One of the gems I often use in my Ruby on Rails projects is Sikekiq. For those of you who don’t know about it, it allows to easily manage background processes.

As I’m now using Hanami more and more for my personal projects it quickly became essential to me to integrate it in Hanami. Fortunately Sidekiq is framework agnostic and easy to get up and running in any Ruby project.

Setting up Sidekiq

As in every other Ruby project, the first thing to do is to add Sidekiq dependency in your Gemfile then bundle install:

gem 'sidekiq'

Once installed we need to configure it, it’s pretty straightforward since the only thing we need to define is the Redis URL to use.

We’re going to encapsulate this configuration in its own file config/sidekiq.rb:

Sidekiq.configure_server do |config|
  config.redis = { url: ENV.fetch('REDIS_URL') }
end

Sidekiq.configure_client do |config|
  config.redis = { url: ENV.fetch('REDIS_URL') }
end

There are two things here. First we make use of environment variable to define and get Redis URL. It is a best practice pushed by Hanami which already setup all you need to use environment variable effectively. This avoid hard-coding it and ease configuration for deployment tools.

The other noticeable thing is that we use fetch to retrieve the value associated to our REDIS_URL key rather than accessing it through []. The advantage with fetch is it will raise an IndexError exception if the key doesn’t exist so we’ll notice the missing key / value pair as soon as we start the server.

We then need to tell Hanami that it should load it on start. We could have put this file in something like apps/web/config/initializers and it would have been loaded automatically without any further configuration but I don’t think that Sidekiq is tied to one of our app, it’s more of a transverse component that can be used by any of our inner apps.

So let’s instruct our Hanami app about this file to load by editing config/environment.rb:

require_relative './sidekiq'

We can now set Redis URL in our .env.development file which will be sourced automatically on server start.

Scheduling tasks from our application

Since our workers are not tied to a given app, we’re going to put them in lib/<application_name>/workers because lib directory is dedicated to business logic and domain model.

So let’s say we create a worker that does an heavy processing, it could be something like lib/<application_name>/workers/heavy_processing.rb:

class HeavyProcessing
  include Sidekiq::Worker

  def perform(some, params)
    # Do some heavy processing
  end
end

As you can see it’s just plain Sidekiq code with a class that includes Sidekiq::Worker and defines a perform method that can take any arguments.

Now you can use it from anywhere in your code to schedule background jobs. In our example the call would be something like:

HeavyProcessing.perform_async(:something, {hard: "to process"})

Ok the task is now scheduled but we still need to run Sidekiq deamon to watch for those scheduled tasks and run them.

Running Sidekiq deamon along with Hanami

The first dumbest way to do this is to run your Hanami app from a terminal:

$ bin/hanami server

then open up another tab and run Sidekiq manually:

$ bin/sidekiq -e development -r ./config/environment.rb

It’s pretty tedious and your workmates won’t thanks you for that.

Another simpler, more reliable way to do this is to use a Procfile. It’s a way to define what must be started and how it should be started. You can then use something like Foreman to read this Procfile and do the job for you:

app: bin/hanami server
sidekiq: bin/sidekiq -e development -r ./config/environment.rb

You’re now able to start every piece of software needed to run the app with a single command:

$ foreman start

If you ever had some more dependencies, you’ll just have to add it to your Procfile.

For Docker’s fan you can also use it with docker-compose to start all your services.

Let’s schedule

This is a pretty long post for such a simple thing to setup but I wanted to be very didactic so even the new comers to Hanami and Sidekiq can understand what happens.

Now you’re ready to schedule background jobs from your Hanami app! Make good use of it.

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