liteq 0.2.1

A lightweight message queue for Python with no dependencies

LiteQ

Translations: 🇷🇺 Русский

A lightweight, minimalist task queue for Python with zero dependencies.

LiteQ is a pure Python task queue built on SQLite, perfect for background job processing without the complexity of Celery or Redis. Just decorate your functions and call .delay() - that's it!

Features

✨ Zero Dependencies - Pure Python 3.10+ with only SQLite
⚡ Dead Simple API - Just @task decorator and .delay()
🔄 Async & Sync - Works with both async and regular functions
📦 Multiple Queues - Organize tasks by queue name
🎯 Task Priorities - Control execution order
🔁 Auto Retry - Configurable retry logic
👷 Multiple Workers - Process tasks in parallel
⏰ Task Scheduling - Cron-like scheduled tasks
⏱️ Task Timeouts - Automatic timeout and stuck task handling
🚀 FastAPI Integration - Built-in FastAPI support
📊 Monitoring - Track stats, workers, and task status
💾 Persistent - SQLite-backed for reliability
🧪 Production Ready - test coverage >80%

Installation

pip install liteq

Quick Start

1. Define your tasks

Create a file tasks.py:

from liteq import task
import time

@task()
def send_email(to: str, subject: str):
    print(f"Sending email to {to}: {subject}")
    time.sleep(1)
    return f"Email sent to {to}"

@task(queue="reports", max_retries=5)
def generate_report(report_id: int):
    print(f"Generating report {report_id}")
    time.sleep(2)
    return {"report_id": report_id, "status": "completed"}

2. Enqueue tasks

from tasks import send_email, generate_report

# Enqueue tasks - they return task IDs
task_id = send_email.delay(to="[e-mail]", subject="Hello!")
print(f"Enqueued task: {task_id}")

# Enqueue to different queue
report_id = generate_report.delay(report_id=123)

3. Check task status

from liteq import get_task_status

# Get task status
status = get_task_status(task_id)
if status:
    print(f"Status: {status['status']}")  # pending/running/done/failed
    print(f"Attempts: {status['attempts']}/{status['max_retries']}")
    
    if status['status'] == 'done':
        print(f"Result: {status['result']}")
    elif status['status'] == 'failed':
        print(f"Error: {status['error']}")

4. Run worker

# Start a worker to process tasks
liteq worker --app tasks.py --queues default,reports --concurrency 4

That's it! Your tasks will be processed in the background.

Examples

FastAPI Integration

from fastapi import FastAPI
from liteq import task, get_task_status
from liteq.fastapi import LiteQBackgroundTasks, enqueue_task

app = FastAPI()

@task(queue="emails", timeout=60)
async def send_email(to: str, subject: str):
    # Send email logic
    return {"sent": True}

# Method 1: Simple .delay()
@app.post("/send-email")
async def api_send_email(to: str, subject: str):
    task_id = send_email.delay(to, subject)
    return {"task_id": task_id}

# Method 2: FastAPI-like BackgroundTasks with status checking
@app.post("/send-email-bg")
async def api_send_email_bg(to: str, background: LiteQBackgroundTasks):
    task_id = background.add_task(send_email, to, "Hello!")
    return {"message": "queued", "task_id": task_id}

# Method 3: Helper function
@app.post("/send-email-helper")
async def api_send_email_helper(to: str):
    task_id = enqueue_task(send_email, to, "Welcome")
    return {"task_id": task_id}

# Check task status
@app.get("/tasks/{task_id}")
async def check_task_status(task_id: int):
    status = get_task_status(task_id)
    if not status:
        return {"error": "Task not found"}, 404
    return {
        "task_id": status["id"],
        "status": status["status"],
        "result": status.get("result"),
        "error": status.get("error")
    }

Scheduled Tasks (Cron)

from liteq import task, register_schedule
from liteq.scheduler import Scheduler

@task()
def daily_backup():
    print("Running backup...")
    return {"status": "success"}

@task()
def cleanup():
    print("Cleaning up...")

# Register schedules
register_schedule(daily_backup, "0 2 * * *")  # Every day at 2 AM
register_schedule(cleanup, "*/5 * * * *")  # Every 5 minutes

# Run scheduler
scheduler = Scheduler(check_interval=60)
scheduler.run()

# Or via CLI
liteq scheduler --app tasks.py --interval 60

Task Timeouts

from liteq import task

# Timeout on task level
@task(timeout=30)  # 30 seconds
def slow_task():
    import time
    time.sleep(100)  # Will be killed after 30s

# Timeout on worker level
# liteq worker --app tasks.py --timeout 60

Delayed Execution

from liteq import task
from datetime import datetime, timedelta

@task()
def reminder(message: str):
    print(f"Reminder: {message}")

# Schedule for later
run_time = datetime.now() + timedelta(hours=1)
task_id = reminder.schedule(run_time, "Meeting in 1 hour")

Async Tasks

import asyncio
from liteq import task

@task()
async def fetch_data(url: str):
    print(f"Fetching {url}")
    await asyncio.sleep(1)
    return {"url": url, "data": "..."}

# Enqueue
task_id = fetch_data.delay(url="https://api.example.com")

Multiple Queues

from liteq import task

@task(queue="emails")
def send_email(to: str):
    print(f"Email to {to}")

@task(queue="reports")
def generate_report(id: int):
    print(f"Report {id}")

@task(queue="notifications")
def send_push(user_id: int, message: str):
    print(f"Push to {user_id}: {message}")

# Enqueue to different queues
send_email.delay(to="[e-mail]")
generate_report.delay(id=42)
send_push.delay(user_id=1, message="Hello!")

Task Priorities

from liteq import task

@task()
def process_item(item_id: int):
    return f"Processed {item_id}"

# Higher priority number = runs first
# These are enqueued to the same queue but with different priorities
# (Note: priority is set in the task definition or database, 
# not in .delay() call in current version)

Custom Task Names and Retries

from liteq import task

@task(name="custom_email_task", max_retries=5)
def send_email(to: str):
    # This task will retry up to 5 times on failure
    print(f"Sending to {to}")

@task(max_retries=0)  # No retries
def one_time_task():
    print("This runs only once")

CLI Usage

# Run worker
liteq worker --app tasks.py

# Multiple queues
liteq worker --app tasks.py --queues emails,reports,notifications

# Custom concurrency
liteq worker --app tasks.py --concurrency 8

# With timeout (kills stuck tasks)
liteq worker --app tasks.py --timeout 300

# Run scheduler
liteq scheduler --app tasks.py --interval 60

# Monitor dashboard
liteq monitor --port 5151

Programmatic Worker

from liteq.db import init_db
from liteq.worker import Worker

# Initialize database
init_db()

# Create and run worker
worker = Worker(queues=["default", "emails"], concurrency=4)
worker.run()  # This blocks

Monitoring

from liteq.monitoring import (
    get_queue_stats,
    get_recent_tasks,
    list_queues,
    get_failed_tasks,
    get_active_workers,
)

# Get queue statistics
stats = get_queue_stats()
for stat in stats:
    print(f"{stat['queue']}: {stat['count']} tasks ({stat['status']})")

# List all queues
queues = list_queues()
print(f"Queues: {queues}")

# Get recent tasks
recent = get_recent_tasks(limit=10)

# Get failed tasks
failed = get_failed_tasks(limit=5)
for task in failed:
    print(f"Task {task['id']} failed: {task['error']}")

# Get active workers
workers = get_active_workers()
for worker in workers:
    print(f"Worker {worker['worker_id']}: {worker['active_tasks']} active tasks")

More Examples

Check out the examples/ directory for complete working examples:

• basic.py - Simple introduction with async and sync tasks
• multiple_queues.py - Multiple queues with different workers
• priorities.py - Task priority demonstration
• monitoring.py - Queue monitoring and statistics
• email_campaign.py - Real-world email campaign example

Run any example:

python examples/basic.py

API Reference

Core Functions

get_task_status(task_id: int) -> dict | None

Get task status and details by task ID.

Arguments:

• task_id (int): Task ID returned by .delay() or .schedule()

Returns: Dictionary with task information or None if not found

Example:

from liteq import task, get_task_status

@task()
def process_data(x: int):
    return x * 2

task_id = process_data.delay(5)

# Check status
status = get_task_status(task_id)
if status:
    print(f"Status: {status['status']}")  # pending/running/done/failed
    print(f"Attempts: {status['attempts']}/{status['max_retries']}")
    if status['status'] == 'done':
        print(f"Result: {status['result']}")

Decorators

@task(queue='default', max_retries=3, name=None, timeout=None)

Decorate a function to make it a task.

Arguments:

• queue (str): Queue name (default: "default")
• max_retries (int): Maximum retry attempts (default: 3)
• name (str, optional): Custom task name (defaults to function name)
• timeout (int, optional): Task timeout in seconds (default: None)

Returns: A callable with .delay(*args, **kwargs) and .schedule(run_at, *args, **kwargs) methods

Example:

@task(queue="emails", max_retries=5, timeout=60)
def send_email(to: str):
    ...

# Enqueue task
task_id = send_email.delay(to="[e-mail]")

# Schedule for later
from datetime import datetime, timedelta
run_time = datetime.now() + timedelta(hours=1)
task_id = send_email.schedule(run_time, to="[e-mail]")

Worker

Worker(queues, concurrency, task_timeout=None)

Create a worker to process tasks.

Arguments:

• queues (list[str]): List of queue names to process
• concurrency (int): Number of concurrent threads
• task_timeout (int, optional): Timeout in seconds for stuck tasks (default: None)

Methods:

• run(): Start processing tasks (blocks)

Example:

from liteq.worker import Worker

# Basic worker
worker = Worker(queues=["default", "emails"], concurrency=4)
worker.run()

# Worker with timeout
worker = Worker(queues=["default"], concurrency=4, task_timeout=300)
worker.run()  # Kills tasks running longer than 5 minutes

Monitoring Functions

All available in liteq.monitoring:

get_queue_stats() -> list[dict]

Get statistics grouped by queue and status.

get_recent_tasks(limit=50) -> list[dict]

Get recent tasks ordered by creation time.

list_queues() -> list[str]

Get list of all unique queue names.

get_failed_tasks(limit=50) -> list[dict]

Get recent failed tasks.

get_active_workers() -> list[dict]

Get currently active workers (heartbeat < 15 seconds ago).

Scheduler Functions

All available in liteq.scheduler:

register_schedule(task_func, cron_expr, queue='default', **kwargs) -> int

Register a task to run on a schedule.

Example:

from liteq import task, register_schedule

@task()
def backup():
    print("Backup running")

# Every day at 2 AM
schedule_id = register_schedule(backup, "0 2 * * *")

# Every 5 minutes
schedule_id = register_schedule(backup, "*/5 * * * *")

Scheduler(check_interval=60)

Scheduler daemon that processes scheduled tasks.

Example:

from liteq.scheduler import Scheduler

scheduler = Scheduler(check_interval=60)
scheduler.run()  # Blocks

FastAPI Integration

All available in liteq.fastapi:

LiteQBackgroundTasks

FastAPI-like background tasks using LiteQ.

Methods:

• add_task(func, *args, **kwargs) -> int - Add task and return task ID
• get_task_status(task_id: int) -> dict | None - Get status of specific task
• get_all_statuses() -> list[dict] - Get statuses of all tasks in this background instance
• task_ids (property) - List of all task IDs

Example:

from fastapi import FastAPI
from liteq.fastapi import LiteQBackgroundTasks
from liteq import task

app = FastAPI()

@task()
def send_email_task(to: str):
    # Send email
    return {"sent": True}

@app.post("/send-email")
async def send_email(to: str, background: LiteQBackgroundTasks):
    task_id = background.add_task(send_email_task, to)
    return {"message": "queued", "task_id": task_id}

@app.post("/batch-emails")
async def batch_emails(recipients: list[str], background: LiteQBackgroundTasks):
    for recipient in recipients:
        background.add_task(send_email_task, recipient)
    
    return {
        "message": f"Queued {len(recipients)} emails",
        "task_ids": background.task_ids
    }

@app.get("/batch-status")
async def batch_status(background: LiteQBackgroundTasks):
    statuses = background.get_all_statuses()
    return {"tasks": statuses}

enqueue_task(task_func, *args, **kwargs) -> int

Helper to enqueue a task.

Database

init_db()

Initialize the database schema. Called automatically by CLI.

Example:

from liteq.db import init_db

init_db()
│   ├── core.py           # Task decorator and registry
│   ├── db.py             # Database layer (SQLite)
│   ├── worker.py         # Worker implementation
│   ├── cli.py            # Command-line interface
│   ├── monitoring.py     # Stats and monitoring
│   └── web.py            # Web dashboard (optional)
├── examples/             # Complete examples
├── tests/                # >80% coverage
├── README.md
## Project Structure

liteq/ ├── liteq/ │ ├── init.py # Main exports │ ├── db.py # Database layer │ ├── decorators.py # @task decorator │ ├── worker.py # Worker implementation │ ├── manager.py # QueueManager │ ├── producer.py # Task enqueueing │ ├── monitoring.py # Stats and monitoring │ ├── recovery.py # Recovery functions │ ├── registry.py # Task registry │ └── signals.py # Signal handling ├── examples/ ├── tests/ ├── README.md ├── LICENSE ├── pyproject.toml └── setup.py

## Development

### Setup

```bash
git clone https://github.com/ddreamboy/liteq.git
cd liteq
python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate
pip install -e ".[dev]"

Or install only test dependencies:

pip install -r requirements-test.txt

Run Tests

# Run all tests
pytest

# With coverage
pytest --cov=liteq --cov-report=html

# Verbose output
pytest -v

Code Quality

# Format code
black .

# Lint code
ruff check .

Publish to PyPI

# Build
python -m build

# Upload to TestPyPI
python -m twine upload --repository testpypi dist/*

# Upload to PyPI
python -m twine upload dist/*

Use Cases

• 📧 Email sending queues

• 📊 Report generation

• Environment Variables

• LITEQ_DB - Database file path (default: liteq.db)

export LITEQ_DB=/path/to/tasks.db
liteq worker --app tasks.py

Database Schema

LiteQ uses a simple SQLite database with two tables:

tasks:

• id - Primary key
• name - Task function name
• payload - JSON args/kwargs
• queue - Queue name
• status - pending/running/done/failed
• priority - Integer (higher = first)
• attempts - Current attempt count
• max_retries - Max retry limit
• worker_id - Processing worker
• run_at - Scheduled run time
• created_at - Creation timestamp
• finished_at - Completion timestamp
• result - JSON result
• error - Error message

workers:

• worker_id - Primary key
• hostname - Worker hostname
• queues - Comma-separated queues
• concurrency - Process count
• last_heartbeat - Last ping time

Use Cases

• 📧 Email sending queues
• 📊 Report generation
• 🖼️ Image/video processing
• 📱 Push notifications
• 🧹 Cleanup/maintenance tasks
• 📈 Analytics pipelines
• 🔄 Webhook delivery
• 📦 Batch operations
• 🔍 Web scraping
• 💾 Data imports

Why LiteQ?

Simple - Minimal API, zero configuration
Lightweight - No dependencies, small codebase
Fast - SQLite is surprisingly performant
Reliable - WAL mode, ACID transactions
Debuggable - It's just SQLite, inspect with any SQL tool
Pythonic - Feels natural, not enterprise-y

When NOT to use LiteQ

• Millions of tasks per second
• Distributed/multi-node setups
• Network filesystems (NFS, SMB)
• Tasks larger than a few MB
• Real-time streaming

For these, use RabbitMQ, Redis, Kafka, or cloud service

Contributing

Contributions welcome! Please feel free to submit a Pull Request.

Links

• PyPI
• GitHub
• Documentation