Synnefo » snf-ganeti

#!/usr/bin/python

#

# Copyright (C) 2009, 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.

"""Ganeti configuration daemon

Ganeti-confd is a daemon to query master candidates for configuration values.

It uses UDP+HMAC for authentication with a global cluster key.

"""

# pylint: disable-msg=C0103

# C0103: Invalid name ganeti-confd

import os

import sys

import logging

import time

try:

  # pylint: disable-msg=E0611

  from pyinotify import pyinotify

except ImportError:

  import pyinotify

from optparse import OptionParser

from ganeti import asyncnotifier

from ganeti import confd

from ganeti.confd import server as confd_server

from ganeti import constants

from ganeti import errors

from ganeti import daemon

class ConfdAsyncUDPServer(daemon.AsyncUDPSocket):

  """The confd udp server, suitable for use with asyncore.

  """

  def __init__(self, bind_address, port, processor):

    """Constructor for ConfdAsyncUDPServer

    @type bind_address: string

    @param bind_address: socket bind address ('' for all)

    @type port: int

    @param port: udp port

    @type processor: L{confd.server.ConfdProcessor}

    @param processor: ConfdProcessor to use to handle queries

    """

    daemon.AsyncUDPSocket.__init__(self)

    self.bind_address = bind_address

    self.port = port

    self.processor = processor

    self.bind((bind_address, port))

    logging.debug("listening on ('%s':%d)", bind_address, port)

  # this method is overriding a daemon.AsyncUDPSocket method

  def handle_datagram(self, payload_in, ip, port):

    try:

      query = confd.UnpackMagic(payload_in)

    except errors.ConfdMagicError, err:

      logging.debug(err)

      return

    answer =  self.processor.ExecQuery(query, ip, port)

    if answer is not None:

      try:

        self.enqueue_send(ip, port, confd.PackMagic(answer))

      except errors.UdpDataSizeError:

        logging.error("Reply too big to fit in an udp packet.")

class ConfdInotifyEventHandler(pyinotify.ProcessEvent):

  def __init__(self, watch_manager, callback,

               filename=constants.CLUSTER_CONF_FILE):

    """Constructor for ConfdInotifyEventHandler

    @type watch_manager: pyinotify.WatchManager

    @param watch_manager: ganeti-confd inotify watch manager

    @type callback: function accepting a boolean

    @param callback: function to call when an inotify event happens

    @type filename: string

    @param filename: config file to watch

    """

    # pylint: disable-msg=W0231

    # no need to call the parent's constructor

    self.watch_manager = watch_manager

    self.callback = callback

    self.mask = pyinotify.EventsCodes.ALL_FLAGS["IN_IGNORED"] | \

                pyinotify.EventsCodes.ALL_FLAGS["IN_MODIFY"]

    self.file = filename

    self.watch_handle = None

  def enable(self):

    """Watch the given file

    """

    if self.watch_handle is None:

      result = self.watch_manager.add_watch(self.file, self.mask)

      if not self.file in result or result[self.file] <= 0:

        raise errors.InotifyError("Could not add inotify watcher")

      else:

        self.watch_handle = result[self.file]

  def disable(self):

    """Stop watching the given file

    """

    if self.watch_handle is not None:

      result = self.watch_manager.rm_watch(self.watch_handle)

      if result[self.watch_handle]:

        self.watch_handle = None

  def process_IN_IGNORED(self, event):

    # Due to the fact that we monitor just for the cluster config file (rather

    # than for the whole data dir) when the file is replaced with another one

    # (which is what happens normally in ganeti) we're going to receive an

    # IN_IGNORED event from inotify, because of the file removal (which is

    # contextual with the replacement). In such a case we need to create

    # another watcher for the "new" file.

    logging.debug("Received 'ignored' inotify event for %s", event.path)

    self.watch_handle = None

    try:

      # Since the kernel believes the file we were interested in is gone, it's

      # not going to notify us of any other events, until we set up, here, the

      # new watch. This is not a race condition, though, since we're anyway

      # going to realod the file after setting up the new watch.

      self.callback(False)

    except:

      # we need to catch any exception here, log it, but proceed, because even

      # if we failed handling a single request, we still want the confd to

      # continue working.

      logging.error("Unexpected exception", exc_info=True)

  def process_IN_MODIFY(self, event):

    # This gets called when the config file is modified. Note that this doesn't

    # usually happen in Ganeti, as the config file is normally replaced by a

    # new one, at filesystem level, rather than actually modified (see

    # utils.WriteFile)

    logging.debug("Received 'modify' inotify event for %s", event.path)

    try:

      self.callback(True)

    except:

      # we need to catch any exception here, log it, but proceed, because even

      # if we failed handling a single request, we still want the confd to

      # continue working.

      logging.error("Unexpected exception", exc_info=True)

  def process_default(self, event):

    logging.error("Received unhandled inotify event: %s", event)

class ConfdConfigurationReloader(object):

  """Logic to control when to reload the ganeti configuration

  This class is able to alter between inotify and polling, to rate-limit the

  number of reloads. When using inotify it also supports a fallback timed

  check, to verify that the reload hasn't failed.

  """

  def __init__(self, processor, mainloop):

    """Constructor for ConfdConfigurationReloader

    @type processor: L{confd.server.ConfdProcessor}

    @param processor: ganeti-confd ConfdProcessor

    @type mainloop: L{daemon.Mainloop}

    @param mainloop: ganeti-confd mainloop

    """

    self.processor = processor

    self.mainloop = mainloop

    self.polling = True

    self.last_notification = 0

    # Asyncronous inotify handler for config changes

    self.wm = pyinotify.WatchManager()

    self.inotify_handler = ConfdInotifyEventHandler(self.wm, self.OnInotify)

    self.notifier = asyncnotifier.AsyncNotifier(self.wm, self.inotify_handler)

    self.timer_handle = None

    self._EnableTimer()

  def OnInotify(self, notifier_enabled):

    """Receive an inotify notification.

    @type notifier_enabled: boolean

    @param notifier_enabled: whether the notifier is still enabled

    """

    current_time = time.time()

    time_delta = current_time - self.last_notification

    self.last_notification = current_time

    if time_delta < constants.CONFD_CONFIG_RELOAD_RATELIMIT:

      logging.debug("Moving from inotify mode to polling mode")

      self.polling = True

      if notifier_enabled:

        self.inotify_handler.disable()

    if not self.polling and not notifier_enabled:

      try:

        self.inotify_handler.enable()

      except errors.InotifyError:

        self.polling = True

    try:

      reloaded = self.processor.reader.Reload()

      if reloaded:

        logging.info("Reloaded ganeti config")

      else:

        logging.debug("Skipped double config reload")

    except errors.ConfigurationError:

      self.DisableConfd()

      self.inotify_handler.disable()

      return

    # Reset the timer. If we're polling it will go to the polling rate, if

    # we're not it will delay it again to its base safe timeout.

    self._ResetTimer()

  def _DisableTimer(self):

    if self.timer_handle is not None:

      self.mainloop.scheduler.cancel(self.timer_handle)

      self.timer_handle = None

  def _EnableTimer(self):

    if self.polling:

      timeout = constants.CONFD_CONFIG_RELOAD_RATELIMIT

    else:

      timeout = constants.CONFD_CONFIG_RELOAD_TIMEOUT

    if self.timer_handle is None:

      self.timer_handle = self.mainloop.scheduler.enter(

        timeout, 1, self.OnTimer, [])

  def _ResetTimer(self):

    self._DisableTimer()

    self._EnableTimer()

  def OnTimer(self):

    """Function called when the timer fires

    """

    self.timer_handle = None

    reloaded = False

    was_disabled = False

    try:

      if self.processor.reader is None:

        was_disabled = True

        self.EnableConfd()

        reloaded = True

      else:

        reloaded = self.processor.reader.Reload()

    except errors.ConfigurationError:

      self.DisableConfd(silent=was_disabled)

      return

    if self.polling and reloaded:

      logging.info("Reloaded ganeti config")

    elif reloaded:

      # We have reloaded the config files, but received no inotify event.  If

      # an event is pending though, we just happen to have timed out before

      # receiving it, so this is not a problem, and we shouldn't alert

      if not self.notifier.check_events() and not was_disabled:

        logging.warning("Config file reload at timeout (inotify failure)")

    elif self.polling:

      # We're polling, but we haven't reloaded the config:

      # Going back to inotify mode

      logging.debug("Moving from polling mode to inotify mode")

      self.polling = False

      try:

        self.inotify_handler.enable()

      except errors.InotifyError:

        self.polling = True

    else:

      logging.debug("Performed configuration check")

    self._EnableTimer()

  def DisableConfd(self, silent=False):

    """Puts confd in non-serving mode

    """

    if not silent:

      logging.warning("Confd is being disabled")

    self.processor.Disable()

    self.polling = False

    self._ResetTimer()

  def EnableConfd(self):

    self.processor.Enable()

    logging.warning("Confd is being enabled")

    self.polling = True

    self._ResetTimer()

def CheckConfd(_, args):

  """Initial checks whether to run exit with a failure.

  """

  if args: # confd doesn't take any arguments

    print >> sys.stderr, ("Usage: %s [-f] [-d] [-b ADDRESS]" % sys.argv[0])

    sys.exit(constants.EXIT_FAILURE)

  # TODO: collapse HMAC daemons handling in daemons GenericMain, when we'll

  # have more than one.

  if not os.path.isfile(constants.CONFD_HMAC_KEY):

    print >> sys.stderr, "Need HMAC key %s to run" % constants.CONFD_HMAC_KEY

    sys.exit(constants.EXIT_FAILURE)

def ExecConfd(options, _):

  """Main confd function, executed with PID file held

  """

  # TODO: clarify how the server and reloader variables work (they are

  # not used)

  # pylint: disable-msg=W0612

  mainloop = daemon.Mainloop()

  # Asyncronous confd UDP server

  processor = confd_server.ConfdProcessor()

  try:

    processor.Enable()

  except errors.ConfigurationError:

    # If enabling the processor has failed, we can still go on, but confd will

    # be disabled

    logging.warning("Confd is starting in disabled mode")

  server = ConfdAsyncUDPServer(options.bind_address, options.port, processor)

  # Configuration reloader

  reloader = ConfdConfigurationReloader(processor, mainloop)

  mainloop.Run()

def main():

  """Main function for the confd daemon.

  """

  parser = OptionParser(description="Ganeti configuration daemon",

                        usage="%prog [-f] [-d] [-b ADDRESS]",

                        version="%%prog (ganeti) %s" %

                        constants.RELEASE_VERSION)

  dirs = [(val, constants.RUN_DIRS_MODE) for val in constants.SUB_RUN_DIRS]

  dirs.append((constants.LOCK_DIR, 1777))

  daemon.GenericMain(constants.CONFD, parser, dirs, CheckConfd, ExecConfd)

if __name__ == "__main__":

  main()