picar/car/MyRaft/messagestrategy.py

import json
from concurrent import futures
import time
import multiprocessing as mp
import threading

import grpc
import zmq

import MyRaft.raft_pb2_grpc as raft_pb2_grpc
import MyRaft.raft_pb2 as raft_pb2

class MessageStrategy:
    def __init__(self):
        pass

    def send_RequestVote(self, request):
        raise NotImplementedError

    def send_AppendEntries(self, request):
        raise NotImplementedError

    def on_VoteReceived(self, future):
        raise NotImplementedError

    def on_EntriesResponse(self, future):
        raise NotImplementedError

    def connect_channels(self):
        raise NotImplementedError


class NodeGrpcServer(raft_pb2_grpc.RaftServicer):
    """Contains the gRPC server for the raft node."""

    def __init__(self, raftNode, port: int):
        self.server = grpc.server(futures.ThreadPoolExecutor(max_workers=10))
        self.server.add_insecure_port('[::]:%d' % port)
        self._raft = raftNode
        
    def AppendEntriesRPC(self, request, context):
        """AppendEntries remote procedural call for raft.

        Args:
            request: The AppendEntries message sent by the leader
            context: RPC-related information and actions -> more here: https://grpc.io/grpc/python/grpc.html
        
        Returns:
            An AppendEntriesResponse message.
        """
        print("Received append entries rpc")
        # Leaving this here for now, just in case we need it later (gets the client ip address)
        # str(context._rpc_event.call_details.host)
        return self._raft.rcv_AppendEntries(request)

    def RequestVoteRPC(self, request, context):
        """RequestVote remote procedural call for raft.

        Args:
            request: The RequestVote message sent by the leader
            context: RPC-related information and actions -> more here: https://grpc.io/grpc/python/grpc.html
        
        Returns:
        A RequestVoteResponse message
        """
        print("Received request vote rpc")
        print(request)
        result = self._raft.vote_requested(request)
        print("Now returning our vote.")
        print(result)
        print(type(result))
        return result

    def start_server(self):
        print("Starting servicer")
        raft_pb2_grpc.add_RaftServicer_to_server(self, self.server)
        self.server.start()
        while True:
            time.sleep(60*60)


class GrpcMessageStrategy(MessageStrategy):
    """This class uses gRPC to communicate between raft nodes."""
    # Only create the channels if we become a candidate or leader.
    # Also need to close the channels when we become the follower.

    def __init__(self, server: NodeGrpcServer, config):
        # Also need to consider TLS/secure connection
        self._cfg = config
        self._neighbours = self._cfg['messaging']['neighbours']
        self._server = server
        self.message_callbacks = []
        self._futures = []
        self.channels = None

    def connect_channels(self):
        print("Creating channels")
        self.channels = []
        for n in self._neighbours:
            channel = grpc.insecure_channel('%s:%d' % (n['ip'], n['port']))
            self.channels.append(channel)

    def send_RequestVote(self, vote):
        print("Sending Request Vote")
        if self.channels is None:
            self.connect_channels()
        for channel in self.channels:
            print("In channel")
            try:
                stub = raft_pb2_grpc.RaftStub(channel)
                print("connected")
                # vote = stub.RequestVoteRPC(vote)
                future = stub.RequestVoteRPC.future(vote)
                future.add_done_callback(self.on_VoteReceived)
                # print("sending vote received back to node.")
                # self._server._raft.vote_received(vote)
            except Exception as e:
                # print("Couldn't message.")
                # print(e)
                pass

    def on_VoteReceived(self, future):
        print("A vote was returned")
        print("sending vote received back to node.")
        self._server._raft.vote_received(future.result())

    def send_AppendEntries(self, entries):
        for channel in self.channels:
            stub = raft_pb2_grpc.RaftStub(channel)
            future = stub.AppendEntriesRPC.future(entries)
            future.add_done_callback(self.on_EntriesResponse)

    def on_EntriesResponse(self, future):
        # Pass to leader? Doesn't matter for now since we aren't using the
        # log yet. 
        print("Received append entries response.")


class ZmqServer:
    # Zmq subscribers can subscribe to multiple publishers. However, 
    # subscribers are not thread safe - Radio-dish pattern aims to solve that.
    def __init__(self, config):
        self._cfg = config
        self.context = zmq.Context()
        self.socketSub = self.context.socket(zmq.SUB)
        self.started = True

    def connect_channels(self):
        # Also need to subscribe to other nodes...
        for n in self._cfg["messaging"]["neighbours"]:
            self.socketSub.connect("tcp://%s:%d" % (n["ip"], n["port"]))
                    
        print("Neighbours are connected.")
    
    def start(self):
        # Start receiving on a new thread.
        t = threading.Thread(target=self.start_receiving)
        t.start()

    def start_receiving(self):
        while self.started:
            self.on_message(self.socketSub.recv())

    def stop(self):
        self.started = False

    def on_message(self, message):
        m = message.deserialise()
        try:
            a = m.leaderId
            # We have append entries
            a = self.context.rcv_AppendEntries(m)
            # Need to send back a message with our response. May be easier
            # to do this with a request reply mechanism, rather than publish
            # subscribe. 
        except:
            pass

        try:
            a = m.leaderId
            # We have request vote.
            self.context.rcv_AppendEntries(m)
        except:
            pass
        
    def on_RequestVote(self, message):
        pass

    def on_AppendEntries(self, messages):
        pass
        
class ZmqMessageStrategy(MessageStrategy):

    def __init__(self, config, vote_callback, entries_callback):
        self._cfg = config
        self._vote_callback = vote_callback
        self._entries_callback = entries_callback

    def connect_nodes(self):
        print("Creating publish socket.")
        self.context = zmq.Context()
        self.socketPub = self.context.socket(zmq.REQ)
        self.socketPub.bind("tcp://%s:%d" % (self._cfg["messaging"]["me"]["ip"], self._cfg["messaging"]["me"]["port"]))        

    def send_RequestVote(self, request):
        self.socketPub.send(request.serialize)

    def send_AppendEntries(self, request):
        self.socketPub.send(request.serialize)

    def on_VoteReceived(self, message):
        self._vote_callback(message)

    def on_EntriesResponse(self, message):
        self._entries_callback(message)