feat(models): acceptor role

konsensus/models/roles/acceptor.py

@@ -0,0 +1,37 @@
+from . import Role
+from ..node import Node
+from ...constants import NULL_BALLOT
+from konsensus.entities.messages_types import Accepting, Promise, Accepted
+
+
+class Acceptor(Role):
+    """
+    This implements the Acceptor Role in the protocol. Therefore, it must store the ballot number representing
+    its most recent promise, along with the set of accepted proposal for each slot. It then responds to Prepare
+    and Accept messages according to the protocol
+
+    This looks like a Simple Paxos with the addition of slot numbers to the messages
+    """
+
+    def __init__(self, node: Node):
+        super().__init__(node)
+        self.ballot_num = NULL_BALLOT
+        # {slot: (ballot_num, proposal)}
+        self.accepted_proposals = {}
+
+    def do_prepare(self, sender, ballot_num: NULL_BALLOT):
+        if ballot_num > self.ballot_num:
+            self.ballot_num = ballot_num
+            # We have heard from a scout, so it might be the next leader
+            self.node.send([self.node.address], Accepting(leader=sender))
+
+        self.node.send([sender], Promise(ballot_num=self.ballot_num, accepted_proposals=self.accepted_proposals))
+
+    def do_accept(self, sender, ballot_num, slot, proposal):
+        if ballot_num >= self.ballot_num:
+            self.ballot_num = ballot_num
+            acc = self.accepted_proposals
+            if slot not in acc or acc[slot][0] < ballot_num:
+                acc[slot] = (ballot_num, proposal)
+
+        self.node.send([sender], Accepted(slot=slot, ballot_num=self.ballot_num))