How to build a Ruby On Rails project in Codefresh

Ruby on Rails is a very popular development framework that combines ease of use and a great amount of programming languages. In Codefresh, ROR projects behave like any other web application. You can easily build them, run integration tests and launch them on demo environments.

The example application is located at

Dockerize your Ruby on Rails project

The first step should be to write a Dockerfile for your Rails project. As an example we will use the following:


FROM ruby:2.3.1-slim

RUN apt-get update && \
    apt-get install -y build-essential libcurl4-openssl-dev libxml2-dev libsqlite3-dev libpq-dev nodejs postgresql-client sqlite3 --no-install-recommends && \ 
    apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*

# throw errors if Gemfile has been modified since Gemfile.lock
RUN bundle config --global frozen 1

ENV APP_PATH /usr/src/app

RUN mkdir -p $APP_PATH

COPY Gemfile.lock $APP_PATH


RUN bundle install


ENV RAILS_ENV development

RUN bin/rake db:migrate 

RUN bin/rake assets:precompile


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

Notice the order of commands and especially the fact that we copy the Gemfile on its own first, so that we take advantage of the Docker layer caching.

Codefresh also supports multi-stage docker builds. You can use one parent docker image for preparing your gem modules and another one for actually deployment the application.

Once you have a Dockerfile, creating a pipeline in Codefresh is very easy either from the GUI or with the yaml syntax.

Simple pipeline with Docker image and unit tests

A very simple pipeline is one that has only two steps:

  1. We build the docker image
  2. We run the tests inside the docker image that was just build

Here is the example codefresh.yml file.


version: '1.0'
    title: Building Docker Image
    type: build
    image_name: ruby-on-rails-sample-app
    working_directory: ./
    dockerfile: Dockerfile
    title: Running Unit Tests
    image: '${{BuildingDockerImage}}'
      - rails db:migrate
      - rails test

The first step is a build step named BuildingDockerImage. It reads the Dockerfile and creates a Docker image out of it. The second step is a freestyle step called RunningUnitTests. It uses the image mentioned in the first step and executes custom commands inside it.

Inspecting your Docker image

All Codefresh accounts come with a built-in Docker registry. Codefresh automatically pushes the last successful image of a pipeline to this internal registry.

You can see all your latest Docker artifacts by selecting Images from the left sidebar

Codefresh built-in Registry

Codefresh built-in Registry

You can click on the image and get extra details. One of the tabs contains a visual explanation of the layers contained in the image. This view can be helpful when you are trying to make your Docker images smaller (which is a recommended practice)

Ruby On Rails image filesystem layers

Ruby On Rails Image filesystem layers

In Codefresh you can also use any other external registry such as Dockerhub, Azure, Google etc.

Previewing the Ruby on Rails application in a Demo environment

Codefresh has the unique capability of launching Docker images within its infrastructure for a quick demonstration (e.g. to customers and colleagues).

In the example Rails repository the default development “environment” is self-contained (it uses sqlite for a database). This makes it very easy to preview.

Launch the environment by clicking at the rocket icon in the images view.

Launching a demo environment

Launching a demo environment

A new build will start. Once it is complete your new environment will be created. You can inspect it by clicking in the Docker Swarm menu on the left sidebar and then clicking Environments.

Inspecting a demo environment

Inspecting a demo environment

Click the Open App icon on the right and your browser will open a new tab with the environment.

Previewing a demo environment

Previewing a demo environment

You can share this link with other people in your team.

Demo environments are not intended for production purposes. Use them only for quick feedback. They also shut-down automatically after a period of inactivity.