SOFAJRaft的SOFAJRaft-RheaKV 是基于 SOFAJRaft 和 RocksDB 实现的嵌入式、分布式、高可用、强一致的 KV 存储类库。SOFAJRaft-RheaKV 集群主要包括三个核心组件：PD，Store 和 Region。
@Author：Akai-yuan
@更新时间：2023/2/3
1.架构设计
SOFAJRaft-RheaKV 存储类库主要包括PD，Store 和 Region 三个核心组件，支持轻量级的状态/元信息存储以及集群同步，分布式锁服务使用场景
（1）调度
PD 是全局的中心总控节点，负责整个集群的调度管理、Region ID 生成、维护 RegionRouteTable 路由表。一个 PDServer 管理多个集群，集群之间基于 clusterId 隔离；PD Server 需要单独部署，很多场景其实并不需要自管理，RheaKV 也支持不启用 PD，不需要自管理的集群可不启用 PD，设置 PlacementDriverOptions 的 fake选项为 true 即可。PD 一般通过 Region 的心跳返回信息进行对 Region 调度，Region 处理完后，PD 则会在下一个心跳返回中收到 Region 的变更信息来更新路由及状态表。
（2）存储
Store 是集群中的一个物理存储节点，一个 Store 包含一个或多个 Region。通常一个 Node 负责一个 Store，Store 可以被看作是 Region 的容器，里面存储着多个分片数据。Store 会向 PD 主动上报 StoreHeartbeatRequest 心跳，心跳交由 PD 的 handleStoreHeartbeat 处理，里面包含该 Store 的基本信息，比如，包含多少 Region，有哪些 Region 的 Leader 在该 Store 等。
（3）数据
Region 是最小的 KV 数据单元，可理解为一个数据分区或者分片，每个 Region 都有一个左闭右开的区间 [startKey, endKey)，能够根据请求流量/负载/数据量大小等指标自动分裂以及自动副本搬迁。Region 有多个副本 Replication 构建 Raft Groups 存储在不同的 Store 节点，通过 Raft 协议日志复制功能数据同步到同 Group 的全部节点。Region对应的是 Store 里某个实际的数据区间。每个 Region 会有多个副本，每个副本存储在不同的 Store，一起组成一个Raft Group。Region 中的 Leader 会向 PD 主动上报 RegionHeartbeatRequest 心跳，交由 PD 的 handleRegionHeartbeat 处理，而 PD 是通过 Region的Epoch 感知 Region 是否有变化。
为了让大家更清楚PD，Store 和 Region 三个核心组件的功能，这里放一张官方图片以便于理解：
2.初始化
我们从JRaft-Example模块的RheaKV部分开始，首先看到com.alipay.sofa.jraft.example.rheakv.Server1的main方法。
- 声明了PlacementDriverOptions、StoreEngineOptions两个配置选项实体
- 定义了RheaKVStoreOptions，并将PDOptions和SEOptions装配到属性中，并初始化声明集群名、是否开启并行压缩、服务的IP:端口列表（"127.0.0.1:8181,127.0.0.1:8182,127.0.0.1:8183"）。
- 声明一个Node节点
- 添加一个钩子函数，实现优雅停机。（作者曾经分析过钩子函数的作用，具体参照：SOFAJRaft源码阅读（叁）-ShutdownHook如何优雅的停机）
public static void main(final String[] args) { final PlacementDriverOptions pdOpts = PlacementDriverOptionsConfigured.newConfigured() .withFake(true) // use a fake pd .config(); final StoreEngineOptions storeOpts = StoreEngineOptionsConfigured.newConfigured() // //StoreEngine 存储引擎支持 MemoryDB 和 RocksDB 两种实现 .withStorageType(StorageType.RocksDB) .withRocksDBOptions(RocksDBOptionsConfigured.newConfigured().withDbPath(Configs.DB_PATH).config()) .withRaftDataPath(Configs.RAFT_DATA_PATH) .withServerAddress(new Endpoint("127.0.0.1", 8181)) .config(); final RheaKVStoreOptions opts = RheaKVStoreOptionsConfigured.newConfigured() // .withClusterName(Configs.CLUSTER_NAME) // .withUseParallelCompress(true) // .withInitialServerList(Configs.ALL_NODE_ADDRESSES) .withStoreEngineOptions(storeOpts) // .withPlacementDriverOptions(pdOpts) // .config(); System.out.println(opts); final Node node = new Node(opts); node.start(); Runtime.getRuntime().addShutdownHook(new Thread(node::stop)); System.out.println("server1 start OK"); } 关于Node节点的实现：
里面维护了一个RheaKVStoreOptions、RheaKVStore。
public class Node { private final RheaKVStoreOptions options; private RheaKVStore rheaKVStore; public Node(RheaKVStoreOptions options) { this.options = options; } public void start() { this.rheaKVStore = new DefaultRheaKVStore(); this.rheaKVStore.init(this.options); } public void stop() { this.rheaKVStore.shutdown(); } public RheaKVStore getRheaKVStore() { return rheaKVStore; } } （1）DefaultRheaKVStore的初始化
可以看到调用了DefaultRheaKVStore，还调用了他的init方法进行初始化。
public synchronized boolean init(final RheaKVStoreOptions opts) { //判断是否已经启动 if (this.started) { LOG.info("[DefaultRheaKVStore] already started."); return true; } DescriberManager.getInstance().addDescriber(RouteTable.getInstance()); this.opts = opts; //根据PlacementDriverOptions初始化PD final PlacementDriverOptions pdOpts = opts.getPlacementDriverOptions(); final String clusterName = opts.getClusterName(); Requires.requireNonNull(pdOpts, "opts.placementDriverOptions"); Requires.requireNonNull(clusterName, "opts.clusterName"); if (Strings.isBlank(pdOpts.getInitialServerList())) { // 如果为空，则继承父级的值 pdOpts.setInitialServerList(opts.getInitialServerList()); } //这里不启用 PD，就实例化一个FakePlacementDriverClient if (pdOpts.isFake()) { this.pdClient = new FakePlacementDriverClient(opts.getClusterId(), clusterName); //启用 PD，就实例化一个RemotePlacementDriverClient } else { this.pdClient = new RemotePlacementDriverClient(opts.getClusterId(), clusterName); } //初始化FakePlacementDriverClient/RemotePlacementDriverClient if (!this.pdClient.init(pdOpts)) { LOG.error("Fail to init [PlacementDriverClient]."); return false; } // 初始化压缩策略 ZipStrategyManager.init(opts); // 初始化存储引擎 final StoreEngineOptions stOpts = opts.getStoreEngineOptions(); if (stOpts != null) { stOpts.setInitialServerList(opts.getInitialServerList()); this.storeEngine = new StoreEngine(this.pdClient, this.stateListenerContainer); if (!this.storeEngine.init(stOpts)) { LOG.error("Fail to init [StoreEngine]."); return false; } } //获取当前节点的ip和端口号 final Endpoint selfEndpoint = this.storeEngine == null ? null : this.storeEngine.getSelfEndpoint(); final RpcOptions rpcOpts = opts.getRpcOptions(); Requires.requireNonNull(rpcOpts, "opts.rpcOptions"); //初始化一个RpcService，并重写getLeader方法 this.rheaKVRpcService = new DefaultRheaKVRpcService(this.pdClient, selfEndpoint) { @Override public Endpoint getLeader(final long regionId, final boolean forceRefresh, final long timeoutMillis) { final Endpoint leader = getLeaderByRegionEngine(regionId); if (leader != null) { return leader; } return super.getLeader(regionId, forceRefresh, timeoutMillis); } }; if (!this.rheaKVRpcService.init(rpcOpts)) { LOG.error("Fail to init [RheaKVRpcService]."); return false; } //获取重试次数，默认重试两次 this.failoverRetries = opts.getFailoverRetries(); //默认5000 this.futureTimeoutMillis = opts.getFutureTimeoutMillis(); //是否只从leader读取数据，默认为true this.onlyLeaderRead = opts.isOnlyLeaderRead(); //初始化kvDispatcher， 这里默认为true if (opts.isUseParallelKVExecutor()) { final int numWorkers = Utils.cpus(); //乘以16 final int bufSize = numWorkers << 4; final String name = "parallel-kv-executor"; final ThreadFactory threadFactory = Constants.THREAD_AFFINITY_ENABLED ? new AffinityNamedThreadFactory(name, true) : new NamedThreadFactory(name, true); //初始化Dispatcher this.kvDispatcher = new TaskDispatcher(bufSize, numWorkers, WaitStrategyType.LITE_BLOCKING_WAIT, threadFactory); } this.batchingOpts = opts.getBatchingOptions(); //默认是true if (this.batchingOpts.isAllowBatching()) { this.getBatching = new GetBatching(KeyEvent::new, "get_batching", new GetBatchingHandler("get", false)); this.getBatchingOnlySafe = new GetBatching(KeyEvent::new, "get_batching_only_safe", new GetBatchingHandler("get_only_safe", true)); this.putBatching = new PutBatching(KVEvent::new, "put_batching", new PutBatchingHandler("put")); } LOG.info("[DefaultRheaKVStore] start successfully, options: {}.", opts); return this.started = true; } （2）StoreEngine初始化
其中有些代码操作与DefaultRheaKVStore的init方法中的某些代码一致，就不再重复赘述，其余的用注释的方式标注在以下代码块中。
public synchronized boolean init(final StoreEngineOptions opts) { if (this.started) { LOG.info("[StoreEngine] already started."); return true; } DescriberManager.getInstance().addDescriber(this); this.storeOpts = Requires.requireNonNull(opts, "opts"); Endpoint serverAddress = Requires.requireNonNull(opts.getServerAddress(), "opts.serverAddress"); //获取ip和端口 final int port = serverAddress.getPort(); final String ip = serverAddress.getIp(); //如果传入的IP为空，那么就设置启动机器ip作为serverAddress的ip if (ip == null || Utils.IP_ANY.equals(ip)) { serverAddress = new Endpoint(NetUtil.getLocalCanonicalHostName(), port); opts.setServerAddress(serverAddress); } //获取度量上报时间 final long metricsReportPeriod = opts.getMetricsReportPeriod(); // 初始化RegionEngineOptions List<RegionEngineOptions> rOptsList = opts.getRegionEngineOptionsList(); //如果RegionEngineOptions为空，则初始化一个 if (rOptsList == null || rOptsList.isEmpty()) { // -1 region final RegionEngineOptions rOpts = new RegionEngineOptions(); rOpts.setRegionId(Constants.DEFAULT_REGION_ID); rOptsList = Lists.newArrayList(); rOptsList.add(rOpts); opts.setRegionEngineOptionsList(rOptsList); } //获取集群名 final String clusterName = this.pdClient.getClusterName(); //遍历rOptsList集合，为其中的RegionEngineOptions对象设置参数 for (final RegionEngineOptions rOpts : rOptsList) { //用集群名+“-”+RegionId 拼接设置为RaftGroupId rOpts.setRaftGroupId(JRaftHelper.getJRaftGroupId(clusterName, rOpts.getRegionId())); rOpts.setServerAddress(serverAddress); if (Strings.isBlank(rOpts.getInitialServerList())) { // if blank, extends parent's value rOpts.setInitialServerList(opts.getInitialServerList()); } if (rOpts.getNodeOptions() == null) { // copy common node options rOpts.setNodeOptions(opts.getCommonNodeOptions() == null ? new NodeOptions() : opts .getCommonNodeOptions().copy()); } //如果原本没有设置度量上报时间，那么就重置一下 if (rOpts.getMetricsReportPeriod() <= 0 && metricsReportPeriod > 0) { // extends store opts rOpts.setMetricsReportPeriod(metricsReportPeriod); } } // 初始化Store和Store里面的region final Store store = this.pdClient.getStoreMetadata(opts); if (store == null || store.getRegions() == null || store.getRegions().isEmpty()) { LOG.error("Empty store metadata: {}.", store); return false; } this.storeId = store.getId(); this.partRocksDBOptions = SystemPropertyUtil.getBoolean(PART_ROCKSDB_OPTIONS_KEY, false); // 初始化执行器 if (this.readIndexExecutor == null) { this.readIndexExecutor = StoreEngineHelper.createReadIndexExecutor(opts.getReadIndexCoreThreads()); } if (this.raftStateTrigger == null) { this.raftStateTrigger = StoreEngineHelper.createRaftStateTrigger(opts.getLeaderStateTriggerCoreThreads()); } if (this.snapshotExecutor == null) { this.snapshotExecutor = StoreEngineHelper.createSnapshotExecutor(opts.getSnapshotCoreThreads(), opts.getSnapshotMaxThreads()); } // init rpc executors final boolean useSharedRpcExecutor = opts.isUseSharedRpcExecutor(); // 初始化rpc远程执行器，用来执行RPCServer的Processors if (!useSharedRpcExecutor) { if (this.cliRpcExecutor == null) { this.cliRpcExecutor = StoreEngineHelper.createCliRpcExecutor(opts.getCliRpcCoreThreads()); } if (this.raftRpcExecutor == null) { this.raftRpcExecutor = StoreEngineHelper.createRaftRpcExecutor(opts.getRaftRpcCoreThreads()); } if (this.kvRpcExecutor == null) { this.kvRpcExecutor = StoreEngineHelper.createKvRpcExecutor(opts.getKvRpcCoreThreads()); } } // 初始化指标度量 startMetricReporters(metricsReportPeriod); // 初始化rpcServer，供其他服务调用 this.rpcServer = RaftRpcServerFactory.createRaftRpcServer(serverAddress, this.raftRpcExecutor, this.cliRpcExecutor); //为server加入各种processor StoreEngineHelper.addKvStoreRequestProcessor(this.rpcServer, this); if (!this.rpcServer.init(null)) { LOG.error("Fail to init [RpcServer]."); return false; } // init db store // 根据不同的类型选择db if (!initRawKVStore(opts)) { return false; } if (this.rawKVStore instanceof Describer) { DescriberManager.getInstance().addDescriber((Describer) this.rawKVStore); } // init all region engine // 为每个region初始化RegionEngine if (!initAllRegionEngine(opts, store)) { LOG.error("Fail to init all [RegionEngine]."); return false; } // heartbeat sender // 如果开启了自管理的集群，那么需要初始化心跳发送器 if (this.pdClient instanceof RemotePlacementDriverClient) { HeartbeatOptions heartbeatOpts = opts.getHeartbeatOptions(); if (heartbeatOpts == null) { heartbeatOpts = new HeartbeatOptions(); } this.heartbeatSender = new HeartbeatSender(this); if (!this.heartbeatSender.init(heartbeatOpts)) { LOG.error("Fail to init [HeartbeatSender]."); return false; } } this.startTime = System.currentTimeMillis(); LOG.info("[StoreEngine] start successfully: {}.", this); return this.started = true; } （3）RegionEngineOptions初始化
在上述StoreEngine的初始化中，可以看到有对regionEngine进行初始化，接下来我们单独再拿出该部分代码进行分析。
- 首先对opts.getRegionEngineOptionsList()判空，若是空则初始化一个RegionEngineOptions()
- 遍历新生成的每一个RegionEngineOptions，并设置参数（RaftGroupId、ServerAddress、InitialServerList、NodeOptions、MetricsReportPeriod）
// init region options List<RegionEngineOptions> rOptsList = opts.getRegionEngineOptionsList(); if (rOptsList == null || rOptsList.isEmpty()) { // -1 region final RegionEngineOptions rOpts = new RegionEngineOptions(); rOpts.setRegionId(Constants.DEFAULT_REGION_ID); rOptsList = Lists.newArrayList(); rOptsList.add(rOpts); opts.setRegionEngineOptionsList(rOptsList); } final String clusterName = this.pdClient.getClusterName(); for (final RegionEngineOptions rOpts : rOptsList) { rOpts.setRaftGroupId(JRaftHelper.getJRaftGroupId(clusterName, rOpts.getRegionId())); rOpts.setServerAddress(serverAddress); if (Strings.isBlank(rOpts.getInitialServerList())) { // if blank, extends parent's value rOpts.setInitialServerList(opts.getInitialServerList()); } if (rOpts.getNodeOptions() == null) { // copy common node options rOpts.setNodeOptions(opts.getCommonNodeOptions() == null ? new NodeOptions() : opts .getCommonNodeOptions().copy()); } if (rOpts.getMetricsReportPeriod() <= 0 && metricsReportPeriod > 0) { // extends store opts rOpts.setMetricsReportPeriod(metricsReportPeriod); } } （4）Store初始化
调用pdClient的getStoreMetadata方法进行初始化：
final Store store = this.pdClient.getStoreMetadata(opts); 当调用FakePlacementDriverClient#getStoreMetadata时：
- 获取之前初始化得到的RegionEngineOptions链表
- 构造一个与RegionEngineOptions链表相同大小的Region链表，因为一个Store里面会有多个region，之前在那张图中能直观看到。
- 对RegionEngineOptions链表中的每个元素执行getLocalRegionMetadata方法，并将结果添加到region链表中。
public Store getStoreMetadata(final StoreEngineOptions opts) { final Store store = new Store(); final List<RegionEngineOptions> rOptsList = opts.getRegionEngineOptionsList(); final List<Region> regionList = Lists.newArrayListWithCapacity(rOptsList.size()); store.setId(-1); store.setEndpoint(opts.getServerAddress()); for (final RegionEngineOptions rOpts : rOptsList) { regionList.add(getLocalRegionMetadata(rOpts)); } store.setRegions(regionList); return store; } 我们来看AbstractPlacementDriverClient#getLocalRegionMetadata方法：
- 保证regionId在合理的范围内
- 设置key的范围（左闭右开）
- 根据initialServerList转换成peer对象
- 将Region添加到regionRouteTable路由表中
protected Region getLocalRegionMetadata(final RegionEngineOptions opts) { final long regionId = Requires.requireNonNull(opts.getRegionId(), "opts.regionId"); Requires.requireTrue(regionId >= Region.MIN_ID_WITH_MANUAL_CONF, "opts.regionId must >= " + Region.MIN_ID_WITH_MANUAL_CONF); Requires.requireTrue(regionId < Region.MAX_ID_WITH_MANUAL_CONF, "opts.regionId must < " + Region.MAX_ID_WITH_MANUAL_CONF); final byte[] startKey = opts.getStartKeyBytes(); final byte[] endKey = opts.getEndKeyBytes(); final String initialServerList = opts.getInitialServerList(); final Region region = new Region(); final Configuration conf = new Configuration(); // region region.setId(regionId); region.setStartKey(startKey); region.setEndKey(endKey); region.setRegionEpoch(new RegionEpoch(-1, -1)); // peers Requires.requireTrue(Strings.isNotBlank(initialServerList), "opts.initialServerList is blank"); conf.parse(initialServerList); region.setPeers(JRaftHelper.toPeerList(conf.listPeers())); this.regionRouteTable.addOrUpdateRegion(region); return region; } RegionEpoch涉及到两个版本号：
（1）confVer：Conf 变化的版本号, 当增加或者移除一个peer时，版本号自增
（2）version：Region 版本号, 分裂或合并时，版本号自增
public RegionEpoch(long confVer, long version) { this.confVer = confVer this.version = version; } 关于RegionRouteTable#addOrUpdateRegion：
public void addOrUpdateRegion(final Region region) { Requires.requireNonNull(region, "region"); Requires.requireNonNull(region.getRegionEpoch(), "regionEpoch"); final long regionId = region.getId(); final byte[] startKey = BytesUtil.nullToEmpty(region.getStartKey()); final StampedLock stampedLock = this.stampedLock; final long stamp = stampedLock.writeLock(); try { this.regionTable.put(regionId, region.copy()); this.rangeTable.put(startKey, regionId); } finally { stampedLock.unlockWrite(stamp); } } 我们看看RegionRouteTable的几个字段：
- keyBytesComparator：是一个LexicographicByteArrayComparator字典序比较器
- stampedLock：比读写锁性能更高的锁
- rangeTable：是一个TreeMap，它实现了NavigableMap，并按照指定的keyBytesComparator排序，键值对为<regionId, region>
- regionTable：是一个hashMap，键值对为<startKey, regionId>
private static final Comparator<byte[]> keyBytesComparator = BytesUtil.getDefaultByteArrayComparator(); private final StampedLock stampedLock = new StampedLock(); private final NavigableMap<byte[], Long> rangeTable = new TreeMap<>(keyBytesComparator); private final Map<Long, Region> regionTable = Maps.newHashMap(); （5）RegionEngine初始化
StoreEngine#initAllRegionEngine
private boolean initAllRegionEngine(final StoreEngineOptions opts, final Store store) { Requires.requireNonNull(opts, "opts"); Requires.requireNonNull(store, "store"); //获取主目录 String baseRaftDataPath = opts.getRaftDataPath(); if (Strings.isNotBlank(baseRaftDataPath)) { try { FileUtils.forceMkdir(new File(baseRaftDataPath)); } catch (final Throwable t) { LOG.error("Fail to make dir for raftDataPath: {}.", baseRaftDataPath); return false; } } else { baseRaftDataPath = ""; } final Endpoint serverAddress = opts.getServerAddress(); //获取RegionEngineOptions和region final List<RegionEngineOptions> rOptsList = opts.getRegionEngineOptionsList(); final List<Region> regionList = store.getRegions(); Requires.requireTrue(rOptsList.size() == regionList.size()); for (int i = 0; i < rOptsList.size(); i++) { final RegionEngineOptions rOpts = rOptsList.get(i); if (!inConfiguration(rOpts.getServerAddress().toString(), rOpts.getInitialServerList())) { continue; } final Region region = regionList.get(i); //检验region路径是否为空，为空则重新设值 if (Strings.isBlank(rOpts.getRaftDataPath())) { final String childPath = "raft_data_region_" + region.getId() + "_" + serverAddress.getPort(); rOpts.setRaftDataPath(Paths.get(baseRaftDataPath, childPath).toString()); } Requires.requireNonNull(region.getRegionEpoch(), "regionEpoch"); //根据Region初始化RegionEngine final RegionEngine engine = new RegionEngine(region, this); if (engine.init(rOpts)) { // 每个 RegionKVService 对应一个 Region，只处理本身 Region 范畴内的请求 final RegionKVService regionKVService = new DefaultRegionKVService(engine); registerRegionKVService(regionKVService); //放入到ConcurrentMap<Long, RegionEngine> regionKVServiceTable 中 this.regionEngineTable.put(region.getId(), engine); } else { LOG.error("Fail to init [RegionEngine: {}].", region); return false; } } return true; } **
public synchronized boolean init(final RegionEngineOptions opts) { if (this.started) { LOG.info("[RegionEngine: {}] already started.", this.region); return true; } this.regionOpts = Requires.requireNonNull(opts, "opts"); //实例化状态机 this.fsm = new KVStoreStateMachine(this.region, this.storeEngine); // node options NodeOptions nodeOpts = opts.getNodeOptions(); if (nodeOpts == null) { nodeOpts = new NodeOptions(); } //如果度量间隔时间大于零，那么开启度量 final long metricsReportPeriod = opts.getMetricsReportPeriod(); if (metricsReportPeriod > 0) { // metricsReportPeriod > 0 means enable metrics nodeOpts.setEnableMetrics(true); } final Configuration initialConf = new Configuration(); if (!initialConf.parse(opts.getInitialServerList())) { LOG.error("Fail to parse initial configuration {}.", opts.getInitialServerList()); return false; } //初始化集群配置 nodeOpts.setInitialConf(initialConf); nodeOpts.setFsm(this.fsm); //初始化各种日志的路径 final String raftDataPath = opts.getRaftDataPath(); try { FileUtils.forceMkdir(new File(raftDataPath)); } catch (final Throwable t) { LOG.error("Fail to make dir for raftDataPath {}.", raftDataPath); return false; } if (Strings.isBlank(nodeOpts.getLogUri())) { final Path logUri = Paths.get(raftDataPath, "log"); nodeOpts.setLogUri(logUri.toString()); } if (Strings.isBlank(nodeOpts.getRaftMetaUri())) { final Path meteUri = Paths.get(raftDataPath, "meta"); nodeOpts.setRaftMetaUri(meteUri.toString()); } if (Strings.isBlank(nodeOpts.getSnapshotUri())) { final Path snapshotUri = Paths.get(raftDataPath, "snapshot"); nodeOpts.setSnapshotUri(snapshotUri.toString()); } LOG.info("[RegionEngine: {}], log uri: {}, raft meta uri: {}, snapshot uri: {}.", this.region, nodeOpts.getLogUri(), nodeOpts.getRaftMetaUri(), nodeOpts.getSnapshotUri()); final Endpoint serverAddress = opts.getServerAddress(); final PeerId serverId = new PeerId(serverAddress, 0); final RpcServer rpcServer = this.storeEngine.getRpcServer(); this.raftGroupService = new RaftGroupService(opts.getRaftGroupId(), serverId, nodeOpts, rpcServer, true); this.node = this.raftGroupService.start(false); //初始化node节点 RouteTable.getInstance().updateConfiguration(this.raftGroupService.getGroupId(), nodeOpts.getInitialConf()); if (this.node != null) { final RawKVStore rawKVStore = this.storeEngine.getRawKVStore(); final Executor readIndexExecutor = this.storeEngine.getReadIndexExecutor(); //RaftRawKVStore 是 RheaKV 基于 Raft 复制状态机 KVStoreStateMachine 的 RawKVStore 接口 KV 存储实现 //RheaKV 的 Raft 入口，从这里开始 Raft 流程 this.raftRawKVStore = new RaftRawKVStore(this.node, rawKVStore, readIndexExecutor); //拦截请求做指标度量 this.metricsRawKVStore = new MetricsRawKVStore(this.region.getId(), this.raftRawKVStore); // metrics config if (this.regionMetricsReporter == null && metricsReportPeriod > 0) { final MetricRegistry metricRegistry = this.node.getNodeMetrics().getMetricRegistry(); if (metricRegistry != null) { final ScheduledExecutorService scheduler = this.storeEngine.getMetricsScheduler(); // start raft node metrics reporter this.regionMetricsReporter = Slf4jReporter.forRegistry(metricRegistry) // .prefixedWith("region_" + this.region.getId()) // .withLoggingLevel(Slf4jReporter.LoggingLevel.INFO) // .outputTo(LOG) // .scheduleOn(scheduler) // .shutdownExecutorOnStop(scheduler != null) // .build(); this.regionMetricsReporter.start(metricsReportPeriod, TimeUnit.SECONDS); } } this.started = true; LOG.info("[RegionEngine] start successfully: {}.", this); } return this.started; } 
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