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"""Example of aiohttp.web.Application.on_startup signal handler""" |
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import asyncio |
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from typing import List |
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import aioredis |
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from aiohttp import web |
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redis_listener = web.AppKey("redis_listener", asyncio.Task[None]) |
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websockets = web.AppKey("websockets", List[web.WebSocketResponse]) |
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async def websocket_handler(request): |
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ws = web.WebSocketResponse() |
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await ws.prepare(request) |
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request.app[websockets].append(ws) |
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try: |
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async for msg in ws: |
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print(msg) |
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await asyncio.sleep(1) |
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finally: |
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request.app[websockets].remove(ws) |
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return ws |
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async def on_shutdown(app: web.Application) -> None: |
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for ws in app[websockets]: |
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await ws.close(code=999, message=b"Server shutdown") |
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async def listen_to_redis(app): |
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try: |
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sub = await aioredis.Redis(host="localhost", port=6379) |
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ch, *_ = await sub.subscribe("news") |
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async for msg in ch.iter(encoding="utf-8"): |
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for ws in app[websockets]: |
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await ws.send_str(f"{ch.name}: {msg}") |
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print(f"message in {ch.name}: {msg}") |
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except asyncio.CancelledError: |
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pass |
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finally: |
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print("Cancel Redis listener: close connection...") |
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await sub.unsubscribe(ch.name) |
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await sub.quit() |
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print("Redis connection closed.") |
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async def start_background_tasks(app: web.Application) -> None: |
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app[redis_listener] = asyncio.create_task(listen_to_redis(app)) |
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async def cleanup_background_tasks(app): |
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print("cleanup background tasks...") |
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app[redis_listener].cancel() |
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await app[redis_listener] |
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def init(): |
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app = web.Application() |
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l: List[web.WebSocketResponse] = [] |
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app[websockets] = l |
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app.router.add_get("/news", websocket_handler) |
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app.on_startup.append(start_background_tasks) |
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app.on_cleanup.append(cleanup_background_tasks) |
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app.on_shutdown.append(on_shutdown) |
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return app |
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web.run_app(init()) |
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