TinyNote - A Phoenix/Livebook/Docker Demo

This repo is a demonstration of running livebook alongside a phoenix app in docker.

We can then use livebook to run code on the phoenix server.

Setup

• Run docker-compose up
• Open http://localhost:4000/users/register and create an account
• Open http://localhost:4000/notes and create a few notes
• Look in the logs for the livebook container to find the livebook URL (docker-compose logs -f livebook)
• Open the livebook URL
• Click "Open" in the top-right, and select example-notebook.livemd
• From a notebook, you can run code in the phoenix node, like TinyNote.Accounts.get_user!(1)

How it works

In docker-compose.yml, we define three services:

• postgres: the postgres database the app will use
• tiny_note: the phoenix application
• livebook: an instance of livebook

tiny_note is started through the start-dev.sh script, which sets the erlang node name (--name) and the secret cookie (--cookie).

livebook is configured to use tiny_note as it's default runtime, via the LIVEBOOK_DEFAULT_RUNTIME env-var. The value takes the form of attached:{node-name}:{cookie}, where {node-name} and {cookie} must match the values we set in start-dev.sh.

In addition, the livebook/ directory is mounted into the livebook container, so we can persist notebook files.

When we open the livebook UI and evaluate some code, it is actually evaluated in the phoenix app node, so we have access to all the modules of our app, and can access the database via ecto.

Notes

• Apparently, for the 'attached' runtime to work, the versions of OTP used by livebook and the other node (in this case, phoenix) must match.