You could use the sucker punch gem which does the background processing along with the rails process, so there shouldn't be the need to start another dyno. Not sure about if we can schedule it to start at a particular point of time.
Btw, just curious. Cant we write cron jobs in heroku? Using something like the whenever gem.
Previously I was using the gem resque and resque-scheduler for this. The problem however is that this requires 2 additional dynos, one for the scheduler and one for the worker task to run on.
I am not sure conventional cron jobs can be made to work on heroku. There is no persistent file storage so even if the crontab file is edited, it wont reflect on any other dyno.
Thats true, I did a google on running cron job in heroku it seems there is an addon called heroku scheduler[1] which would works like cron. But its run hours would cost as as your regular dyno run hours so it wouldn't be a cost efficient substitute.