MongoDB Change Broadcaster

A real-time change stream broadcaster for MongoDB, supporting multiple delivery channels (WebSocket, Redis, HTTP, etc.) with extensible architecture.

Read the blog post on the implementation here.

Features

• 📡 Listen to MongoDB change streams
• 🚀 Built-in channels: WebSocket, Redis, HTTP, and Database Logging
• 🔌 Extensible architecture for custom channels
• ⚡ Async-first implementation
• 🛠️ Configurable pipelines and filtering

Installation

pip install mongo-broadcaster

# Optional dependencies for specific channels:
pip install mongo_broadcaster[fastapi]  # WebSocket
pip install mongo_broadcaster[redis]    # Redis Pub/Sub support

Basic Usage

from mongo_broadcaster import (
    MongoChangeBroadcaster,
    BroadcasterConfig,
    CollectionConfig
)
from mongo_broadcaster.channels import WebSocketChannel

# Initialize with MongoDB connection
config = BroadcasterConfig(
    mongo_uri="mongodb://localhost:27017",
    collections=[
        CollectionConfig(
            collection_name="users",
            fields_to_watch=["name", "email"],
            recipient_identifier="fullDocument._id"
        )
     ]
)

broadcaster = MongoChangeBroadcaster(config)
broadcaster.add_channel(WebSocketChannel())

# Start listening (typically in your app startup)
await broadcaster.start()

Built-in Channels

Channel	Description	Ideal For
WebSocketChannel	Real-time browser updates	Live dashboards
RedisPubSubChannel	Pub/Sub messaging	Microservices
HTTPCallbackChannel	Webhook notifications	Third-party integrations
DatabaseChannel	Persistent change logging	Audit trails

Extending with Custom Channels

Implement your own channel by subclassing BaseChannel:

from mongo_broadcaster.channels.base import BaseChannel
from typing import Any, Dict


class CustomMQTTChannel(BaseChannel):
    def __init__(self, broker_url: str):
        self.broker_url = broker_url
        self.client = None

    async def connect(self):
	"""Initialize your connection"""
	self.client = await setup_mqtt_client(self.broker_url)

    async def send(self, recipient: str, message: Dict[str, Any]):
	"""Send to specific recipient"""
	await self.client.publish(f"changes/{recipient}", message)

    async def broadcast(self, message: Dict[str, Any]):
	"""Send to all subscribers"""
	await self.client.publish("changes/all", message)

    async def disconnect(self):
	"""Clean up resources"""
	await self.client.disconnect()

# Usage:
broadcaster.add_channel(CustomMQTTChannel("mqtt://localhost"))

Configuration Options

CollectionConfig

CollectionConfig(
    collection_name: str,
    database_name: Optional[str] = None,
	# Fields to include in change events
    fields_to_watch: List[str] = [],
	# Dot-notation path to identify recipients (e.g., "fullDocument._id")
    recipient_identifier: Optional[str] = None,
	# MongoDB change stream options
    change_stream_config: ChangeStreamConfig = ChangeStreamConfig()
)

Examples

FastAPI WebSocket Endpoint

from fastapi import FastAPI, WebSocket

app = FastAPI()
ws_channel = WebSocketChannel()


@app.websocket("/ws/{client_id}")
async def websocket_endpoint(websocket: WebSocket, client_id: str):
    await ws_channel.connect(client_id, websocket)
    try:
        while True:
            await websocket.receive_text()
    except WebSocketDisconnect:
	await ws_channel.disconnect(client_id)

Please see the examples folder for more.

Contributing

To add new channels:

1. Create a subclass of BaseChannel
2. Implement required methods:

• connect()
• send()
• broadcast()
• disconnect()

3. Submit a PR!

License

MIT

TODO

• Write tests