Launching the Rails app

Run 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.

What does docker-compose up do?

When you run docker-compose up, Compose makes sure that the necessary resources have been set up, creating any that are missing before launching a container for each service. Specifically, it:

1. creates a separate network just for the app;
2. creates any non-locally mounted volumes defined for the app;
3. builds an image for any services with a build directive;
4. creates a container for each service;
5. launches a container per service.

Pretty impressive for a single command! Let’s run and then observe the results:

Reminder: The image building will take time. In case the terminal gets disconnected, click the Run button again.