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)
