lbry-sdk/lbrynet/dht/protocol.py

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#!/usr/bin/env python
#
# This library is free software, distributed under the terms of
# the GNU Lesser General Public License Version 3, or any later version.
# See the COPYING file included in this archive
#
# The docstrings in this module contain epytext markup; API documentation
# may be created by processing this file with epydoc: http://epydoc.sf.net
import logging
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import binascii
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import time
import socket
import errno
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from twisted.internet import protocol, defer
from twisted.python import failure
from twisted.internet import error
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import twisted.internet.reactor
import constants
import encoding
import msgtypes
import msgformat
from contact import Contact
reactor = twisted.internet.reactor
log = logging.getLogger(__name__)
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class TimeoutError(Exception):
""" Raised when a RPC times out """
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def __init__(self, remote_contact_id):
# remote_contact_id is a binary blob so we need to convert it
# into something more readable
msg = 'Timeout connecting to {}'.format(binascii.hexlify(remote_contact_id))
Exception.__init__(self, msg)
self.remote_contact_id = remote_contact_id
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class Delay(object):
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maxToSendDelay = 10 ** -3 # 0.05
minToSendDelay = 10 ** -5 # 0.01
def __init__(self, start=0):
self._next = start
# TODO: explain why this logic is like it is. And add tests that
# show that it actually does what it needs to do.
def __call__(self):
ts = time.time()
delay = 0
if ts >= self._next:
delay = self.minToSendDelay
self._next = ts + self.minToSendDelay
else:
delay = (self._next - ts) + self.maxToSendDelay
self._next += self.maxToSendDelay
return delay
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class KademliaProtocol(protocol.DatagramProtocol):
""" Implements all low-level network-related functions of a Kademlia node """
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msgSizeLimit = constants.udpDatagramMaxSize - 26
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def __init__(self, node, msgEncoder=encoding.Bencode(),
msgTranslator=msgformat.DefaultFormat()):
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self._node = node
self._encoder = msgEncoder
self._translator = msgTranslator
self._sentMessages = {}
self._partialMessages = {}
self._partialMessagesProgress = {}
self._delay = Delay()
# keep track of outstanding writes so that they
# can be cancelled on shutdown
self._call_later_list = {}
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def sendRPC(self, contact, method, args, rawResponse=False):
""" Sends an RPC to the specified contact
@param contact: The contact (remote node) to send the RPC to
@type contact: kademlia.contacts.Contact
@param method: The name of remote method to invoke
@type method: str
@param args: A list of (non-keyword) arguments to pass to the remote
method, in the correct order
@type args: tuple
@param rawResponse: If this is set to C{True}, the caller of this RPC
will receive a tuple containing the actual response
message object and the originating address tuple as
a result; in other words, it will not be
interpreted by this class. Unless something special
needs to be done with the metadata associated with
the message, this should remain C{False}.
@type rawResponse: bool
@return: This immediately returns a deferred object, which will return
the result of the RPC call, or raise the relevant exception
if the remote node raised one. If C{rawResponse} is set to
C{True}, however, it will always return the actual response
message (which may be a C{ResponseMessage} or an
C{ErrorMessage}).
@rtype: twisted.internet.defer.Deferred
"""
msg = msgtypes.RequestMessage(self._node.id, method, args)
msgPrimitive = self._translator.toPrimitive(msg)
encodedMsg = self._encoder.encode(msgPrimitive)
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log.debug("DHT SEND: %s(%s)", method, args)
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df = defer.Deferred()
if rawResponse:
df._rpcRawResponse = True
# Set the RPC timeout timer
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timeoutCall = reactor.callLater(
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constants.rpcTimeout, self._msgTimeout, msg.id) # IGNORE:E1101
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# Transmit the data
self._send(encodedMsg, msg.id, (contact.address, contact.port))
self._sentMessages[msg.id] = (contact.id, df, timeoutCall)
return df
def datagramReceived(self, datagram, address):
""" Handles and parses incoming RPC messages (and responses)
@note: This is automatically called by Twisted when the protocol
receives a UDP datagram
"""
if datagram[0] == '\x00' and datagram[25] == '\x00':
totalPackets = (ord(datagram[1]) << 8) | ord(datagram[2])
msgID = datagram[5:25]
seqNumber = (ord(datagram[3]) << 8) | ord(datagram[4])
if msgID not in self._partialMessages:
self._partialMessages[msgID] = {}
self._partialMessages[msgID][seqNumber] = datagram[26:]
if len(self._partialMessages[msgID]) == totalPackets:
keys = self._partialMessages[msgID].keys()
keys.sort()
data = ''
for key in keys:
data += self._partialMessages[msgID][key]
datagram = data
del self._partialMessages[msgID]
else:
return
try:
msgPrimitive = self._encoder.decode(datagram)
except encoding.DecodeError:
# We received some rubbish here
return
except IndexError:
log.warning("Couldn't decode dht datagram from %s", address)
return
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message = self._translator.fromPrimitive(msgPrimitive)
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
self._node.addContact(remoteContact)
if isinstance(message, msgtypes.RequestMessage):
# This is an RPC method request
self._handleRPC(remoteContact, message.id, message.request, message.args)
elif isinstance(message, msgtypes.ResponseMessage):
# Find the message that triggered this response
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if message.id in self._sentMessages:
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# Cancel timeout timer for this RPC
df, timeoutCall = self._sentMessages[message.id][1:3]
timeoutCall.cancel()
del self._sentMessages[message.id]
if hasattr(df, '_rpcRawResponse'):
# 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))
elif isinstance(message, msgtypes.ErrorMessage):
# The RPC request raised a remote exception; raise it locally
if message.exceptionType.startswith('exceptions.'):
exceptionClassName = message.exceptionType[11:]
else:
localModuleHierarchy = self.__module__.split('.')
remoteHierarchy = message.exceptionType.split('.')
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# strip the remote hierarchy
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while remoteHierarchy[0] == localModuleHierarchy[0]:
remoteHierarchy.pop(0)
localModuleHierarchy.pop(0)
exceptionClassName = '.'.join(remoteHierarchy)
remoteException = None
try:
exec 'remoteException = %s("%s")' % (exceptionClassName, message.response)
except Exception:
# We could not recreate the exception; create a generic one
remoteException = Exception(message.response)
df.errback(remoteException)
else:
# We got a result from the RPC
df.callback(message.response)
else:
# 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
def _send(self, data, rpcID, address):
""" Transmit the specified data over UDP, breaking it up into several
packets if necessary
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If the data is spread over multiple UDP datagrams, the packets have the
following structure::
| | | | | |||||||||||| 0x00 |
|Transmision|Total number|Sequence number| RPC ID |Header end|
| type ID | of packets |of this packet | | indicator|
| (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
possibly be moved out of the KademliaProtocol class in the
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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"""
if len(data) > self.msgSizeLimit:
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# We have to spread the data over multiple UDP datagrams,
# and provide sequencing information
#
# 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
if len(data) % self.msgSizeLimit > 0:
totalPackets += 1
encTotalPackets = chr(totalPackets >> 8) + chr(totalPackets & 0xff)
seqNumber = 0
startPos = 0
while seqNumber < totalPackets:
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packetData = data[startPos:startPos + self.msgSizeLimit]
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encSeqNumber = chr(seqNumber >> 8) + chr(seqNumber & 0xff)
txData = '\x00%s%s%s\x00%s' % (encTotalPackets, encSeqNumber, rpcID, packetData)
self._scheduleSendNext(txData, address)
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startPos += self.msgSizeLimit
seqNumber += 1
else:
self._scheduleSendNext(data, address)
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def _scheduleSendNext(self, txData, address):
"""Schedule the sending of the next UDP packet """
delay = self._delay()
key = object()
delayed_call = reactor.callLater(delay, self._write_and_remove, key, txData, address)
self._call_later_list[key] = delayed_call
def _write_and_remove(self, key, txData, address):
del self._call_later_list[key]
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if self.transport:
try:
self.transport.write(txData, address)
except socket.error as err:
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if err.errno == errno.EWOULDBLOCK:
# i'm scared this may swallow important errors, but i get a million of these
# on Linux and it doesnt seem to affect anything -grin
log.debug("Can't send data to dht: EWOULDBLOCK")
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else:
raise err
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def _sendResponse(self, contact, rpcID, response):
""" Send a RPC response to the specified contact
"""
msg = msgtypes.ResponseMessage(rpcID, self._node.id, response)
msgPrimitive = self._translator.toPrimitive(msg)
encodedMsg = self._encoder.encode(msgPrimitive)
self._send(encodedMsg, rpcID, (contact.address, contact.port))
def _sendError(self, contact, rpcID, exceptionType, exceptionMessage):
""" Send an RPC error message to the specified contact
"""
msg = msgtypes.ErrorMessage(rpcID, self._node.id, exceptionType, exceptionMessage)
msgPrimitive = self._translator.toPrimitive(msg)
encodedMsg = self._encoder.encode(msgPrimitive)
self._send(encodedMsg, rpcID, (contact.address, contact.port))
def _handleRPC(self, senderContact, rpcID, method, args):
""" Executes a local function in response to an RPC request """
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# Set up the deferred callchain
def handleError(f):
self._sendError(senderContact, rpcID, f.type, f.getErrorMessage())
def handleResult(result):
self._sendResponse(senderContact, rpcID, result)
df = defer.Deferred()
df.addCallback(handleResult)
df.addErrback(handleError)
# Execute the RPC
func = getattr(self._node, method, None)
if callable(func) and hasattr(func, 'rpcmethod'):
# Call the exposed Node method and return the result to the deferred callback chain
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log.debug("DHT RECV CALL %s with args %s", method, args)
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try:
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kwargs = {'_rpcNodeID': senderContact.id, '_rpcNodeContact': senderContact}
result = func(*args, **kwargs)
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except Exception, e:
df.errback(failure.Failure(e))
else:
df.callback(result)
else:
# 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):
""" Called when an RPC request message times out """
# Find the message that timed out
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if not self._sentMessages.has_key(messageID):
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# This should never be reached
log.error("deferred timed out, but is not present in sent messages list!")
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return
remoteContactID, df = self._sentMessages[messageID][0:2]
if self._partialMessages.has_key(messageID):
# We are still receiving this message
self._msgTimeoutInProgress(messageID, remoteContactID, df)
return
del self._sentMessages[messageID]
# The message's destination node is now considered to be dead;
# raise an (asynchronous) TimeoutError exception and update the host node
self._node.removeContact(remoteContactID)
df.errback(failure.Failure(TimeoutError(remoteContactID)))
def _msgTimeoutInProgress(self, messageID, remoteContactID, df):
# See if any progress has been made; if not, kill the message
if self._hasProgressBeenMade(messageID):
# Reset the RPC timeout timer
timeoutCall = reactor.callLater(constants.rpcTimeout, self._msgTimeout, messageID)
self._sentMessages[messageID] = (remoteContactID, df, timeoutCall)
else:
# No progress has been made
del self._partialMessagesProgress[messageID]
del self._partialMessages[messageID]
df.errback(failure.Failure(TimeoutError(remoteContactID)))
def _hasProgressBeenMade(self, messageID):
return (
self._partialMessagesProgress.has_key(messageID) and
(
len(self._partialMessagesProgress[messageID]) !=
len(self._partialMessages[messageID])
)
)
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def stopProtocol(self):
""" Called when the transport is disconnected.
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Will only be called once, after all ports are disconnected.
"""
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log.info('Stopping DHT')
for delayed_call in self._call_later_list.values():
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try:
delayed_call.cancel()
except (error.AlreadyCalled, error.AlreadyCancelled):
log.debug('Attempted to cancel a DelayedCall that was not active')
except Exception:
log.exception('Failed to cancel a DelayedCall')
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# not sure why this is needed, but taking this out sometimes causes
# exceptions.AttributeError: 'Port' object has no attribute 'socket'
# to happen on shutdown
# reactor.iterate()
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log.info('DHT stopped')