src/mailman/runners/rest.py

   1 # Copyright (C) 2009-2016 by the Free Software Foundation, Inc.
   2 #
   3 # This file is part of GNU Mailman.
   4 #
   5 # GNU Mailman is free software: you can redistribute it and/or modify it under
   6 # the terms of the GNU General Public License as published by the Free
   7 # Software Foundation, either version 3 of the License, or (at your option)
   8 # any later version.
   9 #
  10 # GNU Mailman is distributed in the hope that it will be useful, but WITHOUT
  11 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12 # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  13 # more details.
  14 #
  15 # You should have received a copy of the GNU General Public License along with
  16 # GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
  17
  18 """Start the administrative HTTP server."""
  19
  20 import signal
  21 import logging
  22 import threading
  23
  24 from mailman import public
  25 from mailman.core.runner import Runner
  26 from mailman.rest.wsgiapp import make_server
  27
  28
  29 log = logging.getLogger('mailman.http')
  30
  31
  32 @public
  33 class RESTRunner(Runner):
  34     # Don't install the standard signal handlers because as defined, they
  35     # won't actually stop the TCPServer started by .serve_forever().
  36     is_queue_runner = False
  37
  38     def __init__(self, name, slice=None):
  39         """See `IRunner`."""
  40         super().__init__(name, slice)
  41         # Both the REST server and the signal handlers must run in the main
  42         # thread; the former because of SQLite requirements (objects created
  43         # in one thread cannot be shared with the other threads), and the
  44         # latter because of Python's signal handling semantics.
  45         #
  46         # Unfortunately, we cannot issue a TCPServer shutdown in the main
  47         # thread, because that will cause a deadlock.  Yay.   So what we do is
  48         # to use the signal handler to notify a shutdown thread that the
  49         # shutdown should happen.  That thread will wake up and stop the main
  50         # server.
  51         self._server = make_server()
  52         self._event = threading.Event()
  53         def stopper(event, server):                 # flake8: noqa
  54             event.wait()
  55             server.shutdown()
  56         self._thread = threading.Thread(
  57             target=stopper, args=(self._event, self._server))
  58         self._thread.start()
  59
  60     def run(self):
  61         """See `IRunner`."""
  62         self._server.serve_forever()
  63
  64     def signal_handler(self, signum, frame):
  65         super().signal_handler(signum, frame)
  66         if signum in (signal.SIGTERM, signal.SIGINT, signal.SIGUSR1):
  67             # Set the flag that will terminate the TCPserver loop.
  68             self._event.set()
  69
  70     def _one_iteration(self):
  71         # Just keep going
  72         if self._thread.is_alive():
  73             self._thread.join(timeout=0.1)
  74         return 1
  75
  76     def _snooze(self, filecnt):
  77         pass