Docker for Rails Developers

Launching Our App

With our docker-compose.yml in hand, Compose is now set up to manage our application. However, before we start our app, first a tiny bit of housekeeping. By default, Ruby buffers output to stdout, which doesn’t play well with Compose.^[21] Let’s fix this by switching off Ruby’s output buffering.

Add the following line to the top of your config/boot.rb file:

$stdout.sync = true

With that out of the way, we’re ready to launch our app. Instead of the long docker run command, we can now use:

$ docker-compose up

Before we go through the output, let’s discuss what this command does.

When you run docker-compose up, Compose makes sure that the necessary resources have been set up, creating any that are missing before ...