使用Django频道意外收到WebSocket断开连接

编程问答 2022-09-17

问题描述

使用Django渠道向用户更新可能长期运行的任务的当前状态，我面临着要追查的WebSocket disCONNECT。

设置看起来很简单。 settings.py定义频道层：

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文档中的默认建议（该模式只是与一个UUID匹配，我们将其用作面向公众的标识符）：

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),])),})

消费者只不过是通过新建立的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",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).",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",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",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后端已启动并正在运行。

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（德语，翻译错误是我的）：

(!) 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]

因此，服务器收到连接请求，建立了websocket连接并立即断开连接。客户端在大约半秒钟后响应，仅出现代码1006的错误（说明不多）。永远不会调用消费者的disconnect()。

谁可以发起WebSocket disCONNECT？似乎不是任何应用程序代码。感谢您指出这里缺少的内容。

解决方法

这看起来像我描述的here一样。

服务器断开连接前的最后一条消息是它正在尝试发送某些内容（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发送数据。就我而言，这很有帮助。

,

该使用者正在尝试在接受连接之前发送消息。

我刚刚测试过，达芙妮抛出了这个异常：

 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

djangodjango-channelspythonwebsocket