experimental distributed hashtable implementations with 2D topology
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# -*- coding: utf-8 -*-
from __future__ import division
from gevent import socket
from functools import partial
from keyspace import Keyspace
from hashlib import md5
import json
from traceback import print_exc
from topology import GridTopology
from direction import Direction
from geohash import Geohash
class Node(object):
def __init__(self, own_port=None, keyspace=None):
self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) # UDP
self.socket.bind(("localhost", own_port or 0)) # 0 Chooses random port
self.port = self.socket.getsockname()[1]
self.keyspace = keyspace
self.hash = {}
self.neighbours = GridTopology(keyspace)
# keeps track of queries that were routed to us but that we passed on,
# so that we can pass the answer to the original queryee
self.queries = {} # key: query key, value: address of query origin
self.salt = 'asdndslkf' # TODO: should be proper randomized? must be shared among nodes? 🤔
self.pepper = 'sdfjsdfoiwefslkf'
def __str__(self):
return "node:%s" % self.port
def address(self):
return ('127.0.0.1', self.port)
def join_network(self, entry_port):
print ("Sending JOIN from %s to port %s." % (self, entry_port))
self.sendto(("localhost", entry_port), "JOIN")
def hash_key(self, key):
return md5(key.encode('utf-8')).hexdigest()
def key_to_keyspace(self, key):
''' returns a point within the keyspace corresponding to the given key
'''
# keyspace is 2D -> split it
hashX = self.hash_key(key + self.salt)
hashY = self.hash_key(key + self.pepper)
return (
int(hashX, base=16) / (1 << 128), # convert to keyspace [0,1]
int(hashY, base=16) / (1 << 128)
)
def coord_to_keyspace(self, point):
'''
context: Geohash
hmmm.. what do we want to achieve here?
- translate between geographic and keyspace coords?
- translate between hashes and locations?
- address content by location?
we should be able to translate between keyspace and a geohash:
each geohash bitpair divides the space just as we divide our keyspace
-> longer hash -> smaller keyspace.
problem: geohash doesnt encode edges but a single point..
-> keyspace is ID of a node -> can be encoded via interleaved coords, if total size of keyspace is given
-> neighbour topology can be expressed as DHT? but then we basically have a 2D kademlia?
-> content IDs (hash of key) can be assigned to node
'''
x, y = point
# TODO
def sendto(self, address, message):
if address:
self.socket.sendto(message.encode('utf-8'), address)
else: # this was a local query
print (message)
def query_others(self, query, origin=None):
# query is a GET or PUT query, so second element is always a data key
key = query.split()[1]
point = self.key_to_keyspace(key)
address, keyspace = self.neighbours.getNeighbourForPoint(point)
if address:
self.sendto(address, query)
if origin:
# FIXME: very simplistic; should be a list
# -> fails when multiple queries for a key are in flight
self.queries[key] = origin
else:
print ('No neighbour found for %s', point)
def query(self, query, sender=None):
'''
query handler. hacky protocol mixed of magic strings and JSON
queries can be coming from other nodes, or from local input (eg stdin)
'''
respond = partial(self.sendto, sender)
if sender:
print ("Received \"%s\" from %s." % (query, sender))
if not query:
return
try:
if query == "JOIN":
senderKeyspace, splitDirection = self.keyspace.subdivide()
print ("Own keyspace is now %s" % self.keyspace)
# pass ourselves and all our neighbours to the new node, except for the opposite splitDirection
neighbours = self.neighbours.getNeighbours([
d for d in Direction.cardinals if d != -splitDirection
])
neighbours = [(addr, keysp.serialize()) for addr, keysp in neighbours]
neighbours.append((self.address(), self.keyspace.serialize()))
# find content from hashtable that isn't ours anymore
content = {}
for k, v in list(self.hash.items()):
if not self.key_to_keyspace(k) in self.keyspace:
content[k] = v
del self.hash[k]
respond("SETKEYSPACE %s" % json.dumps({
'content': content,
'keyspace': senderKeyspace.serialize(),
'neighbours': neighbours,
}))
# notify our neighbours of our changed keyspace
neighbours = self.neighbours.getNeighbours([
d for d in Direction.cardinals if d != splitDirection
])
for addr, keysp in neighbours:
self.sendto(addr, 'UPDATE_NEIGHBOURS %s' % json.dumps([
(self.address(), self.keyspace.serialize())
]))
self.neighbours.clearNeighbours([splitDirection]) # get rid of non-adjacent neighbours
self.neighbours.addNeighbour(sender, senderKeyspace)
elif query.startswith("STATE"):
print ("port: %s" % self.port)
print ("keyspace: %s" % self.keyspace)
print ("neighbours: %s" % self.neighbours)
print ("hashtable: %s" % self.hash)
print ("query routing: %s" % self.queries)
arg = query.lstrip('STATE ')
# visualize via matplotlib
if arg == 'VIZ':
plt = self.neighbours.visualize()
for k,v in self.hash.items():
x,y = self.key_to_keyspace(k)
plt.plot(x,y)
plt.annotate('%s:%s' % (k,v), (x, y))
plt.show() # FIXME: integrate with gevent to avoid blocking?
elif query.startswith("SETKEYSPACE"):
data = json.loads(query.lstrip("SETKEYSPACE "))
self.keyspace = Keyspace.unserialize(data['keyspace'])
neighbours = [(tuple(address), Keyspace.unserialize(keysp)) for address, keysp in data['neighbours']]
self.neighbours = GridTopology(self.keyspace, neighbours)
self.hash = data['content']
# notify the passed neighbours about the new state
for n in neighbours:
addr, keysp = n
if addr == sender: continue
self.sendto(addr, 'UPDATE_NEIGHBOURS %s' % json.dumps([
(self.address(), self.keyspace.serialize()),
]))
elif query.startswith("UPDATE_NEIGHBOURS"): # replaces SET_ADDRESS
neighbours = [(tuple(addr), Keyspace.unserialize(keysp)) for addr, keysp in json.loads(query[18:])]
for n in neighbours:
self.neighbours.addNeighbour(n[0], n[1])
elif query.startswith("GET"):
key = query.split()[1]
point = self.key_to_keyspace(key)
if point in self.keyspace:
respond('ANSWER %s' % json.dumps({
'key': key,
'value': self.hash.get(key, None),
}))
else:
self.query_others(query, sender)
elif query.startswith("PUT"):
_, key, value = query.split()
point = self.key_to_keyspace(key)
if point in self.keyspace:
self.hash[key] = value
respond('ANSWER %s' % json.dumps({
'key': key,
'value': value,
}))
print ('Own hashtable is now %s' % self.hash)
else:
self.query_others(query, sender)
elif query.startswith("ANSWER"):
data = json.loads(query.lstrip('ANSWER '))
key = data['key']
if key in self.queries:
# this answer is a reply to a query where we just act as router
dest = self.queries[key]
del self.queries[key]
print ('Routing answer to %s:%s' % dest)
self.sendto(dest, query)
else:
# this response is for our query.
self.sendto(None, query)
else:
print ("Unrecognized query \"%s\"." % query)
except Exception as err:
print_exc()