flask源碼分析，run函數(shù)啟動分析

Tony 發(fā)布于2019-07-30 14:31 / 2308人閱讀

摘要：對背后運(yùn)行機(jī)制感興趣，參考網(wǎng)上資料，結(jié)合源碼分析函數(shù)運(yùn)行時的機(jī)制，主要整理出函數(shù)調(diào)用棧。以分析首先官方文檔經(jīng)典示例現(xiàn)在來分析啟動時發(fā)生了什么代碼只列出用到的函數(shù)，去掉注釋等函數(shù)導(dǎo)入運(yùn)行函數(shù)主要運(yùn)行調(diào)用返回類，然后調(diào)用返回類的。

對flask背后運(yùn)行機(jī)制感興趣，參考網(wǎng)上資料，結(jié)合源碼分析run函數(shù)運(yùn)行時的機(jī)制，主要整理出函數(shù)調(diào)用棧。以flask0.1分析

首先
Flask官方文檔經(jīng)典示例 hello.py

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

if __name__ == "__main__":
    app.run()

現(xiàn)在來分析app.run()啟動時發(fā)生了什么？ # 代碼只列出用到的函數(shù)，去掉注釋等
flask.py

class Flask(object):

  def run(self, host="localhost", port=5000, **options):
       
        from werkzeug import run_simple
        if "debug" in options:
            self.debug = options.pop("debug")
        options.setdefault("use_reloader", self.debug)
        options.setdefault("use_debugger", self.debug)
        return run_simple(host, port, self, **options)

run函數(shù)導(dǎo)入from werkzeug import run_simple 運(yùn)行run_simple(host, port, self, **options)

werkzeug/serving.py

def run_simple(hostname, port, application, use_reloader=False, extra_files=None, threaded=False, processes=1):
    
    def inner():
        srv = make_server(hostname, port, application, threaded,
                          processes)
        try:
            srv.serve_forever()
        except KeyboardInterrupt:
            pass
    inner()

run_simple函數(shù)主要運(yùn)行inner(),inner調(diào)用make_server（）返回類，然后調(diào)用返回類的serve_forever()。先來看看make_server（）

werkzeug/serving.py

ddef make_server(host, port, app=None, threaded=False, processes=1):
    
    if threaded and processes > 1:
        raise ValueError("cannot have a multithreaded and "
                         "multi process server.")
    elif threaded:
        class handler(BaseRequestHandler):
            multithreaded = True
        class server(ThreadingMixIn, WSGIServer):
            pass
    elif processes > 1:
        class handler(BaseRequestHandler):
            multiprocess = True
            max_children = processes - 1
        class server(ForkingMixIn, WSGIServer):
            pass
    else:
        handler = BaseRequestHandler
        server = WSGIServer
    srv = server((host, port), handler)
    srv.set_app(app)
    return srv

make_server(hostname, port, application, threaded, processes) 傳入的都是默認(rèn)參數(shù)，起作用的代碼是

else:
        handler = BaseRequestHandler
        server = WSGIServer
    srv = server((host, port), handler)
    srv.set_app(app)
    return srv

可以看出srv = server((host, port), handler) ,其實(shí)就是srv = WSGIServer((host, port), BaseRequestHandler)，返回類就是WSGIServer ，綁定BaseRequestHandler。先看WSGIServer

wsgiref/simple_server.py

class WSGIServer(HTTPServer):
  def __init__=  標(biāo)準(zhǔn)庫 BaseHTTPServer.py  class HTTPServer(SocketServer.TCPServer) : #WSGIServer繼承HTTPServer的__init__函數(shù)，它自己沒有 ，這句是我加的方便理解 ，下同

  def set_app(self,application):    #這個就是make_server函數(shù)中調(diào)用的 set_app
        self.application = application
  def get_app(self):            #
        return self.application

標(biāo)準(zhǔn)庫 BaseHTTPServer.py  
class HTTPServer(SocketServer.TCPServer) 
  def __init__=  標(biāo)準(zhǔn)庫 SocketServer.py class TCPServer(BaseServer):


標(biāo)準(zhǔn)庫 SocketServer.py 
class TCPServer(BaseServer):
   def __init__(self, server_address, RequestHandlerClass, bind_and_activate=True):
        BaseServer.__init__(self, server_address, RequestHandlerClass)
        self.socket = socket.socket(self.address_family,
                                    self.socket_type)
        if bind_and_activate:         # 這里調(diào)用socket.socket綁定端口
            try:
                self.server_bind()
                self.server_activate()
            except:
                self.server_close()
                raise

class BaseServer:
    def __init__(self, server_address, RequestHandlerClass):
        self.server_address = server_address
        self.RequestHandlerClass = RequestHandlerClass
        self.__is_shut_down = threading.Event()
        self.__shutdown_request = False

    def serve_forever(self, poll_interval=0.5):    #這個就是run_simple中調(diào)用的serve_forever
        
        self.__is_shut_down.clear()
        try:
            while not self.__shutdown_request:
                
                r, w, e = _eintr_retry(select.select, [self], [], [],
                                       poll_interval)
                if self in r:
                    self._handle_request_noblock()   #調(diào)用serve_forever時調(diào)用_handle_request_noblock
        finally:
            self.__shutdown_request = False

            self.__is_shut_down.set()
    def _handle_request_noblock(self):   
       
        try:
            request, client_address = self.get_request()
        except socket.error:
            return
        if self.verify_request(request, client_address):
            try:
                self.process_request(request, client_address)  #繼續(xù)
            except:
                self.handle_error(request, client_address)
                self.shutdown_request(request)

    def process_request(self, request, client_address):
        
        self.finish_request(request, client_address)   #繼續(xù)
        self.shutdown_request(request)

    def finish_request(self, request, client_address):
        self.RequestHandlerClass(request, client_address, self)    # #繼續(xù) 并參見 werkzeug/serving.py  make_server()

調(diào)用serve_forever后到了self.RequestHandlerClass(request, client_address, self) ，根據(jù)前面的代碼可知RequestHandlerClass 就是werkzeug/serving.py中的BaseRequestHandler，繼續(xù)

class BaseRequestHandler(WSGIRequestHandler):
    def __init__=  標(biāo)準(zhǔn)庫 wsgiref/simple_server.py class WSGIRequestHandler(BaseHTTPRequestHandler): #這句跟前面一樣繼承父類   
    

wsgiref/simple_server.py

class WSGIRequestHandler(BaseHTTPRequestHandler):
    def __init__=  標(biāo)準(zhǔn)庫 BaseHTTPServer.py class BaseHTTPRequestHandler(SocketServer.StreamRequestHandler): #繼續(xù)父類

BaseHTTPServer.py
class BaseHTTPRequestHandler(SocketServer.StreamRequestHandler):
    def __init__=  標(biāo)準(zhǔn)庫 SocketServer.py  class StreamRequestHandler(BaseRequestHandler):  #繼續(xù)父類


SocketServer.py

class StreamRequestHandler(BaseRequestHandler):
 #繼續(xù)父類

class BaseRequestHandler:

    def __init__(self, request, client_address, server):
        self.request = request
        self.client_address = client_address
        self.server = server
        self.setup()
        try:
            self.handle()   # 運(yùn)行  參見 werkzeug/serving.py  class BaseRequestHandler.handle
        finally:
            self.finish()

最后運(yùn)行了self.handle() 參見 werkzeug/serving.py class BaseRequestHandler.handle
前面有，再貼下看看

class BaseRequestHandler(WSGIRequestHandler):
   def handle(self):     #1、調(diào)用的就是這個handle，覆蓋了父類的handle 
        self.raw_requestline = self.rfile.readline()
        if self.parse_request():
            self.get_handler().run(self.server.get_app())  #2、調(diào)用 get_handler()后，還繼續(xù)調(diào)用 run（） ，get_app就是wsgiref/simple_server.py中WSGIServer類定義的函數(shù)   

    def get_handler(self):  # 3、看看它返回了什么
        handler = self._handler_class
        if handler is None:
            class handler(ServerHandler):  #4、新建一個類 返回的就是這個類 ，繼承ServerHandler
              """   
                  5、直接從其他文件copy出所需代碼，也就是handler的父類
                   wsgiref/simple_server.py  class ServerHandler(SimpleHandler): 繼續(xù)父類 
                   wsgiref/handlers.py  
                       class SimpleHandler(BaseHandler):
                          def __init__(self,stdin,stdout,stderr,environ,multithread=True, multiprocess=False ):
                              self.stdin = stdin
                              self.stdout = stdout
                              self.stderr = stderr
                              self.base_env = environ
                              self.wsgi_multithread = multithread
                              self.wsgi_multiprocess = multiprocess
                       class BaseHandler:  #6、調(diào)用的就是這個類的run函數(shù)
                                  def run(self, application):
                                    try:
                                        self.setup_environ()
                                        self.result = application(self.environ, self.start_response)   #7、調(diào)用app，也就是app=Flask() Flask類的 __call__
                                        self.finish_response()
                                    except:
                                          try:
                                               self.handle_error()
                                          except:
                                             # If we get an error handling an error, just give up already!
                                             self.close()
                                             raise   # ...and let the actual server figure it out.


                 """
                wsgi_multithread = self.multithreaded                      
                wsgi_multiprocess = self.multiprocess
            self._handler_class = handler

        rv = handler(self.rfile, self.wfile, self.get_stderr(),
                     self.get_environ())
        rv.request_handler = self
        return rv

可以看出最后調(diào)用的是application(self.environ, self.start_response) 這個application就是開始的app = Flask(__name__)，調(diào)用類就是調(diào)用類的__call__ 函數(shù) ，繼續(xù)貼一下源碼

class Flask(object):

   def __call__(self, environ, start_response):
        return self.wsgi_app(environ, start_response)

   def wsgi_app(self, environ, start_response):
        
        with self.request_context(environ):
            rv = self.preprocess_request()
            if rv is None:
                rv = self.dispatch_request()
            response = self.make_response(rv)
            response = self.process_response(response)
            return response(environ, start_response)

OK，大功告成，最后調(diào)用wsgi_app(self, environ, start_response)函數(shù)，這個就是返回響應(yīng)的主函數(shù)了！！

從整個流程中，flask利用WSGIServer類啟動監(jiān)聽端口并綁定，BaseRequestHandler類接收、返回相應(yīng)的信息！完全符合WSGI要求。
剩余的工作就太過于底層，不好深入分析了。也畫了調(diào)用流程圖，不過太大不好傳，如果有需要可以繼續(xù)交流！