Synnefo » snf-ganeti

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#

# Copyright (C) 2006, 2007, 2008 Google Inc.

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# 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.

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# 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.

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# 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 os

import select

import signal

import errno

import logging

from ganeti import utils

from ganeti import constants

class Mainloop(object):

  """Generic mainloop for daemons

  """

  def __init__(self):

    """Constructs a new Mainloop instance.

    """

    self._io_wait = {}

    self._signal_wait = []

    self._poller = select.poll()

  @utils.SignalHandled([signal.SIGCHLD])

  @utils.SignalHandled([signal.SIGTERM])

  def Run(self, stop_on_empty=False, signal_handlers=None):

    """Runs the mainloop.

    @type stop_on_empty: bool

    @param stop_on_empty: Whether to stop mainloop once all I/O waiters

                          unregistered

    @type signal_handlers: dict

    @param signal_handlers: signal->L{utils.SignalHandler} passed by decorator

    """

    assert isinstance(signal_handlers, dict) and \

           len(signal_handlers) > 0, \

           "Broken SignalHandled decorator"

    running = True

    # Start actual main loop

    while running:

      # Stop if nothing is listening anymore

      if stop_on_empty and not (self._io_wait):

        break

      # Wait for I/O events

      try:

        io_events = self._poller.poll(None)

      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:

          owner = self._io_wait.get(evfd, None)

          if owner:

            owner.OnIO(evfd, evcond)

      # Check whether a signal was raised

      for sig in signal_handlers:

        handler = signal_handlers[sig]

        if handler.called:

          self._CallSignalWaiters(sig)

          running = (sig != signal.SIGTERM)

          handler.Clear()

  def _CallSignalWaiters(self, signum):

    """Calls all signal waiters for a certain signal.

    @type signum: int

    @param signum: Signal number

    """

    for owner in self._signal_wait:

      owner.OnSignal(signal.SIGCHLD)

  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)

    """

    # select.Poller also supports file() like objects, but we don't.

    assert isinstance(fd, (int, long)), \

      "Only integers are supported for file descriptors"

    self._io_wait[fd] = owner

    self._poller.register(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)

def GenericMain(daemon_name, optionparser, dirs, check_fn, exec_fn):

  """Shared main function for daemons.

  @type daemon_name: string

  @param daemon_name: daemon name

  @type optionparser: L{optparse.OptionParser}

  @param optionparser: initialized optionparser with daemon-specific options

                       (common -f -d options will be handled by this module)

  @type options: object @param options: OptionParser result, should contain at

                 least the fork and the debug options

  @type dirs: list of strings

  @param dirs: list of directories that must exist for this daemon to work

  @type check_fn: function which accepts (options, args)

  @param check_fn: function that checks start conditions and exits if they're

                   not met

  @type exec_fn: function which accepts (options, args)

  @param exec_fn: function that's executed with the daemon's pid file held, and

                  runs the daemon itself.

  """

  optionparser.add_option("-f", "--foreground", dest="fork",

                          help="Don't detach from the current terminal",

                          default=True, action="store_false")

  optionparser.add_option("-d", "--debug", dest="debug",

                          help="Enable some debug messages",

                          default=False, action="store_true")

  if daemon_name in constants.DAEMONS_PORTS:

    # for networked daemons we also allow choosing the bind port and address.

    # by default we use the port provided by utils.GetDaemonPort, and bind to

    # 0.0.0.0 (which is represented by and empty bind address.

    port = utils.GetDaemonPort(daemon_name)

    optionparser.add_option("-p", "--port", dest="port",

                            help="Network port (%s default)." % port,

                            default=port, type="int")

    optionparser.add_option("-b", "--bind", dest="bind_address",

                            help="Bind address",

                            default="", metavar="ADDRESS")

  if daemon_name in constants.DAEMONS_SSL:

    default_cert, default_key = constants.DAEMONS_SSL[daemon_name]

    optionparser.add_option("--no-ssl", dest="ssl",

                            help="Do not secure HTTP protocol with SSL",

                            default=True, action="store_false")

    optionparser.add_option("-K", "--ssl-key", dest="ssl_key",

                            help="SSL key",

                            default=default_key, type="string")

    optionparser.add_option("-C", "--ssl-cert", dest="ssl_cert",

                            help="SSL certificate",

                            default=default_cert, type="string")

  multithread = utils.no_fork = daemon_name in constants.MULTITHREADED_DAEMONS

  options, args = optionparser.parse_args()

  if hasattr(options, 'ssl') and options.ssl:

    if not (options.ssl_cert and options.ssl_key):

      print >> sys.stderr, "Need key and certificate to use ssl"

      sys.exit(constants.EXIT_FAILURE)

    for fname in (options.ssl_cert, options.ssl_key):

      if not os.path.isfile(fname):

        print >> sys.stderr, "Need ssl file %s to run" % fname

        sys.exit(constants.EXIT_FAILURE)

  if check_fn is not None:

    check_fn(options, args)

  utils.EnsureDirs(dirs)

  if options.fork:

    utils.CloseFDs()

    utils.Daemonize(logfile=constants.DAEMONS_LOGFILES[daemon_name])

  utils.WritePidFile(daemon_name)

  try:

    utils.SetupLogging(logfile=constants.DAEMONS_LOGFILES[daemon_name],

                       debug=options.debug,

                       stderr_logging=not options.fork,

                       multithreaded=multithread)

    logging.info("%s daemon startup" % daemon_name)

    exec_fn(options, args)

  finally:

    utils.RemovePidFile(daemon_name)