httpd-true

#!/bin/env python3
import os
import sys
import time
import socket
import http.server


def get_systemd_socket():
    """Shows how to get the socket"""
    SYSTEMD_FIRST_SOCKET_FD = 3
    socket_type = http.server.HTTPServer.socket_type
    address_family = http.server.HTTPServer.address_family
    return socket.fromfd(SYSTEMD_FIRST_SOCKET_FD, address_family, socket_type)


class RequestHandler(http.server.BaseHTTPRequestHandler):
    """Returns the string 'true' to all requests"""
    def do_GET(self):
        self.send_response(200)
        self.end_headers()
        self.wfile.write(b"true")
        self.wfile.write(b"\n")
        return
    do_POST = do_GET


class SockInheritHTTPServer(http.server.HTTPServer):
    def __init__(self, address_info, handler, bind_and_activate=True):
        # Note that we call it with bind_and_activate = False.
        http.server.HTTPServer.__init__(self,
                                        address_info,
                                        handler,
                                        bind_and_activate=False)

        # The socket from systemd needs to be set AFTER calling the parent's
        # class's constructor, otherwise HTTPServer.__init__() will re-set
        # self.socket() and the handover won't work.
        self.socket = get_systemd_socket()

        if bind_and_activate:
            self.server_activate()


def wait_loop(delay=60):
    # The connection/port/host doesn't really matter as we don't allocate the
    # socket ourselves. Pass it in as localhost:80
    httpserv = SockInheritHTTPServer(('localhost', 80), RequestHandler)
    httpserv.timeout = 1
    start = time.monotonic()
    end = start + delay
    while time.monotonic() < end:
        httpserv.handle_request()
    httpserv.server_close()


if __name__ == "__main__":
    if os.environ.get('LISTEN_PID', None) == str(os.getpid()):
        wait_loop()
        print("Done serving, shutting down")
        sys.exit()
    else:
        raise SystemExit("This server should only run from systemd")