timhughes/fastapi_websocket_redis_pubsub.py

## fastapi_websocket_redis_pubsub.py
"""
Usage:

Make sure that redis is running on localhost (or adjust the url)
Install uvicorn or some other asgi server https://asgi.readthedocs.io/en/latest/implementations.html

    pip install -u uvicorn

Install dependencies

    pip install -u aioredis fastapi

Start the application, this will depend on the asgi server

   uvicorn fastapi_websocket_redis_pubsub:app

Open two browser windows to the web interface  http://127.0.0.1:8000

Enter some data in one window and it should appear in the other window.

"""

import asyncio

import logging


from fastapi import FastAPI
from fastapi.responses import HTMLResponse
from fastapi.websockets import WebSocket, WebSocketDisconnect
from aioredis

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)


app = FastAPI()

html = """
<!DOCTYPE html>
<html>
    <head>
        <title>Chat</title>
    </head>
    <body>
        <h1>WebSocket Chat</h1>
        <form action="" onsubmit="sendMessage(event)">
            <input type="text" id="messageText" autocomplete="off"/>
            <button>Send</button>
        </form>
        <ul id='messages'>
        </ul>
        <script>
            var ws = new WebSocket("ws://localhost:8000/ws");
            ws.onmessage = function(event) {
                var messages = document.getElementById('messages')
                var message = document.createElement('li')
                var content = document.createTextNode(event.data)
                message.appendChild(content)
                messages.appendChild(message)
            };
            function sendMessage(event) {
                var input = document.getElementById("messageText")
                ws.send(input.value)
                input.value = ''
                event.preventDefault()
            }
        </script>
    </body>
</html>
"""


@app.get("/")
async def get():
    return HTMLResponse(html)


@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()
    await redis_connector(websocket)


async def redis_connector(
    websocket: WebSocket, redis_uri: str = "redis://localhost:6379"
):
    async def consumer_handler(ws: WebSocket, r):
        try:
            while True:
                message = await ws.receive_text()
                if message:
                    await r.publish("chat:c", message)
        except WebSocketDisconnect as exc:
            # TODO this needs handling better
            logger.error(exc)

    async def producer_handler(r, ws: WebSocket):
        (channel,) = await r.subscribe("chat:c")
        assert isinstance(channel, aioredis.Channel)
        try:
            while True:
                message = await channel.get()
                if message:
                    await ws.send_text(message.decode("utf-8"))
        except Exception as exc:
            # TODO this needs handling better
            logger.error(exc)

    redis = await aioredis.create_redis_pool(redis_uri)

    consumer_task = consumer_handler(websocket, redis)
    producer_task = producer_handler(redis, websocket)
    done, pending = await asyncio.wait(
        [consumer_task, producer_task], return_when=asyncio.FIRST_COMPLETED,
    )
    logger.debug(f"Done task: {done}")
    for task in pending:
        logger.debug(f"Canceling task: {task}")
        task.cancel()
    redis.close()
    await redis.wait_closed()
	"""
	Usage:

	Make sure that redis is running on localhost (or adjust the url)
	Install uvicorn or some other asgi server https://asgi.readthedocs.io/en/latest/implementations.html

	pip install -u uvicorn

	Install dependencies

	pip install -u aioredis fastapi

	Start the application, this will depend on the asgi server

	uvicorn fastapi_websocket_redis_pubsub:app

	Open two browser windows to the web interface http://127.0.0.1:8000

	Enter some data in one window and it should appear in the other window.

	"""

	import asyncio

	import logging


	from fastapi import FastAPI
	from fastapi.responses import HTMLResponse
	from fastapi.websockets import WebSocket, WebSocketDisconnect
	from aioredis

	logging.basicConfig(level=logging.INFO)
	logger = logging.getLogger(__name__)


	app = FastAPI()

	html = """
	<!DOCTYPE html>
	<html>
	<head>
	<title>Chat</title>
	</head>
	<body>
	<h1>WebSocket Chat</h1>
	<form action="" onsubmit="sendMessage(event)">
	<input type="text" id="messageText" autocomplete="off"/>
	<button>Send</button>
	</form>
	<ul id='messages'>
	</ul>
	<script>
	var ws = new WebSocket("ws://localhost:8000/ws");
	ws.onmessage = function(event) {
	var messages = document.getElementById('messages')
	var message = document.createElement('li')
	var content = document.createTextNode(event.data)
	message.appendChild(content)
	messages.appendChild(message)
	};
	function sendMessage(event) {
	var input = document.getElementById("messageText")
	ws.send(input.value)
	input.value = ''
	event.preventDefault()
	}
	</script>
	</body>
	</html>
	"""


	@app.get("/")
	async def get():
	return HTMLResponse(html)


	@app.websocket("/ws")
	async def websocket_endpoint(websocket: WebSocket):
	await websocket.accept()
	await redis_connector(websocket)


	async def redis_connector(
	websocket: WebSocket, redis_uri: str = "redis://localhost:6379"
	):
	async def consumer_handler(ws: WebSocket, r):
	try:
	while True:
	message = await ws.receive_text()
	if message:
	await r.publish("chat:c", message)
	except WebSocketDisconnect as exc:
	# TODO this needs handling better
	logger.error(exc)

	async def producer_handler(r, ws: WebSocket):
	(channel,) = await r.subscribe("chat:c")
	assert isinstance(channel, aioredis.Channel)
	try:
	while True:
	message = await channel.get()
	if message:
	await ws.send_text(message.decode("utf-8"))
	except Exception as exc:
	# TODO this needs handling better
	logger.error(exc)

	redis = await aioredis.create_redis_pool(redis_uri)

	consumer_task = consumer_handler(websocket, redis)
	producer_task = producer_handler(redis, websocket)
	done, pending = await asyncio.wait(
	[consumer_task, producer_task], return_when=asyncio.FIRST_COMPLETED,
	)
	logger.debug(f"Done task: {done}")
	for task in pending:
	logger.debug(f"Canceling task: {task}")
	task.cancel()
	redis.close()
	await redis.wait_closed()