Add files for Paxos decision system.

DecisionSystem/PaxosDecision/acceptor.py

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+from proposer import Proposer
+from paxosmessenger import Messenger
+
+class Acceptor():
+    highest_proposal = None
+    highest_promise = None
+    messenger = None
+
+    def __init__(self, messenger: Messenger):
+        self.messenger = messenger
+
+    def on_message(self, client, userdata, message):
+        pass
+
+    def prepare(self):
+        pass
+
+    def accept_request(self, fromt_uid, proposal_id, value):
+        '''
+        Called when an accept message is received from a proposer
+        '''
+        if proposal_id >= self.highest_promise:
+            self.highest_promise     = proposal_id
+            self.accepted_id     = proposal_id
+            self.accepted_value  = value
+            self.messenger.send_accepted(proposal_id, self.accepted_value)

DecisionSystem/PaxosDecision/learner.py

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+class Learner():
+    pass

DecisionSystem/PaxosDecision/paxos_instance.py

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+'''
+@author Michael Pivato
+
+Much thanks to Tom Cocagne by providing basic paxos code
+which was the basis of this module and algorithm. 
+Check out the original at: https://github.com/cocagne/paxos/blob/master/paxos/essential.py
+'''
+
+from learner import Learner
+from acceptor import Acceptor
+from proposer import Proposer
+
+class PaxosInstance():
+    pass

DecisionSystem/PaxosDecision/paxosmessenger.py

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+from proposal import Proposal
+
+class Messenger():
+    def send_prepare(self, proposal_id):
+        '''
+        Broadcasts a Prepare message to all Acceptors
+        '''
+
+        NotImplementedError
+
+    def send_promise(self, proposer_id, proposal_id, previous_proposal):
+        '''
+        Sends a Promise message to the specified Proposer
+        '''
+
+        NotImplementedError
+
+    def send_accept(self, proposal):
+        '''
+        Broadcasts an Accept message to all Acceptors
+        '''
+
+        NotImplementedError
+
+    def send_accepted(self, proposal):
+        '''
+        Broadcasts an Accepted message to all Learners
+        '''
+
+        NotImplementedError
+
+    def on_resolution(self, proposal_id, value):
+        '''
+        Called when a resolution is reached
+        '''
+
+        NotImplementedError

DecisionSystem/PaxosDecision/proposal.py

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+from Messaging.messaginginterface import Message
+import umsgpack
+
+# Uses MessagePack for message transfer.
+
+class Proposal(Message):
+    ballot_number = None
+    vote = None
+
+    def __init__(self):
+        pass
+
+    def serialise(self) -> str:
+        return umsgpack.packb({"ballot": self.ballot_number, "vote": self.vote})
+
+    def deserialise(self, binary: bytearray):
+        '''
+        Deserialises a given proposal message into a proposal object.
+        '''
+        obj = umsgpack.unpackb(binary)
+        old_ballot = self.ballot_number
+        old_vote = self.vote
+        try:
+            self.ballot_number = obj['ballot']
+            self.vote = obj['vote']
+        except:
+            # Reset the values in case they have been changed.
+            self.ballot_number = old_ballot
+            self.vote = old_vote
+            print("Error: binary object is not a proposal")
+
+    

DecisionSystem/PaxosDecision/proposer.py

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+class Proposer():
+    def propose(self):
+        pass