微服务组件-----Spring Cloud Alibaba 注册中心Nacos的CP架构Raft协议分析
前言
本篇幅是继 注册中心Nacos源码分析 的下半部分。
意义
【1】虽说大部分我们采用注册中心的时候考虑的都是AP架构，为什么呢？因为性能相对于CP架构来说更高，需要等待的时间更少【相对于CP架构，采用的是二段提交，AP架构是直接落盘数据，然后进行数据扩散，来达到最终一致，所以客户端收到响应会更快】；
【2】其次，考虑AP架构会不会存在数据丢失的风险呢？答案是必然的，所以是不是应该考虑CP架构呢？那么问题来了，数据丢失是问题吗？明显不是。基于AP架构的注册中心，明显在客户端那边都会存在重试机制，也就是对于一个集群而言，一台服务器宕机会自动重连到其他机器上去，所以有补充的手段自然也就不考虑CP架构了。
【3】但是对于分布式而言，CP架构确实十分重要的一部分；如zookeeper便是分布式的鼻祖，不过采用的是ZAB强一致性协议，而raft则也是强一致性协议的【两者看似差不多，但也有一些差别】，而且市面上喜欢raft协议的更多。所以研究Raft协议便是比较必要的。
Raft协议详解
【1】演示网站：http://thesecretlivesofdata.com/raft/
【2】Raft定义角色的三种状态
1）Follower state //追随者
2）Candidate state //候选者
3）Leader state //领导者
【3】流程分析
【3.1】所有的节点都以跟随者状态开始的
【3.2】如果追随者没有收到任何领导人的消息，那么他们就可以成为一名候选者【注意：这里的候选者是一个【至于这个候选者是怎么来的还要分析，会不会出现多个的情况，但是能选举成功必然是只有一个候选者】，这也是与ZAB协议的不同之处，ZAB是所有人参与】
【3.3】候选人向其他节点发送投票请求，而节点对投票请求进行回复
【3.4】候选人从大多数节点获得选票，就将成为领导者
【4】数据一致性的流程分析
【4.1】对系统的所有变化现在都要经过领导【哪怕是你请求从节点，从节点也会转发给主节点】，主节点每个更改都将作为节点日志中的一个条目添加，但此日志条目当前未提交，因此不会更新节点的值【注意：此时客户端只是发送了请求还没收到回复】
【4.2】要提交条目，节点首先将其复制到跟踪节点【主节点向从节点发送请求】【一般是通过心跳请求，附带上数据来完成的】
【4.3】领导会等待，直到大多数节点已经写入了条目并回复请求，该条目才会在领导节点上提交【这个时候便会回复客户端的请求】
【4.4】领导再次发送请求通知追随者条目已提交【还是通过心跳进行二次通知】
【4.5】因为标准的Raft中采用的是QUORUM， 即确保至少大部分节点都接收到写操作之后才会返回结果给Client， 而Redis默认采用的实际上是ANY/ONE, 即只要Master节点写入成功后，就立刻返回给Client，然后该写入命令被异步的发送给所有的slave节点，来尽可能地让所有地slave节点与master节点保持一致。
| 写入类型 | 解释说明 |
| ZERO | 接收到写操作后立即返回，不保证写入成功 |
| ANY/ONE | 确保该值被写入至少一个节点 |
| QUORUM | 确保至少大多数节点（节点总数/2+1）接受到写操作之后，再返回 |
| ALL | 确保所有副本节点都接受到写操作之后，再返回 |
【5】多节点下出现脑裂问题【Raft如何保持一致】
【5.1】假设有五个分区
【5.2】模拟网络故障导致分区，AB为一组，CDE为一组。【由于分区后，CDE没有了领导者，收不到心跳之后，便会达到选举超时的时间，由于C优先超时便会成为候选者】
【5.3】此时便会出现B和C都成为领导者的情况
【5.4】如果出现数据更新的情况
【5.4.1】人数少的分区收到写入请求是写入不成功的【因为基于大多数写入成功才算是写入成功，所以最终客户端会是写入请求超时】
【5.4.2】相反数目多的分区【在C写入后，通过心跳传递数据给DE，然后收到回复后明显是符合写入节点数大于或等于（节点总数/2+1）】，所以就会返回客户端响应，并在下一次心跳中让DE进行提交。
【5.5】当分区网络恢复后【其实是根据选举周期判断哪个会保留为领导者，其余将回滚未提交的条目，并匹配新领导者的日志】
【5.6】当然这里面还会出现偶数分区【如ABCD，分为AB,CD，那么其实算是两个分区都不可用，毕竟都不满足（4/2+1）为3的写入】
结合源码分析写入数据部分的验证
【1】基于上个篇幅的【1.1.2】分析addInstance注册方法，里面会根据ephemeral字段属性判断是持久节点还是临时节点
【1.1】RaftConsistencyServiceImpl类#put方法
@Override public void put(String key, Record value) throws NacosException { checkIsStopWork(); try { //利用自己实现的raftCore类 raftCore.signalPublish(key, value); } catch (Exception e) { Loggers.RAFT.error("Raft put failed.", e); throw new NacosException(...); } }
【1.2】raftCore类#signalPublish方法是怎么发送和处理数据的【重点】
/** * Signal publish new record. If not leader, signal to leader. If leader, try to commit publish. * * @param key key * @param value value * @throws Exception any exception during publish */ public void signalPublish(String key, Record value) throws Exception { if (stopWork) { throw new IllegalStateException("old raft protocol already stop work"); } //验证了只有领导者才有权利进行写入 if (!isLeader()) { ObjectNode params = JacksonUtils.createEmptyJsonNode(); params.put("key", key); params.replace("value", JacksonUtils.transferToJsonNode(value)); Map<String, String> parameters = new HashMap<>(1); parameters.put("key", key); final RaftPeer leader = getLeader(); //非领导者将利用请求转发给领导者，待领导者回复后回复 raftProxy.proxyPostLarge(leader.ip, API_PUB, params.toString(), parameters); return; } OPERATE_LOCK.lock(); try { final long start = System.currentTimeMillis(); final Datum datum = new Datum(); datum.key = key; datum.value = value; if (getDatum(key) == null) { datum.timestamp.set(1L); } else { datum.timestamp.set(getDatum(key).timestamp.incrementAndGet()); } ObjectNode json = JacksonUtils.createEmptyJsonNode(); json.replace("datum", JacksonUtils.transferToJsonNode(datum)); json.replace("source", JacksonUtils.transferToJsonNode(peers.local())); //进行数据的发布【1.3】 onPublish(datum, peers.local()); //接下来这一片，便是数据一致性的实现，大体为 //先将数据转成json，然后是发起异步请求【不阻塞，会有回调处理】 //利用CountDownLatch阻塞： peers.size() / 2 + 1，来达成raft的大部分节点响应部分。 //满足就回复客户端，不满足就阻塞至请求超时 final String content = json.toString(); final CountDownLatch latch = new CountDownLatch(peers.majorityCount()); for (final String server : peers.allServersIncludeMyself()) { if (isLeader(server)) { latch.countDown(); continue; } final String url = buildUrl(server, API_ON_PUB); HttpClient.asyncHttpPostLarge(url, Arrays.asList("key", key), content, new Callback<String>() { @Override public void onReceive(RestResult<String> result) { if (!result.ok()) { Loggers.RAFT .warn("[RAFT] failed to publish data to peer, datumId={}, peer={}, http code={}", datum.key, server, result.getCode()); return; } latch.countDown(); } @Override public void onError(Throwable throwable) { Loggers.RAFT.error("[RAFT] failed to publish data to peer", throwable); } @Override public void onCancel() { } }); } if (!latch.await(UtilsAndCommons.RAFT_PUBLISH_TIMEOUT, TimeUnit.MILLISECONDS)) { // only majority servers return success can we consider this update success Loggers.RAFT.error("data publish failed, caused failed to notify majority, key={}", key); throw new IllegalStateException("data publish failed, caused failed to notify majority, key=" + key); } long end = System.currentTimeMillis(); Loggers.RAFT.info("signalPublish cost {} ms, key: {}", (end - start), key); } finally { OPERATE_LOCK.unlock(); } }
【1.3】分析数据发布的onPublish方法
/** * Do publish. If leader, commit publish to store. If not leader, stop publish because should signal to leader. * * @param datum datum * @param source source raft peer * @throws Exception any exception during publish */ public void onPublish(Datum datum, RaftPeer source) throws Exception { if (stopWork) { throw new IllegalStateException("old raft protocol already stop work"); } RaftPeer local = peers.local(); if (datum.value == null) { Loggers.RAFT.warn("received empty datum"); throw new IllegalStateException("received empty datum"); } if (!peers.isLeader(source.ip)) { Loggers.RAFT .warn("peer {} tried to publish data but wasn't leader, leader: {}", JacksonUtils.toJson(source), JacksonUtils.toJson(getLeader())); throw new IllegalStateException("peer(" + source.ip + ") tried to publish " + "data but wasn't leader"); } if (source.term.get() < local.term.get()) { Loggers.RAFT.warn("out of date publish, pub-term: {}, cur-term: {}", JacksonUtils.toJson(source), JacksonUtils.toJson(local)); throw new IllegalStateException( "out of date publish, pub-term:" + source.term.get() + ", cur-term: " + local.term.get()); } local.resetLeaderDue(); // if data should be persisted, usually this is true: if (KeyBuilder.matchPersistentKey(datum.key)) { raftStore.write(datum); //写入磁盘 } datums.put(datum.key, datum); if (isLeader()) { local.term.addAndGet(PUBLISH_TERM_INCREASE_COUNT); } else { if (local.term.get() + PUBLISH_TERM_INCREASE_COUNT > source.term.get()) { //set leader term: getLeader().term.set(source.term.get()); local.term.set(getLeader().term.get()); } else { local.term.addAndGet(PUBLISH_TERM_INCREASE_COUNT); } } raftStore.updateTerm(local.term.get()); NotifyCenter.publishEvent(ValueChangeEvent.builder().key(datum.key).action(DataOperation.CHANGE).build()); //发布事件，异步写入内存 Loggers.RAFT.info("data added/updated, key={}, term={}", datum.key, local.term); }
【1.4】进行磁盘的写入【同步的】
/** * Write datum to cache file. * * @param datum datum * @throws Exception any exception during writing */ public synchronized void write(final Datum datum) throws Exception { String namespaceId = KeyBuilder.getNamespace(datum.key); File cacheFile = new File(cacheFileName(namespaceId, datum.key)); if (!cacheFile.exists() && !cacheFile.getParentFile().mkdirs() && !cacheFile.createNewFile()) { MetricsMonitor.getDiskException().increment(); throw new IllegalStateException("can not make cache file: " + cacheFile.getName()); } ByteBuffer data; data = ByteBuffer.wrap(JacksonUtils.toJson(datum).getBytes(StandardCharsets.UTF_8)); try (FileChannel fc = new FileOutputStream(cacheFile, false).getChannel()) { fc.write(data, data.position()); fc.force(true); } catch (Exception e) { MetricsMonitor.getDiskException().increment(); throw e; } // remove old format file: if (StringUtils.isNoneBlank(namespaceId)) { if (datum.key.contains(Constants.DEFAULT_GROUP + Constants.SERVICE_INFO_SPLITER)) { String oldDatumKey = datum.key .replace(Constants.DEFAULT_GROUP + Constants.SERVICE_INFO_SPLITER, StringUtils.EMPTY); cacheFile = new File(cacheFileName(namespaceId, oldDatumKey)); if (cacheFile.exists() && !cacheFile.delete()) { Loggers.RAFT.error("[RAFT-DELETE] failed to delete old format datum: {}, value: {}", datum.key, datum.value); throw new IllegalStateException("failed to delete old format datum: " + datum.key); } } } } private String cacheFileName(String namespaceId, String datumKey) { String fileName; if (StringUtils.isNotBlank(namespaceId)) { //对应集群节点下面的data/naming/data/public下面 fileName = CACHE_DIR + File.separator + namespaceId + File.separator + encodeDatumKey(datumKey); } else { fileName = CACHE_DIR + File.separator + encodeDatumKey(datumKey); } return fileName; }
【1.5】发布事件写入内存【异步的】
//使用快捷键 Ctrl+Shift+f 或 通过 Edit —> Find —>Find In Path 检索 ValueChangeEvent 看对应的 onEvent处理 PersistentNotifier类#onEvent方法 @Override public void onEvent(ValueChangeEvent event) { notify(event.getKey(), event.getAction(), find.apply(event.getKey())); } public <T extends Record> void notify(final String key, final DataOperation action, final T value) { if (listenerMap.containsKey(KeyBuilder.SERVICE_META_KEY_PREFIX)) { if (KeyBuilder.matchServiceMetaKey(key) && !KeyBuilder.matchSwitchKey(key)) { for (RecordListener listener : listenerMap.get(KeyBuilder.SERVICE_META_KEY_PREFIX)) { try { if (action == DataOperation.CHANGE) { listener.onChange(key, value); } if (action == DataOperation.DELETE) { listener.onDelete(key); } } catch (Throwable e) { Loggers.RAFT.error("[NACOS-RAFT] error while notifying listener of key: {}", key, e); } } } } if (!listenerMap.containsKey(key)) { return; } for (RecordListener listener : listenerMap.get(key)) { try { if (action == DataOperation.CHANGE) { listener.onChange(key, value); continue; } if (action == DataOperation.DELETE) { listener.onDelete(key); } } catch (Throwable e) { Loggers.RAFT.error("[NACOS-RAFT] error while notifying listener of key: {}", key, e); } } } Service类#onChange方法 @Override public void onChange(String key, Instances value) throws Exception { Loggers.SRV_LOG.info("[NACOS-RAFT] datum is changed, key: {}, value: {}", key, value); for (Instance instance : value.getInstanceList()) { if (instance == null) { // Reject this abnormal instance list: throw new RuntimeException("got null instance " + key); } if (instance.getWeight() > 10000.0D) { instance.setWeight(10000.0D); } if (instance.getWeight() < 0.01D && instance.getWeight() > 0.0D) { instance.setWeight(0.01D); } } updateIPs(value.getInstanceList(), KeyBuilder.matchEphemeralInstanceListKey(key)); recalculateChecksum(); }
结合源码分析选举部分的验证
【1】核心类RaftCore类#init()
【1.1】重点说明：该方法利用的是Spring的特性@PostConstruct注解，在初始化类的时候自动启动了两个重要的定时任务【选举任务（MasterElection）和心跳任务（HeartBeat）】
【1.2】代码展示
【2】选举任务的分析
【2.1】选举定时器代码展示
//对选举任务进行注册 public static ScheduledFuture registerMasterElection(Runnable runnable) { return NAMING_TIMER_EXECUTOR.scheduleAtFixedRate(runnable, 0, TICK_PERIOD_MS, TimeUnit.MILLISECONDS); } //从GlobalExecutor类中可以看出，默认的线程数量为JVM可用超线程的两倍 private static final ScheduledExecutorService NAMING_TIMER_EXECUTOR = ExecutorFactory.Managed .newScheduledExecutorService(ClassUtils.getCanonicalName(NamingApp.class), Runtime.getRuntime().availableProcessors() * 2, new NameThreadFactory("com.alibaba.nacos.naming.timer"));
【2.2】选举任务代码展示【在这里你会发现，一个bug，如果先苏醒的节点是缺失数据的节点呢，那么节点必然会丢失，但是这个问题并不严重，就和AP架构是一样的，客户端会重新建立连接补全数据】
public class MasterElection implements Runnable { @Override public void run() { try { if (stopWork) { return; } if (!peers.isReady()) { return; } //这个实在选举的时候会产生 //（而其中的休眠时间是，随机时间是0-15s，与数据量无关，所以选举出来的leader不一定是数据最全的） RaftPeer local = peers.local(); //定时任务默认是500MS local.leaderDueMs -= GlobalExecutor.TICK_PERIOD_MS; if (local.leaderDueMs > 0) { return; } // reset timeout //重置选举时间【15s-20s】 local.resetLeaderDue(); //重置心跳时间5s local.resetHeartbeatDue(); //发起投票 sendVote(); } catch (Exception e) { Loggers.RAFT.warn("[RAFT] error while master election {}", e); } } private void sendVote() { RaftPeer local = peers.get(NetUtils.localServer()); Loggers.RAFT.info(...); //将之前的选票信息清空 peers.reset(); //增加选举周期 local.term.incrementAndGet(); local.voteFor = local.ip; //设置当前节点为候选者 local.state = RaftPeer.State.CANDIDATE; Map<String, String> params = new HashMap<>(1); params.put("vote", JacksonUtils.toJson(local)); //遍历集群 for (final String server : peers.allServersWithoutMySelf()) { final String url = buildUrl(server, API_VOTE); try { //发送异步请求 HttpClient.asyncHttpPost(url, null, params, new Callback<String>() { @Override public void onReceive(RestResult<String> result) { if (!result.ok()) { Loggers.RAFT.error("NACOS-RAFT vote failed: {}, url: {}", result.getCode(), url); return; } RaftPeer peer = JacksonUtils.toObj(result.getData(), RaftPeer.class); Loggers.RAFT.info("received approve from peer: {}", JacksonUtils.toJson(peer)); peers.decideLeader(peer); } @Override public void onError(Throwable throwable) {...} @Override public void onCancel() {} }); } catch (Exception e) {...} } } } //异步情况下对于受到回复 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; ApplicationUtils.publishEvent(new LeaderElectFinishedEvent(this, leader, local())); Loggers.RAFT.info("{} has become the LEADER", leader.ip); } } return leader; }
【2.3】接收到选票的处理
//RaftController类 @PostMapping("/vote") public JsonNode vote(HttpServletRequest request, HttpServletResponse response) throws Exception { if (versionJudgement.allMemberIsNewVersion()) { throw new IllegalStateException("old raft protocol already stop"); } RaftPeer peer = raftCore.receivedVote(JacksonUtils.toObj(WebUtils.required(request, "vote"), RaftPeer.class)); return JacksonUtils.transferToJsonNode(peer); } public synchronized RaftPeer receivedVote(RaftPeer remote) { if (stopWork) { throw new IllegalStateException("old raft protocol already stop work"); } if (!peers.contains(remote)) { throw new IllegalStateException("can not find peer: " + remote.ip); } RaftPeer local = peers.get(NetUtils.localServer()); //这种其实是应对两个节点都发送了选票环节，那么肯定不会去选对方 if (remote.term.get() <= local.term.get()) { String msg = "received illegitimate vote" + ", voter-term:" + remote.term + ", votee-term:" + local.term; Loggers.RAFT.info(msg); if (StringUtils.isEmpty(local.voteFor)) { local.voteFor = local.ip; } return local; } //将选举时间重置，保证这次选举不成功会进入下一轮休眠 local.resetLeaderDue(); local.state = RaftPeer.State.FOLLOWER; local.voteFor = remote.ip; //这里的周期变更的原因是，如果这轮选举不成功的话，下一轮万一我先醒了保证选举周期是最大的 local.term.set(remote.term.get()); Loggers.RAFT.info("vote {} as leader, term: {}", remote.ip, remote.term); return local; }
【3】心跳任务的分析
【3.1】心跳定时器代码展示
//定义了心跳任务500ms一次，而且与选举任务是同一个定时器 public static ScheduledFuture registerHeartbeat(Runnable runnable) { return NAMING_TIMER_EXECUTOR.scheduleWithFixedDelay(runnable, 0, TICK_PERIOD_MS, TimeUnit.MILLISECONDS); }
【3.2】心跳任务代码展示【说白了也就是会发送列表的key值【减少数据量，而对应从节点自动拉取来补全数据】过去，采用时间戳作为版本号】
public class HeartBeat implements Runnable { //非领导者不可发心跳 @Override public void run() { try { if (stopWork) { return; } if (!peers.isReady()) { return; } RaftPeer local = peers.local(); //心跳时间设置在5s内的随机数值 local.heartbeatDueMs -= GlobalExecutor.TICK_PERIOD_MS; if (local.heartbeatDueMs > 0) { return; } local.resetHeartbeatDue(); sendBeat(); } catch (Exception e) {...} } private void sendBeat() throws IOException, InterruptedException { RaftPeer local = peers.local(); if (EnvUtil.getStandaloneMode() || local.state != RaftPeer.State.LEADER) { return; } if (Loggers.RAFT.isDebugEnabled()) {..日志部分忽略..} local.resetLeaderDue(); // build data ObjectNode packet = JacksonUtils.createEmptyJsonNode(); packet.replace("peer", JacksonUtils.transferToJsonNode(local)); ArrayNode array = JacksonUtils.createEmptyArrayNode(); if (switchDomain.isSendBeatOnly()) { Loggers.RAFT.info("[SEND-BEAT-ONLY] {}", switchDomain.isSendBeatOnly()); } if (!switchDomain.isSendBeatOnly()) { for (Datum datum : datums.values()) { ObjectNode element = JacksonUtils.createEmptyJsonNode(); if (KeyBuilder.matchServiceMetaKey(datum.key)) { element.put("key", KeyBuilder.briefServiceMetaKey(datum.key)); } else if (KeyBuilder.matchInstanceListKey(datum.key)) { element.put("key", KeyBuilder.briefInstanceListkey(datum.key)); } //利用时间戳来当版本号 element.put("timestamp", datum.timestamp.get()); array.add(element); } } packet.replace("datums", array); // broadcast Map<String, String> params = new HashMap<String, String>(1); params.put("beat", JacksonUtils.toJson(packet)); String content = JacksonUtils.toJson(params); ByteArrayOutputStream out = new ByteArrayOutputStream(); GZIPOutputStream gzip = new GZIPOutputStream(out); gzip.write(content.getBytes(StandardCharsets.UTF_8)); gzip.close(); byte[] compressedBytes = out.toByteArray(); String compressedContent = new String(compressedBytes, StandardCharsets.UTF_8); if (Loggers.RAFT.isDebugEnabled()) { Loggers.RAFT.debug("raw beat data size: {}, size of compressed data: {}", content.length(), compressedContent.length()); } for (final String server : peers.allServersWithoutMySelf()) { try { final String url = buildUrl(server, API_BEAT); if (Loggers.RAFT.isDebugEnabled()) { Loggers.RAFT.debug("send beat to server " + server); } HttpClient.asyncHttpPostLarge(url, null, compressedBytes, new Callback<String>() { @Override public void onReceive(RestResult<String> result) { if (!result.ok()) { Loggers.RAFT.error("NACOS-RAFT beat failed: {}, peer: {}", result.getCode(), server); MetricsMonitor.getLeaderSendBeatFailedException().increment(); return; } peers.update(JacksonUtils.toObj(result.getData(), RaftPeer.class)); if (Loggers.RAFT.isDebugEnabled()) { Loggers.RAFT.debug("receive beat response from: {}", url); } } @Override public void onError(Throwable throwable) { Loggers.RAFT.error("NACOS-RAFT error while sending heart-beat to peer: {} {}", server, throwable); MetricsMonitor.getLeaderSendBeatFailedException().increment(); } @Override public void onCancel() { } }); } catch (Exception e) { Loggers.RAFT.error("error while sending heart-beat to peer: {} {}", server, e); MetricsMonitor.getLeaderSendBeatFailedException().increment(); } } } }
【3.3】接收到心跳的处理
//RaftController类 @PostMapping("/beat") public JsonNode beat(HttpServletRequest request, HttpServletResponse response) throws Exception { if (versionJudgement.allMemberIsNewVersion()) { throw new IllegalStateException("old raft protocol already stop"); } //解压，转义 String entity = new String(IoUtils.tryDecompress(request.getInputStream()), StandardCharsets.UTF_8); String value = URLDecoder.decode(entity, "UTF-8"); value = URLDecoder.decode(value, "UTF-8"); JsonNode json = JacksonUtils.toObj(value); RaftPeer peer = raftCore.receivedBeat(JacksonUtils.toObj(json.get("beat").asText())); return JacksonUtils.transferToJsonNode(peer); } //处理心跳请求 public RaftPeer receivedBeat(JsonNode beat) throws Exception { if (stopWork) { throw new IllegalStateException("old raft protocol already stop work"); } final RaftPeer local = peers.local(); final RaftPeer remote = new RaftPeer(); JsonNode peer = beat.get("peer"); remote.ip = peer.get("ip").asText(); remote.state = RaftPeer.State.valueOf(peer.get("state").asText()); remote.term.set(peer.get("term").asLong()); remote.heartbeatDueMs = peer.get("heartbeatDueMs").asLong(); remote.leaderDueMs = peer.get("leaderDueMs").asLong(); remote.voteFor = peer.get("voteFor").asText(); if (remote.state != RaftPeer.State.LEADER) { Loggers.RAFT.info("[RAFT] invalid state from master, state: {}, remote peer: {}", remote.state, JacksonUtils.toJson(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(), JacksonUtils.toJson(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: {}", JacksonUtils.toJson(remote)); // mk follower local.state = RaftPeer.State.FOLLOWER; local.voteFor = remote.ip; } final JsonNode beatDatums = beat.get("datums"); //重置心跳和选举任务的时间，这一步确保当领导者宕机后，集群节点因为没有收到领导者的心跳而重新发起选举 local.resetLeaderDue(); local.resetHeartbeatDue(); peers.makeLeader(remote); if (!switchDomain.isSendBeatOnly()) { Map<String, Integer> receivedKeysMap = new HashMap<>(datums.size()); //先将本地数据设置为0，后面将领导有的设置为1，最后面根据设置还为0的便是要删除的 for (Map.Entry<String, Datum> entry : datums.entrySet()) { receivedKeysMap.put(entry.getKey(), 0); } // now check datums List<String> batch = new ArrayList<>(); 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; JsonNode entry = (JsonNode) object; String key = entry.get("key").asText(); 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.get("timestamp").asLong(); 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); } //利用批处理来提高性能，满五十条进行一次处理 //或者不满但是，现在已经到了最后了，就再一批次全部处理 if (batch.size() < 50 && processedCount < beatDatums.size()) { continue; } String keys = StringUtils.join(batch, ","); //如果批次里面没有数据就不进行处理 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); Map<String, String> queryParam = new HashMap<>(1); queryParam.put("keys", URLEncoder.encode(keys, "UTF-8")); HttpClient.asyncHttpGet(url, null, queryParam, new Callback<String>() { @Override public void onReceive(RestResult<String> result) { if (!result.ok()) { return; } List<JsonNode> datumList = JacksonUtils .toObj(result.getData(), new TypeReference<List<JsonNode>>() { }); for (JsonNode datumJson : datumList) { Datum newDatum = null; OPERATE_LOCK.lock(); try { Datum oldDatum = getDatum(datumJson.get("key").asText()); if (oldDatum != null && datumJson.get("timestamp").asLong() <= oldDatum.timestamp .get()) { Loggers.RAFT .info("[NACOS-RAFT] timestamp is smaller than that of mine, key: {}, remote: {}, local: {}", datumJson.get("key").asText(), datumJson.get("timestamp").asLong(), oldDatum.timestamp); continue; } if (KeyBuilder.matchServiceMetaKey(datumJson.get("key").asText())) { Datum<Service> serviceDatum = new Datum<>(); serviceDatum.key = datumJson.get("key").asText(); serviceDatum.timestamp.set(datumJson.get("timestamp").asLong()); serviceDatum.value = JacksonUtils .toObj(datumJson.get("value").toString(), Service.class); newDatum = serviceDatum; } if (KeyBuilder.matchInstanceListKey(datumJson.get("key").asText())) { Datum<Instances> instancesDatum = new Datum<>(); instancesDatum.key = datumJson.get("key").asText(); instancesDatum.timestamp.set(datumJson.get("timestamp").asLong()); instancesDatum.value = JacksonUtils .toObj(datumJson.get("value").toString(), 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.notify(newDatum.key, DataOperation.CHANGE, newDatum.value); 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, JacksonUtils.toJson(remote), local.term); } catch (Throwable e) { Loggers.RAFT .error("[RAFT-BEAT] failed to sync datum from leader, datum: {}", newDatum, e); } finally { OPERATE_LOCK.unlock(); } } try { TimeUnit.MILLISECONDS.sleep(200); } catch (InterruptedException e) { Loggers.RAFT.error("[RAFT-BEAT] Interrupted error ", e); } return; } @Override public void onError(Throwable throwable) { Loggers.RAFT.error("[RAFT-BEAT] failed to sync datum from leader", throwable); } @Override public void onCancel() { } }); 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()); } } //批量删除 for (String deadKey : deadKeys) { try { deleteDatum(deadKey); } catch (Exception e) { Loggers.RAFT.error("[NACOS-RAFT] failed to remove entry, key={} {}", deadKey, e); } } } return local; }
Nacos集群数据一致性(持久化实例CP模式Raft协议实现)
注册中心CAP架构剖析
