How to migrate from Heroku to Fly.io

A couple weeks ago Heroku announced the removal. I have plenty of projects running on free dynos. I have taken some time to move my code to Fly.io. And also I've written a little tutorial of how to perform the migration.

I'll use one of my public repos as an example https://github.com/mliezun/getmyip. It's a simple service that returns the IP from which you're making the request. It's useful when you want to know your public IP.

That project ^ was covered in a previous blogpost.

Migration instructions

The first thing we need to do is to remove heroku from the remotes. Inside your project run:

git remote remove heroku

If you have a heroku.yml file, delete it.

rm -rf heroku.yml

Then, we're ready to start using fly. There are tutorials on the official fly.io docs for many frameworks and languages. We're going to be following the one for a Docker app, since it's the most general case.

First thing you need to do is create an account in Fly.io if you don't have one yet.

Once you created your account, install the flyctl command line tool. After that, login by running the following command:

flyctl auth login

After you've logged in to your account, you're ready to launch your application. Execute the next command and follow the interactive setup.

$ flyctl launch
Scanning source code
Detected a Dockerfile app
? App Name (leave blank to use an auto-generated name): 
Automatically selected personal organization: Miguel Liezun
? Select region: mia (Miami, Florida (US))
Created app morning-breeze-4255 in organization personal
Wrote config file fly.toml
? Would you like to set up a Postgresql database now? No
? Would you like to deploy now? Yes
Deploying morning-breeze-4255
==> Validating app configuration
--> Validating app configuration done
Services
TCP 80/443 -> 8080
Remote builder fly-builder-green-pond-8004 ready
==> Creating build context
--> Creating build context done
==> Building image with Docker
--> docker host: 20.10.12 linux x86_64
...

Make sure your app listens to port 8080, that's the default for fly apps. You can change the port inside the file fly.toml if you want , just search for the internal port and change it. Remember to run launch again if you change the port.

# fly.toml file generated for morning-breeze-4255 on 2022-09-21T21:50:20-03:00

app = "morning-breeze-4255"
kill_signal = "SIGINT"
kill_timeout = 5
processes = []

[env]

[experimental]
  allowed_public_ports = []
  auto_rollback = true

[[services]]
  http_checks = []
  internal_port = 8080 # <- Put your desired port here
# ...

Finally, you only need to open the app and enjoy! You migrated your first app from heroku to fly :-)

$ flyctl open
opening http://morning-breeze-4255.fly.dev ...

Access the newly deployed 'getmyip' service using the link http://morning-breeze-4255.fly.dev.