I'm building a simple HTTP web service, but I want to send information trough a websocket to another server.
For instance when the web service receive a request on /foo, it send on the websocket "request on /foo received".
I'm fairly new to async programming in Python. I choose aiohttp for this, but it's not a hard requirement.
I have some prior experience with websocket and autobahn and I tried at first to mix aiohtpp and autobahn. I even found an example with both but it used wamp and I just want websocket.
Then I tried without autobahn as aiohttp handle websocket.
My last attempt looks like that:
from aiohttp import web, ClientSession, WSMsgType
async def callback(msg):
print(msg)
async def websocket(session):
async with session.ws_connect('http://localhost:8000') as ws:
app['ws'] = ws
async for msg in ws:
if msg.type == WSMsgType.TEXT:
await callback(msg.data)
elif msg.type == WSMsgType.CLOSED:
break
elif msg.type == WSMsgType.ERROR:
break
async def hello(request):
app.ws.send_str('{"hello": "world"}')
return web.Response(text="Hello, world")
async def init(app):
session = ClientSession()
app['websocket_task'] = app.loop.create_task(websocket(session))
app = web.Application()
app.add_routes([web.get('/', hello)])
app.on_startup.append(init)
web.run_app(app, port=7000)
When requesting / it cashes with the following exception: AttributeError: 'Application' object has no attribute 'ws'
How can I mix http serving and writing on websocket as a client? Is it even possible ?
Sometimes a good night of sleep is all you need...
Basically I needed to initialize a resource and use it in the handlers. Exactly like you would do for a database connection.
I used this demo as an example and adapted it to my need. Here is what it looks like:
from aiohttp import web, ClientSession
class Handler:
def __init__(self, ws):
self._ws = ws
async def hello(self):
await self._ws.send_str('{"hello": "world"}')
return web.Response(text="Hello, world")
async def init(app):
session = ClientSession()
ws = await session.ws_connect('http://localhost:8000')
h = Handler(ws)
app.add_routes([web.get('/', h.hello)])
app = web.Application()
app.on_startup.append(init)
web.run_app(app, port=7000)
I hope this can help other asyncio/aiohttp beginners.
Cheers
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