寫了幾年的python web,卻還不知道WSGI是什麼東西,是否是大有人在。 說來也正常,由於做爲開發者不多須要去了解wsgi是什麼,也能把網站作出來。前端
可是若是你想本身寫個web框架玩玩,就不得不去了解wsgi了。python
回顧一下,咱們在用python作web開發的時候,通常基於某個web框架來開發,django或者是flask等其它框架。 業務開發完成後,就要部署到某臺服務器中提供對外的訪問。web
這時候你去網上一搜,他們都會告訴你須要用 gunicorn或者是uwsgi 來部署。 那麼gunicorn、uwsgi 又是什麼玩意。django
看這個圖你就明白了flask
這裏的uwsgi或者gunicorn扮演的角色就是web服務器的角色,這裏的服務器是軟件層面的服務器,用於處理瀏覽器發過來的HTTP請求以及將響應結果返回給前端。而Web框架的主要任務就是處理業務邏輯生成結果給web服務器,再由web服務器返回給瀏覽器。瀏覽器
而web框架和web服務器之間的通訊須要遵循一套規範,這個規範就是WSGI了。服務器
爲何要搞這麼一套規範出來? 規範就是爲了統一標準,方便你們所用app
想象一下,咱們手機充電的接口如今都是Type-c的,Type-c 就是一種規範, 手機廠商按照這個規範去生產手機, 充電器廠商按照Type-c的規範生產充電器,不一樣廠商的手機就能夠和不一樣廠商的充電器搭配使用。 而蘋果卻自成一套規範,最後致使Android充電器沒法給蘋果充電。框架
那如何寫出一個符合 WSGI規範的應用(框架)程序和服務器呢?curl
如上圖所示,左邊是web服務器,右邊是web框架,或者說應用程序。
應用程序
WSGI規定應用程序必須是一個可調用對象(可調用對象能夠是函數,也能夠是類,還能夠是實現了 __call__
的實例對象),並且必須接受兩個參數,該對象的返回值必須是可迭代對象。
咱們能夠寫個最簡單的應用程序的例子
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]
application 是一個函數,確定是可調用對象,而後接收兩個參數,兩個參數分別是:environ和start_response
- environ是一個字典,裏面儲存了HTTP request相關的全部內容,好比header、請求參數等等
- start_response是一個WSGI 服務器傳遞過來的函數,用於將response header,狀態碼傳遞給Server。
調用 start_response 函數負責將響應頭、狀態碼傳遞給服務器, 響應體則由application函數返回給服務器, 一個完整的http response 就由這兩個函數提供。
但凡是實現了wsgi的web框架都會有這樣一個可調用對象
服務器
WSGI 服務器端作的事情就是每次接收HTTP請求,構建environ對象,而後調用application對象,最後將HTTP Response返回給瀏覽器。
下面就是一個完整的wsgi server 的代碼
import socket
import sys
from io import StringIO
class 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', 8080
def make_server(server_address, application):
server = WSGIServer(server_address)
server.set_app(application)
return server
if __name__ == '__main__':
httpd = make_server(SERVER_ADDRESS, application)
print('WSGIServer: Serving HTTP on port {port} ...\n'.format(port=PORT))
httpd.serve_forever()
固然,若是隻是寫個用於開發環境用的server,用不着這麼麻煩本身造輪子,由於python內置模塊中就提供有 wsgi server 的功能。
from wsgiref.simple_server import make_server
srv = make_server('localhost', 8080, application)
srv.serve_forever()
只要3行代碼就能夠提供wsgi服務器,是否是超級方便,最後來訪問測試下瀏覽器發起一個請求的效果
以上就是wsgi簡介,深刻了解wsgi能夠熟悉下PEP333