The Raft Consensus Algorithm

def append_entries(log, prev_index, prev_term, entries) -> bool:
    '''
    Append entries into the Raft log. Return True if it worked, False otherwise.
    Implements the log matching properties as described in Section 5.3.
    '''
    # The log is never allowed to have holes
    if prev_index >= len(log):
        return False

    # Check log matching property - term must match
    if prev_index >= 0 and log[prev_index].term != prev_term:
        return False

    # Append is valid - replace entries from prev_index+1 onwards
    log[prev_index+1:] = entries
    return True

class RaftSimulation:
    def __init__(self, num_nodes):
        self.nodes = []
        for n in range(num_nodes):
            net = raftnet.MockNetwork(n, [x for x in range(num_nodes) if x != n])
            self.nodes.append(raftcontrol.RaftControl(net))

    def step(self):
        """Process all pending messages across all nodes"""
        messages = []
        for node in self.nodes:
            messages.extend(node.outgoing)
            node.outgoing.clear()
        
        # Dispatch messages to destination nodes
        for msg in messages:
            self.nodes[msg.dest].process_event(
                raftcontrol.MessageEvent(msg)
            )
        return bool(messages)

    def step_all(self):
        """Run until no more messages pending"""
        while self.step():
            pass

# Example: Test log replication
sim = RaftSimulation(5)
sim.nodes[0].become_leader()
sim.nodes[0].client_append_entry('x=1')
sim.step_all()

# Verify all logs match
assert all(n.server.log == sim.nodes[0].server.log for n in sim.nodes)