前言
Flask是目前为止我最喜欢的一个Python Web框架了,为了更好的掌握其内部实现机制,这两天准备学习下Flask的源码,将由浅入深跟大家分享下,其中Flask版本为1.1.1。
Flask系列文章:
正文
本文将结合源码跟踪看下Flask是如何启动并运行一个服务的。
首先,继续贴上最简单的应用:
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
return 'Hello Flask!'
if __name__ == '__main__':
app.run()
我们看到,这段代码先初始化了Flask类并被app所指向,然后执行run()来启动程序的。
查看run方法:
def run(self, host=None, port=None, debug=None, load_dotenv=True, **options):
if os.environ.get("FLASK_RUN_FROM_CLI") == "true":
from .debughelpers import explain_ignored_app_run
explain_ignored_app_run()
return
if get_load_dotenv(load_dotenv):
cli.load_dotenv()
# if set, let env vars override previous values
if "FLASK_ENV" in os.environ:
self.env = get_env()
self.debug = get_debug_flag()
elif "FLASK_DEBUG" in os.environ:
self.debug = get_debug_flag()
# debug passed to method overrides all other sources
if debug is not None:
self.debug = bool(debug)
_host = "127.0.0.1"
_port = 5000
server_name = self.config.get("SERVER_NAME")
sn_host, sn_port = None, None
if server_name:
sn_host, _, sn_port = server_name.partition(":")
host = host or sn_host or _host
# pick the first value that's not None (0 is allowed)
port = int(next((p for p in (port, sn_port) if p is not None), _port))
options.setdefault("use_reloader", self.debug)
options.setdefault("use_debugger", self.debug)
options.setdefault("threaded", True)
cli.show_server_banner(self.env, self.debug, self.name, False)
from werkzeug.serving import run_simple
try:
run_simple(host, port, self, **options)
finally:
# reset the first request information if the development server
# reset normally. This makes it possible to restart the server
# without reloader and that stuff from an interactive shell.
self._got_first_request = False
首先入参:
参数 | 说明 |
---|---|
host | 服务器地址,不设置的话默认为127.0.0.1 |
port | 端口,不设置的话默认为5000 |
debug | 是否为调试模式, 默认为否 |
load_dotenv | 设置环境变量 |
options |
该方法的处理流程是:对入参进行配置处理之后,执行werkzeug的run_simple()方法,
run_simple将启动一个WSGI服务。
关于WSGI协议:
- 它是关于HTTP服务器和Web应用的桥梁,定义了标准接口以提升Web应用之间的可移植性,是一套接口交互规范。
- 它的功能是监听指定端口服务,将来自HTTP服务器的请求解析为WSGI格式,调用Flask app处理请求。
run_simple中的inner方法是核心,inner调用make_server().serve_forever()启动服务。关于make_server:
def make_server(host=None, port=None, app=None, threaded=False, processes=1,
request_handler=None, passthrough_errors=False,
ssl_context=None, fd=None):
if threaded and processes > 1:
raise ValueError("cannot have a multithreaded and "
"multi process server.")
elif threaded:
return ThreadedWSGIServer(host, port, app, request_handler,
passthrough_errors, ssl_context, fd=fd)
elif processes > 1:
return ForkingWSGIServer(host, port, app, processes, request_handler,
passthrough_errors, ssl_context, fd=fd)
else:
return BaseWSGIServer(host, port, app, request_handler,
passthrough_errors, ssl_context, fd=fd)
make_server会根据线程或者进程数返回相应的WSGI服务器,默认情况下返回BaseWSGIServer,ThreadedWSGIServer和ForkingWSGIServer均集成了BaserWSGIServer,接下来我们看下serve_forever()方法:
def serve_forever(self):
self.shutdown_signal = False
try:
HTTPServer.serve_forever(self)
except KeyboardInterrupt:
pass
finally:
self.server_close()
最终调用了Python标准类库接口HTTPServer的serve_forever()方法,而HTTPServer又是socketserver.TCPServer的子类,通过server_bind来监听服务:
class HTTPServer(socketserver.TCPServer):
allow_reuse_address = 1 # Seems to make sense in testing environment
def server_bind(self):
"""Override server_bind to store the server name."""
socketserver.TCPServer.server_bind(self)
host, port = self.server_address[:2]
self.server_name = socket.getfqdn(host)
self.server_port = port
以上,就是Flask服务启动的流程。
原文地址:https://www.cnblogs.com/ybjourney/p/11717347.html
时间: 2024-11-06 11:41:32