DEVOCEAN

#출처 : https://ko.wikipedia.org/wiki/%EA%B3%B5%EC%9A%A9_%EA%B2%8C%EC%9D%B4%ED%8A%B8%EC%9B%A8%EC%9D%B4_%EC%9D%B8%ED%84%B0%ED%8E%98%EC%9D%B4%EC%8A%A4
=head1 DESCRIPTION

printenv — 환경을 출력만 하는 CGI 프로그램

=cut
print "Content-type: text/plain\n\n";

for my $var ( sort keys %ENV ) {
 printf "%s = \"%s\"\n", $var, $ENV{$var};
}

#https://docs.python.org/ko/3/library/wsgiref.html#wsgiref.util.setup_testing_defaults
from wsgiref.util import setup_testing_defaults
from wsgiref.simple_server import make_server

# A relatively simple WSGI application. It's going to print out the
# environment dictionary after being updated by setup_testing_defaults
def simple_app(environ, start_response):
    setup_testing_defaults(environ)

    status = '200 OK'
    headers = [('Content-type', 'text/plain; charset=utf-8')]

    start_response(status, headers)

    ret = [("%s: %s\n" % (key, value)).encode("utf-8")
           for key, value in environ.items()]
    return ret

with make_server('', 8000, simple_app) as httpd:
    print("Serving on port 8000...")
    httpd.serve_forever()

#https://github.com/python/cpython/blob/main/Lib/wsgiref/simple_server.py#L146
def make_server(
    host,
    port,
    app,
    server_class=WSGIServer,
    handler_class=WSGIRequestHandler
):
    """Create a new WSGI server listening on `host` and `port` for `app`"""
    server = server_class((host, port), handler_class)
    server.set_app(app)
    return server

#https://github.com/python/cpython/blob/main/Lib/wsgiref/simple_server.py#L42
class WSGIServer(HTTPServer):
    """BaseHTTPServer that implements the Python WSGI protocol"""
    application = None

    def server_bind(self):
        """Override server_bind to store the server name."""
        HTTPServer.server_bind(self)
        self.setup_environ()

    #서버가 사용할 환경변수를 dict형태로 초기화시킴
    def setup_environ(self):
        # Set up base environment
        env = self.base_environ = {}
        env['SERVER_NAME'] = self.server_name
        env['GATEWAY_INTERFACE'] = 'CGI/1.1'
        env['SERVER_PORT'] = str(self.server_port)
        env['REMOTE_HOST']=''
        env['CONTENT_LENGTH']=''
        env['SCRIPT_NAME'] = ''

    def get_app(self):
        return self.application

    #입력받은 콜백을 attr에 저장시킴
    def set_app(self,application):
        self.application = application

#https://github.com/python/cpython/blob/main/Lib/http/server.py#L134
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_bind는 static method가 아니기 때문에
        #사용하려면 아래처럼 self를 별도로 넣어주어야됨
        socketserver.TCPServer.server_bind(self)
        host, port = self.server_address[:2]
        self.server_name = socket.getfqdn(host)
        self.server_port = port

#https://github.com/python/cpython/blob/main/Lib/socketserver.py#L392
class TCPServer(BaseServer):
    address_family = socket.AF_INET
    socket_type = socket.SOCK_STREAM
    request_queue_size = 5
    allow_reuse_address = False
    allow_reuse_port = False

    def __init__(self, server_address, RequestHandlerClass, bind_and_activate=True):
        """Constructor.  May be extended, do not override."""
        BaseServer.__init__(self, server_address, RequestHandlerClass)
        self.socket = socket.socket(self.address_family,
                                    self.socket_type)
        if bind_and_activate:
            try:
                self.server_bind()
                self.server_activate()
            except:
                self.server_close()
                raise

    def server_bind(self):
        """Called by constructor to bind the socket.
        May be overridden.
        """
        if self.allow_reuse_address and hasattr(socket, "SO_REUSEADDR"):
            self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        if self.allow_reuse_port and hasattr(socket, "SO_REUSEPORT"):
            self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
        #열려있는 socket에 server_address(host, port_nm)을 bind시킴
        self.socket.bind(self.server_address)
        self.server_address = self.socket.getsockname()

#https://github.com/python/cpython/blob/main/Lib/socketserver.py#L155
class BaseServer:
    ...
    #https://github.com/python/cpython/blob/main/Lib/socketserver.py#L218
    def serve_forever(self, poll_interval=0.5):
        """Handle one request at a time until shutdown."""
        self.__is_shut_down.clear()
        try:
            with _ServerSelector() as selector:
                selector.register(self, selectors.EVENT_READ)
                
                #shutdown이 되기 전까지 무한루프를 돌면서 server를 돌리게됨
                while not self.__shutdown_request:
                    ready = selector.select(poll_interval)
                    if self.__shutdown_request:
                        break
                    if ready:
                        
                        self._handle_request_noblock()
    
                    #wsgiref의 경우 service_actions를 별도로 사용하지 않음
                    self.service_actions()
        finally:
            self.__shutdown_request = False
            self.__is_shut_down.set()
    #https://github.com/python/cpython/blob/main/Lib/socketserver.py#L305    
    def _handle_request_noblock(self):
        """Handle one request, without blocking."""
        try:
            #자식cls에서 정의되는 get_request()를 사용
            #socket을 통해서 HTTP Requests Msg를 가지고옴
            request, client_address = self.get_request()
        except OSError:
            return
        #이번 예제에서는 사용되지 않지만
        #다른 프래임워크 구현등에서 request verify용으로 overridden필요
        if self.verify_request(request, client_address):
            try:
                self.process_request(request, client_address)
            except Exception:
                self.handle_error(request, client_address)
                self.shutdown_request(request)
            except:
                self.shutdown_request(request)
                raise
        else:
            self.shutdown_request(request)
        
    ...
#https://github.com/python/cpython/blob/main/Lib/socketserver.py#L500
class TCPServer(BaseServer):
    def get_request(self):
        """Get the request and client address from the socket."""
        return self.socket.accept()
    ...