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第一：我是python的绝对初学者，我以前写过PHP，所以如果我遇到了一些错误，请告诉我。

我正在写一个应用程序。它应该通过 websockets 提供它的信息。我为此选择了flask-socketio。在后台我想处理数据。因为我想让应用程序变小，所以我决定反对像 Celery 这样的解决方案。

我已将代码缩短为：

# -*- coding: utf8 -*-

from flask import Flask, jsonify, abort, make_response, url_for, request, render_template
from flask.ext.socketio import SocketIO, emit
from multiprocessing import Pool
from multiprocessing.managers import BaseManager
import time
import os

def background_stuff(args):
    while True:
        try:
            print args
            time.sleep(1)
        except Exception as e:
            return e

thread = None
_pool = None

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

@app.route('/', methods=['GET'])
def get_timers():
    return 'timer'

if __name__=='__main__':
    _pool = Pool(1)
    if os.environ.get('WERKZEUG_RUN_MAIN') == 'true':
        workers = _pool.apply_async(
            func=background_stuff,
            args=('do background stuff',),
        )
    socketio.run(app)
    # app.run()

开始时，我收到以下消息：

python test/multitest.py
 * Running on http://127.0.0.1:5000/
 * Restarting with stat
do background stuff
Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 810, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/threading.py", line 763, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 336, in _handle_tasks
    for taskseq, set_length in iter(taskqueue.get, None):
  File "/usr/lib/python2.7/Queue.py", line 168, in get
    self.not_empty.wait()
  File "/usr/lib/python2.7/threading.py", line 340, in wait
    waiter.acquire()
  File "gevent/_semaphore.pyx", line 112, in gevent._semaphore.Semaphore.acquire (gevent/gevent._semaphore.c:3386)
  File "/home/phil/work/ttimer/server/local/lib/python2.7/site-packages/gevent/hub.py", line 338, in switch
    return greenlet.switch(self)
LoopExit: This operation would block forever

do background stuff
do background stuff
do background stuff
do background stuff
do background stuff
127.0.0.1 - - [2015-09-30 00:06:23] "GET / HTTP/1.1" 200 120 0.001860
do background stuff
do background stuff
do background stuff
do background stuff
^CProcess PoolWorker-1:
Process PoolWorker-1:
Traceback (most recent call last):
Traceback (most recent call last):
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
    self.run()
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
    self._target(*self._args, **self._kwargs)
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 113, in worker
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 102, in worker
    task = get()
    result = (True, func(*args, **kwds))
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 376, in get
  File "test/multitest.py", line 14, in background_stuff
KeyboardInterrupt
    time.sleep(1)
KeyboardInterrupt
    return recv()
KeyboardInterrupt

所以后台进程正在工作，它会响应 http 请求（127.0.0.1 - - [2015-09-30 00:06:23] "GET / HTTP/1.1" 200 120 0.001860）。但是只是忽略一个错误，因为它似乎有效，这对我来说似乎不是一个解决方案。有谁可以告诉我我在这里做错了什么？

如果你说我不能那样做你能告诉我为什么吗？我想学习和理解我做错了什么。

我读了一些关于monkeyepatching的东西，但是所有建议的东西都只是抛出了更多或其他错误。我认为最好解决第一个错误而不是盲目地尝试修复。

python -V
Python 2.7.9

问候

更新

我为猴子补丁添加了 2 行，这就是我得到的：

$python multitest2.py 
 ^CProcess PoolWorker-1:
Traceback (most recent call last):
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 102, in worker
    task = get()
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 376, in get
    return recv()
KeyboardInterrupt
Exception in thread Thread-3:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 810, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/threading.py", line 763, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 380, in _handle_results
    task = get()
KeyboardInterrupt

 * Running on http://127.0.0.1:5000/
 * Restarting with stat
^CProcess PoolWorker-1:
Traceback (most recent call last):
  File "/usr/lib/python2.7/multiprocessing/process.py", line 258, in _bootstrap
Exception in thread Thread-3:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 810, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/threading.py", line 763, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 380, in _handle_results
    task = get()
KeyboardInterrupt

    self.run()
  File "/usr/lib/python2.7/multiprocessing/process.py", line 114, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 102, in worker
    task = get()
  File "/usr/lib/python2.7/multiprocessing/queues.py", line 376, in get
    return recv()
KeyboardInterrupt
do background stuff
FAILED to start flash policy server: [Errno 98] Address already in use: ('127.0.0.1', 10843)
$do background stuff
do background stuff
do background stuff
do background stuff
do background stuff
do background stuff
do background stuff
do background stuff
do background stuff
do background stuff
do background stuff
do background stuff

开始时根本没有输出。在 hittinc ctrl-c 几次之后，我得到了背景的东西输出。这一直持续到我通过 SIGKILL 杀死 python 进程

更新 2

我希望看到的是

 * Running on http://127.0.0.1:5000/
 * Restarting with stat
do background stuff
do background stuff
do background stuff

在脚本运行之后。但是在我按下 ctrl-c 之前什么都没有发生。

4

2 回答 2

0

首先，你需要知道你使用的Flask-SocketIO版本需要gevent，这是一个协程框架。将 gevent 的异步协程与多处理池一起使用是一种奇怪的组合。您正在使用 gevent，所以最有意义的是使用 gevent池功能，以便一切都保持一致。

现在关于这个问题，我认为这可能是由于没有在早期阶段修补标准库猴子。我建议您在脚本的最顶部添加以下行（在您的导入上方，将它们设为第 1 行和第 2 行）：

from gevent import monkey
monkey.patch_all()

这些将确保对标准库的任何调用，例如线程、信号量等，都会转到 gevent 实现。

更新：我试过你的例子。没有猴子补丁的原始版本对我来说很好，我没有看到您报告的 LoopExit 错误。正如您所报告的，添加猴子补丁会阻止后台进程运行。

无论如何，我将您的脚本转换为使用 gevent.pool 并且对我来说可靠。这是编辑后的脚本：

from flask import Flask, jsonify, abort, make_response, url_for, request, render_template
from flask.ext.socketio import SocketIO, emit
from gevent.pool import Pool
import time
import os

def background_stuff(args):
    while True:
        try:
            print args
            time.sleep(1)
        except Exception as e:
            return e

thread = None
_pool = None

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

@app.route('/', methods=['GET'])
def get_timers():
    return 'timer'

if __name__=='__main__':
    _pool = Pool(1)
    workers = _pool.apply_async(
        func=background_stuff,
        args=('do background stuff',),
    )
    socketio.run(app)

希望这可以帮助！

于 2015-09-30T05:22:24.283 回答
0

我阅读了有关 gevent 的教程并找到了一个简单而干净的解决方案，以满足我的需求：

# -*- coding: utf8 -*-

from flask import Flask
from flask.ext.socketio import SocketIO
import gevent
import os

def background_stuff():
    while True:
        try:
            print 'doing background work ... '
            gevent.sleep(1)
        except Exception as e:
            return e

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

@app.route('/', methods=['GET'])
def get_timers():
    return 'timer'

if __name__=='__main__':
    if os.environ.get('WERKZEUG_RUN_MAIN') == 'true':
        gevent.spawn(background_stuff)
    socketio.run(app)

该教程可以在这里找到：http ://sdiehl.github.io/gevent-tutorial/#long-polling

它甚至讲述了 gevent 和 multiprocesing 的问题：http ://sdiehl.github.io/gevent-tutorial/#subprocess ，但是因为我找到了一个适合我需要的简单解决方案，所以我没有尝试其他任何方法。

于 2015-10-01T21:39:37.360 回答