root / lib / confd / client.py @ cc6484c4
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# Copyright (C) 2009 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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"""Ganeti confd client
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Clients can use the confd client library to send requests to a group of master
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candidates running confd. The expected usage is through the asyncore framework,
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by sending queries, and asynchronously receiving replies through a callback.
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This way the client library doesn't ever need to "wait" on a particular answer,
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and can proceed even if some udp packets are lost. It's up to the user to
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reschedule queries if they haven't received responses and they need them.
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Example usage::
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client = ConfdClient(...) # includes callback specification
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req = confd_client.ConfdClientRequest(type=constants.CONFD_REQ_PING)
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client.SendRequest(req)
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# then make sure your client calls asyncore.loop() or daemon.Mainloop.Run()
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# ... wait ...
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# And your callback will be called by asyncore, when your query gets a
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# response, or when it expires.
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You can use the provided ConfdFilterCallback to act as a filter, only passing
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"newer" answer to your callback, and filtering out outdated ones, or ones
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confirming what you already got.
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"""
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# pylint: disable-msg=E0203
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# E0203: Access to member %r before its definition, since we use
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# objects.py which doesn't explicitely initialise its members
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import time |
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import random |
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from ganeti import utils |
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from ganeti import constants |
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from ganeti import objects |
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from ganeti import serializer |
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from ganeti import daemon # contains AsyncUDPSocket |
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from ganeti import errors |
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from ganeti import confd |
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from ganeti import ssconf |
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class ConfdAsyncUDPClient(daemon.AsyncUDPSocket): |
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"""Confd udp asyncore client
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This is kept separate from the main ConfdClient to make sure it's easy to
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implement a non-asyncore based client library.
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"""
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def __init__(self, client): |
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"""Constructor for ConfdAsyncUDPClient
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@type client: L{ConfdClient}
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@param client: client library, to pass the datagrams to
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"""
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daemon.AsyncUDPSocket.__init__(self)
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self.client = client
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# this method is overriding a daemon.AsyncUDPSocket method
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def handle_datagram(self, payload, ip, port): |
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self.client.HandleResponse(payload, ip, port)
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class _Request(object): |
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"""Request status structure.
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@ivar request: the request data
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@ivar args: any extra arguments for the callback
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@ivar expiry: the expiry timestamp of the request
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@ivar sent: the set of contacted peers
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@ivar rcvd: the set of peers who replied
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"""
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def __init__(self, request, args, expiry, sent): |
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self.request = request
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self.args = args
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self.expiry = expiry
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self.sent = frozenset(sent) |
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self.rcvd = set() |
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class ConfdClient: |
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"""Send queries to confd, and get back answers.
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Since the confd model works by querying multiple master candidates, and
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getting back answers, this is an asynchronous library. It can either work
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through asyncore or with your own handling.
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@type _requests: dict
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@ivar _requests: dictionary indexes by salt, which contains data
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about the outstanding requests; the values are objects of type
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L{_Request}
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"""
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def __init__(self, hmac_key, peers, callback, port=None, logger=None): |
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"""Constructor for ConfdClient
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@type hmac_key: string
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@param hmac_key: hmac key to talk to confd
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@type peers: list
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@param peers: list of peer nodes
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@type callback: f(L{ConfdUpcallPayload})
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@param callback: function to call when getting answers
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@type port: integer
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@param port: confd port (default: use GetDaemonPort)
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@type logger: logging.Logger
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@param logger: optional logger for internal conditions
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"""
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if not callable(callback): |
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raise errors.ProgrammerError("callback must be callable") |
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self.UpdatePeerList(peers)
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self._hmac_key = hmac_key
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self._socket = ConfdAsyncUDPClient(self) |
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self._callback = callback
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self._confd_port = port
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self._logger = logger
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self._requests = {}
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if self._confd_port is None: |
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self._confd_port = utils.GetDaemonPort(constants.CONFD)
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def UpdatePeerList(self, peers): |
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"""Update the list of peers
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@type peers: list
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@param peers: list of peer nodes
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"""
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# we are actually called from init, so:
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# pylint: disable-msg=W0201
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if not isinstance(peers, list): |
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raise errors.ProgrammerError("peers must be a list") |
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# make a copy of peers, since we're going to shuffle the list, later
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self._peers = list(peers) |
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def _PackRequest(self, request, now=None): |
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"""Prepare a request to be sent on the wire.
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This function puts a proper salt in a confd request, puts the proper salt,
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and adds the correct magic number.
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"""
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if now is None: |
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now = time.time() |
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tstamp = '%d' % now
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req = serializer.DumpSignedJson(request.ToDict(), self._hmac_key, tstamp)
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return confd.PackMagic(req)
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def _UnpackReply(self, payload): |
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in_payload = confd.UnpackMagic(payload) |
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(dict_answer, salt) = serializer.LoadSignedJson(in_payload, self._hmac_key)
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answer = objects.ConfdReply.FromDict(dict_answer) |
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return answer, salt
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def ExpireRequests(self): |
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"""Delete all the expired requests.
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"""
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now = time.time() |
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for rsalt, rq in self._requests.items(): |
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if now >= rq.expiry:
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del self._requests[rsalt] |
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client_reply = ConfdUpcallPayload(salt=rsalt, |
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type=UPCALL_EXPIRE, |
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orig_request=rq.request, |
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extra_args=rq.args, |
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client=self,
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) |
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self._callback(client_reply)
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def SendRequest(self, request, args=None, coverage=0, async=True): |
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"""Send a confd request to some MCs
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@type request: L{objects.ConfdRequest}
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@param request: the request to send
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@type args: tuple
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@param args: additional callback arguments
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@type coverage: integer
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@param coverage: number of remote nodes to contact; if default
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(0), it will use a reasonable default
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(L{ganeti.constants.CONFD_DEFAULT_REQ_COVERAGE}), if -1 is
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passed, it will use the maximum number of peers, otherwise the
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number passed in will be used
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@type async: boolean
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@param async: handle the write asynchronously
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"""
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if coverage == 0: |
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coverage = min(len(self._peers), constants.CONFD_DEFAULT_REQ_COVERAGE) |
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elif coverage == -1: |
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coverage = len(self._peers) |
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if coverage > len(self._peers): |
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raise errors.ConfdClientError("Not enough MCs known to provide the" |
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" desired coverage")
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if not request.rsalt: |
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raise errors.ConfdClientError("Missing request rsalt") |
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self.ExpireRequests()
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if request.rsalt in self._requests: |
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raise errors.ConfdClientError("Duplicate request rsalt") |
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if request.type not in constants.CONFD_REQS: |
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raise errors.ConfdClientError("Invalid request type") |
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random.shuffle(self._peers)
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targets = self._peers[:coverage]
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now = time.time() |
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payload = self._PackRequest(request, now=now)
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for target in targets: |
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try:
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self._socket.enqueue_send(target, self._confd_port, payload) |
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except errors.UdpDataSizeError:
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raise errors.ConfdClientError("Request too big") |
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expire_time = now + constants.CONFD_CLIENT_EXPIRE_TIMEOUT |
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self._requests[request.rsalt] = _Request(request, args, expire_time,
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targets) |
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if not async: |
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self.FlushSendQueue()
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def HandleResponse(self, payload, ip, port): |
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"""Asynchronous handler for a confd reply
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Call the relevant callback associated to the current request.
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"""
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try:
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try:
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answer, salt = self._UnpackReply(payload)
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except (errors.SignatureError, errors.ConfdMagicError), err:
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if self._logger: |
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self._logger.debug("Discarding broken package: %s" % err) |
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return
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try:
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rq = self._requests[salt]
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except KeyError: |
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if self._logger: |
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self._logger.debug("Discarding unknown (expired?) reply: %s" % err) |
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return
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rq.rcvd.add(ip) |
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client_reply = ConfdUpcallPayload(salt=salt, |
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type=UPCALL_REPLY, |
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server_reply=answer, |
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orig_request=rq.request, |
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server_ip=ip, |
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server_port=port, |
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extra_args=rq.args, |
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client=self,
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) |
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self._callback(client_reply)
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finally:
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self.ExpireRequests()
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def FlushSendQueue(self): |
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"""Send out all pending requests.
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Can be used for synchronous client use.
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"""
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while self._socket.writable(): |
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self._socket.handle_write()
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def ReceiveReply(self, timeout=1): |
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"""Receive one reply.
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@type timeout: float
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@param timeout: how long to wait for the reply
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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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return self._socket.process_next_packet(timeout=timeout) |
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@staticmethod
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def _NeededReplies(peer_cnt): |
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"""Compute the minimum safe number of replies for a query.
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The algorithm is designed to work well for both small and big
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number of peers:
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- for less than three, we require all responses
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- for less than five, we allow one miss
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- otherwise, half the number plus one
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This guarantees that we progress monotonically: 1->1, 2->2, 3->2,
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4->2, 5->3, 6->3, 7->4, etc.
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@type peer_cnt: int
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@param peer_cnt: the number of peers contacted
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@rtype: int
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@return: the number of replies which should give a safe coverage
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"""
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if peer_cnt < 3: |
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return peer_cnt
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elif peer_cnt < 5: |
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return peer_cnt - 1 |
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else:
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return int(peer_cnt/2) + 1 |
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def WaitForReply(self, salt, timeout=constants.CONFD_CLIENT_EXPIRE_TIMEOUT): |
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"""Wait for replies to a given request.
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This method will wait until either the timeout expires or a
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minimum number (computed using L{_NeededReplies}) of replies are
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received for the given salt. It is useful when doing synchronous
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calls to this library.
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@param salt: the salt of the request we want responses for
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@param timeout: the maximum timeout (should be less or equal to
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L{ganeti.constants.CONFD_CLIENT_EXPIRE_TIMEOUT}
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@rtype: tuple
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@return: a tuple of (timed_out, sent_cnt, recv_cnt); if the
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request is unknown, timed_out will be true and the counters
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will be zero
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"""
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def _CheckResponse(): |
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if salt not in self._requests: |
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# expired?
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if self._logger: |
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self._logger.debug("Discarding unknown/expired request: %s" % salt) |
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return MISSING
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rq = self._requests[salt]
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if len(rq.rcvd) >= expected: |
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# already got all replies
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return (False, len(rq.sent), len(rq.rcvd)) |
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# else wait, using default timeout
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self.ReceiveReply()
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raise utils.RetryAgain()
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MISSING = (True, 0, 0) |
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if salt not in self._requests: |
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return MISSING
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# extend the expire time with the current timeout, so that we
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# don't get the request expired from under us
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rq = self._requests[salt]
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rq.expiry += timeout |
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sent = len(rq.sent)
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expected = self._NeededReplies(sent)
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try:
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return utils.Retry(_CheckResponse, 0, timeout) |
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except utils.RetryTimeout:
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if salt in self._requests: |
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rq = self._requests[salt]
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return (True, len(rq.sent), len(rq.rcvd)) |
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else:
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return MISSING
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# UPCALL_REPLY: server reply upcall
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# has all ConfdUpcallPayload fields populated
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UPCALL_REPLY = 1
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# UPCALL_EXPIRE: internal library request expire
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# has only salt, type, orig_request and extra_args
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UPCALL_EXPIRE = 2
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CONFD_UPCALL_TYPES = frozenset([
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UPCALL_REPLY, |
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UPCALL_EXPIRE, |
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]) |
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class ConfdUpcallPayload(objects.ConfigObject): |
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"""Callback argument for confd replies
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@type salt: string
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@ivar salt: salt associated with the query
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@type type: one of confd.client.CONFD_UPCALL_TYPES
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@ivar type: upcall type (server reply, expired request, ...)
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@type orig_request: L{objects.ConfdRequest}
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@ivar orig_request: original request
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@type server_reply: L{objects.ConfdReply}
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@ivar server_reply: server reply
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@type server_ip: string
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@ivar server_ip: answering server ip address
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@type server_port: int
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@ivar server_port: answering server port
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@type extra_args: any
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@ivar extra_args: 'args' argument of the SendRequest function
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@type client: L{ConfdClient}
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@ivar client: current confd client instance
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"""
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__slots__ = [ |
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"salt",
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"type",
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"orig_request",
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"server_reply",
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"server_ip",
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"server_port",
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"extra_args",
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"client",
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] |
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class ConfdClientRequest(objects.ConfdRequest): |
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"""This is the client-side version of ConfdRequest.
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This version of the class helps creating requests, on the client side, by
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filling in some default values.
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"""
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def __init__(self, **kwargs): |
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objects.ConfdRequest.__init__(self, **kwargs)
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if not self.rsalt: |
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self.rsalt = utils.NewUUID()
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if not self.protocol: |
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self.protocol = constants.CONFD_PROTOCOL_VERSION
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if self.type not in constants.CONFD_REQS: |
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raise errors.ConfdClientError("Invalid request type") |
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class ConfdFilterCallback: |
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"""Callback that calls another callback, but filters duplicate results.
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@ivar consistent: a dictionary indexed by salt; for each salt, if
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all responses ware identical, this will be True; this is the
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expected state on a healthy cluster; on inconsistent or
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partitioned clusters, this might be False, if we see answers
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with the same serial but different contents
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"""
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def __init__(self, callback, logger=None): |
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"""Constructor for ConfdFilterCallback
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@type callback: f(L{ConfdUpcallPayload})
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@param callback: function to call when getting answers
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@type logger: logging.Logger
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@param logger: optional logger for internal conditions
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"""
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if not callable(callback): |
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raise errors.ProgrammerError("callback must be callable") |
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self._callback = callback
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self._logger = logger
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# answers contains a dict of salt -> answer
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self._answers = {}
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self.consistent = {}
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def _LogFilter(self, salt, new_reply, old_reply): |
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if not self._logger: |
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return
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if new_reply.serial > old_reply.serial:
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self._logger.debug("Filtering confirming answer, with newer" |
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" serial for query %s" % salt)
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elif new_reply.serial == old_reply.serial:
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if new_reply.answer != old_reply.answer:
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self._logger.warning("Got incoherent answers for query %s" |
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" (serial: %s)" % (salt, new_reply.serial))
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else:
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self._logger.debug("Filtering confirming answer, with same" |
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" serial for query %s" % salt)
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else:
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self._logger.debug("Filtering outdated answer for query %s" |
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" serial: (%d < %d)" % (salt, old_reply.serial,
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new_reply.serial)) |
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def _HandleExpire(self, up): |
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# if we have no answer we have received none, before the expiration.
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if up.salt in self._answers: |
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del self._answers[up.salt] |
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if up.salt in self.consistent: |
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del self.consistent[up.salt] |
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def _HandleReply(self, up): |
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"""Handle a single confd reply, and decide whether to filter it.
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@rtype: boolean
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@return: True if the reply should be filtered, False if it should be passed
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on to the up-callback
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"""
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filter_upcall = False
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salt = up.salt |
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if salt not in self.consistent: |
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self.consistent[salt] = True |
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if salt not in self._answers: |
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# first answer for a query (don't filter, and record)
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self._answers[salt] = up.server_reply
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elif up.server_reply.serial > self._answers[salt].serial: |
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# newer answer (record, and compare contents)
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old_answer = self._answers[salt]
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521 |
self._answers[salt] = up.server_reply
|
522 |
if up.server_reply.answer == old_answer.answer:
|
523 |
# same content (filter) (version upgrade was unrelated)
|
524 |
filter_upcall = True
|
525 |
self._LogFilter(salt, up.server_reply, old_answer)
|
526 |
# else: different content, pass up a second answer
|
527 |
else:
|
528 |
# older or same-version answer (duplicate or outdated, filter)
|
529 |
if (up.server_reply.serial == self._answers[salt].serial and |
530 |
up.server_reply.answer != self._answers[salt].answer):
|
531 |
self.consistent[salt] = False |
532 |
filter_upcall = True
|
533 |
self._LogFilter(salt, up.server_reply, self._answers[salt]) |
534 |
|
535 |
return filter_upcall
|
536 |
|
537 |
def __call__(self, up): |
538 |
"""Filtering callback
|
539 |
|
540 |
@type up: L{ConfdUpcallPayload}
|
541 |
@param up: upper callback
|
542 |
|
543 |
"""
|
544 |
filter_upcall = False
|
545 |
if up.type == UPCALL_REPLY:
|
546 |
filter_upcall = self._HandleReply(up)
|
547 |
elif up.type == UPCALL_EXPIRE:
|
548 |
self._HandleExpire(up)
|
549 |
|
550 |
if not filter_upcall: |
551 |
self._callback(up)
|
552 |
|
553 |
|
554 |
class ConfdCountingCallback: |
555 |
"""Callback that calls another callback, and counts the answers
|
556 |
|
557 |
"""
|
558 |
def __init__(self, callback, logger=None): |
559 |
"""Constructor for ConfdCountingCallback
|
560 |
|
561 |
@type callback: f(L{ConfdUpcallPayload})
|
562 |
@param callback: function to call when getting answers
|
563 |
@type logger: logging.Logger
|
564 |
@param logger: optional logger for internal conditions
|
565 |
|
566 |
"""
|
567 |
if not callable(callback): |
568 |
raise errors.ProgrammerError("callback must be callable") |
569 |
|
570 |
self._callback = callback
|
571 |
self._logger = logger
|
572 |
# answers contains a dict of salt -> count
|
573 |
self._answers = {}
|
574 |
|
575 |
def RegisterQuery(self, salt): |
576 |
if salt in self._answers: |
577 |
raise errors.ProgrammerError("query already registered") |
578 |
self._answers[salt] = 0 |
579 |
|
580 |
def AllAnswered(self): |
581 |
"""Have all the registered queries received at least an answer?
|
582 |
|
583 |
"""
|
584 |
return utils.all(self._answers.values()) |
585 |
|
586 |
def _HandleExpire(self, up): |
587 |
# if we have no answer we have received none, before the expiration.
|
588 |
if up.salt in self._answers: |
589 |
del self._answers[up.salt] |
590 |
|
591 |
def _HandleReply(self, up): |
592 |
"""Handle a single confd reply, and decide whether to filter it.
|
593 |
|
594 |
@rtype: boolean
|
595 |
@return: True if the reply should be filtered, False if it should be passed
|
596 |
on to the up-callback
|
597 |
|
598 |
"""
|
599 |
if up.salt in self._answers: |
600 |
self._answers[up.salt] += 1 |
601 |
|
602 |
def __call__(self, up): |
603 |
"""Filtering callback
|
604 |
|
605 |
@type up: L{ConfdUpcallPayload}
|
606 |
@param up: upper callback
|
607 |
|
608 |
"""
|
609 |
if up.type == UPCALL_REPLY:
|
610 |
self._HandleReply(up)
|
611 |
elif up.type == UPCALL_EXPIRE:
|
612 |
self._HandleExpire(up)
|
613 |
self._callback(up)
|
614 |
|
615 |
|
616 |
class StoreResultCallback: |
617 |
"""Callback that simply stores the most recent answer.
|
618 |
|
619 |
@ivar _answers: dict of salt to (have_answer, reply)
|
620 |
|
621 |
"""
|
622 |
_NO_KEY = (False, None) |
623 |
|
624 |
def __init__(self): |
625 |
"""Constructor for StoreResultCallback
|
626 |
|
627 |
"""
|
628 |
# answers contains a dict of salt -> best result
|
629 |
self._answers = {}
|
630 |
|
631 |
def GetResponse(self, salt): |
632 |
"""Return the best match for a salt
|
633 |
|
634 |
"""
|
635 |
return self._answers.get(salt, self._NO_KEY) |
636 |
|
637 |
def _HandleExpire(self, up): |
638 |
"""Expiration handler.
|
639 |
|
640 |
"""
|
641 |
if up.salt in self._answers and self._answers[up.salt] == self._NO_KEY: |
642 |
del self._answers[up.salt] |
643 |
|
644 |
def _HandleReply(self, up): |
645 |
"""Handle a single confd reply, and decide whether to filter it.
|
646 |
|
647 |
"""
|
648 |
self._answers[up.salt] = (True, up) |
649 |
|
650 |
def __call__(self, up): |
651 |
"""Filtering callback
|
652 |
|
653 |
@type up: L{ConfdUpcallPayload}
|
654 |
@param up: upper callback
|
655 |
|
656 |
"""
|
657 |
if up.type == UPCALL_REPLY:
|
658 |
self._HandleReply(up)
|
659 |
elif up.type == UPCALL_EXPIRE:
|
660 |
self._HandleExpire(up)
|
661 |
|
662 |
|
663 |
def GetConfdClient(callback): |
664 |
"""Return a client configured using the given callback.
|
665 |
|
666 |
This is handy to abstract the MC list and HMAC key reading.
|
667 |
|
668 |
@attention: This should only be called on nodes which are part of a
|
669 |
cluster, since it depends on a valid (ganeti) data directory;
|
670 |
for code running outside of a cluster, you need to create the
|
671 |
client manually
|
672 |
|
673 |
"""
|
674 |
ss = ssconf.SimpleStore() |
675 |
mc_file = ss.KeyToFilename(constants.SS_MASTER_CANDIDATES_IPS) |
676 |
mc_list = utils.ReadFile(mc_file).splitlines() |
677 |
hmac_key = utils.ReadFile(constants.CONFD_HMAC_KEY) |
678 |
return ConfdClient(hmac_key, mc_list, callback)
|