306 lines
14 KiB
Python
306 lines
14 KiB
Python
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#!/usr/bin/env python
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#
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# This library is free software, distributed under the terms of
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# the GNU Lesser General Public License Version 3, or any later version.
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# See the COPYING file included in this archive
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#
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# The docstrings in this module contain epytext markup; API documentation
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# may be created by processing this file with epydoc: http://epydoc.sf.net
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import time
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from twisted.internet import protocol, defer
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from twisted.python import failure
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import twisted.internet.reactor
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import constants
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import encoding
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import msgtypes
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import msgformat
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from contact import Contact
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reactor = twisted.internet.reactor
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class TimeoutError(Exception):
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""" Raised when a RPC times out """
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class KademliaProtocol(protocol.DatagramProtocol):
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""" Implements all low-level network-related functions of a Kademlia node """
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msgSizeLimit = constants.udpDatagramMaxSize-26
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maxToSendDelay = 10**-3#0.05
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minToSendDelay = 10**-5#0.01
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def __init__(self, node, msgEncoder=encoding.Bencode(), msgTranslator=msgformat.DefaultFormat()):
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self._node = node
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self._encoder = msgEncoder
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self._translator = msgTranslator
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self._sentMessages = {}
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self._partialMessages = {}
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self._partialMessagesProgress = {}
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self._next = 0
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self._callLaterList = {}
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def sendRPC(self, contact, method, args, rawResponse=False):
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""" Sends an RPC to the specified contact
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@param contact: The contact (remote node) to send the RPC to
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@type contact: kademlia.contacts.Contact
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@param method: The name of remote method to invoke
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@type method: str
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@param args: A list of (non-keyword) arguments to pass to the remote
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method, in the correct order
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@type args: tuple
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@param rawResponse: If this is set to C{True}, the caller of this RPC
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will receive a tuple containing the actual response
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message object and the originating address tuple as
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a result; in other words, it will not be
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interpreted by this class. Unless something special
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needs to be done with the metadata associated with
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the message, this should remain C{False}.
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@type rawResponse: bool
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@return: This immediately returns a deferred object, which will return
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the result of the RPC call, or raise the relevant exception
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if the remote node raised one. If C{rawResponse} is set to
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C{True}, however, it will always return the actual response
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message (which may be a C{ResponseMessage} or an
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C{ErrorMessage}).
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@rtype: twisted.internet.defer.Deferred
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"""
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msg = msgtypes.RequestMessage(self._node.id, method, args)
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msgPrimitive = self._translator.toPrimitive(msg)
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encodedMsg = self._encoder.encode(msgPrimitive)
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df = defer.Deferred()
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if rawResponse:
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df._rpcRawResponse = True
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# Set the RPC timeout timer
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timeoutCall = reactor.callLater(constants.rpcTimeout, self._msgTimeout, msg.id) #IGNORE:E1101
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# Transmit the data
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self._send(encodedMsg, msg.id, (contact.address, contact.port))
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self._sentMessages[msg.id] = (contact.id, df, timeoutCall)
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return df
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def datagramReceived(self, datagram, address):
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""" Handles and parses incoming RPC messages (and responses)
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@note: This is automatically called by Twisted when the protocol
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receives a UDP datagram
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"""
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if datagram[0] == '\x00' and datagram[25] == '\x00':
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totalPackets = (ord(datagram[1]) << 8) | ord(datagram[2])
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msgID = datagram[5:25]
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seqNumber = (ord(datagram[3]) << 8) | ord(datagram[4])
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if msgID not in self._partialMessages:
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self._partialMessages[msgID] = {}
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self._partialMessages[msgID][seqNumber] = datagram[26:]
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if len(self._partialMessages[msgID]) == totalPackets:
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keys = self._partialMessages[msgID].keys()
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keys.sort()
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data = ''
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for key in keys:
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data += self._partialMessages[msgID][key]
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datagram = data
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del self._partialMessages[msgID]
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else:
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return
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try:
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msgPrimitive = self._encoder.decode(datagram)
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except encoding.DecodeError:
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# We received some rubbish here
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return
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message = self._translator.fromPrimitive(msgPrimitive)
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remoteContact = Contact(message.nodeID, address[0], address[1], self)
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# Refresh the remote node's details in the local node's k-buckets
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self._node.addContact(remoteContact)
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if isinstance(message, msgtypes.RequestMessage):
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# This is an RPC method request
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self._handleRPC(remoteContact, message.id, message.request, message.args)
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elif isinstance(message, msgtypes.ResponseMessage):
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# Find the message that triggered this response
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if self._sentMessages.has_key(message.id):
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# Cancel timeout timer for this RPC
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df, timeoutCall = self._sentMessages[message.id][1:3]
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timeoutCall.cancel()
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del self._sentMessages[message.id]
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if hasattr(df, '_rpcRawResponse'):
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# The RPC requested that the raw response message and originating address be returned; do not interpret it
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df.callback((message, address))
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elif isinstance(message, msgtypes.ErrorMessage):
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# The RPC request raised a remote exception; raise it locally
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if message.exceptionType.startswith('exceptions.'):
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exceptionClassName = message.exceptionType[11:]
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else:
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localModuleHierarchy = self.__module__.split('.')
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remoteHierarchy = message.exceptionType.split('.')
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#strip the remote hierarchy
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while remoteHierarchy[0] == localModuleHierarchy[0]:
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remoteHierarchy.pop(0)
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localModuleHierarchy.pop(0)
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exceptionClassName = '.'.join(remoteHierarchy)
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remoteException = None
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try:
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exec 'remoteException = %s("%s")' % (exceptionClassName, message.response)
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except Exception:
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# We could not recreate the exception; create a generic one
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remoteException = Exception(message.response)
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df.errback(remoteException)
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else:
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# We got a result from the RPC
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df.callback(message.response)
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else:
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# If the original message isn't found, it must have timed out
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#TODO: we should probably do something with this...
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pass
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def _send(self, data, rpcID, address):
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""" Transmit the specified data over UDP, breaking it up into several
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packets if necessary
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If the data is spread over multiple UDP datagrams, the packets have the
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following structure::
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|Transmision|Total number|Sequence number| RPC ID |Header end|
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| type ID | of packets |of this packet | | indicator|
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| (1 byte) | (2 bytes) | (2 bytes) |(20 bytes)| (1 byte) |
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@note: The header used for breaking up large data segments will
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possibly be moved out of the KademliaProtocol class in the
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future, into something similar to a message translator/encoder
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class (see C{kademlia.msgformat} and C{kademlia.encoding}).
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"""
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if len(data) > self.msgSizeLimit:
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# We have to spread the data over multiple UDP datagrams, and provide sequencing information
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# 1st byte is transmission type id, bytes 2 & 3 are the total number of packets in this transmission, bytes 4 & 5 are the sequence number for this specific packet
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totalPackets = len(data) / self.msgSizeLimit
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if len(data) % self.msgSizeLimit > 0:
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totalPackets += 1
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encTotalPackets = chr(totalPackets >> 8) + chr(totalPackets & 0xff)
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seqNumber = 0
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startPos = 0
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while seqNumber < totalPackets:
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#reactor.iterate() #IGNORE:E1101
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packetData = data[startPos:startPos+self.msgSizeLimit]
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encSeqNumber = chr(seqNumber >> 8) + chr(seqNumber & 0xff)
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txData = '\x00%s%s%s\x00%s' % (encTotalPackets, encSeqNumber, rpcID, packetData)
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self._sendNext(txData, address)
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startPos += self.msgSizeLimit
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seqNumber += 1
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else:
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self._sendNext(data, address)
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def _sendNext(self, txData, address):
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""" Send the next UDP packet """
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ts = time.time()
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delay = 0
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if ts >= self._next:
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delay = self.minToSendDelay
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self._next = ts + self.minToSendDelay
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else:
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delay = (self._next-ts) + self.maxToSendDelay
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self._next += self.maxToSendDelay
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if self.transport:
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laterCall = reactor.callLater(delay, self.transport.write, txData, address)
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for key in self._callLaterList.keys():
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if key <= ts:
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del self._callLaterList[key]
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self._callLaterList[self._next] = laterCall
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def _sendResponse(self, contact, rpcID, response):
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""" Send a RPC response to the specified contact
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"""
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msg = msgtypes.ResponseMessage(rpcID, self._node.id, response)
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msgPrimitive = self._translator.toPrimitive(msg)
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encodedMsg = self._encoder.encode(msgPrimitive)
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self._send(encodedMsg, rpcID, (contact.address, contact.port))
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def _sendError(self, contact, rpcID, exceptionType, exceptionMessage):
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""" Send an RPC error message to the specified contact
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"""
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msg = msgtypes.ErrorMessage(rpcID, self._node.id, exceptionType, exceptionMessage)
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msgPrimitive = self._translator.toPrimitive(msg)
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encodedMsg = self._encoder.encode(msgPrimitive)
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self._send(encodedMsg, rpcID, (contact.address, contact.port))
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def _handleRPC(self, senderContact, rpcID, method, args):
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""" Executes a local function in response to an RPC request """
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# Set up the deferred callchain
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def handleError(f):
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self._sendError(senderContact, rpcID, f.type, f.getErrorMessage())
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def handleResult(result):
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self._sendResponse(senderContact, rpcID, result)
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df = defer.Deferred()
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df.addCallback(handleResult)
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df.addErrback(handleError)
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# Execute the RPC
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func = getattr(self._node, method, None)
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if callable(func) and hasattr(func, 'rpcmethod'):
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# Call the exposed Node method and return the result to the deferred callback chain
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try:
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##try:
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## # Try to pass the sender's node id to the function...
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result = func(*args, **{'_rpcNodeID': senderContact.id, '_rpcNodeContact': senderContact})
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##except TypeError:
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## # ...or simply call it if that fails
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## result = func(*args)
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except Exception, e:
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df.errback(failure.Failure(e))
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else:
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df.callback(result)
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else:
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# No such exposed method
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df.errback( failure.Failure( AttributeError('Invalid method: %s' % method) ) )
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def _msgTimeout(self, messageID):
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""" Called when an RPC request message times out """
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# Find the message that timed out
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if self._sentMessages.has_key(messageID):
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remoteContactID, df = self._sentMessages[messageID][0:2]
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if self._partialMessages.has_key(messageID):
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# We are still receiving this message
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# See if any progress has been made; if not, kill the message
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if self._partialMessagesProgress.has_key(messageID):
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if len(self._partialMessagesProgress[messageID]) == len(self._partialMessages[messageID]):
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# No progress has been made
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del self._partialMessagesProgress[messageID]
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del self._partialMessages[messageID]
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df.errback(failure.Failure(TimeoutError(remoteContactID)))
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return
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# Reset the RPC timeout timer
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timeoutCall = reactor.callLater(constants.rpcTimeout, self._msgTimeout, messageID) #IGNORE:E1101
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self._sentMessages[messageID] = (remoteContactID, df, timeoutCall)
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return
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del self._sentMessages[messageID]
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# The message's destination node is now considered to be dead;
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# raise an (asynchronous) TimeoutError exception and update the host node
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self._node.removeContact(remoteContactID)
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df.errback(failure.Failure(TimeoutError(remoteContactID)))
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else:
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# This should never be reached
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print "ERROR: deferred timed out, but is not present in sent messages list!"
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def stopProtocol(self):
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""" Called when the transport is disconnected.
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Will only be called once, after all ports are disconnected.
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"""
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for key in self._callLaterList.keys():
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try:
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if key > time.time():
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self._callLaterList[key].cancel()
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except Exception, e:
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print e
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del self._callLaterList[key]
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#TODO: test: do we really need the reactor.iterate() call?
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reactor.iterate()
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