LiteFS

This is a technology preview. It shows how to do multi-region deployments using Sqlite3 and Litefs. See LiteFS - Distributed SQLite for background.

In order to run this demo, you need flyctl to be version 0.1.9 or later.

Deploying a Rails project as a Fly.io Machine

Let’s start with a very simple Rails project:

rails new list
cd list
bin/rails generate scaffold Name name
echo 'Rails.application.routes.draw {root "names#index"}' >> config/routes.rb

Launching this will require a litefs configuration file (litefs.yml) and a number of changes to your dockerfile. Fly.io provides a dockerfile generator which will do this for you. Run it immediately after fly launch thus:

fly launch
bin/rails generate dockerfile --litefs

fly launch will prompt you for a name, region, and whether or not you want postgres or redis databases. Say no to the databases, you won’t need them for this demo.

generate dockerfile will prompt you whether or not you want to accept the changes. Feel free to peruse the diffs, but ultimately accept the changes. If you would rather not even be prompted to see the diffs, you can add a --force option the command.

Before we deploy, let’s make a one-line change to our fly.toml to keep our machines running so that we can ssh into them whenever we want:

  auto_stop_machines = false

Now we can deploy normally:

fly deploy

Once the application has been deployed, running fly apps open will open a browser. Add one name.

Return back to your terminal window and run:

fly machines list -q

You will see that only one copy of your application is running. You can deploy a second machine in a different region using:

fly machine clone --region lhr 3d8d9930b32189

Feel free to pick a different region. Substitute the machine id with the one that you see in the response to fly machines list -q. Once both instances are running, enter the following command and select the instance that is furthest from you:

% fly ssh console -s
? Select VM:  [Use arrows to move, type to filter]
  atl: 3d8d9930b32189 fdaa:0:d445:a7b:e5:b340:6b3d:2 autumn-breeze-5346
> lhr: e784e90ea17928 fdaa:0:d445:a7b:13e:8621:f8bd:2 muddy-moon-3291

Once you see a prompt, verify that you landed where you expected:

printenv FLY_REGION

Now run rails console and display the last name:

% /rails/bin/rails console
Loading production environment (Rails 7.0.4)
irb(main):001:0> Name.last

Return to the browser and change the value of this name, and then once again use the rails console to verify that the name has been updated.

Current limitations

• What Litefs Can Do Today describes current capabilities and future plans.