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# Copyright (C) 2011 Johan Rydberg | |||
# | |||
# Permission is hereby granted, free of charge, to any person | |||
# obtaining a copy of this software and associated documentation files | |||
# (the "Software"), to deal in the Software without restriction, | |||
# including without limitation the rights to use, copy, modify, merge, | |||
# publish, distribute, sublicense, and/or sell copies of the Software, | |||
# and to permit persons to whom the Software is furnished to do so, | |||
# subject to the following conditions: | |||
# | |||
# The above copyright notice and this permission notice shall be | |||
# included in all copies or substantial portions of the Software. | |||
# | |||
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, | |||
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF | |||
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND | |||
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS | |||
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN | |||
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN | |||
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | |||
# SOFTWARE. | |||
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from txgossip.gossip import Gossiper | |||
from twisted.internet import reactor | |||
import random | |||
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class KeyStoreParticipant(object): | |||
"""Example showing a simple key-value store with eventual | |||
consistency. | |||
Each value is annotated with a timestamp. When there's two | |||
conflicting changes, the one with the latest timestamp wins. | |||
The implementation expects all participants to have synced clocks. | |||
""" | |||
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def __init__(self, clock, storage): | |||
self.clock = clock | |||
self.storage = storage | |||
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def value_changed(self, peer, key, timestamp_value): | |||
if key == '__heartbeat__': | |||
# We do not care about updates to the heartbeat value. | |||
return | |||
print self.gossiper.name, "got", key | |||
timestamp, value = timestamp_value | |||
if key in self.storage: | |||
current_timestamp, current_value = self.storage[key] | |||
if timestamp <= current_timestamp: | |||
return | |||
self.storage[key] = (timestamp, value) | |||
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def __setitem__(self, key, value): | |||
self.gossiper.set_local_state(key, | |||
(self.clock.seconds(), value)) | |||
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def __getitem__(self, key): | |||
return self.storage[key][1] | |||
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def peer_alive(self, peer): | |||
"""The gossip tells us that there's a new peer.""" | |||
for key in self.gossiper.get_peer_keys(peer): | |||
self.value_changed(peer, key, self.gossiper.get_peer_value( | |||
peer, key)) | |||
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def peer_dead(self, peer): | |||
"""The gossip tells us that there's a peer down.""" | |||
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def get_value(members): | |||
participant = random.choice(members) | |||
print "Got value", participant['test-key'] | |||
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def set_value(members): | |||
print "Set value" | |||
participant = random.choice(members) | |||
participant['test-key'] = 'test-value' | |||
reactor.callLater(8, get_value, members) | |||
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def runtest(): | |||
CNT = 20 | |||
print "Starting test with %d participants" % (CNT,) | |||
members = [] | |||
peers = [] | |||
for i in range(0, CNT): | |||
port = 9000 + i | |||
participant = KeyStoreParticipant(reactor, {}) | |||
gossiper = Gossiper(reactor, '127.0.0.1:%d' % (port), participant) | |||
reactor.listenUDP(port, gossiper) | |||
members.append(participant) | |||
peers.append(gossiper) | |||
for m in peers[1:]: | |||
m.handle_new_peers([peers[0].name]) | |||
reactor.callLater(10, set_value, members) | |||
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if __name__ == '__main__': | |||
reactor.callLater(0, runtest) | |||
reactor.run() |