Liang Xie created HBASE-12767: --------------------------------- Summary: 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
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 next 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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)