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 reimport socketimport selectimport timeclass 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'\r\n\r\n', 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('\r\n') 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] = vclass 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._readyclass 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._readyclass 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 Snowfrom snow import HttpResponsedef 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 Snowfrom snow import HttpResponsefrom snow import TimeoutFuturerequest_list = []def async(request): obj = TimeoutFuture(5) yield objdef 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 Snowfrom snow import HttpResponsefrom snow import Futurerequest_list = []def callback(request, future): return HttpResponse(future.value)def req(request): obj = Future(callback=callback) request_list.append(obj) yield objdef 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)

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