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https://issues.apache.org/jira/browse/HBASE-12767?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Liang Xie updated HBASE-12767:
------------------------------
Status: Patch Available (was: Open)
> Fix a StoreFileScanner NPE in reverse scan flow
> -----------------------------------------------
>
> Key: HBASE-12767
> URL: https://issues.apache.org/jira/browse/HBASE-12767
> Project: HBase
> Issue Type: Bug
> Components: regionserver, Scanners
> Affects Versions: 0.98.9, 1.0.0, 2.0.0
> Reporter: Liang Xie
> Assignee: Liang Xie
> Attachments: HBASE-12767.txt
>
>
> we observed a NPE in our internal 0.94 branch prd env:
> ERROR org.apache.hadoop.hbase.regionserver.HRegionServer: Failed openScanner
> java.lang.NullPointerException
> at
> org.apache.hadoop.hbase.regionserver.StoreFileScanner.seekToPreviousRow(StoreFileScanner.java:409)
> at
> org.apache.hadoop.hbase.regionserver.StoreFileScanner.backwardSeek(StoreFileScanner.java:467)
> at
> org.apache.hadoop.hbase.regionserver.ReversedStoreScanner.seekScanners(ReversedStoreScanner.java:78)
> at
> org.apache.hadoop.hbase.regionserver.StoreScanner.<init>(StoreScanner.java:154)
> at
> org.apache.hadoop.hbase.regionserver.ReversedStoreScanner.<init>(ReversedStoreScanner.java:49)
> at org.apache.hadoop.hbase.regionserver.Store.getScanner(Store.java:2216)
> at
> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.<init>(HRegion.java:3984)
> at
> org.apache.hadoop.hbase.regionserver.ReversedRegionScannerImpl.<init>(ReversedRegionScannerImpl.java:43)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.instantiateRegionScanner(HRegion.java:1851)
> at org.apache.hadoop.hbase.regionserver.HRegion.getScanner(HRegion.java:1837)
> at org.apache.hadoop.hbase.regionserver.HRegion.getScanner(HRegion.java:1812)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.internalOpenScanner(HRegionServer.java:2752)
> at
> org.apache.hadoop.hbase.regionserver.HRegionServer.openScanner(HRegionServer.java:2715)
> After tracing, it turned out a boundary bug at HalfStoreFileReader. If we
> have a reverse scan request at "bottom" part, once the start row >= the last
> row at bottom part, the NPE will be encourtered, since we will invoke
> "next()", and "atEnd = true" will be called in HalfStoreFileReader, then when
> we want to do "seekBefore" or other sth in StoreFileScanner,
> StoreFileScanner.cur will call:
> {code}
> public Cell getKeyValue() {
> if (atEnd) return null;
> {code}
> The fix is simple, we need to reset the "atEnd" flag once seekBefore op is
> successful. You can undo my HalfStoreFileReader change and run the new added
> case to see NPE.
> ps: I also found some cases in TestHRegion missing the "@Test" annotation, so
> fix them in the same patch as well.
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