Python的Web框架中Tornado以异步非阻塞而闻名。本篇将使用200行代码完成一个微型异步非阻塞Web框架：Snow。

一、源码

本文基于非阻塞的Socket以及IO多路复用从而实现异步非阻塞的Web框架，其中便是众多异步非阻塞Web框架内部原理。

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import re
import socket
import select
import time
class HttpResponse(object):
 """
 封装响应信息
 """
 def init(self, content=''):
 self.content = content
 self.headers = {}
 self.cookies = {}
 def response(self):
 return bytes(self.content, encoding='utf-8')
class HttpNotFound(HttpResponse):
 """
 404时的错误提示
 """
 def init(self):
 super(HttpNotFound, self).init('404 Not Found')
class HttpRequest(object):
 """
 用户封装用户请求信息
 """
 def init(self, conn):
 self.conn = conn
 self.header_bytes = bytes()
 self.header_dict = {}
 self.body_bytes = bytes()
 self.method = ""
 self.url = ""
 self.protocol = ""
 self.initialize()
 self.initialize_headers()
 def initialize(self):
 header_flag = False
 while True:
 try:
 received = self.conn.recv(8096)
 except Exception as e:
 received = None
 if not received:
 break
 if header_flag:
 self.body_bytes += received
 continue
 temp = received.split(b'

', 1)
 if len(temp) == 1:
 self.header_bytes += temp
 else:
 h, b = temp
 self.header_bytes += h
 self.body_bytes += b
 header_flag = True
 @property
 def header_str(self):
 return str(self.header_bytes, encoding='utf-8')
 def initialize_headers(self):
 headers = self.header_str.split('
')
 first_line = headers[0].split(' ')
 if len(first_line) == 3:
 self.method, self.url, self.protocol = headers[0].split(' ')
 for line in headers:
 kv = line.split(':')
 if len(kv) == 2:
 k, v = kv
 self.header_dict[k] = v
class Future(object):
 """
 异步非阻塞模式时封装回调函数以及是否准备就绪
 """
 def init(self, callback):
 self.callback = callback
 self._ready = False
 self.value = None
 def set_result(self, value=None):
 self.value = value
 self._ready = True
 @property
 def ready(self):
 return self._ready
class TimeoutFuture(Future):
 """
 异步非阻塞超时
 """
 def init(self, timeout):
 super(TimeoutFuture, self).init(callback=None)
 self.timeout = timeout
 self.start_time = time.time()
 @property
 def ready(self):
 current_time = time.time()
 if current_time > self.start_time + self.timeout:
 self._ready = True
 return self._ready
class Snow(object):
 """
 微型Web框架类
 """
 def init(self, routes):
 self.routes = routes
 self.inputs = set()
 self.request = None
 self.async_request_handler = {}
 def run(self, host='localhost', port=9999):
 """
 事件循环
 :param host:
 :param port:
 :return:
 """
 sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 sock.bind((host, port,))
 sock.setblocking(False)
 sock.listen(128)
 sock.setblocking(0)
 self.inputs.add(sock)
 try:
 while True:
 readable_list, writeable_list, error_list = select.select(self.inputs, [], self.inputs,0.005)
 for conn in readable_list:
 if sock == conn:
 client, address = conn.accept()
 client.setblocking(False)
 self.inputs.add(client)
 else:
 gen = self.process(conn)
 if isinstance(gen, HttpResponse):
 conn.sendall(gen.response())
 self.inputs.remove(conn)
 conn.close()
 else:
 yielded = next(gen)
self.async_request_handler[conn] = yielded
 self.polling_callback()
except Exception as e:
 pass
 finally:
 sock.close()
def polling_callback(self):
 """
 遍历触发异步非阻塞的回调函数
 :return:
 """
 for conn in list(self.async_request_handler.keys()):
 yielded = self.async_request_handler[conn]
 if not yielded.ready:
 continue
 if yielded.callback:
 ret = yielded.callback(self.request, yielded)
 conn.sendall(ret.response())
 self.inputs.remove(conn)
 del self.async_request_handler[conn]
 conn.close()
 def process(self, conn):
 """
 处理路由系统以及执行函数
 :param conn:
 :return:
 """
 self.request = HttpRequest(conn)
 func = None
 for route in self.routes:
 if re.match(route[0], self.request.url):
 func = route[1]
 break
 if not func:
 return HttpNotFound()
 else:
 return func(self.request)
snow.py

二、使用

1. 基本使用

from snow import Snow
from snow import HttpResponse
def index(request):
return HttpResponse('OK')
routes = [
 (r'/index/', index),
]
app = Snow(routes)
app.run(port=8012)

2.异步非阻塞：超时

from snow import Snow
from snow import HttpResponse
from snow import TimeoutFuture
request_list = []
def async(request):
 obj = TimeoutFuture(5)
 yield obj
def home(request):
 return HttpResponse('home')
routes = [
 (r'/home/', home),
 (r'/async/', async),
]
app = Snow(routes)
app.run(port=8012)

3.异步非阻塞：等待

基于等待模式可以完成自定制操作

from snow import Snow
from snow import HttpResponse
from snow import Future
request_list = []
def callback(request, future):
 return HttpResponse(future.value)
def req(request):
 obj = Future(callback=callback)
 request_list.append(obj)
 yield obj
def stop(request):
 obj = request_list[0]
 del request_list[0]
 obj.set_result('done')
 return HttpResponse('stop')
routes = [
 (r'/req/', req),
 (r'/stop/', stop),
]
app = Snow(routes)
app.run(port=8012)