# we're saying to put the data in /var/lib/postgresql/data. # PostgreSQL has to put its data somewhere. # often use when Dockerizing development environments. # very lightweight Linux distribution that people # image that uses the Alpine Linux distribution, # Docker Hub hosts images of common services for # We give each service an arbitrary name. In this case there's only one: PostgreSQL. # The "services" directive lists all the services your I’ve annotated the file to help you understand what’s what. This file, again, is what specifies our development environment’s dependencies. It’s called docker-compose.yml and goes at the project root. $ rails new my_app -d postgresql Adding a Docker Compose config file Initializing the Rails appīefore we do anything Docker-related, let’s initialize a new Rails app that uses PostgreSQL. Docker Compose is a tool that a) lets you specify and configure your development environment’s dependencies, b) installs those dependencies for you, and c) runs those dependencies. In order to Dockerize our database we’re going to use Docker Compose. So I want to be clear that this Docker setup is for development only. We’d have a separate database server instead. In a production environment we wouldn’t run PostgreSQL and a Rails server on the same machine. Development environments and production environments of course have vastly different needs and so a different Docker setup is required for each. There are two ways to Dockerize an app: for a development environment and for a production environment.
The Docker setups I’ve been discussing so far are all development setups. I’m doing it this way in the interest of showing the simplest possible example. Rather than Dockerizing PostgreSQL and Redis, we’re only going to Dockerize PostgreSQL. The example I’m going to show you shortly is an even simpler case.
New rails postgres app full#
This makes it so I don’t have to live with the downsides of full Dockerization but I still get to skip installing some of my dependencies.
New rails postgres app install#
I install all my other dependencies manually. I let Docker handle my PostgreSQL and Redis dependencies. The Docker setup I use at work is a hybrid approach. None of these obstacles is insurmountable, but if you don’t want to deal with these issues, you can choose to Dockerize just some of your app’s dependencies instead of all of them. When working with a Dockerized app, there’s a performance hit, there are some issues with using binding.pry, and system specs/system tests in such a way that you can see them run in a browser is next to impossible. Unfortunately, fully Dockerizing a Rails app isn’t without trade-offs. If you want to, you can create a Docker setup that will make it so you don’t have to install anything manually: no Ruby, no Rails, no RVM, no PostgreSQL, no Redis, nothing. This ideal is in fact possible if you fully Dockerize your app. It would be really nice if that developer could just run a single command and have all that app’s dependencies installed on their computer rather than having to install dependencies manually. Part of the tedium is the chore of manually installing all the dependencies: Ruby, RVM, Rails, PostgreSQL, Redis, etc. Getting a new developer set up with a Rails app (or any app) can be tedious. Why to Dockerize your database Dockerizing helps ease the pain of dependencies
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