前言

最近做物聯網專案的時候需要搭建一個非同步非阻塞的HTTP伺服器，經過查詢資料，發現可以使用gevent包。

關於gevent

Gevent 是一個 Python 併發網路庫，它使用了基於 libevent 事件迴圈的 greenlet 來提供一個高階同步 API。下面是程式碼示例：

from gevent.wsgi import WSGIServer
from yourapplication import app

http_server = WSGIServer(('', 5000), app)
http_server.serve_forever()

程式碼清單

下面放上Flask非同步非阻塞的程式碼清單，以後需要用到的時候直接移植即可。

# coding=utf-8
# Python Version: 3.5.1

# Flask
from flask import Flask, request, g

# gevent
from gevent import monkey
from gevent.pywsgi import WSGIServer
monkey.patch_all()
# gevent end

import time

app = Flask(__name__)
app.config.update(DEBUG=True)

@app.route('/asyn/', methods=['GET'])
def test_asyn_one
 
():
    print("asyn has a request!")
    time.sleep(10)
    return 'hello asyn'


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


if __name__ == "__main__":
    # app.run()
    http_server = WSGIServer(('', 5000), app)
    http_server.serve_forever()

關於monkey.patch_all()

為什麼要加monkey.patch_all()

monkey carefully replace functions and classes in the standard socket module with their cooperative counterparts. That way even the modules that are unaware of gevent can benefit from running in a multi-greenlet environment.

翻譯：猴子補丁仔細的用並行程式碼副本替換標準socket模組的函式和類，這種方式可以使模組在不知情的情況下讓gevent更好的運行於multi-greenlet環境中。

測試

開啟瀏覽器，首先請求http://127.0.0.1:5000/asyn/，然後
再請求http://127.0.0.1:5000/test/這個介面十次。如果是一般的Flask框架，後面的介面是沒有響應的。

列印內容如下：

asyn has a request!
127.0.0.1 - - [2016-10-24 20:45:10] "GET /test/ HTTP/1.1" 200 126 0.000000
127.0.0.1 - - [2016-10-24 20:45:11] "GET /test/ HTTP/1.1" 200 126 0.000000
127.0.0.1 - - [2016-10-24 20:45:11] "GET /test/ HTTP/1.1" 200 126 0.000000
127.0.0.1 - - [2016-10-24 20:45:12] "GET /test/ HTTP/1.1" 200 126 0.000000
127.0.0.1 - - [2016-10-24 20:45:12] "GET /test/ HTTP/1.1" 200 126 0.000998
127.0.0.1 - - [2016-10-24 20:45:13] "GET /test/ HTTP/1.1" 200 126 0.001001
127.0.0.1 - - [2016-10-24 20:45:14] "GET /test/ HTTP/1.1" 200 126 0.000000
127.0.0.1 - - [2016-10-24 20:45:14] "GET /test/ HTTP/1.1" 200 126 0.001014
127.0.0.1 - - [2016-10-24 20:45:15] "GET /test/ HTTP/1.1" 200 126 0.001000
127.0.0.1 - - [2016-10-24 20:45:15] "GET /test/ HTTP/1.1" 200 126 0.000000
127.0.0.1 - - [2016-10-24 20:45:18] "GET /asyn/ HTTP/1.1" 200 126 10.000392

參考資料