socket_activated_webserver.py

#!/usr/bin/env python

# webhook.py
#
# Copyright (C) 2016 Intel Corporation
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

import socket
import os
from http.server import BaseHTTPRequestHandler, HTTPServer

class SocketEnvironmentError(Exception):
    pass

# Same as HTTPServer, just requires you to pass in a socket or for it to get
# one from the environment.
class HTTPServerInherit(HTTPServer):
    def __init__(self, *args, **kwargs):
        newsocket = self._get_socket_from_systemd()

        # Since we can't prevent the server from creating a socket, just close
        # it and use the new one before activating the server.
        super().__init__(*args, bind_and_activate=False, **kwargs)
        self.socket.close()
        self.socket = newsocket

    def _get_socket_from_systemd(self):
        if 'LISTEN_PID' in os.environ:
            if os.environ['LISTEN_PID'] != str(os.getpid()):
                raise SocketEnvironmentError("LISTEN_PID not correct")
        else:
            raise SocketEnvironmentError("LISTEN_PID not in environment")

        # Macro typically specified by systemd code
        SD_LISTEN_FDS_START = 3
        return socket.socket(fileno=SD_LISTEN_FDS_START)

class PostHandler(BaseHTTPRequestHandler):
    def do_POST(self):
        length = int(self.headers.get('Content-Length'))
        if not length:
            self.send_response(400, 'foo not in headers')
            self.end_headers()
        else:
            print(self.rfile.read(length))
            self.send_response(200, 'OK')
            self.end_headers()

if __name__ == "__main__":
    try:
        httpd = HTTPServerInherit(("127.0.0.1", 18000), PostHandler)
        httpd.serve_forever()
    except SocketEnvironmentError as e:
        print(e)