Heroku: Cannot run more than 1 Free size dynos

I was trying to run

heroku run rake db:migrate

And was getting the error

Cannot run more than 1 Free size dynos.

See below for how to fix...

Solution 1:

Most Efective

in console run:

heroku ps

the result is some like this:

run.4859 (Free): up 2016/01/12 21:28:41 (~ 7m ago): rails c

So the numbers 4859 represent the session that is open and needs to be closed. To fix the error you need to run(Obviusly, replace the number 4859 by the number obtained):

heroku ps:stop run.4859

It is a very simple solution.

Solution 2:

The answer is to look for any open heroku sessions (you can use 'heroku ps' as john points out below), in my case I already had a started a heroku console session 30mins earlier and just forgot about it. So if you see the "Cannot run more than 1 Free size dynos" error just close any existing console or other heroku sessions you have open.

Hopefully this saves someone the ten minutes it took me to come to my senses.