Celery Task Queue

Introduction

Celery provides distributed task queues for asynchronous task execution.

Basic Setup

# tasks.py
from celery import Celery

app = Celery("tasks", broker="redis://localhost:6379")

@app.task
def send_email(recipient, subject):
    # Email sending logic
    return {"sent": True, "recipient": recipient}

Running Workers

celery -A tasks worker --loglevel=info

Calling Tasks

# Call asynchronously
result = send_email.delay("user@email.com", "Hello")
result.get(timeout=10)  # Wait for result

# With ETA
from datetime import timedelta
send_email.apply_async(
    args=["user@email.com"],
    eta=datetime.now() + timedelta(hours=1)
)

Periodic Tasks

@app.task
def daily_report():
    pass

app.conf.beat_schedule = {
    "daily-report": {
        "task": "tasks.daily_report",
        "schedule": 86400.0,  # Every 24 hours
    }
}

Practice Problems

1. Create basic Celery tasks
2. Configure Redis broker
3. Schedule periodic tasks
4. Handle task retries
5. Monitor with Flower