Spring Cloud 2.2.2 源码之六十八nacos的raft选举原理解析三

raft竞选基本流程

RaftController的beat处理心跳

RaftCore的receivedBeat

核心的列出来了，主要就是比对一下信息，更新本地信息。当然如果有需要同步信息的话，还要给leader发消息，获取同步的信息，我这里基本略过了，很长，有兴趣的可以细看。

    public RaftPeer receivedBeat(JSONObject beat) throws Exception {
        final RaftPeer local = peers.local();//本地的
        final RaftPeer remote = new RaftPeer();//远程的leader
        remote.ip = beat.getJSONObject("peer").getString("ip");
        remote.state = RaftPeer.State.valueOf(beat.getJSONObject("peer").getString("state"));
        remote.term.set(beat.getJSONObject("peer").getLongValue("term"));
        remote.heartbeatDueMs = beat.getJSONObject("peer").getLongValue("heartbeatDueMs");
        remote.leaderDueMs = beat.getJSONObject("peer").getLongValue("leaderDueMs");
        remote.voteFor = beat.getJSONObject("peer").getString("voteFor");
        //如果远程不是leader，无效
        if (remote.state != RaftPeer.State.LEADER) {
            Loggers.RAFT.info("[RAFT] invalid state from master, state: {}, remote peer: {}",
                remote.state, JSON.toJSONString(remote));
            throw new IllegalArgumentException("invalid state from master, state: " + remote.state);
        }
        //如果本地大于远程的，心跳信息过期了
        if (local.term.get() > remote.term.get()) {
            Loggers.RAFT.info("[RAFT] out of date beat, beat-from-term: {}, beat-to-term: {}, remote peer: {}, and leaderDueMs: {}"
                , remote.term.get(), local.term.get(), JSON.toJSONString(remote), local.leaderDueMs);
            throw new IllegalArgumentException("out of date beat, beat-from-term: " + remote.term.get()
                + ", beat-to-term: " + local.term.get());
        }
        //本地不是跟随者，可能是候选人，所以将自己变为跟随者，选远程的leader
        if (local.state != RaftPeer.State.FOLLOWER) {

            Loggers.RAFT.info("[RAFT] make remote as leader, remote peer: {}", JSON.toJSONString(remote));
            // mk follower
            local.state = RaftPeer.State.FOLLOWER;
            local.voteFor = remote.ip;
        }
		//数据key集合
        final JSONArray beatDatums = beat.getJSONArray("datums");
        local.resetLeaderDue();//刷新竞选时间
        local.resetHeartbeatDue();
        //设置leader
        peers.makeLeader(remote);
        //不只是心跳，可能还要获取leader的数据同步
        if (!switchDomain.isSendBeatOnly()) {
			...
        }

        return local;
    }

RaftPeerSet的makeLeader

因为现在集群里面可能有其以前的leader存在，并不是和新的leader是同一个，所以要去获得以前leader的信息进行更新，其实就是把集群信息更新下。其实除了leader可以获取到其他结点的信息，其他结点只知道自己和leader的最新信息。

public RaftPeer makeLeader(RaftPeer candidate) {
        if (!Objects.equals(leader, candidate)) {//leader改变了
            leader = candidate;//设置
            applicationContext.publishEvent(new MakeLeaderEvent(this, leader));//通知
            Loggers.RAFT.info("{} has become the LEADER, local: {}, leader: {}",
                leader.ip, JSON.toJSONString(local()), JSON.toJSONString(leader));
        }

        for (final RaftPeer peer : peers.values()) {
            Map<String, String> params = new HashMap<>(1);
            if (!Objects.equals(peer, candidate) && peer.state == RaftPeer.State.LEADER) {//如果存在其他以前的leader
                try {//请求以前过期的leader的信息
                    String url = RaftCore.buildURL(peer.ip, RaftCore.API_GET_PEER);
                    HttpClient.asyncHttpGet(url, null, params, new AsyncCompletionHandler<Integer>() {
                        @Override
                        public Integer onCompleted(Response response) throws Exception {
                            if (response.getStatusCode() != HttpURLConnection.HTTP_OK) {
                                Loggers.RAFT.error("[NACOS-RAFT] get peer failed: {}, peer: {}",
                                    response.getResponseBody(), peer.ip);
                                peer.state = RaftPeer.State.FOLLOWER;
                                return 1;
                            }
                            //更新
                            update(JSON.parseObject(response.getResponseBody(), RaftPeer.class));

                            return 0;
                        }
                    });
                } catch (Exception e) {
                    peer.state = RaftPeer.State.FOLLOWER;
                    Loggers.RAFT.error("[NACOS-RAFT] error while getting peer from peer: {}", peer.ip);
                }
            }
        }
        //更新
        return update(candidate);
    }

RaftController的getPeer获取结点信息

 @GetMapping("/peer")
    public JSONObject getPeer(HttpServletRequest request, HttpServletResponse response) {
        List<RaftPeer> peers = raftCore.getPeers();
        RaftPeer peer = null;

        for (RaftPeer peer1 : peers) {
            if (StringUtils.equals(peer1.ip, NetUtils.localServer())) {
                peer = peer1;
            }
        }

        if (peer == null) {
            peer = new RaftPeer();
            peer.ip = NetUtils.localServer();
        }

        return JSON.parseObject(JSON.toJSONString(peer));
    }

还有一部分就是心跳带来的服务信息的同步下次说。

好了，今天就到这里了，希望对学习理解有帮助，大神看见勿喷，仅为自己的学习理解，能力有限，请多包涵。