聊聊nacos的RaftPeerSet

序

本文主要研究一下nacos的RaftPeerSet

RaftPeerSet

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/consistency/persistent/raft/RaftPeerSet.java

@Component
@DependsOn("serverListManager")
public class RaftPeerSet implements ServerChangeListener, ApplicationContextAware {

    @Autowired
    private ServerListManager serverListManager;

    private ApplicationContext applicationContext;

    private AtomicLong localTerm = new AtomicLong(0L);

    private RaftPeer leader = null;

    private Map<String, RaftPeer> peers = new HashMap<>();

    private Set<String> sites = new HashSet<>();

    private boolean ready = false;

    public RaftPeerSet() {

    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {

        this.applicationContext = applicationContext;
    }

    @PostConstruct
    public void init() {
        serverListManager.listen(this);
    }

    public RaftPeer getLeader() {
        if (STANDALONE_MODE) {
            return local();
        }
        return leader;
    }

    public Set<String> allSites() {
        return sites;
    }

    public boolean isReady() {
        return ready;
    }

    public void remove(List<String> servers) {
        for (String server : servers) {
            peers.remove(server);
        }
    }

    public RaftPeer update(RaftPeer peer) {
        peers.put(peer.ip, peer);
        return peer;
    }

    public boolean isLeader(String ip) {
        if (STANDALONE_MODE) {
            return true;
        }

        if (leader == null) {
            Loggers.RAFT.warn("[IS LEADER] no leader is available now!");
            return false;
        }

        return StringUtils.equals(leader.ip, ip);
    }

    public Set<String> allServersIncludeMyself() {
        return peers.keySet();
    }

    public Set<String> allServersWithoutMySelf() {
        Set<String> servers = new HashSet<String>(peers.keySet());

        // exclude myself
        servers.remove(local().ip);

        return servers;
    }

    public Collection<RaftPeer> allPeers() {
        return peers.values();
    }

    public int size() {
        return peers.size();
    }

    public RaftPeer decideLeader(RaftPeer candidate) {
        peers.put(candidate.ip, candidate);

        SortedBag ips = new TreeBag();
        int maxApproveCount = 0;
        String maxApprovePeer = null;
        for (RaftPeer peer : peers.values()) {
            if (StringUtils.isEmpty(peer.voteFor)) {
                continue;
            }

            ips.add(peer.voteFor);
            if (ips.getCount(peer.voteFor) > maxApproveCount) {
                maxApproveCount = ips.getCount(peer.voteFor);
                maxApprovePeer = peer.voteFor;
            }
        }

        if (maxApproveCount >= majorityCount()) {
            RaftPeer peer = peers.get(maxApprovePeer);
            peer.state = RaftPeer.State.LEADER;

            if (!Objects.equals(leader, peer)) {
                leader = peer;
                applicationContext.publishEvent(new LeaderElectFinishedEvent(this, leader));
                Loggers.RAFT.info("{} has become the LEADER", leader.ip);
            }
        }

        return leader;
    }

    public RaftPeer makeLeader(RaftPeer candidate) {
        if (!Objects.equals(leader, candidate)) {
            leader = candidate;
            applicationContext.publishEvent(new MakeLeaderEvent(this, leader));
            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) {
                try {
                    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;
                            }

                            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);
                }
            }
        }

        return update(candidate);
    }

    public RaftPeer local() {
        RaftPeer peer = peers.get(NetUtils.localServer());
        if (peer == null && SystemUtils.STANDALONE_MODE) {
            RaftPeer localPeer = new RaftPeer();
            localPeer.ip = NetUtils.localServer();
            localPeer.term.set(localTerm.get());
            peers.put(localPeer.ip, localPeer);
            return localPeer;
        }
        if (peer == null) {
            throw new IllegalStateException("unable to find local peer: " + NetUtils.localServer() + ", all peers: "
                + Arrays.toString(peers.keySet().toArray()));
        }

        return peer;
    }

    public RaftPeer get(String server) {
        return peers.get(server);
    }

    public int majorityCount() {
        return peers.size() / 2 + 1;
    }

    public void reset() {

        leader = null;

        for (RaftPeer peer : peers.values()) {
            peer.voteFor = null;
        }
    }

    public void setTerm(long term) {
        localTerm.set(term);
    }

    public long getTerm() {
        return localTerm.get();
    }

    public boolean contains(RaftPeer remote) {
        return peers.containsKey(remote.ip);
    }

    //......
}

• RaftPeerSet提供了remove、update、isLeader、allServersIncludeMyself、allServersWithoutMySelf、allPeers、decideLeader、makeLeader、majorityCount、reset等方法
• decideLeader方法会遍历peers，然后使用TreeBag来统计peer.voteFor，当maxApproveCount大于等于majorityCount()，则将对应的peer的state标记为RaftPeer.State.LEADER，然后判断leader是否变更，变更则发布LeaderElectFinishedEvent事件
• makeLeader方法判断candidate与当前leader是否一致，不一致则更新leader为candidate，发布MakeLeaderEvent事件，然后遍历peers给非candidate且state是LEADER状态的的节点发送API_GET_PEER请求，然后更新该peer在本地的信息，如果请求失败则更新其state为RaftPeer.State.FOLLOWER

RaftCore.MasterElection

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/consistency/persistent/raft/RaftCore.java

    public class MasterElection implements Runnable {
        @Override
        public void run() {
            try {

                if (!peers.isReady()) {
                    return;
                }

                RaftPeer local = peers.local();
                local.leaderDueMs -= GlobalExecutor.TICK_PERIOD_MS;

                if (local.leaderDueMs > 0) {
                    return;
                }

                // reset timeout
                local.resetLeaderDue();
                local.resetHeartbeatDue();

                sendVote();
            } catch (Exception e) {
                Loggers.RAFT.warn("[RAFT] error while master election {}", e);
            }

        }

        public void sendVote() {

            RaftPeer local = peers.get(NetUtils.localServer());
            Loggers.RAFT.info("leader timeout, start voting,leader: {}, term: {}",
                JSON.toJSONString(getLeader()), local.term);

            peers.reset();

            local.term.incrementAndGet();
            local.voteFor = local.ip;
            local.state = RaftPeer.State.CANDIDATE;

            Map<String, String> params = new HashMap<>(1);
            params.put("vote", JSON.toJSONString(local));
            for (final String server : peers.allServersWithoutMySelf()) {
                final String url = buildURL(server, API_VOTE);
                try {
                    HttpClient.asyncHttpPost(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 vote failed: {}, url: {}", response.getResponseBody(), url);
                                return 1;
                            }

                            RaftPeer peer = JSON.parseObject(response.getResponseBody(), RaftPeer.class);

                            Loggers.RAFT.info("received approve from peer: {}", JSON.toJSONString(peer));

                            peers.decideLeader(peer);

                            return 0;
                        }
                    });
                } catch (Exception e) {
                    Loggers.RAFT.warn("error while sending vote to server: {}", server);
                }
            }
        }
    }

• RaftCore.MasterElection的sendVote方法在请求成功时会执行peers.decideLeader(peer)方法来选举leader

RaftCore.receivedBeat

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/consistency/persistent/raft/RaftCore.java

@Component
public class RaftCore {

    //......

    public RaftPeer receivedBeat(JSONObject beat) throws Exception {
        final RaftPeer local = peers.local();
        final RaftPeer remote = new RaftPeer();
        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");

        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);
        }

        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());
        }

        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;
        }

        final JSONArray beatDatums = beat.getJSONArray("datums");
        local.resetLeaderDue();
        local.resetHeartbeatDue();

        peers.makeLeader(remote);

        Map<String, Integer> receivedKeysMap = new HashMap<>(datums.size());

        for (Map.Entry<String, Datum> entry : datums.entrySet()) {
            receivedKeysMap.put(entry.getKey(), 0);
        }

        // now check datums
        List<String> batch = new ArrayList<>();
        if (!switchDomain.isSendBeatOnly()) {
            int processedCount = 0;
            if (Loggers.RAFT.isDebugEnabled()) {
                Loggers.RAFT.debug("[RAFT] received beat with {} keys, RaftCore.datums' size is {}, remote server: {}, term: {}, local term: {}",
                    beatDatums.size(), datums.size(), remote.ip, remote.term, local.term);
            }
            for (Object object : beatDatums) {
                processedCount = processedCount + 1;

                JSONObject entry = (JSONObject) object;
                String key = entry.getString("key");
                final String datumKey;

                if (KeyBuilder.matchServiceMetaKey(key)) {
                    datumKey = KeyBuilder.detailServiceMetaKey(key);
                } else if (KeyBuilder.matchInstanceListKey(key)) {
                    datumKey = KeyBuilder.detailInstanceListkey(key);
                } else {
                    // ignore corrupted key:
                    continue;
                }

                long timestamp = entry.getLong("timestamp");

                receivedKeysMap.put(datumKey, 1);

                try {
                    if (datums.containsKey(datumKey) && datums.get(datumKey).timestamp.get() >= timestamp && processedCount < beatDatums.size()) {
                        continue;
                    }

                    if (!(datums.containsKey(datumKey) && datums.get(datumKey).timestamp.get() >= timestamp)) {
                        batch.add(datumKey);
                    }

                    if (batch.size() < 50 && processedCount < beatDatums.size()) {
                        continue;
                    }

                    String keys = StringUtils.join(batch, ",");

                    if (batch.size() <= 0) {
                        continue;
                    }

                    Loggers.RAFT.info("get datums from leader: {}, batch size is {}, processedCount is {}, datums' size is {}, RaftCore.datums' size is {}"
                        , getLeader().ip, batch.size(), processedCount, beatDatums.size(), datums.size());

                    // update datum entry
                    String url = buildURL(remote.ip, API_GET) + "?keys=" + URLEncoder.encode(keys, "UTF-8");
                    HttpClient.asyncHttpGet(url, null, null, new AsyncCompletionHandler<Integer>() {
                        @Override
                        public Integer onCompleted(Response response) throws Exception {
                            if (response.getStatusCode() != HttpURLConnection.HTTP_OK) {
                                return 1;
                            }

                            List<JSONObject> datumList = JSON.parseObject(response.getResponseBody(), new TypeReference<List<JSONObject>>() {
                            });

                            for (JSONObject datumJson : datumList) {
                                OPERATE_LOCK.lock();
                                Datum newDatum = null;
                                try {

                                    Datum oldDatum = getDatum(datumJson.getString("key"));

                                    if (oldDatum != null && datumJson.getLongValue("timestamp") <= oldDatum.timestamp.get()) {
                                        Loggers.RAFT.info("[NACOS-RAFT] timestamp is smaller than that of mine, key: {}, remote: {}, local: {}",
                                            datumJson.getString("key"), datumJson.getLongValue("timestamp"), oldDatum.timestamp);
                                        continue;
                                    }

                                    if (KeyBuilder.matchServiceMetaKey(datumJson.getString("key"))) {
                                        Datum<Service> serviceDatum = new Datum<>();
                                        serviceDatum.key = datumJson.getString("key");
                                        serviceDatum.timestamp.set(datumJson.getLongValue("timestamp"));
                                        serviceDatum.value =
                                            JSON.parseObject(JSON.toJSONString(datumJson.getJSONObject("value")), Service.class);
                                        newDatum = serviceDatum;
                                    }

                                    if (KeyBuilder.matchInstanceListKey(datumJson.getString("key"))) {
                                        Datum<Instances> instancesDatum = new Datum<>();
                                        instancesDatum.key = datumJson.getString("key");
                                        instancesDatum.timestamp.set(datumJson.getLongValue("timestamp"));
                                        instancesDatum.value =
                                            JSON.parseObject(JSON.toJSONString(datumJson.getJSONObject("value")), Instances.class);
                                        newDatum = instancesDatum;
                                    }

                                    if (newDatum == null || newDatum.value == null) {
                                        Loggers.RAFT.error("receive null datum: {}", datumJson);
                                        continue;
                                    }

                                    raftStore.write(newDatum);

                                    datums.put(newDatum.key, newDatum);
                                    notifier.addTask(newDatum.key, ApplyAction.CHANGE);

                                    local.resetLeaderDue();

                                    if (local.term.get() + 100 > remote.term.get()) {
                                        getLeader().term.set(remote.term.get());
                                        local.term.set(getLeader().term.get());
                                    } else {
                                        local.term.addAndGet(100);
                                    }

                                    raftStore.updateTerm(local.term.get());

                                    Loggers.RAFT.info("data updated, key: {}, timestamp: {}, from {}, local term: {}",
                                        newDatum.key, newDatum.timestamp, JSON.toJSONString(remote), local.term);

                                } catch (Throwable e) {
                                    Loggers.RAFT.error("[RAFT-BEAT] failed to sync datum from leader, datum: {}", newDatum, e);
                                } finally {
                                    OPERATE_LOCK.unlock();
                                }
                            }
                            TimeUnit.MILLISECONDS.sleep(200);
                            return 0;
                        }
                    });

                    batch.clear();

                } catch (Exception e) {
                    Loggers.RAFT.error("[NACOS-RAFT] failed to handle beat entry, key: {}", datumKey);
                }

            }

            List<String> deadKeys = new ArrayList<>();
            for (Map.Entry<String, Integer> entry : receivedKeysMap.entrySet()) {
                if (entry.getValue() == 0) {
                    deadKeys.add(entry.getKey());
                }
            }

            for (String deadKey : deadKeys) {
                try {
                    deleteDatum(deadKey);
                } catch (Exception e) {
                    Loggers.RAFT.error("[NACOS-RAFT] failed to remove entry, key={} {}", deadKey, e);
                }
            }

        }

        return local;
    }

    //......
}

• receivedBeat方法会调用peers.makeLeader(remote)来更新leader

小结

• RaftPeerSet提供了remove、update、isLeader、allServersIncludeMyself、allServersWithoutMySelf、allPeers、decideLeader、makeLeader、majorityCount、reset等方法
• decideLeader方法会遍历peers，然后使用TreeBag来统计peer.voteFor，当maxApproveCount大于等于majorityCount()，则将对应的peer的state标记为RaftPeer.State.LEADER，然后判断leader是否变更，变更则发布LeaderElectFinishedEvent事件
• makeLeader方法判断candidate与当前leader是否一致，不一致则更新leader为candidate，发布MakeLeaderEvent事件，然后遍历peers给非candidate且state是LEADER状态的的节点发送API_GET_PEER请求，然后更新该peer在本地的信息，如果请求失败则更新其state为RaftPeer.State.FOLLOWER

doc

• RaftPeerSet