“Whenever” gem running cron jobs on Heroku

Question

I created an app that uses the whenever gem. The gem creates cron jobs. I got it working locally but can\'t seem to get it working on heroku cedar. What\'s the command to do

Answer 1

If you want to:

• Use Heroku Scheduler
• Run tasks every minute (not 10 min)
• Don't care about dyno hours

This was my solution hack to run jobs every minute - assuming the task completes in under 60 seconds.

task start_my_service: :environment do
  1.upto(9) do |iteration|
    start_time = DateTime.now
    Services::MyService.call
    end_time = DateTime.now
    wait_time = 60 - ((end_time - start_time) * 24 * 60 * 60).to_i
    sleep wait_time if wait_time > 0
  end
end

Answer 2

You need to add Heroku Scheduler addon.

You can add it directly from your dashboard or using following commands:

1. install the add-on:

   heroku addons:create scheduler:standard
   

2. Create a rake task in lib/tasks

   # lib/tasks/scheduler.rake
   task :send_reminders => :environment do
     User.send_reminders
   end
   

3. Schedule job

   • Visit Heroku Dashboard
   • Open your app
   • Select Scheduler from add-ons list

   • Click Add Job, enter a task and select frequency.

     e.g. Add rake send_reminders, select "Daily" and "00:00" to send reminders every day at midnight.

Answer 3

Short answer: use the scheduler add-on: http://addons.heroku.com/scheduler

Long answer: When you do heroku run, we

1. spin up a dyno
2. put your code on it
3. execute your command, wait for it to finish
4. throw the dyno away

Any changes you made to crontab would be immediately thrown away. Everything is ephemeral, you cannot edit files on heroku, just push new code.