Quebec

Quebec is a simple background task queue for processing asynchronous tasks. The name is derived from the NATO phonetic alphabet for "Q", representing "Queue".

This project is inspired by Solid Queue.

Warning: This project is in early development stage. Not recommended for production use.

Why Quebec?

• Simplified Architecture: No dependencies on Redis or message queues
• Database-Powered: Leverages RDBMS capabilities for complex task queries and management
• Rust Implementation: High performance and safety with Python compatibility
• Framework Agnostic: Works with asyncio, Trio, threading, SQLAlchemy, Django, FastAPI, etc.

Features

• Scheduled tasks
• Recurring tasks
• Concurrency control
• Web dashboard
• Automatic retries
• Signal handling
• Lifecycle hooks

Control Plane

Built-in web dashboard for monitoring jobs, queues, and workers in real-time.

Database Support

• SQLite
• PostgreSQL
• MySQL

Quick Start

Module Runner (Recommended)

Define jobs in a package:

# jobs/email_job.py
import quebec

class EmailJob(quebec.BaseClass):
    queue_as = "default"

    def perform(self, to, subject):
        self.logger.info(f"Sending email to {to}: {subject}")

Export them in __init__.py:

# jobs/__init__.py
from .email_job import EmailJob

Run with python -m quebec:

DATABASE_URL=sqlite:///demo.db?mode=rwc python -m quebec jobs

All configuration via QUEBEC_* environment variables — no boilerplate entry script needed.

Script Mode

For more control, use Quebec directly in a script:

import logging
from pathlib import Path
from quebec.logger import setup_logging

setup_logging(level=logging.DEBUG)

import quebec

db_path = Path('demo.db')
qc = quebec.Quebec(f'sqlite://{db_path}?mode=rwc')


@qc.register_job
class FakeJob(quebec.BaseClass):
    def perform(self, *args, **kwargs):
        self.logger.info(f"Processing job {self.id}: args={args}, kwargs={kwargs}")


if __name__ == "__main__":
    # Enqueue a job
    FakeJob.perform_later(qc, 123, foo='bar')

    # Start Quebec (handles signal, spawns workers, runs main loop)
    qc.run(
        create_tables=not db_path.exists(),
        control_plane='127.0.0.1:5006',  # Optional: web dashboard
    )

Or run the quickstart script directly:

curl -O https://raw.githubusercontent.com/ratazzi/quebec/refs/heads/master/quickstart.py
uv run quickstart.py

qc.run() Options

Parameter	Type	Default	Description
create_tables	bool	False	Create database tables (requires DDL permissions)
control_plane	str	None	Web dashboard address, e.g. '127.0.0.1:5006'
spawn	list[str]	None	Components to spawn: ['worker', 'dispatcher', 'scheduler']. None = all
threads	int	1	Number of worker threads to run jobs

Delayed Jobs

from datetime import timedelta

# Run after 1 hour
FakeJob.set(wait=3600).perform_later(qc, arg1)

# Run at specific time
FakeJob.set(wait_until=tomorrow_9am).perform_later(qc, arg1)

# Override queue and priority
FakeJob.set(queue='critical', priority=1).perform_later(qc, arg1)

Automatic Retries

from datetime import timedelta

class PaymentJob(quebec.BaseClass):
    retry_on = [
        quebec.RetryStrategy(
            (ConnectionError, TimeoutError),
            wait=timedelta(seconds=30),
            attempts=3,
        ),
        quebec.RetryStrategy(
            (ValueError,),
            wait=timedelta(seconds=5),
            attempts=1,
            handler=lambda exc: True,  # optional callback
        ),
    ]

    def perform(self, order_id):
        process_payment(order_id)

Multiple RetryStrategy entries can target different exception types with independent wait/attempts.

Concurrency Control

Limit how many jobs with the same key can run simultaneously:

class ReportJob(quebec.BaseClass):
    concurrency_limit = 3          # max 3 concurrent executions per key
    concurrency_duration = 120     # semaphore TTL in seconds

    def concurrency_key(self, account_id, **kwargs):
        return str(account_id)     # final key: "ReportJob/123"

    def perform(self, account_id):
        generate_report(account_id)

The actual concurrency key is "ClassName/key" (e.g. "ReportJob/123"), so different job classes never conflict. When the limit is reached, new jobs are blocked until a slot becomes available. The concurrency_duration acts as a safety TTL — the semaphore is released automatically if a worker crashes.

Lifecycle Hooks

Quebec provides several lifecycle hooks that you can use to execute code at different stages of the application lifecycle:

• @qc.on_start: Called when Quebec starts
• @qc.on_stop: Called when Quebec stops
• @qc.on_worker_start: Called when a worker starts
• @qc.on_worker_stop: Called when a worker stops
• @qc.on_shutdown: Called during graceful shutdown

These hooks are useful for:

• Initializing resources
• Cleaning up resources
• Logging application state
• Monitoring worker lifecycle
• Graceful shutdown handling