Heroku: Upgrade apps to the latest Stack

Heroku "Stack" is an OS image that is curated and maintained by Heroku. The image below should explain it pretty well:

Some of my old apps are on heroku-16 stack, and I want to upgrade them to heroku-18 that is based on Ubuntu 18.04.

Inspect your Heroku app stack

heroku apps:info
===
Addons: ...
Dynos: ...
Stack: heroku-16
...

Upgrade to heroku-18

Set the stack, create an empty commit, git push to trigger a rebuild.
Make sure test it on a staging environment first 🙂.

heroku stack:set heroku-18

git commit --allow-empty -m "Upgrade to heroku-18 stack"
git push heroku master

You can also upgrade via the dashboard. Command line tools are more convenient for me as I have many apps hosted on Heroku.

Tip: You can use Parity to manage multiple heroku apps easily.

Seems like heroku-18 is the default stack for new apps, so if you just created one recently, you'd probably don't need to bother with this post 😁.