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Docker-Rails

Simple Rails 6 application to demonstrate using Docker for production deployment. The application is a very simple kind of CMS (content management system) allowing to manage posts. Beside the boring CRUD functionality it has some non-default features.

This project aims to build a lean Docker image for use in production. Therefore it's based on the official Alpine Ruby image, uses multi-stage building and some optimizations that I described in my blog. This results in an image size of ~80MB.

Features

• Auto refresh via ActionCable: If a displayed post gets changed by another user/instance, it refreshes automatically using the publish/subscribe pattern
• Full text search via Elasticsearch and the Searchkick gem to find post content (with suggestions)
• Autocompletion with autocompleter
• Editing HTML content with the WYSIWYG JavaScript editor Trix
• Uploading images directly to S3 with the Shrine gem and jQuery-File-Upload
• Background jobs with ActiveJob and the Sidekiq gem (to handle full text indexing, image processing and ActionCable broadcasting)
• Cron scheduling with Sidekiq-Cron to handle daily data updates from Wikipedia
• Permalinks using the FriendlyId gem
• Infinitive scrolling (using the Kaminari gem and some JavaScript)
• User authentication with the Clearance gem
• Sending HTML e-mails with Premailer and the Really Simple Responsive HTML Email Template
• Admin dashboards with Blazer gem
• JavaScript with Stimulus
• Bundle JavaScript libraries with Yarn

Why?

This project demonstrates my way of building Rails applications. The techniques used to build the app should not be considered as "best practice", maybe there are better ways to build. Any feedback would be appreciated.

Multi container architecture

There is a separate docker-compose.yml for development and production. The whole stack is divided into multiple different containers:

• app: Main part. It contains the Rails code to handle web requests (by using the Puma gem). See the Dockerfile for details. The image is based on the Alpine variant of the official Ruby image and uses multi-stage building.
• worker: Background processing. It contains the same Rails code, but only runs Sidekiq
• db: PostgreSQL database
• elasticsearch: Full text search engine
• redis: In-memory key/value store (used by Sidekiq, ActionCable and for caching)
• backup: Regularly backups the database as a dump via CRON to an Amazon S3 bucket

Check it out!

To start up the application in your local Docker environment:

git clone https://github.com/ledermann/docker-rails.git
cd docker-rails
docker-compose build
docker-compose run app yarn install
docker-compose up

Wait some minutes while the database will be prepared by fetching articles from Wikipedia. Then, navigate your browser to http://[DOCKER_HOST]:[DOCKER_PORT].

Sign in to the admin account:

• Username: admin@example.org
• Password: secret

Enjoy!

Tests / CI

On every push, the test suite (including RuboCop checks) is performed via GitHub Actions. If successful, a production image is built and pushed to a private GitLab Docker Registry.

Production deployment

The Docker image build for production is different from development. It includes precompiled assets only (no node_modules and no sources). The spec folder is removed and the Alpine packages for Node and Yarn are not installed.

The stack is ready to host with traefik or nginx proxy and letsencrypt-nginx-proxy-companion. See docker-compose.production.yml for example setup.

Demo

A demo installation is set up on https://docker-rails.georg-ledermann.de.