delayed_job queue not being processed on Heroku

Question

I'm running a Rails 3 app with delayed_job. The issue I've come across is that though the app is correctly adding jobs to the queue, they are never being processed.

My Class

class User < ActiveRecord::Base
  after_create :send_welcome_email

  private

    def send_welcome_email
      UserMailer.delay.welcome_email(self)
    end
end

Inspecting things through the Rails console I can see that there are jobs in the queue. I can also see that there have been 0 attempts to perform the jobs. Spinning up a Heroku worker doesn't cause the jobs to be processed.

Any ideas?

Thanks!

Edit: Trying to clear the jobs queue as suggested below I ran rake jobs:clear and received the following error

rake aborted!
uninitialized constant Rake::DSL
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.0/lib/rake/tasklib.rb:8:in `<class:TaskLib>'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.0/lib/rake/tasklib.rb:6:in `<module:Rake>'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.0/lib/rake/tasklib.rb:3:in `<top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.0/lib/rake/rdoctask.rb:20:in `<top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.7/lib/rails/tasks/documentation.rake:1:in `<top (requ
ired)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.7/lib/rails/tasks.rb:15:in `block in <top (required)>
'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.7/lib/rails/tasks.rb:6:in `each'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.7/lib/rails/tasks.rb:6:in `<top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.7/lib/rails/application.rb:214:in `initialize_tasks'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.7/lib/rails/application.rb:139:in `load_tasks'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.7/lib/rails/application.rb:77:in `method_missing'
/app/Rakefile:7:in `<top (required)>'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2373:in `load'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2373:in `raw_load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2007:in `block in load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2058:in `standard_exception_handling'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2006:in `load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:1991:in `run'
/usr/ruby1.9.2/bin/rake:31:in `<main>'

Answer 1

In the end, the problem turned out to be a bug in Rake 0.9.0. As Rails depends on Rake, running bundle install after this release of Rake broke my delayed jobs.

The fix is to add gem 'rake', '0.8.7' to your gemfile.

More details can be found below...

DHH's tweet: http://twitter.com/dhh/status/71966528744071169

Discussion in rails_admin's issue tracker: https://github.com/sferik/rails_admin/issues/428

Answer 2

Two options for you:

These two gems watch delayed_jobs queue and automatically 'hires' background workers to process the thread:

• Option 1: https://github.com/michelson/hirefire (This is what I am using because it supports mongoid)
• Option 2: This branch of delayed_job developed by a heroku engineer has a similar autoscale feature: https://github.com/pedro/delayed_job/tree/autoscaling

Good luck

Answer 3

Are you running the delayed_job daemon in the same environment in which the application is running?

Try working the jobs manually using:
rake RAILS_ENV=development jobs:work

If you are running your app in production mode then you need to start delayed_job daemon as:
RAILS_ENV=production script/delayed_job start

Answer 4

This is kinda a long shot but make sure you are using the same Ruby version on Heroku as you are on your local machine. I had a problem with delayed jobs on Heroku before because of this.