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Qiang Tian commented on HBASE-12274: ------------------------------------ Hi Ted, is it worth to find who close the scanner(is it possible to close it due to bug)? I asked this because I have the same question for StoreScanner, it looks only itself can call close. Regarding synchronized, I did not test it myself, synchronized method cost may be big, but googled synchronized block is fine, even better than lock. > Race between RegionScannerImpl#nextInternal() and RegionScannerImpl#close() > may produce null pointer exception > -------------------------------------------------------------------------------------------------------------- > > Key: HBASE-12274 > URL: https://issues.apache.org/jira/browse/HBASE-12274 > Project: HBase > Issue Type: Bug > Affects Versions: 0.98.6.1 > Reporter: Ted Yu > Assignee: Ted Yu > Fix For: 2.0.0, 0.98.8, 0.99.2 > > Attachments: 12274-v2.txt, 12274-v2.txt, 12274-v3.txt > > > I saw the following in region server log: > {code} > 2014-10-15 03:28:36,976 ERROR > [B.DefaultRpcServer.handler=0,queue=0,port=60020] ipc.RpcServer: Unexpected > throwable object > java.lang.NullPointerException > at > org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextInternal(HRegion.java:5023) > at > org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRaw(HRegion.java:4932) > at > org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRaw(HRegion.java:4923) > at > org.apache.hadoop.hbase.regionserver.HRegionServer.scan(HRegionServer.java:3245) > at > org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:29994) > at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2078) > at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:108) > at > org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:114) > at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:94) > at java.lang.Thread.run(Thread.java:745) > {code} > This is where the NPE happened: > {code} > // Let's see what we have in the storeHeap. > KeyValue current = this.storeHeap.peek(); > {code} > The cause was race between nextInternal(called through nextRaw) and close > methods. > nextRaw() is not synchronized. -- This message was sent by Atlassian JIRA (v6.3.4#6332)