Background Jobs Setup (Sidekiq/Celery/Bull) for Web Application

Background Tasks Setup: Sidekiq, Celery, Bull

Background tasks are moved out of HTTP cycle: user doesn't wait for operation to complete. Tool choice depends on stack: Sidekiq — Ruby/Rails, Celery — Python/Django/FastAPI, Bull/BullMQ — Node.js.

Sidekiq (Ruby/Rails)

Sidekiq uses Redis as queue storage, supports retries, dead jobs, scheduler.

# Gemfile
gem 'sidekiq', '~> 7.0'
gem 'sidekiq-scheduler'

# config/sidekiq.yml
:concurrency: 10
:queues:
  - [critical, 5]
  - [default, 3]
  - [mailers, 2]
  - [low, 1]

# app/workers/email_worker.rb
class EmailWorker
  include Sidekiq::Job

  sidekiq_options queue: :mailers, retry: 3, backtrace: true

  def perform(user_id, template, variables = {})
    user = User.find(user_id)
    UserMailer.send(template, user, variables).deliver_now
  end
end

# Usage
EmailWorker.perform_async(user.id, :welcome)
EmailWorker.perform_in(5.minutes, user.id, :follow_up)
EmailWorker.perform_at(Time.zone.parse('2024-01-01 09:00'), user.id, :new_year)

Celery (Python/Django)

# celery.py
from celery import Celery
from celery.schedules import crontab

app = Celery('myapp')
app.config_from_object('django.conf:settings', namespace='CELERY')

# settings.py
CELERY_BROKER_URL = 'redis://redis:6379/0'
CELERY_RESULT_BACKEND = 'redis://redis:6379/1'
CELERY_TASK_SERIALIZER = 'json'
CELERY_RESULT_EXPIRES = 3600
CELERY_WORKER_PREFETCH_MULTIPLIER = 1

CELERY_BEAT_SCHEDULE = {
    'send-daily-digest': {
        'task': 'myapp.tasks.send_daily_digest',
        'schedule': crontab(hour=9, minute=0),
    },
    'cleanup-tokens': {
        'task': 'myapp.tasks.cleanup_expired_tokens',
        'schedule': crontab(minute=0),  # every hour
    },
}

# tasks.py
from celery import shared_task
from myapp.models import User
from myapp.services import send_email

@shared_task(
    bind=True,
    max_retries=3,
    default_retry_delay=60,  # seconds before retry
    queue='emails',
)
def send_welcome_email(self, user_id: int) -> dict:
    try:
        user = User.objects.get(pk=user_id)
        send_email(user.email, 'welcome', {'name': user.first_name})
        return {'status': 'sent', 'user_id': user_id}
    except Exception as exc:
        raise self.retry(exc=exc, countdown=2 ** self.request.retries * 60)

# Usage
send_welcome_email.delay(user.id)
send_welcome_email.apply_async(args=[user.id], countdown=300)  # in 5 minutes

# docker-compose: Celery workers
celery-worker:
  build: .
  command: celery -A myapp worker --loglevel=info --concurrency=4 -Q emails,default
  depends_on: [redis, db]
  environment: *app_env

celery-beat:
  build: .
  command: celery -A myapp beat --loglevel=info --scheduler django_celery_beat.schedulers:DatabaseScheduler
  depends_on: [redis, db]

celery-flower:
  build: .
  command: celery -A myapp flower --port=5555 --basic-auth=admin:password
  ports:
    - "5555:5555"

BullMQ (Node.js)

See separate article. Brief comparison:

Sidekiq Monitoring

# config/routes.rb
require 'sidekiq/web'

authenticate :user, ->(u) { u.admin? } do
  mount Sidekiq::Web => '/sidekiq'
end

Flower for Celery is available on port 5555. Shows tasks, workers, delays, retries.

Implementation timeline

Sidekiq or Celery for Django/Rails with basic tasks and monitoring: 2–3 days. With beat scheduler, monitoring and alerting: 3–4 days.