Synnefo » snf-ganeti » ganeti-local

#

#

# 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.

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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.

"""Ganeti confd client

Clients can use the confd client library to send requests to a group of master

candidates running confd. The expected usage is through the asyncore framework,

by sending queries, and asynchronously receiving replies through a callback.

This way the client library doesn't ever need to "wait" on a particular answer,

and can proceed even if some udp packets are lost. It's up to the user to

reschedule queries if they haven't received responses and they need them.

Example usage::

  client = ConfdClient(...) # includes callback specification

  req = confd_client.ConfdClientRequest(type=constants.CONFD_REQ_PING)

  client.SendRequest(req)

  # then make sure your client calls asyncore.loop() or daemon.Mainloop.Run()

  # ... wait ...

  # And your callback will be called by asyncore, when your query gets a

  # response, or when it expires.

You can use the provided ConfdFilterCallback to act as a filter, only passing

"newer" answer to your callback, and filtering out outdated ones, or ones

confirming what you already got.

"""

# pylint: disable-msg=E0203

# E0203: Access to member %r before its definition, since we use

# objects.py which doesn't explicitely initialise its members

import time

import random

from ganeti import utils

from ganeti import constants

from ganeti import objects

from ganeti import serializer

from ganeti import daemon # contains AsyncUDPSocket

from ganeti import errors

from ganeti import confd

from ganeti import ssconf

class ConfdAsyncUDPClient(daemon.AsyncUDPSocket):

  """Confd udp asyncore client

  This is kept separate from the main ConfdClient to make sure it's easy to

  implement a non-asyncore based client library.

  """

  def __init__(self, client):

    """Constructor for ConfdAsyncUDPClient

    @type client: L{ConfdClient}

    @param client: client library, to pass the datagrams to

    """

    daemon.AsyncUDPSocket.__init__(self)

    self.client = client

  # this method is overriding a daemon.AsyncUDPSocket method

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

    self.client.HandleResponse(payload, ip, port)

class _Request(object):

  """Request status structure.

  @ivar request: the request data

  @ivar args: any extra arguments for the callback

  @ivar expiry: the expiry timestamp of the request

  @ivar sent: the set of contacted peers

  @ivar rcvd: the set of peers who replied

  """

  def __init__(self, request, args, expiry, sent):

    self.request = request

    self.args = args

    self.expiry = expiry

    self.sent = frozenset(sent)

    self.rcvd = set()

class ConfdClient:

  """Send queries to confd, and get back answers.

  Since the confd model works by querying multiple master candidates, and

  getting back answers, this is an asynchronous library. It can either work

  through asyncore or with your own handling.

  @type _requests: dict

  @ivar _requests: dictionary indexes by salt, which contains data

      about the outstanding requests; the values are objects of type

      L{_Request}

  """

  def __init__(self, hmac_key, peers, callback, port=None, logger=None):

    """Constructor for ConfdClient

    @type hmac_key: string

    @param hmac_key: hmac key to talk to confd

    @type peers: list

    @param peers: list of peer nodes

    @type callback: f(L{ConfdUpcallPayload})

    @param callback: function to call when getting answers

    @type port: integer

    @param port: confd port (default: use GetDaemonPort)

    @type logger: logging.Logger

    @param logger: optional logger for internal conditions

    """

    if not callable(callback):

      raise errors.ProgrammerError("callback must be callable")

    self.UpdatePeerList(peers)

    self._hmac_key = hmac_key

    self._socket = ConfdAsyncUDPClient(self)

    self._callback = callback

    self._confd_port = port

    self._logger = logger

    self._requests = {}

    if self._confd_port is None:

      self._confd_port = utils.GetDaemonPort(constants.CONFD)

  def UpdatePeerList(self, peers):

    """Update the list of peers

    @type peers: list

    @param peers: list of peer nodes

    """

    # we are actually called from init, so:

    # pylint: disable-msg=W0201

    if not isinstance(peers, list):

      raise errors.ProgrammerError("peers must be a list")

    # make a copy of peers, since we're going to shuffle the list, later

    self._peers = list(peers)

  def _PackRequest(self, request, now=None):

    """Prepare a request to be sent on the wire.

    This function puts a proper salt in a confd request, puts the proper salt,

    and adds the correct magic number.

    """

    if now is None:

      now = time.time()

    tstamp = '%d' % now

    req = serializer.DumpSignedJson(request.ToDict(), self._hmac_key, tstamp)

    return confd.PackMagic(req)

  def _UnpackReply(self, payload):

    in_payload = confd.UnpackMagic(payload)

    (dict_answer, salt) = serializer.LoadSignedJson(in_payload, self._hmac_key)

    answer = objects.ConfdReply.FromDict(dict_answer)

    return answer, salt

  def ExpireRequests(self):

    """Delete all the expired requests.

    """

    now = time.time()

    for rsalt, rq in self._requests.items():

      if now >= rq.expiry:

        del self._requests[rsalt]

        client_reply = ConfdUpcallPayload(salt=rsalt,

                                          type=UPCALL_EXPIRE,

                                          orig_request=rq.request,

                                          extra_args=rq.args,

                                          client=self,

                                          )

        self._callback(client_reply)

  def SendRequest(self, request, args=None, coverage=None, async=True):

    """Send a confd request to some MCs

    @type request: L{objects.ConfdRequest}

    @param request: the request to send

    @type args: tuple

    @param args: additional callback arguments

    @type coverage: integer

    @param coverage: number of remote nodes to contact

    @type async: boolean

    @param async: handle the write asynchronously

    """

    if coverage is None:

      coverage = min(len(self._peers), constants.CONFD_DEFAULT_REQ_COVERAGE)

    if coverage > len(self._peers):

      raise errors.ConfdClientError("Not enough MCs known to provide the"

                                    " desired coverage")

    if not request.rsalt:

      raise errors.ConfdClientError("Missing request rsalt")

    self.ExpireRequests()

    if request.rsalt in self._requests:

      raise errors.ConfdClientError("Duplicate request rsalt")

    if request.type not in constants.CONFD_REQS:

      raise errors.ConfdClientError("Invalid request type")

    random.shuffle(self._peers)

    targets = self._peers[:coverage]

    now = time.time()

    payload = self._PackRequest(request, now=now)

    for target in targets:

      try:

        self._socket.enqueue_send(target, self._confd_port, payload)

      except errors.UdpDataSizeError:

        raise errors.ConfdClientError("Request too big")

    expire_time = now + constants.CONFD_CLIENT_EXPIRE_TIMEOUT

    self._requests[request.rsalt] = _Request(request, args, expire_time,

                                             targets)

    if not async:

      self.FlushSendQueue()

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

    """Asynchronous handler for a confd reply

    Call the relevant callback associated to the current request.

    """

    try:

      try:

        answer, salt = self._UnpackReply(payload)

      except (errors.SignatureError, errors.ConfdMagicError), err:

        if self._logger:

          self._logger.debug("Discarding broken package: %s" % err)

        return

      try:

        rq = self._requests[salt]

      except KeyError:

        if self._logger:

          self._logger.debug("Discarding unknown (expired?) reply: %s" % err)

        return

      rq.rcvd.add(ip)

      client_reply = ConfdUpcallPayload(salt=salt,

                                        type=UPCALL_REPLY,

                                        server_reply=answer,

                                        orig_request=rq.request,

                                        server_ip=ip,

                                        server_port=port,

                                        extra_args=rq.args,

                                        client=self,

                                       )

      self._callback(client_reply)

    finally:

      self.ExpireRequests()

  def FlushSendQueue(self):

    """Send out all pending requests.

    Can be used for synchronous client use.

    """

    while self._socket.writable():

      self._socket.handle_write()

  def ReceiveReply(self, timeout=1):

    """Receive one reply.

    @type timeout: float

    @param timeout: how long to wait for the reply

    @rtype: boolean

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

    """

    return self._socket.process_next_packet(timeout=timeout)

  @staticmethod

  def _NeededReplies(peer_cnt):

    """Compute the minimum safe number of replies for a query.

    The algorithm is designed to work well for both small and big

    number of peers:

        - for less than three, we require all responses

        - for less than five, we allow one miss

        - otherwise, half the number plus one

    This guarantees that we progress monotonically: 1->1, 2->2, 3->2,

    4->2, 5->3, 6->3, 7->4, etc.

    @type peer_cnt: int

    @param peer_cnt: the number of peers contacted

    @rtype: int

    @return: the number of replies which should give a safe coverage

    """

    if peer_cnt < 3:

      return peer_cnt

    elif peer_cnt < 5:

      return peer_cnt - 1

    else:

      return int(peer_cnt/2) + 1

  def WaitForReply(self, salt, timeout=constants.CONFD_CLIENT_EXPIRE_TIMEOUT):

    """Wait for replies to a given request.

    This method will wait until either the timeout expires or a

    minimum number (computed using L{_NeededReplies}) of replies are

    received for the given salt. It is useful when doing synchronous

    calls to this library.

    @param salt: the salt of the request we want responses for

    @param timeout: the maximum timeout (should be less or equal to

        L{ganeti.constants.CONFD_CLIENT_EXPIRE_TIMEOUT}

    @rtype: tuple

    @return: a tuple of (timed_out, sent_cnt, recv_cnt); if the

        request is unknown, timed_out will be true and the counters

        will be zero

    """

    def _CheckResponse():

      if salt not in self._requests:

        # expired?

        if self._logger:

          self._logger.debug("Discarding unknown/expired request: %s" % salt)

        return MISSING

      rq = self._requests[salt]

      if len(rq.rcvd) >= expected:

        # already got all replies

        return (False, len(rq.sent), len(rq.rcvd))

      # else wait, using default timeout

      self.ReceiveReply()

      raise utils.RetryAgain()

    MISSING = (True, 0, 0)

    if salt not in self._requests:

      return MISSING

    # extend the expire time with the current timeout, so that we

    # don't get the request expired from under us

    rq = self._requests[salt]

    rq.expiry += timeout

    sent = len(rq.sent)

    expected = self._NeededReplies(sent)

    try:

      return utils.Retry(_CheckResponse, 0, timeout)

    except utils.RetryTimeout:

      if salt in self._requests:

        rq = self._requests[salt]

        return (True, len(rq.sent), len(rq.rcvd))

      else:

        return MISSING

# UPCALL_REPLY: server reply upcall

# has all ConfdUpcallPayload fields populated

UPCALL_REPLY = 1

# UPCALL_EXPIRE: internal library request expire

# has only salt, type, orig_request and extra_args

UPCALL_EXPIRE = 2

CONFD_UPCALL_TYPES = frozenset([

  UPCALL_REPLY,

  UPCALL_EXPIRE,

  ])

class ConfdUpcallPayload(objects.ConfigObject):

  """Callback argument for confd replies

  @type salt: string

  @ivar salt: salt associated with the query

  @type type: one of confd.client.CONFD_UPCALL_TYPES

  @ivar type: upcall type (server reply, expired request, ...)

  @type orig_request: L{objects.ConfdRequest}

  @ivar orig_request: original request

  @type server_reply: L{objects.ConfdReply}

  @ivar server_reply: server reply

  @type server_ip: string

  @ivar server_ip: answering server ip address

  @type server_port: int

  @ivar server_port: answering server port

  @type extra_args: any

  @ivar extra_args: 'args' argument of the SendRequest function

  @type client: L{ConfdClient}

  @ivar client: current confd client instance

  """

  __slots__ = [

    "salt",

    "type",

    "orig_request",

    "server_reply",

    "server_ip",

    "server_port",

    "extra_args",

    "client",

    ]

class ConfdClientRequest(objects.ConfdRequest):

  """This is the client-side version of ConfdRequest.

  This version of the class helps creating requests, on the client side, by

  filling in some default values.

  """

  def __init__(self, **kwargs):

    objects.ConfdRequest.__init__(self, **kwargs)

    if not self.rsalt:

      self.rsalt = utils.NewUUID()

    if not self.protocol:

      self.protocol = constants.CONFD_PROTOCOL_VERSION

    if self.type not in constants.CONFD_REQS:

      raise errors.ConfdClientError("Invalid request type")

class ConfdFilterCallback:

  """Callback that calls another callback, but filters duplicate results.

  @ivar consistent: a dictionary indexed by salt; for each salt, if

      all responses ware identical, this will be True; this is the

      expected state on a healthy cluster; on inconsistent or

      partitioned clusters, this might be False, if we see answers

      with the same serial but different contents

  """

  def __init__(self, callback, logger=None):

    """Constructor for ConfdFilterCallback

    @type callback: f(L{ConfdUpcallPayload})

    @param callback: function to call when getting answers

    @type logger: logging.Logger

    @param logger: optional logger for internal conditions

    """

    if not callable(callback):

      raise errors.ProgrammerError("callback must be callable")

    self._callback = callback

    self._logger = logger

    # answers contains a dict of salt -> answer

    self._answers = {}

    self.consistent = {}

  def _LogFilter(self, salt, new_reply, old_reply):

    if not self._logger:

      return

    if new_reply.serial > old_reply.serial:

      self._logger.debug("Filtering confirming answer, with newer"

                         " serial for query %s" % salt)

    elif new_reply.serial == old_reply.serial:

      if new_reply.answer != old_reply.answer:

        self._logger.warning("Got incoherent answers for query %s"

                             " (serial: %s)" % (salt, new_reply.serial))

      else:

        self._logger.debug("Filtering confirming answer, with same"

                           " serial for query %s" % salt)

    else:

      self._logger.debug("Filtering outdated answer for query %s"

                         " serial: (%d < %d)" % (salt, old_reply.serial,

                                                 new_reply.serial))

  def _HandleExpire(self, up):

    # if we have no answer we have received none, before the expiration.

    if up.salt in self._answers:

      del self._answers[up.salt]

    if up.salt in self.consistent:

      del self.consistent[up.salt]

  def _HandleReply(self, up):

    """Handle a single confd reply, and decide whether to filter it.

    @rtype: boolean

    @return: True if the reply should be filtered, False if it should be passed

             on to the up-callback

    """

    filter_upcall = False

    salt = up.salt

    if salt not in self.consistent:

      self.consistent[salt] = True

    if salt not in self._answers:

      # first answer for a query (don't filter, and record)

      self._answers[salt] = up.server_reply

    elif up.server_reply.serial > self._answers[salt].serial:

      # newer answer (record, and compare contents)

      old_answer = self._answers[salt]

      self._answers[salt] = up.server_reply

      if up.server_reply.answer == old_answer.answer:

        # same content (filter) (version upgrade was unrelated)

        filter_upcall = True

        self._LogFilter(salt, up.server_reply, old_answer)

      # else: different content, pass up a second answer

    else:

      # older or same-version answer (duplicate or outdated, filter)

      if (up.server_reply.serial == self._answers[salt].serial and

          up.server_reply.answer != self._answers[salt].answer):

        self.consistent[salt] = False

      filter_upcall = True

      self._LogFilter(salt, up.server_reply, self._answers[salt])

    return filter_upcall

  def __call__(self, up):

    """Filtering callback

    @type up: L{ConfdUpcallPayload}

    @param up: upper callback

    """

    filter_upcall = False

    if up.type == UPCALL_REPLY:

      filter_upcall = self._HandleReply(up)

    elif up.type == UPCALL_EXPIRE:

      self._HandleExpire(up)

    if not filter_upcall:

      self._callback(up)

class ConfdCountingCallback:

  """Callback that calls another callback, and counts the answers

  """

  def __init__(self, callback, logger=None):

    """Constructor for ConfdCountingCallback

    @type callback: f(L{ConfdUpcallPayload})

    @param callback: function to call when getting answers

    @type logger: logging.Logger

    @param logger: optional logger for internal conditions

    """

    if not callable(callback):

      raise errors.ProgrammerError("callback must be callable")

    self._callback = callback

    self._logger = logger

    # answers contains a dict of salt -> count

    self._answers = {}

  def RegisterQuery(self, salt):

    if salt in self._answers:

      raise errors.ProgrammerError("query already registered")

    self._answers[salt] = 0

  def AllAnswered(self):

    """Have all the registered queries received at least an answer?

    """

    return utils.all(self._answers.values())

  def _HandleExpire(self, up):

    # if we have no answer we have received none, before the expiration.

    if up.salt in self._answers:

      del self._answers[up.salt]

  def _HandleReply(self, up):

    """Handle a single confd reply, and decide whether to filter it.

    @rtype: boolean

    @return: True if the reply should be filtered, False if it should be passed

             on to the up-callback

    """

    if up.salt in self._answers:

      self._answers[up.salt] += 1

  def __call__(self, up):

    """Filtering callback

    @type up: L{ConfdUpcallPayload}

    @param up: upper callback

    """

    if up.type == UPCALL_REPLY:

      self._HandleReply(up)

    elif up.type == UPCALL_EXPIRE:

      self._HandleExpire(up)

    self._callback(up)

def GetConfdClient(callback):

  """Return a client configured using the given callback.

  This is handy to abstract the MC list and HMAC key reading.

  @attention: This should only be called on nodes which are part of a

      cluster, since it depends on a valid (ganeti) data directory;

      for code running outside of a cluster, you need to create the

      client manually

  """

  ss = ssconf.SimpleStore()

  mc_file = ss.KeyToFilename(constants.SS_MASTER_CANDIDATES_IPS)

  mc_list = utils.ReadFile(mc_file).splitlines()

  hmac_key = utils.ReadFile(constants.CONFD_HMAC_KEY)

  return ConfdClient(hmac_key, mc_list, callback)