feat(role): bootstrap role

konsensus/models/roles/bootstrap.py

@@ -0,0 +1,41 @@
+from typing import List, Callable
+from itertools import cycle
+from . import Role
+from .replica import Replica
+from .acceptor import Acceptor
+from .leader import Leader
+from .commander import Commander
+from .scout import Scout
+from ..node import Node
+from konsensus.entities.messages_types import Join
+from konsensus.constants import JOIN_RETRANSMIT
+
+
+class Bootstrap(Role):
+    """
+    When a node joins the cluster, it must determine the current cluster state before it can participate. 
+    The bootstrap role handles this by sending Join messages to each peer in turn until it receives a Welcome. 
+    """
+    def __init__(self, node: Node, peers: List, execute_fn: Callable, replica: Replica=Replica, acceptor: Acceptor=Acceptor, leader: Leader=Leader, commander: Commander=Commander, scout: Scout=Scout) -> None:
+        super().__init__(node)
+        self.execute_fn = execute_fn
+        self.peers = peers
+        self.peers_cycle = cycle(peers)
+        self.replica = replica
+        self.acceptor = acceptor
+        self.leader = leader
+        self.commander = commander
+        self.scout = scout
+
+    def start(self):
+        self.join()
+
+    def join(self):
+        self.node.send([next(self.peers_cycle)], Join())
+        self.set_timer(JOIN_RETRANSMIT, self.join)
+
+    def do_welcome(self, sender, state, slot: int, decisions):
+        self.acceptor(self.node)
+        self.replica(self.node, execute_fn=self.execute_fn, peers=self.peers, state=self.state, slot=self.slot, decision=self.decisions)
+        self.leader(self.node, peers=self.peers, commander=self.commander, scout=self.scout).start()
+        self.stop

konsensus/models/roles/commander.py

@@ -1,9 +1,9 @@
-from typing import List, Dict
+from typing import List
 from . import Role
 from ..node import Node
 from konsensus.entities.data_types import Ballot, Proposal
-from konsensus.entities.messages_types import Prepare, Adopted, Preempted, Accept, Decided, Decision
-from konsensus.constants import PREPARE_RETRANSMIT, ACCEPT_RETRANSMIT
+from konsensus.entities.messages_types import Preempted, Accept, Decided, Decision
+from konsensus.constants import ACCEPT_RETRANSMIT
 
 
 class Commander(Role):