调用 WebSocket.close 时现有等待会发生什么

【问题标题】：What happens to existing awaits when WebSocket.close is called调用 WebSocket.close 时现有等待会发生什么
【发布时间】：2020-08-24 13:24:32
【问题描述】：

如果我打开 Starlette/FastAPI WebSocket，如果我从协程外部关闭 WebSocket，当前等待从客户端接收数据的协程会发生什么情况？对receive 的调用是否引发异常，或者协程是否因为永远不会收到任何东西而永远驻留在内存中？

from fastapi import FastAPI
from fastapi.websockets import WebSocket

app = FastAPI()

open_sockets = {}

@app.websocket('/connection/')
async def connection(websocket: WebSocket):
    await websocket.accept()

    id = await websocket.receive_json()['id']
    open_sockets[id] = websocket

    while True:
        data = await websocket.receive_json()

@app.post('/kill/{id}/')
async def kill(id=str):
    # What does this do to the above `await websocket.receive_json()`?
    await open_sockets[id].close()
    del open_sockets[id]

【问题讨论】：

标签： python websocket python-asyncio fastapi starlette

【解决方案1】：

它引发starlette.websockets.WebSocketDisconnect，代码为 1006

  File ".\websocket_close_test.py", line 27, in connection
    data = await websocket.receive_json()
  File "C:\Apps\Python38\lib\site-packages\starlette\websockets.py", line 98, in receive_json
    self._raise_on_disconnect(message)
  File "C:\Apps\Python38\lib\site-packages\starlette\websockets.py", line 80, in _raise_on_disconnect
    raise WebSocketDisconnect(message["code"])

我确实注意到 .close() 调用被阻塞了一段时间。

这是我用来测试的代码，第二个ws.send 从未收到。

import time

import requests
import websocket

ws = websocket.WebSocket()
ws.connect("ws://localhost:8000/connection/")
print('Sending id 0')
ws.send('{ "id": "0" }')
time.sleep(2)
print('Closing id 0')
requests.post('http://localhost:8000/kill/0/')
print('id 0 is closed')
time.sleep(2)
print('Trying to send data on closed connection')
ws.send('{ "id": "10" }')

【讨论】：