[jira] [Resolved] (HBASE-23044) CatalogJanitor#cleanMergeQualifier may clean wrong parent regions

["Guanghao Zhang (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-23044?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Guanghao Zhang resolved HBASE-23044.
------------------------------------
    Fix Version/s: 2.2.2
                   2.1.7
                   2.3.0
                   3.0.0
       Resolution: Fixed

> CatalogJanitor#cleanMergeQualifier may clean wrong parent regions
> -----------------------------------------------------------------
>
>                 Key: HBASE-23044
>                 URL: https://issues.apache.org/jira/browse/HBASE-23044
>             Project: HBase
>          Issue Type: Improvement
>    Affects Versions: 2.0.6, 2.2.1, 2.1.6
>            Reporter: Guanghao Zhang
>            Assignee: Guanghao Zhang
>            Priority: Critical
>             Fix For: 3.0.0, 2.3.0, 2.1.7, 2.2.2
>
>
> 2019-09-17,19:42:40,539 INFO [PEWorker-1] org.apache.hadoop.hbase.procedure2.ProcedureExecutor: Finished pid=1223589, state=SUCCESS; GCMultipleMergedRegionsProcedure child={color:red}647600d28633bb2fe06b40682bab0593{color}, 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={color:red}647600d28633bb2fe06b40682bab0593{color}, parents:[9c52f24e0a9cc9b4959c1ebdfea29d64], [a623f298870df5581bcfae7f83311b33] in 1.0340sec
> The child is same region {color:red}647600d28633bb2fe06b40682bab0593{color} but the parent regions are different.
> MergeTableRegionProcedure#prepareMergeRegion will try to cleanMergeQualifier for the regions to merge.
> {code:java}
> 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";
>         LOG.warn(msg);
>         throw new MergeRegionException(msg);
>       }
> {code}
> 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......
> {code:java}
> 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(),
>         region.getRegionName());
>     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).
>         setOneRowLimit().
>         readVersions(1).
>         addFamily(HConstants.CATALOG_FAMILY).
>         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();
>     }
>   }
> {code}



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