Rails Background Jobs

EVERY job MUST have its test written and validated BEFORE implementation.
  1. Write the job spec (idempotency, retry, error handling)
  2. Run the spec — verify it fails because the job does not exist yet
  3. ONLY THEN write the job class
See rspec-best-practices for the full gate cycle.

EVERY job that performs side effects (charge, email, API call) MUST have
an idempotency check before the side effect.

# In controller:
SomeJob.perform_later(@order) # @order is an ActiveRecord object

# In job:
class SomeJob < ApplicationJob
  def perform(order) # If @order is stale or deleted, this will fail
    order.process!
  end
end

# In controller:
SomeJob.perform_later(@order.id) # Only pass the ID

# In job:
class SomeJob < ApplicationJob
  def perform(order_id)
    order = Order.find(order_id) # Always re-load fresh data inside the job
    order.process!
  end
end

class NotifyOrderShippedJob < ApplicationJob
  queue_as :default
  retry_on Net::OpenTimeout, wait: :polynomially_longer, attempts: 5
  discard_on ActiveRecord::RecordNotFound

  def perform(order_id)
    order = Order.find(order_id)
    return if order.shipped_notification_sent?
    OrderMailer.shipped(order).deliver_now
    order.update!(shipped_notification_sent_at: Time.current)
  end
end

# config/recurring.yml
production:
  nightly_cleanup:
    class: "NightlyCleanupJob"
    schedule: "0 2 * * *"
  hourly_sync:
    class: "HourlySyncJob"
    schedule: "every 1 hour"
    queue: low