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

Deploying a Rails Project as a Machine

Let's start with a very simple Rails project:

rails new list; cd list; bin/rails generate scaffold Name name

At this point you have two choices. You can run fly launch and follow the instructions in Getting Started with LiteFS which would require you to make the following modifications:

  • In Dockerfile, add FROM flyio/litefs:pr-109, fuse package, COPY --from=lite fs, COPY config/litefls.yml, mkdir /data. Change SERVER_COMMAND to litefs.
  • In lit/tasks/fly.rake, remove the release step.
  • In fly.toml, change SERVER_COMMAND to litefs, remove [deploy] section, set DATABASE_URL to "sqlite3:///data/production.sqlite3", add enable_consul to the [experimental] section, and add a [mount] section.
  • Add config/litefs.yml, with data-dir set to /mnt/volume and exec set to bin/rails fly:server.
  • create two volumes with the same name and in two different regions.

Or you could install a gem which will do all of the above:

bundle add
bin/rails generate fly:app --nomad --litefs --region iad lhr

Feel free to add to or change the regions in the list above.

Now let the fun begin.

fly deploy

Once the application has been deployed, running fly open will open a browser and show you that The page you were looking for doesn't exist. This is because we didn't set up a root. Add /names to the path and you will see the scaffolded view. Add one name.

Return back to your terminal window and run:

fly status

You will see that only one copy of your application is running. You can increase the count by running:

fly scale count 2

This may take a minute or so to complete. Run fly status to see the progress.

Once both instances are running, enter the following command and select the instance that is furthest from you:

% fly ssh console -s
? Select instance:  [Use arrows to move, type to filter]

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

printenv FLY_REGION

Now run rails console and display the last name:

% /app/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

  • litefs currently only works with Nomad, not with machines.
  • VMs with Consul enabled never exit, making releases impossible. Additionally litefs write forwarding needs work. Perhaps fly-ruby would address this, or could readily be adapted. What Litefs Can Do Today describes current capabilities and future plans.