Flask 和 Flask SocketIO：从外部模块内部接收事件

Question

我正在开发一个应用程序来从科学仪器中读取一些信息并使用远程 Web 客户端显示这些信息。我用 Flask 和 Flask-SocketIO 实现了这一点。我有一个 application.py 主文件，其中包含一个名为 app 的 Flask 实例。我将它与 Flask-SocketIO 一起使用。 Flask 部署的 HTML 页面包含一个 Javascript Socketio 实例，它与服务器应用程序通信（在 python 中）。

此外，我还有一个代表我的科学仪器的外部模块。我想从网站（Javascript）接收事件到这个模块-class。我尝试将 app 和 socketio python 对象传递给构造函数，以便从 Flask app 请求上下文。这非常有效仅适用于从模块发出事件。

简而言之，application.py 具有以下基本结构：

from gevent import monkey
monkey.patch_all()
from flask import Flask, Response, render_template, session, request, g
from flask_socketio import SocketIO, emit, disconnect, Namespace
from Instrument import *

app = Flask(__name__)
app.debug = True
socketio = SocketIO(app)

# some stuff here with @app.routes
@app.route('/instrument')
def inst(arg):
    t = Instrument(arg, app, socketio)

if __name__ == '__main__':
    socketio.run(app, port=8000, log_output=True)

对于外部模块Instrument.py，我尝试使用装饰器语法失败（有点@self.socketio.on，我不太熟悉它们）。所以我尝试了以下代码：

class Instrument():
    def __init__(self, arg, app, socketio):
        self.app = app
        self.socketio = socketio
        self.socketio.on_event('someCoolEvent', self.someCoolMethod, namespace='/coolapp') # THIS GIVES ME ERRORS

    def someCoolMethod():
        with self.app.test_request_context('/coolapp'):
            self.socketio.emit('emittedEvent', namespace='/telescope') # THIS WORKS FINE

我收到的错误如下（已编辑：添加了两行有用的内容）：

[2017-03-03 06:31:31,456][INFO] - _handle_event: received event "my event" from a40724e9e60e4a61ace9e19e59ceabda [/telescope]
[2017-03-03 06:31:31,604][INFO] - handle_get_request: a40724e9e60e4a61ace9e19e59ceabda: Received request to upgrade to websocket
[2017-03-03 06:31:33 +0000] [6333] [ERROR] Error handling request /socket.io/?EIO=3&transport=websocket&sid=24e7d134ea4c4840888c28e0e3ff1f6d
Traceback (most recent call last):
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/gunicorn/workers/async.py", line 52, in handle
    self.handle_request(listener_name, req, client, addr)
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/gunicorn/workers/ggevent.py", line 152, in handle_request
    super(GeventWorker, self).handle_request(*args)
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/gunicorn/workers/async.py", line 103, in handle_request
    respiter = self.wsgi(environ, resp.start_response)
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/flask/app.py", line 1994, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/flask_socketio/__init__.py", line 42, in __call__
    start_response)
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/engineio/middleware.py", line 47, in __call__
    return self.engineio_app.handle_request(environ, start_response)
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/socketio/server.py", line 353, in handle_request
    return self.eio.handle_request(environ, start_response)
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/engineio/server.py", line 260, in handle_request
    environ, start_response)
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/engineio/socket.py", line 86, in handle_get_request
    start_response)
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/engineio/socket.py", line 127, in _upgrade_websocket
    return ws(environ, start_response)
  File "/home/user/instr_gui/venv/local/lib/python2.7/site-packages/engineio/async_gevent.py", line 34, in __call__
    raise RuntimeError('You need to use the gevent-websocket server. '
RuntimeError: You need to use the gevent-websocket server. See the Deployment section of the documentation for more information.

应用程序初始化时，日志显示：

2017-03-04 02:52:04 [23530] [INFO] Starting gunicorn 18.0
2017-03-04 02:52:04 [23530] [INFO] Listening at: http://127.0.0.1:8000 (23530)
2017-03-04 02:52:04 [23530] [INFO] Using worker: gevent
2017-03-04 02:52:04 [23534] [INFO] Booting worker with pid: 23534

所以我尝试用 gunicorn -k gevent -w 1 module:app 和 gunicorn -k geventwebsocket.gunicorn.workers.GeventWebSocketWorker -w 1 module:app 配置文件 /etc/init/myapp.conf 但我遇到了同样的错误。

在浏览器中我看到另一个错误，它与 'main' 错误同时出现：

WebSocket connection to 'ws://somewebpage.com:2080/socket.io/?
EIO=3&transport=websocket&sid=572923d1b8fd402795bba50823941520' 
failed: Error during WebSocket handshake: Unexpected response code: 500

如何正确接收来自外部模块的事件？也许有更好的方法可以达到我想要的结果。如果有人帮我解决这个问题，我将不胜感激。

Answer 1

你可以尝试在 socketio.run(app, port=8000, log_output=True,policy_server=False)

中添加 policy_server=False

Answer 2

我认为您遇到的错误与您的问题无关。它是说您正在为 gevent 使用标准的 gunicorn worker，但是您需要为 websocket 使用 gevent-websocket worker 才能工作。请参阅文档 section 中的最后一个示例。

Answer 3

我自己回答。我找到了 following post，它解释了错误：

WebSocket connection to 'ws://somewebpage.com:2080/socket.io/?
EIO=3&transport=websocket&sid=572923d1b8fd402795bba50823941520' 
failed: Error during WebSocket handshake: Unexpected response code: 500

是nginx配置文件配置错误导致的。应该是这样的：

...
location / {
    proxy_pass http://127.0.0.1:8000;
    proxy_redirect off;

    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "Upgrade";

    proxy_set_header Host $http_host;
}
...

现在工作起来很有魅力：从导入的模块和主 python 脚本发出和接收事件。

Flask 和 Flask SocketIO：从外部模块内部接收事件

Flask and Flask SocketIO: receiving an event from inside of an external module

python

flask

flask-socketio