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  1. HBase
  2. HBASE-23044

CatalogJanitor#cleanMergeQualifier may clean wrong parent regions



    • Type: Improvement
    • Status: Resolved
    • Priority: Critical
    • Resolution: Fixed
    • Affects Version/s: 2.0.6, 2.2.1, 2.1.6
    • Fix Version/s: 3.0.0-alpha-1, 2.3.0, 2.1.7, 2.2.2
    • Component/s: None
    • Labels:


      2019-09-17,19:42:40,539 INFO [PEWorker-1] org.apache.hadoop.hbase.procedure2.ProcedureExecutor: Finished pid=1223589, state=SUCCESS; GCMultipleMergedRegionsProcedure child=647600d28633bb2fe06b40682bab0593, parents:[81b6fc3c560a00692bc7c3cd266a626a], [472500358997b0dc8f0002ec86593dcf] in 2.6470sec
      2019-09-17,19:59:54,179 INFO [PEWorker-6] org.apache.hadoop.hbase.procedure2.ProcedureExecutor: Finished pid=1223651, state=SUCCESS; GCMultipleMergedRegionsProcedure child=647600d28633bb2fe06b40682bab0593, parents:[9c52f24e0a9cc9b4959c1ebdfea29d64], [a623f298870df5581bcfae7f83311b33] in 1.0340sec

      The child is same region 647600d28633bb2fe06b40682bab0593 but the parent regions are different.

      MergeTableRegionProcedure#prepareMergeRegion will try to cleanMergeQualifier for the regions to merge.

      for (RegionInfo ri: this.regionsToMerge) {
            if (!catalogJanitor.cleanMergeQualifier(ri)) {
              String msg = "Skip merging " + RegionInfo.getShortNameToLog(regionsToMerge) +
                  ", because parent " + RegionInfo.getShortNameToLog(ri) + " has a merge qualifier";
              throw new MergeRegionException(msg);

      If region A and B merge to C, region D and E merge to F. When merge C and F, it will try to cleanMergeQualifier for C and F. catalogJanitor.cleanMergeQualifier for region C succeed but catalogJanitor.cleanMergeQualifier for region F failed as there are references in region F.
      When merge C and F again, it will try to cleanMergeQualifier for C and F again. But MetaTableAccessor.getMergeRegions will get wrong parents now. It use scan with filter to scan result. But region C's MergeQualifier already was deleted before. Then the scan will return a wrong result, may be anther region......

      public boolean cleanMergeQualifier(final RegionInfo region) throws IOException {
          // Get merge regions if it is a merged region and already has merge qualifier
          List<RegionInfo> parents = MetaTableAccessor.getMergeRegions(this.services.getConnection(),
          if (parents == null || parents.isEmpty()) {
            // It doesn't have merge qualifier, no need to clean
            return true;
          return cleanMergeRegion(region, parents);
      public static List<RegionInfo> getMergeRegions(Connection connection, byte[] regionName)
            throws IOException {
          return getMergeRegions(getMergeRegionsRaw(connection, regionName));
      private static Cell [] getMergeRegionsRaw(Connection connection, byte [] regionName)
            throws IOException {
          Scan scan = new Scan().withStartRow(regionName).
              setFilter(new QualifierFilter(CompareOperator.EQUAL,
                new RegexStringComparator(HConstants.MERGE_QUALIFIER_PREFIX_STR+ ".*")));
          try (Table m = getMetaHTable(connection); ResultScanner scanner = m.getScanner(scan)) {
            // Should be only one result in this scanner if any.
            Result result = scanner.next();
            if (result == null) {
              return null;
            // Should be safe to just return all Cells found since we had filter in place.
            // All values should be RegionInfos or something wrong.
            return result.rawCells();


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              • Assignee:
                zghao Guanghao Zhang
                zghao Guanghao Zhang
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                • Created: