How to set a default queue name for all jobs in Rails?

I'm working on a gem for sharing common Rails code between my apps. I just added there a first job and hit a problem - the job from the gem was using default queue which doesn't exist.

Well I knew I will have this problem but I didn't expect that figuring out how to change the default name will take me so much time.

I use shoryuken for running jobs, the configuration looks like this:

aws:
  access_key_id: <%= ENV["AWS_ACCESS_KEY_ID"] %>
  secret_access_key: <%= ENV["AWS_SECRET_ACCESS_KEY"] %>
  region: "us-east-1"
  receive_message:
    wait_time_seconds: 10
concurrency: 2
delay: 10
queues:
  - 'customer-feedback'
  - 'customer-feedback-mailer'

As you can see there's no default queue. It's not a problem as I can use queue_as in ApplicationJob. But the job from the gem cannot extend ApplicationJob. Also it must not have a hard coded name either.

I expected there should be a way in Rails to set the default queue name for all jobs and there is but it was really difficult to find it.

The documentation mentioned config.active_job.default_queue_name and looking at the code it should be picked up. But as I found out the default is picked up too early before the application can override it.

The most interesting code is in ActiveJob::QueueName

included do
  class_attribute :queue_name, instance_accessor: false
  class_attribute :queue_name_delimiter, instance_accessor: false

  self.queue_name = default_queue_name
  self.queue_name_delimiter = "_" # set default delimiter to '_'
end

# Returns the name of the queue the job will be run on.
def queue_name
  if @queue_name.is_a?(Proc)
    @queue_name = self.class.queue_name_from_part(instance_exec(&@queue_name))
  end
  @queue_name
end

As you can see when included into ActiveJob::Base it will establish queue_name class attribute. You can check class_attribute documentation - it's a very interesting method - you can propagate value from a parent class to all sub classes, and allow subclasses to override the value. Propagation happens even after objects were created provided the subclass didn't override.

Playing with it I discovered you can use following code to override queue name:

config.active_job.queue_name = 'customer-feedback'

That worked (almost), as there's no customer-feedback queue. I use prefixed queue names:

config.active_job.queue_name_prefix = Rails.env

So the real name of the queue should be something like development_customer-feedback.

As you noticed above queue_name method will take the name as is when it's a string, but will calculate it when it's Proc, so simple change fixed this:

config.active_job.queue_name = Proc.new { 'customer-feedback' }

Now all jobs can use a proper queue, even without an explicit queue_as.

PS

You can also set a queue name and other attributes when executing the job:

VideoJob.set(
  queue: :some_queue, 
  wait: 5.minutes
).perform_later(Video.last)