How to manage websockets across multiple servers / workers

aiohttp has built-in support for websockets. It's very simple and works well.

A simplified version of the example in the docs is:

async def handler(request):
    ws = web.WebSocketResponse()
    await ws.prepare(request)

    # Async iterate the messages the client sends
    async for message in ws:
        ws.send_str('You sent: %s' % (message.data,))

    print('websocket connection closed')

In the example, ws is a reference to a websocket connection with a client. I could easily put this references into request.app, like @Crandel does here (i.e., global state), but not in a production app, because each app server (and even each worker) will have its own app instance.

Is there an accepted pattern for this? Is there another way?

Note: I'm not referring to sessions. I'm referring to connections. I want to send a message to clients that connected to server A when events occur in application code in server B, etc.