[ActiveJob / DelayedJob example class] with tests and Docker Compose setup

docker-compose.yml

volumes:
  postgresql:
    name: automotiontv-postgresql
    external: true

x-restart_policy: &default_restart_policy
  deploy:
    restart_policy:
      condition: on-failure
      delay: 5s
      max_attempts: 3

services:
  web:
    << : *default_restart_policy
    build: .
    image: automotiontv-server
    container_name: automotiontv-server
    env_file: .env
    volumes:
      - .:/app
    ports:
      - 3000:3000
    command: ["wait-for-it", "--strict", "--timeout=60", "db:5432", "--", "./run.sh"]
    depends_on:
      - db

  delayed_job:
    << : *default_restart_policy
    build: .
    image: automotiontv-server
    container_name: delayed-job
    env_file: .env
    volumes:
      - .:/app
    command: ["wait-for-it", "--strict", "--timeout=60", "web:3000", "--", "bin/rails", "jobs:work"]
    depends_on:
      - db
      - web

  db:
    image: postgres:15
    container_name: automotiontv-db
    env_file: .env
    volumes:
      - postgresql:/var/lib/postgresql/data
      - .:/app
    ports:
      - '5432:5432'

  adminer:
    image: adminer
    container_name: adminer
    ports:
      - 8080:8080
    depends_on:
      - db

generate_google_places_report_job.rb

# frozen_string_literal: true

# A job to generate an account locations report using the Google Places API
class GenerateGooglePlacesReportJob < ApplicationJob
  queue_as :default
  before_enqueue :prevent_job_duplication, :validate_email_address
  before_perform :validate_email_address
  after_perform :send_email

  class << self
    # Determine if job is already enqueued
    #
    # @return [Boolean]
    def job_already_enqueued?
      Delayed::Job.any? { |j| j.handler.include?(" job_class: #{self}\n") }
    end
  end

  # Generate an account locations report using the Google Places API
  #
  # Email is passed into this method in order to be used by the .send_email method.
  #
  # @param email_address [String] Email address to send download link to
  # @return [void]
  def perform(email_address:) # rubocop:disable Lint/UnusedMethodArgument
    client = GooglePlacesApiClient.new
    client.accounts_with_places(format: :csv_file, filename: GooglePlacesApiClient::DEFAULT_CSV_FILEPATH)
  end

  private

  # Prevent this job from being enqueued if email address is invalid
  #
  # @private
  #
  # @return [void]
  def validate_email_address
    return if email_address.match?(URI::MailTo::EMAIL_REGEXP)

    msg = "Unable to enqueue #{self.class} because email address is invalid."
    Rails.logger.info msg
    throw :abort
  end

  # Prevent this job from being duplicated in the queue. It should only generate one report at a time.
  #
  # @private
  #
  # @return [void]
  def prevent_job_duplication
    return unless self.class.job_already_enqueued?

    msg = "Unable to enqueue #{self.class} because it is already enqueued."
    Rails.logger.info msg
    throw :abort
  end

  # Send email to the user letting them know the report is ready to download
  #
  # @private
  #
  # @return [void]
  def send_email
    Rails.logger.info "Sending Google Places report email to #{email_address}"
    Notifications.google_places_report_ready(email: email_address).deliver_now
  end

  # Email address to send the download link to
  #
  # @private
  #
  # @return [String]
  def email_address
    @email_address ||= arguments.first[:email_address].to_s
  end
end

generate_google_places_report_job_spec.rb

# frozen_string_literal: true

require 'rails_helper'

RSpec.describe GenerateGooglePlacesReportJob, type: :job do
  let(:tmpdir) { Dir.mktmpdir }
  let(:csv_path) { File.join(tmpdir, GooglePlacesApiClient::DEFAULT_CSV_FILENAME) }
  let(:perform_now) { described_class.perform_now(email_address: '[email protected]') }
  let(:perform_later) { described_class.perform_later(email_address: '[email protected]') }

  before(:example) do
    # Generate test reports in a tmp directory
    stub_const('GooglePlacesApiClient', GooglePlacesApiClient)
    stub_const('GooglePlacesApiClient::DEFAULT_CSV_FILEPATH', csv_path)
  end

  after(:example) do
    # Cleanup tmp directory
    FileUtils.rm_rf(tmpdir)
  end

  context 'when the job is not already running' do
    it 'enqueues a background job' do
      expect { perform_later }.to have_enqueued_job(described_class)
    end

    it 'creates a report file' do
      perform_now
      expect(File).to exist(csv_path)
    end

    it 'sends an email' do
      expect { perform_now }.to change { ActionMailer::Base.deliveries.count }.by(1)
    end
  end

  context 'when the job is already running' do
    before(:example) do
      allow(GenerateGooglePlacesReportJob).to receive(:job_already_enqueued?).and_return(true)
    end

    it 'prevents the job from being duplicated' do
      expect { perform_later }.not_to have_enqueued_job(described_class)
    end
  end

  context 'when the email address is invalid' do
    let(:invalid_job) { described_class.perform_later(email_address: 'not_a_real_email') }

    it 'prevents the job from being performed' do
      expect { invalid_job }.not_to have_enqueued_job(described_class)
    end
  end
end