Dokku: how to change heroku stack to heroku-20 or heroku-22 (from heroku-18)

Question

I have been working on a Django (Python) project using Dokku (thus Heroku) for deployments. Up until today, all deployments worked just fine, but since this morning, I get this error message:

Requested runtime 'python-3.10.12' is not available for this stack (heroku-18).

I know that python-3.10.12 is available on heroku-18 so I assume I (finally) have to change stack since heroku-18 is deprecated.

I have tried using this command on Dokku:

dokku buildpacks:add --index 1 {APP-NAME} https://github.com/heroku/heroku-buildpack-python.git,

but it doesn't solve my problem (heroku-18 is still being used).

Any help would be greatly appreciated

Answer 1

Facing a similar situation, the solution in my case was to upgrade the used stack builder (not the targeted buildpacks). You can take a look at this dokku herokuish documentation.

You'll need to check which stack is currently used by your application:

dokku buildpacks:report my-app

You can update or download your targeted herokuish gliderlabs image using docker commands.

In my case, I configured my app to use the gliderlabs/herokuish:latest-20 image, shipped with Heroku 20:

dokku buildpacks:set-property my-app stack gliderlabs/herokuish:latest-20.