hbase region split ：

split执行调用流程：

1.HbaseAdmin发起split：###

2.RSRpcServices实现类执行split（Implements the regionserver RPC services.）###

3.CompactSplitThread类与SplitRequest类用来执行region切割:###

4.splitRequest执行doSplitting操作###

4.1初始化两个子region###

4.2执行切割####

4.2.1：（创建子region。stepsBeforePONR函数）#####

4.2.2：子region执行：stepsAfterPONR函数执行(包含openDaughters函数)：#####

4.2.3：HRegionServer添加子region到meta表，加入RegionServer#####

4.3等待region切分完成，修改meta表信息，报告master####

1.HbaseAdmin发起split：

public void split(final TableName tableName) throws IOException {split(tableName, null);  }   public void split(final ServerName sn, final HRegionInfo hri,  byte[] splitPoint) throws IOException {if (hri.getStartKey() != null && splitPoint != null && Bytes.compareTo(hri.getStartKey(), splitPoint) == 0) {   throw new IOException("should not give a splitkey which equals to startkey!");}// TODO: There is no timeout on this controller. Set one!HBaseRpcController controller = rpcControllerFactory.newController();controller.setPriority(hri.getTable());// TODO: this does not do retries, it should. Set priority and timeout in controllerAdminService.BlockingInterface admin = this.connection.getAdmin(sn);//hbase中split调用请求通过protobuf（AdminProtos）实现ProtobufUtil.split(controller, admin, hri, splitPoint);    实现代码：     try {        admin.splitRegion(controller, request);        }

2.RSRpcServices实现类执行split（Implements the regionserver RPC services.）

代码：      try {  checkOpen();  requestCount.increment();  Region region = getRegion(request.getRegion());  region.startRegionOperation(Operation.SPLIT_REGION);  if (region.getRegionInfo().getReplicaId() != HRegionInfo.DEFAULT_REPLICA_ID) {throw new IOException("Can't split replicas directly. "+ "Replicas are auto-split when their primary is split.");  }  LOG.info("Splitting " + region.getRegionInfo().getRegionNameAsString());  region.flush(true);  byte[] splitPoint = null;  if (request.hasSplitPoint()) {  //确定切割点splitpointsplitPoint = request.getSplitPoint().toByteArray();  }  ((HRegion)region).forceSplit(splitPoint);  //请求region切割  regionServer.compactSplitThread.requestSplit(region, ((HRegion)region).checkSplit(),RpcServer.getRequestUser());  return SplitRegionResponse.newBuilder().build();}

3.CompactSplitThread类与SplitRequest类用来执行region切割:

代码：    try {  this.splits.execute(new SplitRequest(r, midKey, this.server, user));  if (LOG.isDebugEnabled()) {LOG.debug("Split requested for " + r + ".  " + this);  }}try {  //acquire a shared read lock on the table, so that table schema modifications  //do not happen concurrently  //获取table的读锁。。  tableLock = server.getTableLockManager().readLock(parent.getTableDesc().getTableName()  , "SPLIT_REGION:" + parent.getRegionInfo().getRegionNameAsString());  try {tableLock.acquire();  }

4.splitRequest执行doSplitting操作

4.1###

//初始化两个子region信息this.hri_a = new HRegionInfo(hri.getTable(), startKey, this.splitrow, false, rid);    this.hri_b = new HRegionInfo(hri.getTable(), this.splitrow, endKey, false, rid);

4.2###

//执行切割   st.execute(this.server, this.server, user);

4.2.1：（创建子region。stepsBeforePONR函数）####

//创建两个子region        PairOfSameType
     
       regions = createDaughters(server, services, user);
     

4.2.2：stepsAfterPONR函数执行（openDaughters）：####

// 两个子region DaughterOpener线程 start        DaughterOpener aOpener = new DaughterOpener(server, (HRegion)a);        DaughterOpener bOpener = new DaughterOpener(server, (HRegion)b);        //向hdfs上写入.regionInfo文件以便meta挂掉以便恢复         writeRegionInfoOnFilesystem(content, true);        //初始化所有的hstore        initializeStores(reporter, status);        //LoadStoreFiles函数执行：        if (files == null || files.size() == 0) {        return new ArrayList
     
      ();        }             // initialize the thread pool for opening store files in parallel..            ThreadPoolExecutor storeFileOpenerThreadPool =            this.region.getStoreFileOpenAndCloseThreadPool("StoreFileOpenerThread-" +         this.getColumnFamilyName());             CompletionService
      
        completionService =            new ExecutorCompletionService
       
        (storeFileOpenerThreadPool);            int totalValidStoreFile = 0;            for (final StoreFileInfo storeFileInfo: files) {            //HDFS上对应的路径和文件            completionService.submit(new Callable
        
         () {             @Override            public StoreFile call() throws IOException {            //每个文件创建一个StoreFile对象，对每个storefile对象会读取文件上的内容创建一个             HalfStoreFileReader读对象来操作该region的父region上的相应的文件，及该             region上目前存储的是引用文件，其指向的是其父region上的相应的文件，对该             region的所有读或写都将关联到父region上         StoreFile storeFile = createStoreFileAndReader(storeFileInfo);         return storeFile;             }            });             totalValidStoreFile++;             }             //将子Region添加到rs的online region列表上，并添加到meta表上              {         if (useZKForAssignment) {          // add 2nd daughter first (see HBASE-4335)          services.postOpenDeployTasks(b);         } else if (!services.reportRegionStateTransition(TransitionCode.SPLIT,           parent.getRegionInfo(), hri_a, hri_b)) {         throw new IOException("Failed to report split region to master: "          + parent.getRegionInfo().getShortNameToLog());         }         // Should add it to OnlineRegions         services.addToOnlineRegions(b);         if (useZKForAssignment) {           services.postOpenDeployTasks(a);        }         services.addToOnlineRegions(a);         }
        
       
      
     

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