#New rails postgres app apk
#New rails postgres app install

The reason we don’t just the entire directory contents to the image in this step is that it means anytime we change our application files, Docker will consider the image out-of-date. What we’re doing here is adding only our Gemfile and Gemfile.lock files to /app and then running bundle install.

#New rails postgres app install

RUN gem install rails -v '5.1.6' WORKDIR /appĪDD Gemfile Gemfile.

#New rails postgres app apk

FROM ruby :alpine RUN apk add -update build -base postgresql -dev tzdata

So to fix this, we need to make sure our base image has these gems installed. We did this because all we needed to accomplish was getting the Gemfile's onto our local filesystem using the volume mount we setup. This is complicated because when we ran rails new just now, it installed a bunch of gems and generated files inside of a temporary filesystem. However, when using Docker + Docker Compose, gems must be installed inside of the image instead since it has a separate filesystem. So when you run commands such as rails server it loads the gems locally. When using a traditional development style Bundler installs gems onto your local filesystem. One of the caveats of developing with Docker Compose and Rails is how gems work. Īfter this has completed successfully, our directory should be filled with all of the necessary files and folders for a simple rails application and a generated Gemfile and Gemfile.lock. $ docker -compose run web rails new -database =postgresql - J -skip -coffee. We're going to skip javascript related configuration as well. Let's generate our application with configuration to use Postgres as its database. Once we have our modifications in place, we can scaffold our rails application using rails new. Next, we need to modify our docker-compose.yml to add volumes and a working directory: This will re-build our image with the Rails gem inside of it so we can easily run rails new here in a second. It now looks like: FROM ruby :alpine RUN apk add -update build -base postgresql -dev tzdataĪfter you’ve added this modification to the file, run: Let’s modify our Dockerfile first to install Rails inside of the container. This allows us to generate the files from inside of web and have them appear on our local file system. To do this inside of our container, we need to mount our local file system inside of the web container we've set up. Next, we need to initialize our Rails project using rails new. This should pull down the Ruby alpine image and install our runtime dependencies on top of it. Once you’ve created this file, let’s try running: It also uses the current directory for context when building the image. as the value for the build config, compose automatically assumes there's a Dockerfile present in the directory. Now we need to reference this Dockerfile from a docker-compose.yml file:

Tzdata is used by Rails for timezone information when available so we install it here. The postgresql-dev package is used when installing the pg gem. Since gems like nokogiri are native extensions and are compiled when doing gem install nokogiri, this is necessary. The build-base package which contains the necessary tools for compiling things from source. Alpine linux is a much smaller base image and ideal for working with to keep things compact. Once in this directory, create a file called Dockerfile with this content: FROM ruby :alpine RUN apk add -update build -baseįROM ruby:alpine tells Docker to derive our image off of the latest Ruby image with the Alpine distribution. I like creating my projects in my ~/Sites folder: To create our initial rails project with rails new we need to set up a simple Dockerfile with our basic environment in it. In this tutorial we’re going to run basically all commands inside of the Docker containers that Docker Compose spins up for us. Basic knowledge of Docker is also helpful. It also uses version 3.6 compose file syntax. This tutorial was built using Docker Compose 1.20.1. Running tasks like gem installation and migrations Setting up a new Rails application in Docker Compose It allows you to easily isolate your ruby environment, database, and even Redis if you use something like Sidekiq. Docker Compose is a great tool to develop your Ruby on Rails application locally.