为什么 flask_socketio.disconnect 会阻止线程完成？

Question

我有以下系统：[Client] - [Web Server] - [Connecotr].

连接器是网络服务器和数据源之间的一种中间代码。

我需要用连接器监视服务器连接。如果连接丢失，那么我必须通知客户端。

Web 服务器和连接器之间的通信是使用 socketio 组织的。

问题是如果连接器停止工作，Web 服务器将在一分钟后才知道它（这是最好的情况）。

我决定服务器应该每秒检查一次连接器的状态。

连接器连接到服务器后，后台任务启动。任务本质：每一秒：1）固定时间； 2）将固定时间存入栈； 3) 向连接器发送回显消息。（参见 server.background_thread）

连接器接受回显消息和时间戳作为参数，并向 Web 服务器发送回显消息，作为参数传递接收到的时间戳。（参见 client.echo）

网络服务器收到回显消息，如果时间戳等于堆栈中的最后一个值，则从堆栈中删除该值。（参见 server.on_echo_connector）

在网络服务器上，每次迭代都会检查堆栈大小（参见 server.background_thread）。如果大于5，则表示连接器5次没有响应回显信息，我们认为连接器不可用，断开连接。

当服务器意识到连接器不可用时，有必要终止向连接器发送回显消息的线程。

一旦堆栈大小大于 5，我就退出无限循环并调用 flask_socketio.disconnect (connector_sid, '/ connector')。在这个调用之后没有任何效果（例如 print）

在 on_disconnect_connector（服务器）方法中，thread.join() 被调用并且永不终止。

而且我需要完成线程，这样当连接器再次启动时，它会连接成功，一切从头再来。

如何解决这个问题？

服务器

# -*- coding: utf-8 -*-

import os
import threading
import time
import collections
from datetime import datetime

import flask
import flask_socketio

def get_unix_time():
    return int(time.mktime(datetime.now().timetuple()))

class Stack(collections.deque):

    def __init__(self, iterable=(), maxlen=None):
        collections.deque.__init__(self, iterable, maxlen)

    @property
    def size(self):
        return len(self)

    @property
    def empty(self):
        return self.size == 0

    @property
    def head(self):
        return self[-1]

    @property
    def tail(self):
        return self[0]

    def push(self, x):
        self.append(x)

# SERVER

app = flask.Flask(__name__)
sio = flask_socketio.SocketIO(app, async_mode='gevent')

connector_sid = None
echo_stack = Stack()

thread = None
thread_lock = threading.Lock()


def background_thread(app):
    time.sleep(2)  # delay for normal connection

    while True:
        if echo_stack.size >= 5:
            break
        time_ = get_unix_time()
        echo_stack.push(time_)
        sio.emit('echo', time_, namespace='/connector')
        sio.sleep(1)

    with app.app_context():
        flask_socketio.disconnect(connector_sid, '/connector')


@sio.on('connect', namespace='/connector')
def on_connect_connector():
    """Connector connection event handler."""
    global connector_sid, thread
    print 'Attempt to connect a connector {}...'.format(request.sid)

    # if the connector is already connected, reject the connection
    if connector_sid is not None:
        print 'Connection for connector {} rejected'.format(request.sid)
        return False
        # raise flask_socketio.ConnectionRefusedError('Connector already connected')

    connector_sid = request.sid
    print('Connector {} connected'.format(request.sid))

    with thread_lock:
        if thread is None:
            thread = sio.start_background_task(
                background_thread, current_app._get_current_object())

    # notify clients about connecting a connector
    sio.emit('set_connector_status', True, namespace='/client')


@sio.on('disconnect', namespace='/connector')
def on_disconnect_connector():
    """Connector disconnect event handler."""
    global connector_sid, thread

    print 'start join'
    thread.join()
    print 'end join'
    thread = None
    print 'after disconet:', thread

    connector_sid = None

    echo_stack.clear()

    print('Connector {} disconnect'.format(request.sid))

    # notify clients of disconnected connector
    sio.emit('set_connector_status', False, namespace='/client')


@sio.on('echo', namespace='/connector')
def on_echo_connector(time_):
    if not echo_stack.empty:
        if echo_stack.head == time_:
            echo_stack.pop()


@sio.on('message', namespace='/connector')
def on_message_connector(cnt):
    # print 'Msg: {}'.format(cnt)
    pass

if __name__ == '__main__':
    sio.run(app)

客户

# -*- coding: utf-8 -*-

import sys
import threading
import time

import socketio
import socketio.exceptions

sio = socketio.Client()
thread = None
thread_lock = threading.Lock()
work = False


def background_thread():
    # example task
    cnt = 0
    while work:
        cnt += 1
        if cnt % 10 == 0:
            sio.emit('message', cnt // 10, namespace='/connector')
        sio.sleep(0.1)


@sio.on('connect', namespace='/connector')
def on_connect():
    """Server connection event handler."""
    global thread, work

    print '\n-----            Connected to server            -----' \
          '\n----- My SID:  {} -----\n'.format(sio.sid)

    work = True  # set flag

    # run test task
    with thread_lock:
        if thread is None:
            thread = sio.start_background_task(background_thread)


@sio.on('disconnect', namespace='/connector')
def on_disconnect():
    """Server disconnect event handler."""
    global thread, work

    # clear the work flag so that at the next iteration the endless loop ends
    work = False
    thread.join()
    thread = None

    # disconnect from server
    sio.disconnect()
    print '\n-----         Disconnected from server          -----\n'

    # switch to the mode of infinite attempts to connect to the server
    main()


@sio.on('echo', namespace='/connector')
def on_echo(time_):
    sio.emit('echo', time_, namespace='/connector')


def main():
    while True:
        try:
            sio.connect('http://localhost:5000/connector',
                        namespaces=['/connector'])
            sio.wait()
        except socketio.exceptions.ConnectionError:
            print 'Trying to connect to the server...'
            time.sleep(1)
        except KeyboardInterrupt:
            print '\n---------- EXIT ---------\n'
            sys.exit()
        except Exception as e:
            print e


if __name__ == '__main__':
    print '\n---------- START CLIENT ----------\n'
    main()

Python 2.7

Answer 1

需要为客户端安装额外的库(see)

pip install "python-socketio[client]"

多亏了这个库，WebSocket 传输才能正常工作。现在断开连接器是立即可见的。

为什么 flask_socketio.disconnect 会阻止线程完成？

Why does flask_socketio.disconnect prevent the thread from completing?

python

flask-socketio

gevent-socketio

python-socketio