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#!/usr/bin/env python3
"""Example of aiohttp.web.Application.on_startup signal handler"""
import asyncio
from contextlib import suppress
from typing import AsyncIterator, List
import valkey.asyncio as valkey
from aiohttp import web
valkey_listener = web.AppKey("valkey_listener", asyncio.Task[None])
websockets = web.AppKey("websockets", List[web.WebSocketResponse])
async def websocket_handler(request):
ws = web.WebSocketResponse()
await ws.prepare(request)
request.app[websockets].append(ws)
try:
async for msg in ws:
print(msg)
await asyncio.sleep(1)
finally:
request.app[websockets].remove(ws)
return ws
async def on_shutdown(app: web.Application) -> None:
for ws in app[websockets]:
await ws.close(code=999, message=b"Server shutdown")
async def listen_to_valkey(app: web.Application) -> None:
r = valkey.Valkey(host="localhost", port=6379, decode_responses=True)
channel = "news"
async with r.pubsub() as sub:
await sub.subscribe(channel)
async for msg in sub.listen():
if msg["type"] != "message":
continue
# Forward message to all connected websockets:
for ws in app[websockets]:
await ws.send_str(f"{channel}: {msg}")
print(f"message in {channel}: {msg}")
async def background_tasks(app: web.Application) -> AsyncIterator[None]:
app[valkey_listener] = asyncio.create_task(listen_to_valkey(app))
yield
print("cleanup background tasks...")
app[valkey_listener].cancel()
with suppress(asyncio.CancelledError):
await app[valkey_listener]
def init():
app = web.Application()
l: List[web.WebSocketResponse] = []
app[websockets] = l
app.router.add_get("/news", websocket_handler)
app.cleanup_ctx.append(background_tasks)
app.on_shutdown.append(on_shutdown)
return app
web.run_app(init())