SOFAJRaft的SOFAJRaft-RheaKV 是基於 SOFAJRaft 和 RocksDB 實現的嵌入式、分散式、高可用、強一致的 KV 儲存類庫。SOFAJRaft-RheaKV 叢集主要包括三個核心元件：PD，Store 和 Region。
@Author：Akai-yuan
@更新時間：2023/2/3
1.架構設計
SOFAJRaft-RheaKV 儲存類庫主要包括** PD，Store 和 Region 三個核心元件**，支援輕量級的狀態/元資訊儲存以及叢集同步，分散式鎖服務使用場景
（1）排程
PD 是全域性的中心總控節點，負責整個叢集的排程管理、Region ID 生成、維護 RegionRouteTable 路由表。一個 PDServer 管理多個叢集，叢集之間基於 clusterId 隔離；PD Server 需要單獨部署，很多場景其實並不需要自管理，RheaKV 也支援不啟用 PD，不需要自管理的叢集可不啟用 PD，設定 PlacementDriverOptions 的 fake選項為 true 即可。PD 一般透過 Region 的心跳返回資訊進行對 Region 排程，Region 處理完後，PD 則會在下一個心跳返回中收到 Region 的變更資訊來更新路由及狀態表。
（2）儲存
Store 是叢集中的一個物理儲存節點，一個 Store 包含一個或多個 Region。通常一個 Node 負責一個 Store，Store 可以被看作是 Region 的容器，裡面儲存著多個分片資料。Store 會向 PD 主動上報 StoreHeartbeatRequest 心跳，心跳交由 PD 的 handleStoreHeartbeat 處理，裡面包含該 Store 的基本資訊，比如，包含多少 Region，有哪些 Region 的 Leader 在該 Store 等。
（3）資料
Region 是最小的 KV 資料單元，可理解為一個資料分割槽或者分片，每個 Region 都有一個左閉右開的區間 [startKey, endKey)，能夠根據請求流量/負載/資料量大小等指標自動分裂以及自動副本搬遷。Region 有多個副本 Replication 構建 Raft Groups 儲存在不同的 Store 節點，透過 Raft 協議日誌複製功能資料同步到同 Group 的全部節點。Region對應的是 Store 裡某個實際的資料區間。每個 Region 會有多個副本，每個副本儲存在不同的 Store，一起組成一個Raft Group。Region 中的 Leader 會向 PD 主動上報 RegionHeartbeatRequest 心跳，交由 PD 的 handleRegionHeartbeat 處理，而 PD 是透過 Region的Epoch 感知 Region 是否有變化。
為了讓大家更清楚PD，Store 和 Region 三個核心元件的功能，這裡放一張官方圖片以便於理解：
2.初始化
我們從JRaft-Example模組的RheaKV部分開始，首先看到com.alipay.sofa.jraft.example.rheakv.Server1的main方法。
- 宣告瞭PlacementDriverOptions、StoreEngineOptions兩個配置選項實體
- 定義了RheaKVStoreOptions，並將PDOptions和SEOptions裝配到屬性中，並初始化宣告叢集名、是否開啟並行壓縮、服務的IP:埠列表（"127.0.0.1:8181,127.0.0.1:8182,127.0.0.1:8183"）。
- 宣告一個Node節點
- 新增一個鉤子函式，實現優雅停機。（作者曾經分析過鉤子函式的作用，具體參照：SOFAJRaft原始碼閱讀（叄）-ShutdownHook如何優雅的停機）
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 儲存引擎支援 MemoryDB 和 RocksDB 兩種實現
.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");
}
關於Node節點的實現：
裡面維護了一個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
可以看到呼叫了DefaultRheaKVStore，還呼叫了他的init方法進行初始化。
public synchronized boolean init(final RheaKVStoreOptions opts) {
//判斷是否已經啟動
if (this.started) {
LOG.info("[DefaultRheaKVStore] already started.");
return true;
}
DescriberManager.getInstance().addDescriber(RouteTable.getInstance());
this.opts = opts;
//根據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())) {
// 如果為空，則繼承父級的值
pdOpts.setInitialServerList(opts.getInitialServerList());
}
//這裡不啟用 PD，就例項化一個FakePlacementDriverClient
if (pdOpts.isFake()) {
this.pdClient = new FakePlacementDriverClient(opts.getClusterId(), clusterName);
//啟用 PD，就例項化一個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;
}
// 初始化壓縮策略
ZipStrategyManager.init(opts);
// 初始化儲存引擎
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;
}
}
//獲取當前節點的ip和埠號
final Endpoint selfEndpoint = this.storeEngine == null ? null : this.storeEngine.getSelfEndpoint();
final RpcOptions rpcOpts = opts.getRpcOptions();
Requires.requireNonNull(rpcOpts, "opts.rpcOptions");
//初始化一個RpcService，並重寫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;
}
//獲取重試次數，預設重試兩次
this.failoverRetries = opts.getFailoverRetries();
//預設5000
this.futureTimeoutMillis = opts.getFutureTimeoutMillis();
//是否只從leader讀取資料，預設為true
this.onlyLeaderRead = opts.isOnlyLeaderRead();
//初始化kvDispatcher， 這裡預設為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();
//預設是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
其中有些程式碼操作與DefaultRheaKVStore的init方法中的某些程式碼一致，就不再重複贅述，其餘的用註釋的方式標註在以下程式碼塊中。
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");
//獲取ip和埠
final int port = serverAddress.getPort();
final String ip = serverAddress.getIp();
//如果傳入的IP為空，那麼就設定啟動機器ip作為serverAddress的ip
if (ip == null || Utils.IP_ANY.equals(ip)) {
serverAddress = new Endpoint(NetUtil.getLocalCanonicalHostName(), port);
opts.setServerAddress(serverAddress);
}
//獲取度量上報時間
final long metricsReportPeriod = opts.getMetricsReportPeriod();
// 初始化RegionEngineOptions
List<RegionEngineOptions> rOptsList = opts.getRegionEngineOptionsList();
//如果RegionEngineOptions為空，則初始化一個
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);
}
//獲取叢集名
final String clusterName = this.pdClient.getClusterName();
//遍歷rOptsList集合，為其中的RegionEngineOptions物件設定引數
for (final RegionEngineOptions rOpts : rOptsList) {
//用叢集名+“-”+RegionId 拼接設定為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());
}
//如果原本沒有設定度量上報時間，那麼就重置一下
if (rOpts.getMetricsReportPeriod() <= 0 && metricsReportPeriod > 0) {
// extends store opts
rOpts.setMetricsReportPeriod(metricsReportPeriod);
}
}
// 初始化Store和Store裡面的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);
// 初始化執行器
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遠端執行器，用來執行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());
}
}
// 初始化指標度量
startMetricReporters(metricsReportPeriod);
// 初始化rpcServer，供其他服務呼叫
this.rpcServer = RaftRpcServerFactory.createRaftRpcServer(serverAddress, this.raftRpcExecutor,
this.cliRpcExecutor);
//為server加入各種processor
StoreEngineHelper.addKvStoreRequestProcessor(this.rpcServer, this);
if (!this.rpcServer.init(null)) {
LOG.error("Fail to init [RpcServer].");
return false;
}
// init db store
// 根據不同的型別選擇db
if (!initRawKVStore(opts)) {
return false;
}
if (this.rawKVStore instanceof Describer) {
DescriberManager.getInstance().addDescriber((Describer) this.rawKVStore);
}
// init all region engine
// 為每個region初始化RegionEngine
if (!initAllRegionEngine(opts, store)) {
LOG.error("Fail to init all [RegionEngine].");
return false;
}
// heartbeat sender
// 如果開啟了自管理的叢集，那麼需要初始化心跳傳送器
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，可以看到有對regionEngine進行初始化，接下來我們單獨再拿出該部分程式碼進行分析。
- 首先對opts.getRegionEngineOptionsList()判空，若是空則初始化一個RegionEngineOptions()
- 遍歷新生成的每一個RegionEngineOptions，並設定引數（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
呼叫pdClient的getStoreMetadata方法進行初始化：
final Store store = this.pdClient.getStoreMetadata(opts);
當呼叫FakePlacementDriverClient#getStoreMetadata時：
- 獲取之前初始化得到的RegionEngineOptions連結串列
- 構造一個與RegionEngineOptions連結串列相同大小的Region連結串列，因為一個Store裡面會有多個region，之前在那張圖中能直觀看到。
- 對RegionEngineOptions連結串列中的每個元素執行getLocalRegionMetadata方法，並將結果新增到region連結串列中。
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;
}
我們來看AbstractPlacementDriverClient#getLocalRegionMetadata方法：
- 保證regionId在合理的範圍內
- 設定key的範圍（左閉右開）
- 根據initialServerList轉換成peer物件
- 將Region新增到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涉及到兩個版本號：
（1）confVer：Conf 變化的版本號, 當增加或者移除一個peer時，版本號自增
（2）version：Region 版本號, 分裂或合併時，版本號自增
public RegionEpoch(long confVer, long version) {
this.confVer = confVer
this.version = version;
}
關於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);
}
}
我們看看RegionRouteTable的幾個欄位：
- keyBytesComparator：是一個LexicographicByteArrayComparator字典序比較器
- stampedLock：比讀寫鎖效能更高的鎖
- rangeTable：是一個TreeMap，它實現了NavigableMap，並按照指定的keyBytesComparator排序，鍵值對為<regionId, region>
- regionTable：是一個hashMap，鍵值對為<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");
//獲取主目錄
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();
//獲取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);
//檢驗region路徑是否為空，為空則重新設值
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");
//根據Region初始化RegionEngine
final RegionEngine engine = new RegionEngine(region, this);
if (engine.init(rOpts)) {
// 每個 RegionKVService 對應一個 Region，只處理本身 Region 範疇內的請求
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");
//例項化狀態機
this.fsm = new KVStoreStateMachine(this.region, this.storeEngine);
// node options
NodeOptions nodeOpts = opts.getNodeOptions();
if (nodeOpts == null) {
nodeOpts = new NodeOptions();
}
//如果度量間隔時間大於零，那麼開啟度量
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;
}
//初始化叢集配置
nodeOpts.setInitialConf(initialConf);
nodeOpts.setFsm(this.fsm);
//初始化各種日誌的路徑
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節點
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 基於 Raft 複製狀態機 KVStoreStateMachine 的 RawKVStore 介面 KV 儲存實現
//RheaKV 的 Raft 入口，從這裡開始 Raft 流程
this.raftRawKVStore = new RaftRawKVStore(this.node, rawKVStore, readIndexExecutor);
//攔截請求做指標度量
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;
}