Running delayed jobs on Heroku for free

Question

Is it possible to run delayed jobs on Heroku for free?

I'm trying to use delayed_job_active_record on Heroku. However, it requires a worker dyno and it would cost money if I turned this dyno on for full time.

I thought using Unicorn and making its workers run delayed jobs instead of the Heroku worker, would cost nothing, while successfully running all the jobs. However, Unicorn workers do not seem to start "working" automatically.

I have the following in my Procfile.

web: bundle exec unicorn -p $PORT -c ./config/unicorn.rb
worker: bundle exec rake jobs:work

and the following in my unicorn.rb

worker_processes 3
timeout 30
preload_app true

before_fork do |server, worker|
  # Replace with MongoDB or whatever
  if defined?(ActiveRecord::Base)
    ActiveRecord::Base.connection.disconnect!
    Rails.logger.info('Disconnected from ActiveRecord')
  end

  # If you are using Redis but not Resque, change this
  if defined?(Resque)
    Resque.redis.quit
    Rails.logger.info('Disconnected from Redis')
  end

  sleep 1
end

after_fork do |server, worker|
  # Replace with MongoDB or whatever
  if defined?(ActiveRecord::Base)
    ActiveRecord::Base.establish_connection
    Rails.logger.info('Connected to ActiveRecord')
  end

  # If you are using Redis but not Resque, change this
  if defined?(Resque)
    Resque.redis = ENV['REDIS_URI']
    Rails.logger.info('Connected to Redis')
  end
end

Delayed jobs only seem to work when I scale the Heroku worker from 0 to 1. Again, is it not possible to use Unicorn workers instead of Heroku worker to do the delayed jobs?

Do I have to use a gem like workless to run delayed jobs on Heroku for free? (reference)

Answer 1

Splitting the process like that can incur problems - your best bet is it not try and get it 'free' but use something like http://hirefireapp.com/ which will start up a worker when there are jobs to perform reducing the cost significantly rather than running a worker 24x7.

Also note, Heroku will only ever autostart a 'web' process for you, starting other named processes is a manual task.