python - Django Channels/Daphne 中的 Websocket 超时

Question

简短问题版本:我在 Daphne 配置、消费者代码或客户端代码中做错了什么？

channels==1.1.8
daphne==1.3.0
Django==1.11.7

详情如下:

---

我正在尝试使用 Django Channels 和 Daphne 接口(interface)服务器保持持久的 Websocket 连接打开。我将使用大多数默认参数启动 Daphne:daphne -b 0.0.0.0 -p 8000 my_app.asgi:channel_layer。

我看到连接在浏览器中经过一段空闲时间(即 20 多秒)后关闭。随断开连接发送的 CloseEvent 的 code 值为 1006(异常关闭)，未设置 reason，并且wasClean 设置为 false。这应该是服务器关闭连接而不发送明确的关闭帧。

Daphne CLI 具有 --ping-interval 和 --ping-timeout 标志，默认值分别为 20 秒和 30 秒。对于前者，这被记录为“发送 keepalive ping 之前 WebSocket 必须空闲的秒数”，对于后者，记录为“如果没有响应 keepalive ping，WebSocket 关闭之前的秒数”。我读到这个是因为 Daphne 会等到 WebSocket 空闲 20 秒后发送 ping，如果 30 秒后没有收到响应，则会关闭 Websocket。相反，我看到的是连接在空闲 20 秒后关闭。 (跨越 3 次默认尝试，分别在 20081 毫秒、20026 毫秒和 20032 毫秒后关闭)

如果我将服务器更改为使用 daphne -b 0.0.0.0 -p 8000 --ping-interval 10 --ping-timeout 60 my_app.asgi:channel_layer 启动，连接仍然关闭，大约 20 秒的空闲时间。 (尝试更新 ping 3 次后，分别在 19892 毫秒、20011 毫秒、19956 毫秒后关闭)

代码如下:

---

consumer.py:

import logging

from channels import Group
from channels.generic.websockets import JsonWebsocketConsumer

from my_app import utilities

logger = logging.getLogger(__name__)

class DemoConsumer(JsonWebsocketConsumer):
    """
    Consumer echos the incoming message to all connected Websockets,
    and attaches the username to the outgoing message.
    """
    channel_session = True
    http_user_and_session = True

    @classmethod
    def decode_json(cls, text):
        return utilities.JSONDecoder.loads(text)

    @classmethod
    def encode_json(cls, content):
        return utilities.JSONEncoder.dumps(content)

    def connection_groups(self, **kwargs):
        return ['demo']

    def connect(self, message, **kwargs):
        super(DemoConsumer, self).connect(message, **kwargs)
        logger.info('Connected to DemoConsumer')

    def disconnect(self, message, **kwargs):
        super(DemoConsumer, self).disconnect(message, **kwargs)
        logger.info('Disconnected from DemoConsumer')

    def receive(self, content, **kwargs):
        super(DemoConsumer, self).receive(content, **kwargs)
        content['user'] = self.message.user.username
        # echo back content to all groups
        for group in self.connection_groups():
            self.group_send(group, content)

routing.py:

from channels.routing import route

from . import consumers

channel_routing = [
    consumers.DemoConsumer.as_route(path=r'^/demo/'),
]

demo.js:

// Tracks the cursor and sends position via a Websocket
// Listens for updated cursor positions and moves an icon to that location
$(function () {
  var socket = new WebSocket('ws://' + window.location.host + '/demo/');
  var icon;
  var moveTimer = null;
  var position = {x: null, y: null};
  var openTime = null;
  var lastTime = null;
  function sendPosition() {
    if (socket.readyState === socket.OPEN) {
      console.log('Sending ' + position.x + ', ' + position.y);
      socket.send(JSON.stringify(position));
      lastTime = Date.now();
    } else {
      console.log('Socket is closed');
    }
    // sending at-most 20Hz
    setTimeout(function () { moveTimer = null; }, 50);
  };
  socket.onopen = function (e) {
    var box = $('#websocket_box');
    icon = $('<div class="pointer_icon"></div>').insertAfter(box);
    box.on('mousemove', function (me) {
      // some browsers will generate these events much closer together
      // rather than overwhelm the server, batch them up and send at a reasonable rate
      if (moveTimer === null) {
        moveTimer = setTimeout(sendPosition, 0);
      }
      position.x = me.offsetX;
      position.y = me.offsetY;
    });
    openTime = lastTime = Date.now();
  };
  socket.onclose = function (e) {
    console.log("!!! CLOSING !!! " + e.code + " " + e.reason + " --" + e.wasClean);
    console.log('Time since open: ' + (Date.now() - openTime) + 'ms');
    console.log('Time since last: ' + (Date.now() - lastTime) + 'ms');
    icon.remove();
  };
  socket.onmessage = function (e) {
    var msg, box_offset;
    console.log(e);
    msg = JSON.parse(e.data);
    box_offset = $('#websocket_box').offset();
    if (msg && Number.isFinite(msg.x) && Number.isFinite(msg.y)) {
      console.log((msg.x + box_offset.left) + ', ' + (msg.y + box_offset.top));
      icon.offset({
        left: msg.x + box_offset.left,
        top: msg.y + box_offset.top
      }).text(msg.user || '');
    }
  };
});

asgi.py:

import os
from channels.asgi import get_channel_layer

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "my_project.settings")

channel_layer = get_channel_layer()

settings.py:

CHANNEL_LAYERS = {
    'default': {
        'BACKEND': 'asgi_redis.RedisChannelLayer',
        'ROUTING': 'main.routing.channel_routing',
        'CONFIG': {
            'hosts': [
                'redis://redis:6379/2',
            ],
            'symmetric_encryption_keys': [
                SECRET_KEY,
            ],
        }
    }
}

Answer 1

原来问题出在接口(interface)服务器前面的nginx代理上。代理设置为 proxy_read_timeout 20s;。如果服务器生成了 keepalive ping，则这些不会被计入上游读取超时。将此超时增加到一个更大的值允许 Websocket 保持打开更长时间。我将 proxy_connect_timeout 和 proxy_send_timeout 保持在 20s。