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Simple broadcast channels.

Project description


Broadcaster helps you develop realtime streaming functionality in by providing a simple broadcast API onto a number of different backend services.

It currently supports Redis PUB/SUB, and Postgres LISTEN/NOTIFY, plus a simple in-memory backend, that you can use for local development or during testing.

Here's a complete example of the backend code for a simple websocket chat app:

# Requires: `starlette`, `uvicorn`, `jinja2`
# Run with `uvicorn example:app`
from broadcaster import Broadcast
from starlette.applications import Starlette
from starlette.concurrency import run_until_first_complete
from starlette.routing import Route, WebSocketRoute
from starlette.templating import Jinja2Templates

broadcast = Broadcast("redis://localhost:6379")
templates = Jinja2Templates("templates")

async def homepage(request):
    template = "index.html"
    context = {"request": request}
    return templates.TemplateResponse(template, context)

async def chatroom_ws(websocket):
    await websocket.accept()
    await run_until_first_complete(
        (chatroom_ws_receiver, {"websocket": websocket}),
        (chatroom_ws_sender, {"websocket": websocket}),

async def chatroom_ws_receiver(websocket):
    async for message in websocket.iter_text():
        await broadcast.publish(channel="chatroom", message=message)

async def chatroom_ws_sender(websocket):
    async with broadcast.subscribe(channel="chatroom") as subscriber:
        async for event in subscriber:
            await websocket.send_text(event.message)

routes = [
    Route("/", homepage),
    WebSocketRoute("/", chatroom_ws, name='chatroom_ws'),

app = Starlette(
    routes=routes, on_startup=[broadcast.connect], on_shutdown=[broadcast.disconnect],


  • pip install broadcaster
  • pip install broadcaster[redis]
  • pip install broadcaster[postgres]

## Available backends

  • Broadcast('memory://')
  • Broadcast("redis://localhost:6379")
  • Broadcast("postgres://localhost:5432/hostedapi")

Where next?

  • Serialization / deserialization to support broadcasting structured data.
  • Backends for Redis Streams, Apache Kafka, and RabbitMQ.
  • Add support for subscribe('chatroom', history=100) for backends which provide persistence. (Redis Streams, Apache Kafka) This will allow applications to subscribe to channel updates, while also being given an initial window onto the most recent events.

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