Run an application in background

Question

As far as I know, it's impossible to run a custom application on Heroku and AppHarbor. I emailed them but there is no answer yet. What I want is run a Linux application (a web app also uses Linux) I made myself in background. Let's say it puts a text-copyright on every uploaded image.

Isn't it possible to run such an application? And if not, why not?

Answer 1

AppHarbor has background workers and Heroku has worker dynos.