写了几年的python web,却还不知道WSGI是什么东西,是不是大有人在。 说来也正常,因为作为开发者很少需要去了解wsgi是什么,也能把网站做出来。
但是如果你想自己写个web框架玩玩,就不得不去了解wsgi了。
回顾一下,我们在用python做web开发的时候,一般基于某个web框架来开发,django或者是flask等其它框架。 业务开发完成后,就要部署到某台服务器中提供对外的访问。
这时候你去网上一搜,他们都会告诉你需要用 gunicorn或者是uwsgi 来部署。 那么gunicorn、uwsgi 又是什么玩意。
看这个图你就明白了,图我是从网上找的
这里的uwsgi或者gunicorn扮演的角色就是web服务器的角色,这里的服务器是软件层面的服务器,用于处理浏览器发过来的HTTP请求以及将响应结果返回给前端。而Web框架的主要任务就是处理业务逻辑生成结果给web服务器,再由web服务器返回给浏览器。
而web框架和web服务器之间的通信需要遵循一套规范,这个规范就是WSGI了。
为什么要搞这么一套规范出来? 规范就是为了统一标准,方便大家所用
想象一下,我们手机充电的接口现在都是Type-c的,Type-c 就是一种规范, 手机厂商按照这个规范去生产手机, 充电器厂商按照Type-c的规范生产充电器,不同厂商的手机就可以和不同厂商的充电器搭配使用。 而苹果却自成一套规范,最后导致Android充电器无法给苹果充电。
](p9-juejin.byteimg.com/tos-cn-i-k3…)
那如何写出一个符合 WSGI规范的应用(框架)程序和服务器呢?
如上图所示,左边是web服务器,右边是web框架,或者说应用程序。
WSGI规定应用程序必须是一个可调用对象(可调用对象可以是函数,也可以是类,还可以是实现了 __call__
的实例对象),而且必须接受两个参数,该对象的返回值必须是可迭代对象。
我们可以写个最简单的应用程序的例子
HELLO_WORLD = b"Hello world!\n"def application(environ, start_response): status = '200 OK' response_headers = [('Content-type', 'text/plain')] start_response(status, response_headers) return [HELLO_WORLD]复制代码
application 是一个函数,肯定是可调用对象,然后接收两个参数,两个参数分别是:environ和start_response
调用 start_response 函数负责将响应头、状态码传递给服务器, 响应体则由application函数返回给服务器, 一个完整的http response 就由这两个函数提供。
但凡是实现了wsgi的web框架都会有这样一个可调用对象
WSGI 服务器端做的事情就是每次接收HTTP请求,构建environ对象,然后调用application对象,最后将HTTP Response返回给浏览器。
下面就是一个完整的wsgi server 的代码
import socketimport sysfrom io import StringIOclass WSGIServer(object): address_family = socket.AF_INET socket_type = socket.SOCK_STREAM request_queue_size = 1 def __init__(self, server_address): # Create a listening socket self.listen_socket = listen_socket = socket.socket( self.address_family, self.socket_type ) # Allow to reuse the same address listen_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) # Bind listen_socket.bind(server_address) # Activate listen_socket.listen(self.request_queue_size) # Get server host name and port host, port = self.listen_socket.getsockname()[:2] self.server_name = socket.getfqdn(host) self.server_port = port # Return headers set by Web framework/Web application self.headers_set = [] def set_app(self, application): self.application = application def serve_forever(self): listen_socket = self.listen_socket while True: # New client connection self.client_connection, client_address = listen_socket.accept() # Handle one request and close the client connection. Then # loop over to wait for another client connection self.handle_one_request() def handle_one_request(self): self.request_data = request_data = self.client_connection.recv(1024) # Print formatted request data a la 'curl -v' print(''.join( '< {line}\n'.format(line=line) for line in request_data.splitlines() )) self.parse_request(request_data) # Construct environment dictionary using request data env = self.get_environ() # It's time to call our application callable and get # back a result that will become HTTP response body result = self.application(env, self.start_response) # Construct a response and send it back to the client self.finish_response(result) def parse_request(self, text): request_line = text.splitlines()[0] request_line = request_line.rstrip('\r\n') # Break down the request line into components (self.request_method, # GET self.path, # /hello self.request_version # HTTP/1.1 ) = request_line.split() def get_environ(self): env = {} # The following code snippet does not follow PEP8 conventions # but it's formatted the way it is for demonstration purposes # to emphasize the required variables and their values # # Required WSGI variables env['wsgi.version'] = (1, 0) env['wsgi.url_scheme'] = 'http' env['wsgi.input'] = StringIO.StringIO(self.request_data) env['wsgi.errors'] = sys.stderr env['wsgi.multithread'] = False env['wsgi.multiprocess'] = False env['wsgi.run_once'] = False # Required CGI variables env['REQUEST_METHOD'] = self.request_method # GET env['PATH_INFO'] = self.path # /hello env['SERVER_NAME'] = self.server_name # localhost env['SERVER_PORT'] = str(self.server_port) # 8888 return env def start_response(self, status, response_headers, exc_info=None): # Add necessary server headers server_headers = [ ('Date', 'Tue, 31 Mar 2015 12:54:48 GMT'), ('Server', 'WSGIServer 0.2'), ] self.headers_set = [status, response_headers + server_headers] # To adhere to WSGI specification the start_response must return # a 'write' callable. We simplicity's sake we'll ignore that detail # for now. # return self.finish_response def finish_response(self, result): try: status, response_headers = self.headers_set response = 'HTTP/1.1 {status}\r\n'.format(status=status) for header in response_headers: response += '{0}: {1}\r\n'.format(*header) response += '\r\n' for data in result: response += data # Print formatted response data a la 'curl -v' print(''.join( '> {line}\n'.format(line=line) for line in response.splitlines() )) self.client_connection.sendall(response) finally: self.client_connection.close() SERVER_ADDRESS = (HOST, PORT) = 'localhost', 8080def make_server(server_address, application): server = WSGIServer(server_address) server.set_app(application) return serverif __name__ == '__main__': httpd = make_server(SERVER_ADDRESS, application) print('WSGIServer: Serving HTTP on port {port} ...\n'.format(port=PORT)) httpd.serve_forever()复制代码
当然,如果只是写个用于开发环境用的server,用不着这么麻烦自己造轮子,因为python内置模块中就提供有 wsgi server 的功能。
from wsgiref.simple_server import make_server srv = make_server('localhost', 8080, application) srv.serve_forever()复制代码
只要3行代码就可以提供wsgi服务器,是不是超级方便,最后来访问测试下浏览器发起一个请求的效果
以上就是wsgi简介,深入了解wsgi可以熟悉下PEP333
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