Python 服务 html 异步

Question

我有一个服务于 HTML 的服务器，带有 nginx、uwsgi 和 flask。这是一个简单的网络应用程序。当您刷新页面时，webapp 会在其他地方进行一些 API 调用，然后处理从 API 编辑的结果 return 并生成 HTML，然后 returned.

现在，大部分时间都在等待 API 回复。因此，我正在使用 gevent 进行 API 调用和猴子修补等，以使其全部并发。如果每次页面刷新都需要进行 3 次 API 调用，则无需等待第一次调用 return 来发起第二次调用。您启动所有三个，等待他们的响应，然后生成 HTML 以 returned。

然而，一个单独的问题是页面从头到尾的刷新是否本身是并发的。为了测试这个，我写了一个小的并发脚本来刷新我的服务器：

from gevent import monkey
monkey.patch_all()

import requests, datetime

import gevent

def call_func(n):
    before = datetime.datetime.now()
    print 'initiating call '+str(n),before
    requests.get('http://examplemyserver.com')
    after = datetime.datetime.now()
    print 'finishing call '+str(n),after, after-before

gevent_list = [ gevent.spawn(call_func, n=n) for n in range(10) ]

gevent.joinall(gevent_list)

结果如下：

initiating call 0 2016-05-04 23:03:49.437540
initiating call 1 2016-05-04 23:03:49.446304
initiating call 2 2016-05-04 23:03:49.447911
initiating call 3 2016-05-04 23:03:49.450232
initiating call 4 2016-05-04 23:03:49.451774
initiating call 5 2016-05-04 23:03:49.453331
initiating call 6 2016-05-04 23:03:49.454759
initiating call 7 2016-05-04 23:03:49.456301
initiating call 8 2016-05-04 23:03:49.457663
initiating call 9 2016-05-04 23:03:49.458981
finishing call 0 2016-05-04 23:03:51.270078 0:00:01.832538
finishing call 6 2016-05-04 23:03:52.169842 0:00:02.715083
finishing call 3 2016-05-04 23:03:52.907892 0:00:03.457660
finishing call 1 2016-05-04 23:03:53.498008 0:00:04.051704
finishing call 8 2016-05-04 23:03:54.150188 0:00:04.692525
finishing call 4 2016-05-04 23:03:55.032089 0:00:05.580315
finishing call 7 2016-05-04 23:03:55.994570 0:00:06.538269
finishing call 2 2016-05-04 23:03:56.659146 0:00:07.211235
finishing call 9 2016-05-04 23:03:57.149156 0:00:07.690175
finishing call 5 2016-05-04 23:03:58.002210 0:00:08.548879

所以你看，十个页面刷新实际上是同时启动的，但是它们是按顺序 return 编辑的，相差大约 1 秒。这表明虽然内部外部 API 调用是同时完成的，但在给出 HTTP 响应之前，不会接受新的 HTTP 响应。

因此，考虑到 webapp 的大部分时间都花在等待 API 响应上，我怎样才能使整个过程并发？这是我需要用 nginx 改变的东西吗？用uwsgi？用烧瓶？我对这些东西的架构一无所知。

谢谢。

编辑 1：按照Rob的想法，我把要调用的服务器换成了'http://httpbin.org/delay/1'。这是我得到的结果：

initiating call 0 2016-05-04 23:36:18.697813
initiating call 1 2016-05-04 23:36:18.706510
initiating call 2 2016-05-04 23:36:18.708645
initiating call 3 2016-05-04 23:36:18.711055
initiating call 4 2016-05-04 23:36:18.712679
initiating call 5 2016-05-04 23:36:18.714051
initiating call 6 2016-05-04 23:36:18.715471
initiating call 7 2016-05-04 23:36:18.717015
initiating call 8 2016-05-04 23:36:18.718412
initiating call 9 2016-05-04 23:36:18.720193
finishing call 0 2016-05-04 23:36:20.599483 0:00:01.901670
finishing call 2 2016-05-04 23:36:20.600829 0:00:01.892184
finishing call 8 2016-05-04 23:36:20.611292 0:00:01.892880
finishing call 5 2016-05-04 23:36:20.618842 0:00:01.904791
finishing call 7 2016-05-04 23:36:20.620065 0:00:01.903050
finishing call 6 2016-05-04 23:36:20.621344 0:00:01.905873
finishing call 1 2016-05-04 23:36:20.622407 0:00:01.915897
finishing call 4 2016-05-04 23:36:20.623392 0:00:01.910713
finishing call 9 2016-05-04 23:36:20.624236 0:00:01.904043
finishing call 3 2016-05-04 23:36:20.625075 0:00:01.914020

这就是您对可以并发接受 HTTP 调用的服务器的期望。所以这说明我上面测试的代码是正确的，问题确实出在服务器上。它不会同时进行 HTTP 调用。

EDIT2：我在玩弄并检查了最简单的烧瓶应用程序是否具有与我的服务器相同的行为，所以我将其作为我的 "minimal example"

考虑以下服务器：

import time

from flask import Flask, jsonify
app = Flask(__name__)

@app.route("/")
def hello():
    time.sleep(2)
    return ''

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=80, debug=True)

现在通过获取之前的代码并将其指向 http://localhost 来连接它。结果如下：

initiating call 0 2016-05-04 23:49:12.629250
initiating call 1 2016-05-04 23:49:12.638554
initiating call 2 2016-05-04 23:49:12.643844
initiating call 3 2016-05-04 23:49:12.645630
initiating call 4 2016-05-04 23:49:12.647866
initiating call 5 2016-05-04 23:49:12.649332
initiating call 6 2016-05-04 23:49:12.650853
initiating call 7 2016-05-04 23:49:12.652448
initiating call 8 2016-05-04 23:49:12.653865
initiating call 9 2016-05-04 23:49:12.655348
finishing call 0 2016-05-04 23:49:14.671281 0:00:02.042031
finishing call 1 2016-05-04 23:49:16.673649 0:00:04.035095
finishing call 2 2016-05-04 23:49:18.676576 0:00:06.032732
finishing call 3 2016-05-04 23:49:20.679746 0:00:08.034116
finishing call 4 2016-05-04 23:49:22.681615 0:00:10.033749
finishing call 5 2016-05-04 23:49:24.683817 0:00:12.034485
finishing call 6 2016-05-04 23:49:26.686309 0:00:14.035456
finishing call 7 2016-05-04 23:49:28.688079 0:00:16.035631
finishing call 8 2016-05-04 23:49:30.691382 0:00:18.037517
finishing call 9 2016-05-04 23:49:32.696471 0:00:20.041123

所以基本上一个简单的 flask webapp 不会并发进行 HTTP 调用。我该如何更改？

Answer 1

简答：启动uwsgi时使用--processes=Nand/or--threads=M。

长答案：您所描述的堆栈涉及三个组件：nginx 作为反向代理网络服务器； uwsgi 扮演应用服务器的角色；和 flask 作为应用程序框架。数据流以该顺序发生，响应以相反的顺序流动。

nginx 本质上是多任务的，而 flask 本质上是单任务的。 uwsgi 可以配置为两者之一。默认情况下，uwsgi 是单任务的。

这是我用来调查这个的设置。我的 OS 是 Ubuntu 14.04.

/etc/nginx/sites-available/myapp:

server {
        listen 8100;
        location / {
                include uwsgi_params;
                uwsgi_pass unix:/tmp/uwsgi.sock;
        }
}

uwsgi 命令行:

One of:
  uwsgi -s /tmp/uwsgi.sock -w app:app
  uwsgi -s /tmp/uwsgi.sock -w app:app --processes=4
  uwsgi -s /tmp/uwsgi.sock -w app:app --threads=4

Followed by:

  chmod 777 /tmp/uwsgi.sock

app.py:

import time
from flask import Flask, render_template_string
app = Flask(__name__)

@app.route('/')
@app.route('/<name>')
def hello(name='World'):
    time.sleep(1)
    return render_template_string('''
        <html><body><p>
        Hello, <b>{{ name }}</b>!
        </p></body></html>''', name=name)

if __name__=="__main__":
    app.run(debug=True)

客户端：我使用了上面的 gevent/requests 客户端，替换为以下内容 url：http://localhost:8100/World.

典型结果：

initiating call 0 2016-05-04 21:08:16.473978
initiating call 1 2016-05-04 21:08:16.485589
initiating call 2 2016-05-04 21:08:16.487258
initiating call 3 2016-05-04 21:08:16.490140
initiating call 4 2016-05-04 21:08:16.493158
initiating call 5 2016-05-04 21:08:16.494417
initiating call 6 2016-05-04 21:08:16.495620
initiating call 7 2016-05-04 21:08:16.497180
initiating call 8 2016-05-04 21:08:16.498413
initiating call 9 2016-05-04 21:08:16.499528
finishing call 3 2016-05-04 21:08:17.512949 0:00:01.022809
finishing call 6 2016-05-04 21:08:17.515944 0:00:01.020324
finishing call 7 2016-05-04 21:08:17.517655 0:00:01.020475
finishing call 4 2016-05-04 21:08:17.519555 0:00:01.026397
finishing call 2 2016-05-04 21:08:18.520249 0:00:02.032991
finishing call 0 2016-05-04 21:08:18.522902 0:00:02.048924
finishing call 5 2016-05-04 21:08:18.524902 0:00:02.030485
finishing call 1 2016-05-04 21:08:18.526682 0:00:02.041093
finishing call 9 2016-05-04 21:08:19.526909 0:00:03.027381
finishing call 8 2016-05-04 21:08:19.528926 0:00:03.030513

参考文献：

http://uwsgi-docs.readthedocs.io/en/latest/ThingsToKnow.html - "There is no magic rule for setting the number of processes or threads to use. It is very much application and system dependent"
https://www.digitalocean.com/community/tutorials/how-to-deploy-python-wsgi-applications-using-uwsgi-web-server-with-nginx
http://uwsgi-docs.readthedocs.io/en/latest/Configuration.html
http://flask.pocoo.org/docs/0.10/deploying/uwsgi/
http://uwsgi-docs.readthedocs.io/en/latest/Nginx.html

Python 服务 html 异步

Python serving html async

python

concurrency

nginx

flask

uwsgi