使用 Django Channels 意外收到 WebSocket 断开连接

Question

使用 Django 通道向用户更新可能很长的运行任务的当前状态，我正面临一个 WebSocket DISCONNECT 我想追查的问题。

设置看起来非常简单。 settings.py定义通道层：

ASGI_APPLICATION = "config.routing.application"
CHANNEL_LAYERS = {
    'default': {
        'BACKEND': 'channels_redis.core.RedisChannelLayer',
        'CONFIG': {
            "hosts": [('127.0.0.1', 6379)],
        },
    },
}

在 routing.py 中，我们基本上遵循 Channels 文档的默认建议（该模式只是匹配一个 UUID，我们将其用作 public 面向标识符）：

from channels.auth import AuthMiddlewareStack
from channels.routing import ProtocolTypeRouter, URLRouter
from django.conf.urls import url
from lektomat.consumers import analysis

application = ProtocolTypeRouter({
    # (http->django views is added by default)
    "websocket": AuthMiddlewareStack(
        URLRouter([
            # Use a regex to match the UUID as the Django version with its '<uuid:analysis_id>' does not work for Channels.
            url(r"^ws/analysis/(?P<analysis_id>[a-f0-9]{8}-[a-f0-9]{4}-[1-5][a-f0-9]{3}-[89aAbB][a-f0-9]{3}-[a-f0-9]{12})/$",
                analysis.AnalysisConsumer),
        ])),
})

消费者只是通过新建立的 websockets 连接发送一些初始数据，并在各处记录信息：

import logging
import json
from channels.db import database_sync_to_async
from uuid import UUID
from typing import Tuple
from django.utils import timezone
from channels.generic.websocket import AsyncWebsocketConsumer
from myapp.models import AnalysisResult

logger = logging.getLogger(__name__)


class AnalysisConsumer(AsyncWebsocketConsumer):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.analysis_id = None
        self.analysis_group_name = 'analysis_'

    async def connect(self):
        self.analysis_id = self.scope['url_route']['kwargs']['analysis_id']
        self.analysis_group_name = "analysis_{}".format(self.analysis_id)
        await self.channel_layer.group_add(self.analysis_group_name, self.channel_name)
        logger.info("%s – AnalysisConsumer: connect()ed and joined group %s.", str(timezone.now()), self.analysis_group_name)
        dummy_percent = 11
        dummy_text = 'Dummy'
        logger.debug("%s – Sending initial channel update to group %s with a %d percent and status_text=%s", str(timezone.now()), self.analysis_group_name, dummy_percent, dummy_text)
        await self.send(text_data=json.dumps({
            'progress_percent': progress_percent,
            'status_text': status_text
        }))
        await self.accept()

    async def disconnect(self, code):
        logger.info("%s – AnalysisConsumer: disconnecting with code=%s (internal group name=%s).", str(timezone.now()), code, self.analysis_group_name)
        await self.channel_layer.group_discard(self.analysis_group_name, self.channel_name)
        logger.info("%s – AnalysisConsumer: disconnect(%s)ed and left room %s", str(timezone.now()), code, self.analysis_group_name)

    async def receive(self, text_data=None, bytes_data=None):
        logger.info("%s – unexpectedly received data from the websocket, text_data=%s, bytes_data=%s", str(timezone.now()), text_data, str(bytes_data))

最后，客户端的 javascript 正在连接到 websocket 端点：

var ws_scheme = window.location.protocol == "https:" ? "wss" : "ws";
var ws_uri = ws_scheme + '://' + window.location.host + '/ws/analysis/' + '{{ result_id }}' + '/';
var socket = new WebSocket(ws_uri);
socket.onopen = function open() {
    let now = new Date();
    console.info(now.toLocaleString() + ':' + now.getMilliseconds() + ' – WebSocket connection created.');
};

socket.onmessage = function(e) {
    console.log("WebSocket message received.")
    const data = JSON.parse(e.data);
    console.log("WebSocket message: " + data.status_text + " at " + data.progress_percent + " percent.");
};

socket.onclose = function(e) {
    let now = new Date();
    console.error(now.toLocaleString() + ':' + now.getMilliseconds() + ' – Analysis socket closed with event code = ' + e.code + ' and reason=' + e.reason);
};

socket.onerror = function(error) {
    let now = new Date();
    let msg = now.toLocaleString() + ':' + now.getMilliseconds() + ' – WebSocket error: ' + error;
    console.error(msg);
}

Redis 后端已启动并且运行。

但是：websocket 连接在启动后立即关闭。更准确地说，浏览器的 JS 控制台日志（德文，错误的翻译是我的）：

(!) Firefox cannot connect to server at ws://localhost:8000/ws/analysis/d222ebe1-5a2a-4797-9466-24db1de5d24b/
(!) 10.8.2020, 22:30:21:317 – WebSocket error: [object Event]
    onerror http://localhost:8000/analysis/d222ebe1-5a2a-4797-9466-24db1de5d24b:149
    (Async: EventHandlerNonNull)
    <anonym> http://localhost:8000/analysis/d222ebe1-5a2a-4797-9466-24db1de5d24b:146
(!) 10.8.2020, 22:30:21:319 – Analysis socket closed with event code = 1006 and reason=
    onclose http://localhost:8000/analysis/d222ebe1-5a2a-4797-9466-24db1de5d24b:143
    (Async: EventHandlerNonNull)
    <anonym> http://localhost:8000/analysis/d222ebe1-5a2a-4797-9466-24db1de5d24b:141

服务器控制台显示：

request: <AsgiRequest: GET '/analysis/d222ebe1-5a2a-4797-9466-24db1de5d24b'>
HTTP GET /analysis/d222ebe1-5a2a-4797-9466-24db1de5d24b 200 [1.37, 127.0.0.1:51562]
WebSocket HANDSHAKING /ws/analysis/d222ebe1-5a2a-4797-9466-24db1de5d24b/ [127.0.0.1:51574]
2020-08-10 20:30:20.549519+00:00 – AnalysisConsumer: connect()ed and joined group analysis_d222ebe1-5a2a-4797-9466-24db1de5d24b.
2020-08-10 20:30:20.610167+00:00 – Sending initial channel update to group analysis_d222ebe1-5a2a-4797-9466-24db1de5d24b with a 11 percent and status_text=Dummy
WebSocket DISCONNECT /ws/analysis/d222ebe1-5a2a-4797-9466-24db1de5d24b/ [127.0.0.1:51574]

这样，服务端收到连接请求，建立websocket连接后立即断开。大约半秒后，客户端仅响应代码 1006 的错误（这并不能说明什么）。永远不会调用消费者的 disconnect()。

可能是谁发起了 WebSocket DISCONNECT？它似乎不是任何应用程序代码。感谢您指出此处缺少的内容。

Answer 1

这看起来与我描述的问题相同 here。

你的服务器在断开连接之前的最后一条消息是它正在尝试发送一些东西（大？）。我发现发送大型 WebSocket 消息可能会导致断开连接并出现错误 1006。

您可以尝试将 WebSocket 服务器配置为以小块的形式发送数据。它对我的情况有所帮助。

Answer 2

该消费者正在尝试在接受连接之前发送消息。

我刚测试过，Daphne 抛出这个异常：

 File "...site-packages/daphne/ws_protocol.py", line 193, in handle_reply
 "Socket has not been accepted, so cannot send over it"

客户端收到代码为 1006 的 CloseEvent

使用 Django Channels 意外收到 WebSocket 断开连接

WebSocket disconnect received unexpectedly by using Django Channels

python

django

websocket

django-channels