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#

# Copyright (C) 2006, 2007, 2008, 2010 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.

#

# 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 asyncore

import asynchat

import collections

import os

import signal

import logging

import sched

import time

import socket

import select

import sys

from ganeti import utils

from ganeti import constants

from ganeti import errors

from ganeti import netutils

from ganeti import ssconf

class SchedulerBreakout(Exception):

  """Exception used to get out of the scheduler loop

  """

def AsyncoreDelayFunction(timeout):

  """Asyncore-compatible scheduler delay function.

  This is a delay function for sched that, rather than actually sleeping,

  executes asyncore events happening in the meantime.

  After an event has occurred, rather than returning, it raises a

  SchedulerBreakout exception, which will force the current scheduler.run()

  invocation to terminate, so that we can also check for signals. The main loop

  will then call the scheduler run again, which will allow it to actually

  process any due events.

  This is needed because scheduler.run() doesn't support a count=..., as

  asyncore loop, and the scheduler module documents throwing exceptions from

  inside the delay function as an allowed usage model.

  """

  asyncore.loop(timeout=timeout, count=1, use_poll=True)

  raise SchedulerBreakout()

class AsyncoreScheduler(sched.scheduler):

  """Event scheduler integrated with asyncore

  """

  def __init__(self, timefunc):

    sched.scheduler.__init__(self, timefunc, AsyncoreDelayFunction)

class GanetiBaseAsyncoreDispatcher(asyncore.dispatcher):

  """Base Ganeti Asyncore Dispacher

  """

  # this method is overriding an asyncore.dispatcher method

  def handle_error(self):

    """Log an error in handling any request, and proceed.

    """

    logging.exception("Error while handling asyncore request")

  # this method is overriding an asyncore.dispatcher method

  def writable(self):

    """Most of the time we don't want to check for writability.

    """

    return False

class AsyncStreamServer(GanetiBaseAsyncoreDispatcher):

  """A stream server to use with asyncore.

  Each request is accepted, and then dispatched to a separate asyncore

  dispatcher to handle.

  """

  _REQUEST_QUEUE_SIZE = 5

  def __init__(self, family, address):

    """Constructor for AsyncUnixStreamSocket

    @type family: integer

    @param family: socket family (one of socket.AF_*)

    @type address: address family dependent

    @param address: address to bind the socket to

    """

    GanetiBaseAsyncoreDispatcher.__init__(self)

    self.family = family

    self.create_socket(self.family, socket.SOCK_STREAM)

    self.set_reuse_addr()

    self.bind(address)

    self.listen(self._REQUEST_QUEUE_SIZE)

  # this method is overriding an asyncore.dispatcher method

  def handle_accept(self):

    """Accept a new client connection.

    Creates a new instance of the handler class, which will use asyncore to

    serve the client.

    """

    accept_result = utils.IgnoreSignals(self.accept)

    if accept_result is not None:

      connected_socket, client_address = accept_result

      if self.family == socket.AF_UNIX:

        # override the client address, as for unix sockets nothing meaningful

        # is passed in from accept anyway

        client_address = netutils.GetSocketCredentials(connected_socket)

      logging.info("Accepted connection from %s",

                   netutils.FormatAddress(client_address, family=self.family))

      self.handle_connection(connected_socket, client_address)

  def handle_connection(self, connected_socket, client_address):

    """Handle an already accepted connection.

    """

    raise NotImplementedError

class AsyncTerminatedMessageStream(asynchat.async_chat):

  """A terminator separated message stream asyncore module.

  Handles a stream connection receiving messages terminated by a defined

  separator. For each complete message handle_message is called.

  """

  def __init__(self, connected_socket, peer_address, terminator, family,

               unhandled_limit):

    """AsyncTerminatedMessageStream constructor.

    @type connected_socket: socket.socket

    @param connected_socket: connected stream socket to receive messages from

    @param peer_address: family-specific peer address

    @type terminator: string

    @param terminator: terminator separating messages in the stream

    @type family: integer

    @param family: socket family

    @type unhandled_limit: integer or None

    @param unhandled_limit: maximum unanswered messages

    """

    # python 2.4/2.5 uses conn=... while 2.6 has sock=... we have to cheat by

    # using a positional argument rather than a keyword one.

    asynchat.async_chat.__init__(self, connected_socket)

    self.connected_socket = connected_socket

    # on python 2.4 there is no "family" attribute for the socket class

    # FIXME: when we move to python 2.5 or above remove the family parameter

    #self.family = self.connected_socket.family

    self.family = family

    self.peer_address = peer_address

    self.terminator = terminator

    self.unhandled_limit = unhandled_limit

    self.set_terminator(terminator)

    self.ibuffer = []

    self.receive_count = 0

    self.send_count = 0

    self.oqueue = collections.deque()

    self.iqueue = collections.deque()

  # this method is overriding an asynchat.async_chat method

  def collect_incoming_data(self, data):

    self.ibuffer.append(data)

  def _can_handle_message(self):

    return (self.unhandled_limit is None or

            (self.receive_count < self.send_count + self.unhandled_limit) and

             not self.iqueue)

  # this method is overriding an asynchat.async_chat method

  def found_terminator(self):

    message = "".join(self.ibuffer)

    self.ibuffer = []

    message_id = self.receive_count

    # We need to increase the receive_count after checking if the message can

    # be handled, but before calling handle_message

    can_handle = self._can_handle_message()

    self.receive_count += 1

    if can_handle:

      self.handle_message(message, message_id)

    else:

      self.iqueue.append((message, message_id))

  def handle_message(self, message, message_id):

    """Handle a terminated message.

    @type message: string

    @param message: message to handle

    @type message_id: integer

    @param message_id: stream's message sequence number

    """

    pass

    # TODO: move this method to raise NotImplementedError

    # raise NotImplementedError

  def send_message(self, message):

    """Send a message to the remote peer. This function is thread-safe.

    @type message: string

    @param message: message to send, without the terminator

    @warning: If calling this function from a thread different than the one

    performing the main asyncore loop, remember that you have to wake that one

    up.

    """

    # If we just append the message we received to the output queue, this

    # function can be safely called by multiple threads at the same time, and

    # we don't need locking, since deques are thread safe. handle_write in the

    # asyncore thread will handle the next input message if there are any

    # enqueued.

    self.oqueue.append(message)

  # this method is overriding an asyncore.dispatcher method

  def readable(self):

    # read from the socket if we can handle the next requests

    return self._can_handle_message() and asynchat.async_chat.readable(self)

  # this method is overriding an asyncore.dispatcher method

  def writable(self):

    # the output queue may become full just after we called writable. This only

    # works if we know we'll have something else waking us up from the select,

    # in such case, anyway.

    return asynchat.async_chat.writable(self) or self.oqueue

  # this method is overriding an asyncore.dispatcher method

  def handle_write(self):

    if self.oqueue:

      # if we have data in the output queue, then send_message was called.

      # this means we can process one more message from the input queue, if

      # there are any.

      data = self.oqueue.popleft()

      self.push(data + self.terminator)

      self.send_count += 1

      if self.iqueue:

        self.handle_message(*self.iqueue.popleft())

    self.initiate_send()

  def close_log(self):

    logging.info("Closing connection from %s",

                 netutils.FormatAddress(self.peer_address, family=self.family))

    self.close()

  # this method is overriding an asyncore.dispatcher method

  def handle_expt(self):

    self.close_log()

  # this method is overriding an asyncore.dispatcher method

  def handle_error(self):

    """Log an error in handling any request, and proceed.

    """

    logging.exception("Error while handling asyncore request")

    self.close_log()

class AsyncUDPSocket(GanetiBaseAsyncoreDispatcher):

  """An improved asyncore udp socket.

  """

  def __init__(self, family):

    """Constructor for AsyncUDPSocket

    """

    GanetiBaseAsyncoreDispatcher.__init__(self)

    self._out_queue = []

    self._family = family

    self.create_socket(family, socket.SOCK_DGRAM)

  # this method is overriding an asyncore.dispatcher method

  def handle_connect(self):

    # Python thinks that the first udp message from a source qualifies as a

    # "connect" and further ones are part of the same connection. We beg to

    # differ and treat all messages equally.

    pass

  # this method is overriding an asyncore.dispatcher method

  def handle_read(self):

    recv_result = utils.IgnoreSignals(self.recvfrom,

                                      constants.MAX_UDP_DATA_SIZE)

    if recv_result is not None:

      payload, address = recv_result

      if self._family == socket.AF_INET6:

        # we ignore 'flow info' and 'scope id' as we don't need them

        ip, port, _, _ = address

      else:

        ip, port = address

      self.handle_datagram(payload, ip, port)

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

    """Handle an already read udp datagram

    """

    raise NotImplementedError

  # this method is overriding an asyncore.dispatcher method

  def writable(self):

    # We should check whether we can write to the socket only if we have

    # something scheduled to be written

    return bool(self._out_queue)

  # this method is overriding an asyncore.dispatcher method

  def handle_write(self):

    if not self._out_queue:

      logging.error("handle_write called with empty output queue")

      return

    (ip, port, payload) = self._out_queue[0]

    utils.IgnoreSignals(self.sendto, payload, 0, (ip, port))

    self._out_queue.pop(0)

  def enqueue_send(self, ip, port, payload):

    """Enqueue a datagram to be sent when possible

    """

    if len(payload) > constants.MAX_UDP_DATA_SIZE:

      raise errors.UdpDataSizeError('Packet too big: %s > %s' % (len(payload),

                                    constants.MAX_UDP_DATA_SIZE))

    self._out_queue.append((ip, port, payload))

  def process_next_packet(self, timeout=0):

    """Process the next datagram, waiting for it if necessary.

    @type timeout: float

    @param timeout: how long to wait for data

    @rtype: boolean

    @return: True if some data has been handled, False otherwise

    """

    result = utils.WaitForFdCondition(self, select.POLLIN, timeout)

    if result is not None and result & select.POLLIN:

      self.handle_read()

      return True

    else:

      return False

class AsyncAwaker(GanetiBaseAsyncoreDispatcher):

  """A way to notify the asyncore loop that something is going on.

  If an asyncore daemon is multithreaded when a thread tries to push some data

  to a socket, the main loop handling asynchronous requests might be sleeping

  waiting on a select(). To avoid this it can create an instance of the

  AsyncAwaker, which other threads can use to wake it up.

  """

  def __init__(self, signal_fn=None):

    """Constructor for AsyncAwaker

    @type signal_fn: function

    @param signal_fn: function to call when awaken

    """

    GanetiBaseAsyncoreDispatcher.__init__(self)

    assert signal_fn == None or callable(signal_fn)

    (self.in_socket, self.out_socket) = socket.socketpair(socket.AF_UNIX,

                                                          socket.SOCK_STREAM)

    self.in_socket.setblocking(0)

    self.in_socket.shutdown(socket.SHUT_WR)

    self.out_socket.shutdown(socket.SHUT_RD)

    self.set_socket(self.in_socket)

    self.need_signal = True

    self.signal_fn = signal_fn

    self.connected = True

  # this method is overriding an asyncore.dispatcher method

  def handle_read(self):

    utils.IgnoreSignals(self.recv, 4096)

    if self.signal_fn:

      self.signal_fn()

    self.need_signal = True

  # this method is overriding an asyncore.dispatcher method

  def close(self):

    asyncore.dispatcher.close(self)

    self.out_socket.close()

  def signal(self):

    """Signal the asyncore main loop.

    Any data we send here will be ignored, but it will cause the select() call

    to return.

    """

    # Yes, there is a race condition here. No, we don't care, at worst we're

    # sending more than one wakeup token, which doesn't harm at all.

    if self.need_signal:

      self.need_signal = False

      self.out_socket.send("\0")

class Mainloop(object):

  """Generic mainloop for daemons

  @ivar scheduler: A sched.scheduler object, which can be used to register

    timed events

  """

  def __init__(self):

    """Constructs a new Mainloop instance.

    """

    self._signal_wait = []

    self.scheduler = AsyncoreScheduler(time.time)

  @utils.SignalHandled([signal.SIGCHLD])

  @utils.SignalHandled([signal.SIGTERM])

  @utils.SignalHandled([signal.SIGINT])

  def Run(self, signal_handlers=None):

    """Runs the mainloop.

    @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:

      if not self.scheduler.empty():

        try:

          self.scheduler.run()

        except SchedulerBreakout:

          pass

      else:

        asyncore.loop(count=1, use_poll=True)

      # Check whether a signal was raised

      for sig in signal_handlers:

        handler = signal_handlers[sig]

        if handler.called:

          self._CallSignalWaiters(sig)

          running = sig not in (signal.SIGTERM, signal.SIGINT)

          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(signum)

  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, check_fn, exec_fn,

                multithreaded=False, console_logging=False,

                default_ssl_cert=None, default_ssl_key=None):

  """Shared main function for daemons.

  @type daemon_name: string

  @param daemon_name: daemon name

  @type optionparser: optparse.OptionParser

  @param optionparser: initialized optionparser with daemon-specific options

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

  @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.

  @type multithreaded: bool

  @param multithreaded: Whether the daemon uses threads

  @type console_logging: boolean

  @param console_logging: if True, the daemon will fall back to the system

                          console if logging fails

  @type default_ssl_cert: string

  @param default_ssl_cert: Default SSL certificate path

  @type default_ssl_key: string

  @param default_ssl_key: Default SSL key path

  """

  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")

  optionparser.add_option("--syslog", dest="syslog",

                          help="Enable logging to syslog (except debug"

                          " messages); one of 'no', 'yes' or 'only' [%s]" %

                          constants.SYSLOG_USAGE,

                          default=constants.SYSLOG_USAGE,

                          choices=["no", "yes", "only"])

  if daemon_name in constants.DAEMONS_PORTS:

    default_bind_address = constants.IP4_ADDRESS_ANY

    family = ssconf.SimpleStore().GetPrimaryIPFamily()

    # family will default to AF_INET if there is no ssconf file (e.g. when

    # upgrading a cluster from 2.2 -> 2.3. This is intended, as Ganeti clusters

    # <= 2.2 can not be AF_INET6

    if family == netutils.IP6Address.family:

      default_bind_address = constants.IP6_ADDRESS_ANY

    default_port = netutils.GetDaemonPort(daemon_name)

    # For networked daemons we allow choosing the port and bind address

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

                            help="Network port (default: %s)" % default_port,

                            default=default_port, type="int")

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

                            help=("Bind address (default: '%s')" %

                                  default_bind_address),

                            default=default_bind_address, metavar="ADDRESS")

  if default_ssl_key is not None and default_ssl_cert is not None:

    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 path (default: %s)" %

                                  default_ssl_key),

                            default=default_ssl_key, type="string",

                            metavar="SSL_KEY_PATH")

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

                            help=("SSL certificate path (default: %s)" %

                                  default_ssl_cert),

                            default=default_ssl_cert, type="string",

                            metavar="SSL_CERT_PATH")

  # Disable the use of fork(2) if the daemon uses threads

  utils.no_fork = multithreaded

  options, args = optionparser.parse_args()

  if getattr(options, "ssl", False):

    ssl_paths = {

      "certificate": options.ssl_cert,

      "key": options.ssl_key,

      }

    for name, path in ssl_paths.iteritems():

      if not os.path.isfile(path):

        print >> sys.stderr, "SSL %s file '%s' was not found" % (name, path)

        sys.exit(constants.EXIT_FAILURE)

    # TODO: By initiating http.HttpSslParams here we would only read the files

    # once and have a proper validation (isfile returns False on directories)

    # at the same time.

  if check_fn is not None:

    check_fn(options, args)

  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=multithreaded,

                       program=daemon_name,

                       syslog=options.syslog,

                       console_logging=console_logging)

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

    exec_fn(options, args)

  finally:

    utils.RemovePidFile(daemon_name)