Commit 821d9e43 authored by Michael Hanselmann's avatar Michael Hanselmann

Add daemon library with mainloop

This mainloop can be used in daemons like ganeti-noded.

Reviewed-by: iustinp
parent e9f242e4
......@@ -66,6 +66,7 @@ pkgpython_PYTHON = \
lib/cmdlib.py \
lib/config.py \
lib/constants.py \
lib/daemon.py \
lib/errors.py \
lib/http.py \
lib/jqueue.py \
......
#
#
# Copyright (C) 2006, 2007, 2008 Google Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# 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.
"""Module with helper classes and functions for daemons"""
import select
import signal
import errno
from ganeti import utils
class Mainloop(object):
"""Generic mainloop for daemons
"""
def __init__(self):
self._io_wait = []
self._signal_wait = []
self.sigchld_handler = {}
def Run(self):
# TODO: Does not yet support adding new event sources while running
poller = select.poll()
for (owner, fd, conditions) in self._io_wait:
poller.register(fd, conditions)
self.sigchld_handler = utils.SignalHandler([signal.SIGCHLD])
try:
while True:
try:
io_events = poller.poll(1000)
except select.error, err:
# EINTR can happen when signals are sent
if err.args and err.args[0] in (errno.EINTR,):
io_events = None
else:
raise
if io_events:
# Check for I/O events
for (evfd, evcond) in io_events:
for (owner, fd, conditions) in self._io_wait:
if fd == evfd and evcond & conditions:
owner.OnIO(fd, evcond)
# Check whether signal was raised
if self.sigchld_handler.called:
for owner in self._signal_wait:
owner.OnSignal(signal.SIGCHLD)
self.sigchld_handler.Clear()
finally:
self.sigchld_handler.Reset()
self.sigchld_handler = None
def RegisterIO(self, owner, fd, condition):
"""Registers a receiver for I/O notifications
The receiver must support a "OnIO(self, fd, conditions)" function.
@type owner: instance
@param owner: Receiver
@type fd: int
@param fd: File descriptor
@type condition: int
@param condition: ORed field of conditions to be notified
(see select module)
"""
self._io_wait.append((owner, fd, condition))
def RegisterSignal(self, owner):
"""Registers a receiver for signal notifications
The receiver must support a "OnSignal(self, signum)" function.
@type owner: instance
@param owner: Receiver
"""
self._signal_wait.append(owner)
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