Run Services in the Background

Some time ago Marcin wrote about basic design patterns in Ruby on Rails. I’d like to go back to Service pattern in this post. I really like it, it's a good idea to place application’s business logic there. At Naturaily we use it quite often.

It happens that we need to run our service in the background. What's the easiest way to achieve this? Wrap our Service in a Job of course! Right... But we don't want to end up with dozens of very similar jobs. So... Here’s the solution. Let’s create universal Job for all the services.

Create the Job

Our job will be called ServiceInvocationJob. It's a good name for our universal job. To create a new Job we need to run one simple task:

1rails g job service_invocation

And now we should edit newly created file. Right now it looks like this:

1# app/jobs/service_invocation_job.rb
2class ServiceInvocationJob < ApplicationJob
3  queue_as :default
4
5  def perform(*args)
6    # Do something later
7  end
8end

What do we need to run some service? Service's arguments, of course, and Service class itself! We can't pass class as argument, so we'll pass class' name. At the end our Job will be as simple as that:

1class ServiceInvocationJob < ApplicationJob
2  queue_as :default
3
4  def perform(service_name, args)
5    service_name.constantize.call(*args)
6  end
7end

Very nice? Don't you think?

Update BaseService class

We already run our services in the background jobs! Everywhere, where we want to run our service in background, we need to change classic invocation:

1DoSomething.call(first_argument, second_argument)

to this

1ServiceInvocationJob.perform_later("DoSomething", [first_argument, second_argument])

But it doesn't look well. I think this one would be better:

1DoSomething.async_call(first_argument, second_argument) # note that async_ prefix!

Right?

So now we need to update our BaseService a bit! Nothing big. Just add a new static method called async_call. There's the updated file:

1class BaseService
2  private_methods :new
3
4  class << self
5    def call(*args)
6      new(*args).call
7    end
8
9    def async_call(*args)
10      ServiceInvocationJob.perform_later(self.to_s, args)
11    end
12  end
13end