使用 Flask Web 应用程序监控实时数据流

Question

这是基于

上发布的答案

我想监控数据流并将其推送到与上面的答案类似的前端，但是一旦应用程序启动，流就会开始 generating/monitoring 数据，并且客户端总是看到数据流的当前状态（无论他们是否从服务器请求数据，它都会保持运行ning）。

我很确定我需要通过线程将数据流与前端分开，但我对 threaded/asynchronous 编程不是很熟悉，我认为我做错了。也许我需要使用多处理而不是 threading？这大致是我正在尝试做的事情（根据上面链接的答案修改）：

app.py

#!/usr/bin/env python
from __future__ import division
import itertools
import time
from flask import Flask, Response, redirect, request, url_for
from random import gauss
import threading

app = Flask(__name__)

# Generate streaming data and calculate statistics from it
class MyStreamMonitor(object):
    def __init__(self):
        self.sum   = 0
        self.count = 0
    @property
    def mu(self):
        try:
            outv = self.sum/self.count
        except:
            outv = 0
        return outv
    def generate_values(self):
        while True:
            time.sleep(.1)  # an artificial delay
            yield gauss(0,1)
    def monitor(self, report_interval=1):
        print "Starting data stream..."
        for x in self.generate_values():
            self.sum   += x
            self.count += 1 

stream = MyStreamMonitor()

@app.route('/')
def index():
    if request.headers.get('accept') == 'text/event-stream':
        def events():
            while True:
                yield "data: %s %d\n\n" % (stream.count, stream.mu)
                time.sleep(.01) # artificial delay. would rather push whenever values are updated. 
        return Response(events(), content_type='text/event-stream')
    return redirect(url_for('static', filename='index.html'))

if __name__ == "__main__":
    # Data monitor should start as soon as the app is started.
    t = threading.Thread(target=stream.monitor() )
    t.start()
    print "Starting webapp..." # we never get to this point.
    app.run(host='localhost', port=23423)

static/index.html

<!doctype html>
<title>Server Send Events Demo</title>
<style>
  #data {
    text-align: center;
  }
</style>
<script src="http://code.jquery.com/jquery-latest.js"></script>
<script>
if (!!window.EventSource) {
  var source = new EventSource('/');
  source.onmessage = function(e) {
    $("#data").text(e.data);
  }
}
</script>
<div id="data">nothing received yet</div>

此代码无效。 "Starting webapp..." 消息永远不会打印，正常的烧瓶消息也不会打印，访问服务的 URL 确认应用程序不是运行ning。

如何让数据监视器在后台进入运行以便 flask 可以访问它看到的值并将当前状态推送到客户端（更好的是：只要客户端正在监听，当相关值改变时推送当前状态）？

Answer 1

我只需要更改此行

t = threading.Thread(target=stream.monitor())

对此：

t = threading.Thread(target=stream.monitor)

使用 Flask Web 应用程序监控实时数据流

Monitoring a real-time data stream with a flask web-app

python

multithreading

network-programming

stream

flask