Delayed Job as a Rake TaskRunning delayed job on-demand with a rake task and Heroku Scheduler
Delayed Job is a great and simple solution for background jobs in a Rails application. But if you don’t have the memory or resources to run a background thread 24hrs on a server what do you do?
We were in a similar situation for a client, who was strictly on a shoe string budget, running off Heroku. The background job was to process some applications, verify and sent emails if they had errors. This was to be done once a day. Running a background job just for this was a bad choice.
Another option was to run this as a rake task, at a set time, use Heroku Scheduler to run this at 04:00am every day. But we wanted to try a bit more generic solution.
We decided to stick to write Delayed Job classes, so that in future, it can serve 2 purposes
- For more background processing, more jobs we just have to write new classes with
- When the app is moved into it’s own private hosting VPS, run a background thread more often, to scale it.
So delayed job it was!
But in the current setup, we had to run the jobs as a rake task, triggered once a day at a specific time, while leaving room for a full fledged background process in the future.
Looking at the delayed_job source at Github we figured that this could be easily implemented. It internally creates a
Delayed::Worker class and works off all the jobs in the
The solution was really simple. Create a rake task in
# File lib/tasks/delayed_job.rake namespace :delayed_job do desc 'Run Delayed job worker' task work: :environment do worker = Delayed::Worker.new worker.work_off #by default runs 100 rows end end
For more information on the sources:
- The rake task for starting delayed job – delayed/tasks.rb
- The Delayed::Worker start – delayed/worker.rb
- Delayed::Worker work_off definition – delayed/worker.rb#work_off