Is there any down time when committing to a clojure app running on Heroku?

Question

Is there any potential downtime when I do a commit to a clojure/Java app running on Heroku?

I am guessing not - but can't find out for sure.

Thanks.

Answer 1

When you push to Heroku, you invoke the slug compiler, which does all the heavy lifting needed to turn your application into a self-contained archive. That can take a little while, as you see whenever you run git push. However, during this time, your application is running normally.

When your slug finishes compiling, Heroku then pushes it out to the dyno grid. This causes existing web dynos to stop and causes new ones to start. Your application will be unresponsive between the time that the old dynos stop and the new ones begin serving requests -- probably only a few seconds. During this interval, Heroku's routing layer will queue incoming requests.

TL;DR: users might notice a pause (but not an error!) as your application is updated. You can simulate this at any time by running heroku restart.