_1        | gyp verb cli   '/usr/bin/node',
web_1        | gyp verb cli   '/app/node_modules/node-gyp/bin/node-gyp.js',
web_1        | gyp verb cli   'rebuild',
web_1        | gyp verb cli   '--verbose',
web_1        | gyp verb cli   '--libsass_ext=',
web_1        | gyp verb cli   '--libsass_cflags=',
web_1        | gyp verb cli   '--libsass_ldflags=',
web_1        | gyp verb cli   '--libsass_library='
web_1        | gyp verb cli ]
web_1        | gyp info using [email protected]
web_1        | gyp info using [email protected] | linux | x64
web_1        | gyp verb command rebuild []
web_1        | gyp verb command clean []
web_1        | gyp verb clean removing "build" directory
web_1        | gyp verb command configure []
web_1        | gyp verb check python checking for Python executable "python2" in the PATH
web_1        | gyp verb `which` succeeded python2 /usr/bin/python2
web_1        | gyp verb check python version `/usr/bin/python2 -c "import sys; print "2.7.18
web_1        | gyp verb check python version .%s.%s" % sys.version_info[:3];"` returned: %j
web_1        | gyp verb get node dir no --target version specified, falling back to host node version: 12.20.1
web_1        | gyp verb command install [ '12.20.1' ]
web_1        | gyp verb install input version string "12.20.1"
web_1        | gyp verb install installing version: 12.20.1
web_1        | gyp verb install --ensure was passed, so won't reinstall if already installed
web_1        | gyp verb install version not already installed, continuing with install 12.20.1
web_1        | gyp verb ensuring nodedir is created /root/.node-gyp/12.20.1
web_1        | gyp verb created nodedir /root/.node-gyp
web_1        | gyp http GET https://nodejs.org/download/release/v12.20.1/node-v12.20.1-headers.tar.gz
web_1        | gyp WARN install got an error, rolling back install
web_1        | gyp verb command remove [ '12.20.1' ]
web_1        | gyp verb remove using node-gyp dir: /root/.node-gyp
web_1        | gyp verb remove removing target version: 12.20.1
web_1        | gyp verb remove removing development files for version: 12.20.1
web_1        | gyp ERR! configure error 
web_1        | gyp ERR! stack Error: getaddrinfo EAI_AGAIN nodejs.org
web_1        | gyp ERR! stack     at GetAddrInfoReqWrap.onlookup [as oncomplete](dns.js:66:26)
web_1        | gyp ERR! System Linux 4.19.121-linuxkit
web_1        | gyp ERR! command "/usr/bin/node" "/app/node_modules/node-gyp/bin/node-gyp.js" "rebuild" "--verbose" "--libsass_ext=" "--libsass_cflags=" "--libsass_ldflags=" "--libsass_library="
web_1        | gyp ERR! cwd /app/node_modules/node-sass
web_1        | gyp ERR! node -v v12.20.1
web_1        | gyp ERR! node-gyp -v v3.8.0
web_1        | gyp ERR! not ok

Image weight reduction in multi-stage builds

I will try it when further efficiency is needed, such as shortening the time.

Finally

There was an article about building a new Rails app with Docker, but I had a hard time because there weren't many articles about containerizing existing Rails apps. Since it was built once as a development environment, we will consider and work on how to divide and build the test environment and production environment.

In addition, I would like to work on the following contents, so I will write an article if possible.

Introduction of nginx as a web server
Introduction of CI/CD
Environment construction on AWS

Articles that I used as a reference

** ・ How to create a Rails on Docker environment that is easy to develop --Qiita ** ** ・ From Rails new until it works in production mode --Qiita ** ** ・ Building Docker environment with Rails 6.0 x MySQL8 (Alpine base) --Qiita ** ** · More efficient with Docker Compose volumes-Qiita ** ** ・ [Dockerfile full explanation] Create the simplest Docker image for Rails production environment --Qiita ** ** ・ [Docker] I want to know about Rails development! Talk about improving work efficiency by making gem persistent | Enjoy IT Life ** ** ・ Points to keep in mind when building an environment with docker-compose --Qiita ** ** ・ Build Rails + webpacker on Docker environment with docker-compose --RoadMovie **

Migrate existing Rails 6 apps to Docker environment