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https://issues.apache.org/jira/browse/HBASE-18221?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ramkrishna.s.vasudevan updated HBASE-18221:
-------------------------------------------
    Attachment: HBASE-18221_2.patch

The patch with the fix that solves the problem. 
Adds recreateScanners() API in Store. It will acquire the HStore's reentrant 
lock while creating the scanners. 
One question is that given the fact we are now trying to avoid unnecessary APIs 
from the LimitedPrivate interfaces this method could add on to that. But as 
part of clean up this should also be taken into account.

> Switch from pread to stream should happen under HStore's reentrant lock
> -----------------------------------------------------------------------
>
>                 Key: HBASE-18221
>                 URL: https://issues.apache.org/jira/browse/HBASE-18221
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Scanners
>    Affects Versions: 2.0.0, 3.0.0, 2.0.0-alpha-1
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 2.0.0, 3.0.0, 2.0.0-alpha-2
>
>         Attachments: HBASE-18221_2_fortestcasefailure.patch, 
> HBASE-18221_2.patch
>
>
> Found this while debugging HBASE-18186. When we try to reopen the scanners on 
> the storefiles while trying to switch over from pread to stream, we do not 
> use the HStore's reentrant lock to get the current Storefiles from the 
> StoreFileManager. All the scan APIs are guarded under that and we must do it 
> here also other wise the CompactedHfileDischarger may cause race issues with 
> the HStore's datastructures like here
> {code}
> 2017-06-14 18:16:17,223 WARN  
> [RpcServer.default.FPBQ.Fifo.handler=23,queue=1,port=16020] 
> regionserver.StoreScanner: failed to switch to stream read
> java.lang.NullPointerException
>         at 
> org.apache.hadoop.hbase.regionserver.StoreFileScanner.getScannersForStoreFiles(StoreFileScanner.java:133)
>         at 
> org.apache.hadoop.hbase.regionserver.HStore.getScanners(HStore.java:1221)
>         at 
> org.apache.hadoop.hbase.regionserver.StoreScanner.trySwitchToStreamRead(StoreScanner.java:997)
>         at 
> org.apache.hadoop.hbase.regionserver.StoreScanner.shipped(StoreScanner.java:1134)
>         at 
> org.apache.hadoop.hbase.regionserver.KeyValueHeap.shipped(KeyValueHeap.java:445)
>         at 
> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.shipped(HRegion.java:6459)
>         at 
> org.apache.hadoop.hbase.regionserver.RSRpcServices$RegionScannerShippedCallBack.run(RSRpcServices.java:339)
>         at 
> org.apache.hadoop.hbase.ipc.ServerCall.setResponse(ServerCall.java:252)
>         at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:166)
>         at 
> org.apache.hadoop.hbase.ipc.RpcExecutor$Handler.run(RpcExecutor.java:278)
>         at 
> org.apache.hadoop.hbase.ipc.RpcExecutor$Handler.run(RpcExecutor.java:258)
> {code}
> I have a working patch fixing this problem. Will do some more testing and try 
> to upload the patch after I write a test case for this. 



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