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 = contentself.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 = connself.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 = Falsewhile True:try:received = self.conn.recv(8096)except Exception as e:received = Noneif not received:breakif header_flag:self.body_bytes += receivedcontinuetemp = received.split(b'\r\n\r\n', 1)if len(temp) == 1:self.header_bytes += tempelse:h, b = tempself.header_bytes += hself.body_bytes += bheader_flag = True@propertydef 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 = kvself.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 = callbackself._ready = Falseself.value = Nonedef set_result(self, value=None):self.value = valueself._ready = True@propertydef 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 = timeoutself.start_time = time.time()@propertydef ready(self):current_time = time.time()if current_time > self.start_time + self.timeout:self._ready = Truereturn self._readyclass Snow(object):"""微型Web框架类"""def __init__(self, routes):self.routes = routesself.inputs = set()self.request = Noneself.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.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)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] = yieldedself.polling_callback()except Exception as e:passfinally: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:continueif 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 = Nonefor route in self.routes:if re.match(route[0], self.request.url):func = route[1]breakif not func:return HttpNotFound()else:return func(self.request)
二、使用
1. 基本使用
'''遇到问题没人解答？小编创建了一个Python学习交流QQ群：85766 寻找有志同道合的小伙伴，互帮互助,群里还有不错的视频学习教程和PDF电子书！'''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
'''遇到问题没人解答？小编创建了一个Python学习交流QQ群：85766 寻找有志同道合的小伙伴，互帮互助,群里还有不错的视频学习教程和PDF电子书！'''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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