We recently migrated our app from heroku to fly.io server with minimum downtime (almost 5 seconds of downtime) to be more precise. Here is how we did that.

First step obviously is to create a new branch and setup fly configuration. For that fly has a really nice CLI command which generates all the necessary configurations for you by inspecting your project files. For that first thing you need to do is Install fly CTL tool

• Install https://fly.io/docs/hands-on/install-flyctl/

• login to your fly app with

fly auth login

Now you are ready to move forward.

Now follow https://fly.io/docs/rails/getting-started/existing/ to configure your existing ruby on rails application.

fly launch

and provide all necessary information if needed. This will generate Dockerfile if missing and fly.toml file and bunch of configuration files for your project.

Once your setup are done, it will also create a fly app in the fly dashboard, you can check it and confirm everything is fine.

Now next step is to Deploy our application with:

fly deploy

This command will build docker, push it to registry, run assets pre-compilation and so on, you can configure your Dockerfile as needed and finally it will deploy your app to fly server.

You will also see a fly domain where you can confirm all of the app features are working fine.

fly apps open

Migration from Heroku

Now that we our app is working as expected we need to migrate from Heroku for that follow: https://fly.io/docs/rails/getting-started/migrate-from-heroku/

You can see, you can easily move all of your production Heroku Config vars with one single command:

heroku config -s | grep -v -e "RAILS_MASTER_KEY" -e "DATABASE_URL" -e "REDIS_URL" -e "REDIS_TLS_URL" | fly secrets import

I will keep sharing the migration process in upcoming articles.