root / lib / daemon.py @ 5a062513
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# Copyright (C) 2006, 2007, 2008 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Module with helper classes and functions for daemons"""
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import asyncore |
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import os |
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import signal |
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import errno |
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import logging |
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import sched |
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import time |
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import socket |
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import select |
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import sys |
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from ganeti import utils |
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from ganeti import constants |
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from ganeti import errors |
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class SchedulerBreakout(Exception): |
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"""Exception used to get out of the scheduler loop
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"""
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def AsyncoreDelayFunction(timeout): |
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"""Asyncore-compatible scheduler delay function.
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This is a delay function for sched that, rather than actually sleeping,
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executes asyncore events happening in the meantime.
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After an event has occurred, rather than returning, it raises a
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SchedulerBreakout exception, which will force the current scheduler.run()
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invocation to terminate, so that we can also check for signals. The main loop
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will then call the scheduler run again, which will allow it to actually
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process any due events.
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This is needed because scheduler.run() doesn't support a count=..., as
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asyncore loop, and the scheduler module documents throwing exceptions from
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inside the delay function as an allowed usage model.
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"""
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asyncore.loop(timeout=timeout, count=1, use_poll=True) |
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raise SchedulerBreakout()
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class AsyncoreScheduler(sched.scheduler): |
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"""Event scheduler integrated with asyncore
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"""
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def __init__(self, timefunc): |
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sched.scheduler.__init__(self, timefunc, AsyncoreDelayFunction)
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class AsyncUDPSocket(asyncore.dispatcher): |
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"""An improved asyncore udp socket.
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"""
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def __init__(self): |
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"""Constructor for AsyncUDPSocket
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"""
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asyncore.dispatcher.__init__(self)
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self._out_queue = []
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self.create_socket(socket.AF_INET, socket.SOCK_DGRAM)
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# this method is overriding an asyncore.dispatcher method
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def handle_connect(self): |
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# Python thinks that the first udp message from a source qualifies as a
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# "connect" and further ones are part of the same connection. We beg to
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# differ and treat all messages equally.
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pass
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def do_read(self): |
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try:
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payload, address = self.recvfrom(constants.MAX_UDP_DATA_SIZE)
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except socket.error, err:
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if err.errno == errno.EINTR:
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# we got a signal while trying to read. no need to do anything,
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# handle_read will be called again if there is data on the socket.
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return
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else:
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raise
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ip, port = address |
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self.handle_datagram(payload, ip, port)
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# this method is overriding an asyncore.dispatcher method
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def handle_read(self): |
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try:
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self.do_read()
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except: # pylint: disable-msg=W0702 |
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# we need to catch any exception here, log it, but proceed, because even
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# if we failed handling a single request, we still want to continue.
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logging.error("Unexpected exception", exc_info=True) |
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def handle_datagram(self, payload, ip, port): |
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"""Handle an already read udp datagram
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"""
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raise NotImplementedError |
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# this method is overriding an asyncore.dispatcher method
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def writable(self): |
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# We should check whether we can write to the socket only if we have
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# something scheduled to be written
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return bool(self._out_queue) |
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def handle_write(self): |
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try:
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if not self._out_queue: |
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logging.error("handle_write called with empty output queue")
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return
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(ip, port, payload) = self._out_queue[0] |
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try:
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self.sendto(payload, 0, (ip, port)) |
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except socket.error, err:
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if err.errno == errno.EINTR:
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# we got a signal while trying to write. no need to do anything,
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# handle_write will be called again because we haven't emptied the
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# _out_queue, and we'll try again
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return
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else:
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raise
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self._out_queue.pop(0) |
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except: # pylint: disable-msg=W0702 |
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# we need to catch any exception here, log it, but proceed, because even
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# if we failed sending a single datagram we still want to continue.
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logging.error("Unexpected exception", exc_info=True) |
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def enqueue_send(self, ip, port, payload): |
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"""Enqueue a datagram to be sent when possible
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"""
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if len(payload) > constants.MAX_UDP_DATA_SIZE: |
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raise errors.UdpDataSizeError('Packet too big: %s > %s' % (len(payload), |
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constants.MAX_UDP_DATA_SIZE)) |
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self._out_queue.append((ip, port, payload))
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def process_next_packet(self, timeout=0): |
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"""Process the next datagram, waiting for it if necessary.
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@type timeout: float
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@param timeout: how long to wait for data
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@rtype: boolean
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@return: True if some data has been handled, False otherwise
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"""
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result = utils.WaitForFdCondition(self, select.POLLIN, timeout)
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if result is not None and result & select.POLLIN: |
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self.do_read()
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return True |
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else:
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return False |
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class Mainloop(object): |
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"""Generic mainloop for daemons
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@ivar scheduler: A sched.scheduler object, which can be used to register
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timed events
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"""
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def __init__(self): |
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"""Constructs a new Mainloop instance.
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"""
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self._signal_wait = []
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self.scheduler = AsyncoreScheduler(time.time)
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@utils.SignalHandled([signal.SIGCHLD])
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@utils.SignalHandled([signal.SIGTERM])
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def Run(self, signal_handlers=None): |
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"""Runs the mainloop.
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@type signal_handlers: dict
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@param signal_handlers: signal->L{utils.SignalHandler} passed by decorator
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"""
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assert isinstance(signal_handlers, dict) and \ |
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len(signal_handlers) > 0, \ |
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"Broken SignalHandled decorator"
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running = True
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# Start actual main loop
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while running:
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if not self.scheduler.empty(): |
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try:
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self.scheduler.run()
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except SchedulerBreakout:
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pass
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else:
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asyncore.loop(count=1, use_poll=True) |
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# Check whether a signal was raised
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for sig in signal_handlers: |
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handler = signal_handlers[sig] |
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if handler.called:
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self._CallSignalWaiters(sig)
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running = (sig != signal.SIGTERM) |
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handler.Clear() |
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def _CallSignalWaiters(self, signum): |
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"""Calls all signal waiters for a certain signal.
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@type signum: int
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@param signum: Signal number
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"""
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for owner in self._signal_wait: |
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owner.OnSignal(signum) |
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def RegisterSignal(self, owner): |
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"""Registers a receiver for signal notifications
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The receiver must support a "OnSignal(self, signum)" function.
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@type owner: instance
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@param owner: Receiver
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"""
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self._signal_wait.append(owner)
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def GenericMain(daemon_name, optionparser, dirs, check_fn, exec_fn): |
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"""Shared main function for daemons.
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@type daemon_name: string
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@param daemon_name: daemon name
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@type optionparser: optparse.OptionParser
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@param optionparser: initialized optionparser with daemon-specific options
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(common -f -d options will be handled by this module)
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@type dirs: list of (string, integer)
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@param dirs: list of directories that must be created if they don't exist,
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and the permissions to be used to create them
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@type check_fn: function which accepts (options, args)
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@param check_fn: function that checks start conditions and exits if they're
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not met
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@type exec_fn: function which accepts (options, args)
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@param exec_fn: function that's executed with the daemon's pid file held, and
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runs the daemon itself.
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"""
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optionparser.add_option("-f", "--foreground", dest="fork", |
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help="Don't detach from the current terminal",
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default=True, action="store_false") |
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optionparser.add_option("-d", "--debug", dest="debug", |
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help="Enable some debug messages",
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default=False, action="store_true") |
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optionparser.add_option("--syslog", dest="syslog", |
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help="Enable logging to syslog (except debug"
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" messages); one of 'no', 'yes' or 'only' [%s]" %
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constants.SYSLOG_USAGE, |
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default=constants.SYSLOG_USAGE, |
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choices=["no", "yes", "only"]) |
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if daemon_name in constants.DAEMONS_PORTS: |
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# for networked daemons we also allow choosing the bind port and address.
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# by default we use the port provided by utils.GetDaemonPort, and bind to
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# 0.0.0.0 (which is represented by and empty bind address.
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port = utils.GetDaemonPort(daemon_name) |
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optionparser.add_option("-p", "--port", dest="port", |
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help="Network port (%s default)." % port,
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default=port, type="int")
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optionparser.add_option("-b", "--bind", dest="bind_address", |
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help="Bind address",
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default="", metavar="ADDRESS") |
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if daemon_name in constants.DAEMONS_SSL: |
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default_cert, default_key = constants.DAEMONS_SSL[daemon_name] |
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optionparser.add_option("--no-ssl", dest="ssl", |
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help="Do not secure HTTP protocol with SSL",
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default=True, action="store_false") |
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optionparser.add_option("-K", "--ssl-key", dest="ssl_key", |
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help="SSL key",
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default=default_key, type="string")
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optionparser.add_option("-C", "--ssl-cert", dest="ssl_cert", |
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help="SSL certificate",
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default=default_cert, type="string")
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multithread = utils.no_fork = daemon_name in constants.MULTITHREADED_DAEMONS
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options, args = optionparser.parse_args() |
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if hasattr(options, 'ssl') and options.ssl: |
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if not (options.ssl_cert and options.ssl_key): |
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print >> sys.stderr, "Need key and certificate to use ssl" |
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sys.exit(constants.EXIT_FAILURE) |
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for fname in (options.ssl_cert, options.ssl_key): |
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if not os.path.isfile(fname): |
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print >> sys.stderr, "Need ssl file %s to run" % fname |
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sys.exit(constants.EXIT_FAILURE) |
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if check_fn is not None: |
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check_fn(options, args) |
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utils.EnsureDirs(dirs) |
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if options.fork:
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utils.CloseFDs() |
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utils.Daemonize(logfile=constants.DAEMONS_LOGFILES[daemon_name]) |
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utils.WritePidFile(daemon_name) |
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try:
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utils.SetupLogging(logfile=constants.DAEMONS_LOGFILES[daemon_name], |
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debug=options.debug, |
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stderr_logging=not options.fork,
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multithreaded=multithread, |
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program=daemon_name, |
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syslog=options.syslog) |
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logging.info("%s daemon startup", daemon_name)
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exec_fn(options, args) |
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finally:
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utils.RemovePidFile(daemon_name) |