hbase region split 源码分析

再次吐槽公司的sb环境，不让上网不能插优盘，今天有事回家写一下笔记HBase region split

在管理集群时，最容易导致hbase节点发生故障的恐怕就是hbase region split和compact的了，日志有split时间太长；文件找不到；split的时候response too slow等等，所以先看看hbase region split源码，希望对以后能有帮助

HBase region split源码分析

一、流程概述

1.HBaseAdmin 发起 hbase split

2.HRegionServer 确定分割点 region split point

3.CompactSplitThread和SplitRequest 进行region分割

  3.1SplitTransaction st.prepare()初始化两个子region

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  3.2splitTransaction execute执行分割

        3.2.1两个子region DaughterOpener线程 start

        3.2.2若region 需要compact，进行compact路程

        3.2.3HRegionServer添加子region到meta表，加入到RegionServer里

   3.3修改zk节点状态，等待split结束

二 、hbase region split UML图

三、详细分析

1.HBaseAdmin 发起 hbase split

  public void split(final byte [] tableNameOrRegionName,
      final byte [] splitPoint) throws IOException, InterruptedException {
    CatalogTracker ct = getCatalogTracker();
    try {
      Pair<HRegionInfo, ServerName> regionServerPair
        = getRegion(tableNameOrRegionName, ct);//获得HRI，若是但region
      if (regionServerPair != null) {
        if (regionServerPair.getSecond() == null) {
            throw new NoServerForRegionException(Bytes.toStringBinary(tableNameOrRegionName));
        } else {
          //split region 重点分析方法
          split(regionServerPair.getSecond(), regionServerPair.getFirst(), splitPoint);
        }
      } else {
        //table split流程
        final String tableName = tableNameString(tableNameOrRegionName, ct);
        List<Pair<HRegionInfo, ServerName>> pairs =
          MetaReader.getTableRegionsAndLocations(ct,
              tableName);
        for (Pair<HRegionInfo, ServerName> pair: pairs) {
          // May not be a server for a particular row
          if (pair.getSecond() == null) continue;
          HRegionInfo r = pair.getFirst();
          // check for parents
          if (r.isSplitParent()) continue;
          // if a split point given, only split that particular region
          if (splitPoint != null && !r.containsRow(splitPoint)) continue;
          // call out to region server to do split now
          split(pair.getSecond(), pair.getFirst(), splitPoint);
        }
      }
    } finally {
      cleanupCatalogTracker(ct);
    }
  }

 

2.HRegionServer 确定分割点 region split point

  @Override
  public void splitRegion(HRegionInfo regionInfo, byte[] splitPoint)
      throws NotServingRegionException, IOException {
    checkOpen();//检查server和hdfs是否可用
    HRegion region = getRegion(regionInfo.getRegionName());//根据HRI获取region
    region.flushcache();//flush cache 有几种情况不进行flush
     //the cache is empte | the region is closed.| a flush is already in progress | writes are disabled
    region.forceSplit(splitPoint);//设置split point
    compactSplitThread.requestSplit(region, region.checkSplit());//获取split point，进行split
  }

   获得split point详细过程，获取最适合的store-hbase现在就是取最大的，获取store的midkey作为splitpoint

protected byte[] getSplitPoint() {
    byte[] explicitSplitPoint = this.region.getExplicitSplitPoint();
    if (explicitSplitPoint != null) {
      return explicitSplitPoint;
    }
    Map<byte[], Store> stores = region.getStores();

    byte[] splitPointFromLargestStore = null;
    long largestStoreSize = 0;
    for (Store s : stores.values()) {
      byte[] splitPoint = s.getSplitPoint();
      long storeSize = s.getSize();
      if (splitPoint != null && largestStoreSize < storeSize) {//获得最大store
        splitPointFromLargestStore = splitPoint;
        largestStoreSize = storeSize;
      }
    }
    
    return splitPointFromLargestStore;
  }

3.CompactSplitThread和SplitRequest 进行region分割

这里是split中较为复杂的过程

public void run() {
    if (this.server.isStopping() || this.server.isStopped()) {
      LOG.debug("Skipping split because server is stopping=" +
        this.server.isStopping() + " or stopped=" + this.server.isStopped());
      return;
    }
    try {
      final long startTime = System.currentTimeMillis();
      SplitTransaction st = new SplitTransaction(parent, midKey);
      // If prepare does not return true, for some reason -- logged inside in
      // the prepare call -- we are not ready to split just now. Just return.
      // 3.1SplitTransaction st.prepare()初始化两个子region
      if (!st.prepare()) return;
      try {
        st.execute(this.server, this.server);//3.2splitTransaction execute执行分割
        this.server.getMetrics().incrementSplitSuccessCount();
      } catch (Exception e) {
。。。。。。。。。。。。

  3.2splitTransaction execute执行分割

  public PairOfSameType<HRegion> execute(final Server server,
      final RegionServerServices services)
  throws IOException {
    PairOfSameType<HRegion> regions = createDaughters(server, services);
  //创建split临时目录，改变region zk状态，关闭region，停止所有store服务
  //创建daughter目录，将region storefile放入目录中
  //创建子region A、B，在zk上注册，并且设置原HRI下线
    openDaughters(server, services, regions.getFirst(), regions.getSecond());
    transitionZKNode(server, services, regions.getFirst(), regions.getSecond());
    return regions;
  }

       

加一个同样复杂的

3.2.0 createDaughters函数的操作

这里创建两个子Region，包括他们的regioninfo，并且将父region的hfile引用写入子Region中

生成两个子region的代码： SplitTransaction.stepsBeforePONR

Java代码  

1. public PairOfSameType<HRegion> stepsBeforePONR(final Server server,  
2.      final RegionServerServices services, boolean testing) throws IOException {  
3.    // Set ephemeral SPLITTING znode up in zk.  Mocked servers sometimes don't  
4.    // have zookeeper so don't do zk stuff if server or zookeeper is null  
5.    if (server != null && server.getZooKeeper() != null) {  
6.      try {  
7.         //步骤1@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@  
8.        createNodeSplitting(server.getZooKeeper(),  
9.          parent.getRegionInfo(), server.getServerName(), hri_a, hri_b);  
10.      } catch (KeeperException e) {  
11.        throw new IOException("Failed creating PENDING_SPLIT znode on " +  
12.          this.parent.getRegionNameAsString(), e);  
13.      }  
14.    }  
15.    this.journal.add(JournalEntry.SET_SPLITTING_IN_ZK);  
16.    if (server != null && server.getZooKeeper() != null) {  
17.      // After creating the split node, wait for master to transition it  
18.      // from PENDING_SPLIT to SPLITTING so that we can move on. We want master  
19.      // knows about it and won't transition any region which is splitting.  
20.     //步骤2@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@  
21.      znodeVersion = getZKNode(server, services);  
22.    }  
23.   
24.    //步骤3@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@  
25.    this.parent.getRegionFileSystem().createSplitsDir();  
26.    this.journal.add(JournalEntry.CREATE_SPLIT_DIR);  
27.   
28.    Map<byte[], List<StoreFile>> hstoreFilesToSplit = null;  
29.    Exception exceptionToThrow = null;  
30.    try{  
31.     //步骤4@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@  
32.      hstoreFilesToSplit = this.parent.close(false);  
33.    } catch (Exception e) {  
34.      exceptionToThrow = e;  
35.    }  
36.    if (exceptionToThrow == null && hstoreFilesToSplit == null) {  
37.      // The region was closed by a concurrent thread.  We can't continue  
38.      // with the split, instead we must just abandon the split.  If we  
39.      // reopen or split this could cause problems because the region has  
40.      // probably already been moved to a different server, or is in the  
41.      // process of moving to a different server.  
42.      exceptionToThrow = closedByOtherException;  
43.    }  
44.    if (exceptionToThrow != closedByOtherException) {  
45.      this.journal.add(JournalEntry.CLOSED_PARENT_REGION);  
46.    }  
47.    if (exceptionToThrow != null) {  
48.      if (exceptionToThrow instanceof IOException) throw (IOException)exceptionToThrow;  
49.      throw new IOException(exceptionToThrow);  
50.    }  
51.    if (!testing) {  
52.     //步骤5@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@  
53.      services.removeFromOnlineRegions(this.parent, null);  
54.    }  
55.    this.journal.add(JournalEntry.OFFLINED_PARENT);  
56.   
57.    // TODO: If splitStoreFiles were multithreaded would we complete steps in  
58.    // less elapsed time?  St.Ack 20100920  
59.    //  
60.    // splitStoreFiles creates daughter region dirs under the parent splits dir  
61.    // Nothing to unroll here if failure -- clean up of CREATE_SPLIT_DIR will  
62.    // clean this up.  
63.    //步骤6@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@  
64.    splitStoreFiles(hstoreFilesToSplit);  
65.   
66.    // Log to the journal that we are creating region A, the first daughter  
67.    // region.  We could fail halfway through.  If we do, we could have left  
68.    // stuff in fs that needs cleanup -- a storefile or two.  Thats why we  
69.    // add entry to journal BEFORE rather than AFTER the change.  
70.    //步骤7@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@  
71.    this.journal.add(JournalEntry.STARTED_REGION_A_CREATION);  
72.    HRegion a = this.parent.createDaughterRegionFromSplits(this.hri_a);  
73.   
74.    // Ditto  
75.    this.journal.add(JournalEntry.STARTED_REGION_B_CREATION);  
76.    HRegion b = this.parent.createDaughterRegionFromSplits(this.hri_b);  
77.    return new PairOfSameType<HRegion>(a, b);  
78.  }  

  1.RegionSplitPolicy.getSplitPoint()获得region split的split point  ，最大store的中间点midpoint最为split point

  2.SplitRequest.run()

            实例化SplitTransaction

            st.prepare()：split前准备：region是否关闭，所有hfile是否被引用

            st.execute:执行split操作

 

 1.createDaughters 创建两个region，获得parent region的写锁

      1在zk上创建一个临时的node splitting point，

      2等待master直到这个region转为splitting状态

      3之后建立splitting的文件夹，

      4等待region的flush和compact都完成后，关闭这个region

      5从HRegionServer上移除，加入到下线region中

      6进行regionsplit操作，创建线程池，用StoreFileSplitter类将region下的所有Hfile（StoreFile）进行split，

      （split row在hfile中的不管，其他的都进行引用，把引用文件分别写到region下边）

      7.生成左右两个子region，删除meta上parent，根据引用文件生成子region的regioninfo，写到hdfs上

 2.stepsAfterPONR 调用DaughterOpener类run打开两个子region，调用initilize

     a)向hdfs上写入.regionInfo文件以便meta挂掉以便恢复 

  b)初始化其下的HStore，主要是LoadStoreFiles函数： 

      对于该store函数会构造storefile对象，从hdfs上获取路径和文件，每个文件一个 

     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 

    将子Region添加到rs的online region列表上，并添加到meta表上 

 （0.98版本，包含以下3.2.1~3）

 （0.94版本，两个方法之后给合在了stepsAfterPONR里边）

3.2.1两个子region DaughterOpener线程 start

   final RegionServerServices services, HRegion a, HRegion b)
      throws IOException {
    boolean stopped = server != null && server.isStopped();
    boolean stopping = services != null && services.isStopping();
    // TODO: Is this check needed here?
    if (stopped || stopping) {
      LOG.info("Not opening daughters " +
          b.getRegionInfo().getRegionNameAsString() +
          " and " +
          a.getRegionInfo().getRegionNameAsString() +
          " because stopping=" + stopping + ", stopped=" + stopped);
    } else {
      // Open daughters in parallel.创建两个字region打开操作类
      DaughterOpener aOpener = new DaughterOpener(server, a);
      DaughterOpener bOpener = new DaughterOpener(server, b);
      aOpener.start();
      bOpener.start();
      try {
        aOpener.join();
        bOpener.join();
      } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
        throw new IOException("Interrupted " + e.getMessage());
      }
      if (aOpener.getException() != null) {
        throw new IOException("Failed " +
          aOpener.getName(), aOpener.getException());
      }
      if (bOpener.getException() != null) {
        throw new IOException("Failed " +
          bOpener.getName(), bOpener.getException());
      }
      if (services != null) {
        try {
          // add 2nd daughter first (see HBASE-4335)
          services.postOpenDeployTasks(b, server.getCatalogTracker(), true);
          // Should add it to OnlineRegions
          services.addToOnlineRegions(b);
          services.postOpenDeployTasks(a, server.getCatalogTracker(), true);
          services.addToOnlineRegions(a);
        } catch (KeeperException ke) {
          throw new IOException(ke);
        }
      }
    }
  }

 调用HRegion 打开方法openHRegion

  

  protected HRegion openHRegion(final CancelableProgressable reporter)
  throws IOException {
    checkCompressionCodecs();

    long seqid = initialize(reporter);
//初始化region，
//1.checkRegionInfoOnFilesystem将HRegionInfo写入文件
//2.cleanupTempDir 清空老region临时目录
//3.初始化HRegion store，加载hfile
//4.获得recover.edit文件，找到对应的store，将读取的keyvalue输出到store，恢复hregion
    if (this.log != null) {
      this.log.setSequenceNumber(seqid);
    }
    return this;
  }

        3.2.2若region 需要compact，进行compact过程

   compact过程有点复杂，过程如下：

1.将所有storefile放入compact候选者

2.交给coprocessor做处理，选择compact storefile

3.若coprocessor没有做处理，则采用系统算法选择

  3.1必须要进行compact的文件，文件大小大于compact最大值并且没有其他被引用

  3.2必须要进行compact文件小于compact文件最小数

  3.3 isMajorCompaction判断是否需要major compact

          3.3.1当ttl大于storefile中最大文件compact time，则不需要

          3.3.2 以上反之，需要

          3.3.3 最后一次major compaction时间大于majorCompactionTime，需要

  3.4 当compact文件大于compact文件最大数，且需要major compaction活强制major compaction，则进行major compaction

  3.5或则进行minor compact，他两个的区别在于一个compact文件数是所有并且删除就tts和version的数据，一个compact文件数不大于maxcompactfile配置

public CompactionRequest requestCompaction(int priority) throws IOException {
    // don't even select for compaction if writes are disabled
    if (!this.region.areWritesEnabled()) {
      return null;
    }

    CompactionRequest ret = null;
    this.lock.readLock().lock();
    try {
      synchronized (filesCompacting) {
        // candidates = all storefiles not already in compaction queue
        List<StoreFile> candidates = Lists.newArrayList(storefiles);
        if (!filesCompacting.isEmpty()) {
          // exclude all files older than the newest file we're currently
          // compacting. this allows us to preserve contiguity (HBASE-2856)
          StoreFile last = filesCompacting.get(filesCompacting.size() - 1);
          int idx = candidates.indexOf(last);
          Preconditions.checkArgument(idx != -1);
          candidates.subList(0, idx + 1).clear();
        }

        boolean override = false;
        if (region.getCoprocessorHost() != null) {
          override = region.getCoprocessorHost().preCompactSelection(
              this, candidates);
        }
        CompactSelection filesToCompact;
        if (override) {
          // coprocessor is overriding normal file selection
          filesToCompact = new CompactSelection(conf, candidates);
        } else {
          filesToCompact = compactSelection(candidates, priority);
        }

        if (region.getCoprocessorHost() != null) {
          region.getCoprocessorHost().postCompactSelection(this,
              ImmutableList.copyOf(filesToCompact.getFilesToCompact()));
        }

        // no files to compact
        if (filesToCompact.getFilesToCompact().isEmpty()) {
          return null;
        }

        // basic sanity check: do not try to compact the same StoreFile twice.
        if (!Collections.disjoint(filesCompacting, filesToCompact.getFilesToCompact())) {
          // TODO: change this from an IAE to LOG.error after sufficient testing
          Preconditions.checkArgument(false, "%s overlaps with %s",
              filesToCompact, filesCompacting);
        }
        filesCompacting.addAll(filesToCompact.getFilesToCompact());
        Collections.sort(filesCompacting, StoreFile.Comparators.FLUSH_TIME);

        // major compaction iff all StoreFiles are included
        boolean isMajor = (filesToCompact.getFilesToCompact().size() == this.storefiles.size());
        if (isMajor) {
          // since we're enqueuing a major, update the compaction wait interval
          this.forceMajor = false;
        }

        // everything went better than expected. create a compaction request
        int pri = getCompactPriority(priority);
        ret = new CompactionRequest(region, this, filesToCompact, isMajor, pri);
      }
    } finally {
      this.lock.readLock().unlock();
    }
    if (ret != null) {
      CompactionRequest.preRequest(ret);
    }
    return ret;
  }

在贴一段选compact文件的

public CompactionRequest selectCompaction(Collection<StoreFile> candidateFiles,
      final List<StoreFile> filesCompacting, final boolean isUserCompaction,
      final boolean mayUseOffPeak, final boolean forceMajor) throws IOException {
    // Preliminary compaction subject to filters
    ArrayList<StoreFile> candidateSelection = new ArrayList<StoreFile>(candidateFiles);
    // Stuck and not compacting enough (estimate). It is not guaranteed that we will be
    // able to compact more if stuck and compacting, because ratio policy excludes some
    // non-compacting files from consideration during compaction (see getCurrentEligibleFiles).
    int futureFiles = filesCompacting.isEmpty() ? 0 : 1;
    boolean mayBeStuck = (candidateFiles.size() - filesCompacting.size() + futureFiles)
        >= storeConfigInfo.getBlockingFileCount();
    candidateSelection = getCurrentEligibleFiles(candidateSelection, filesCompacting);
    LOG.debug("Selecting compaction from " + candidateFiles.size() + " store files, " +
        filesCompacting.size() + " compacting, " + candidateSelection.size() +
        " eligible, " + storeConfigInfo.getBlockingFileCount() + " blocking");

    long cfTtl = this.storeConfigInfo.getStoreFileTtl();
    if (!forceMajor) {
      // If there are expired files, only select them so that compaction deletes them
      if (comConf.shouldDeleteExpired() && (cfTtl != Long.MAX_VALUE)) {
        ArrayList<StoreFile> expiredSelection = selectExpiredStoreFiles(
            candidateSelection, EnvironmentEdgeManager.currentTimeMillis() - cfTtl);
        if (expiredSelection != null) {
          return new CompactionRequest(expiredSelection);
        }
      }
      candidateSelection = skipLargeFiles(candidateSelection);
    }

    // Force a major compaction if this is a user-requested major compaction,
    // or if we do not have too many files to compact and this was requested
    // as a major compaction.
    // Or, if there are any references among the candidates.
    boolean majorCompaction = (
      (forceMajor && isUserCompaction)
      || ((forceMajor || isMajorCompaction(candidateSelection))
          && (candidateSelection.size() < comConf.getMaxFilesToCompact()))
      || StoreUtils.hasReferences(candidateSelection)
      );

    if (!majorCompaction) {
      // we're doing a minor compaction, let's see what files are applicable
      candidateSelection = filterBulk(candidateSelection);
      candidateSelection = applyCompactionPolicy(candidateSelection, mayUseOffPeak, mayBeStuck);
      candidateSelection = checkMinFilesCriteria(candidateSelection);
    }
    candidateSelection = removeExcessFiles(candidateSelection, isUserCompaction, majorCompaction);
    CompactionRequest result = new CompactionRequest(candidateSelection);
    result.setOffPeak(!candidateSelection.isEmpty() && !majorCompaction && mayUseOffPeak);
    return result;
  }

  

        3.2.3HRegionServer添加子region到meta表，加入到RegionServer里

       更新meta表

        // If daughter of a split, update whole row, not just location.更新meta表 loaction和rowkey
        MetaEditor.addDaughter(ct, r.getRegionInfo(),
          this.serverNameFromMasterPOV);

      加入regionserver

 public void addToOnlineRegions(HRegion region) {
    this.onlineRegions.put(region.getRegionInfo().getEncodedName(), region);
  }

   3.3修改zk节点状态，等待split结束

/* package */void transitionZKNode(final Server server,
      final RegionServerServices services, HRegion a, HRegion b)
      throws IOException {
    // Tell master about split by updating zk.  If we fail, abort.
    if (server != null && server.getZooKeeper() != null) {
      try {
        this.znodeVersion = transitionNodeSplit(server.getZooKeeper(),
          parent.getRegionInfo(), a.getRegionInfo(), b.getRegionInfo(),
          server.getServerName(), this.znodeVersion);

        int spins = 0;
        // Now wait for the master to process the split. We know it's done
        // when the znode is deleted. The reason we keep tickling the znode is
        // that it's possible for the master to miss an event.
        do {
          if (spins % 10 == 0) {
            LOG.debug("Still waiting on the master to process the split for " +
                this.parent.getRegionInfo().getEncodedName());
          }
          Thread.sleep(100);
          // When this returns -1 it means the znode doesn't exist
          this.znodeVersion = tickleNodeSplit(server.getZooKeeper(),
            parent.getRegionInfo(), a.getRegionInfo(), b.getRegionInfo(),
            server.getServerName(), this.znodeVersion);
          spins++;
        } while (this.znodeVersion != -1 && !server.isStopped()
            && !services.isStopping());

结束了，有时间再看看compact过程，其实在split中已经包含compact的过程，不知道是不是所有的compact流程都一样