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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8547) Fix java.lang.RuntimeException: Cached an already cached block
Date Tue, 14 May 2013 18:15:16 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13657316#comment-13657316
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Enis Soztutar commented on HBASE-8547:
--------------------------------------

I am more in favor of (2), but we may also want to change the exception to be IOException
in 1, otherwise, this causes ipc handler to die, and scan returns partial results. Other suggestions
welcome. 
                
> Fix java.lang.RuntimeException: Cached an already cached block
> --------------------------------------------------------------
>
>                 Key: HBASE-8547
>                 URL: https://issues.apache.org/jira/browse/HBASE-8547
>             Project: HBase
>          Issue Type: Bug
>          Components: io, regionserver
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 0.98.0, 0.94.8, 0.95.1
>
>
> In one test, one of the region servers received the following on 0.94. 
> Note HalfStoreFileReader in the stack trace. I think the root cause is that after the
region is split, the mid point can be in the middle of the block (for store files that the
mid point is not chosen from). Each half store file tries to load the half block and put it
in the block cache. Since IdLock is instantiated per store file reader, they do not share
the same IdLock instance, thus does not lock against each other effectively. 
> {code}
> 2013-05-12 01:30:37,733 ERROR org.apache.hadoop.hbase.regionserver.HRegionServer:ยท
> java.lang.RuntimeException: Cached an already cached block
>   at org.apache.hadoop.hbase.io.hfile.LruBlockCache.cacheBlock(LruBlockCache.java:279)
>   at org.apache.hadoop.hbase.io.hfile.HFileReaderV2.readBlock(HFileReaderV2.java:353)
>   at org.apache.hadoop.hbase.io.hfile.HFileBlockIndex$BlockIndexReader.loadDataBlockWithScanInfo(HFileBlockIndex.java:254)
>   at org.apache.hadoop.hbase.io.hfile.HFileReaderV2$AbstractScannerV2.seekTo(HFileReaderV2.java:480)
>   at org.apache.hadoop.hbase.io.hfile.HFileReaderV2$AbstractScannerV2.seekTo(HFileReaderV2.java:501)
>   at org.apache.hadoop.hbase.io.HalfStoreFileReader$1.seekTo(HalfStoreFileReader.java:237)
>   at org.apache.hadoop.hbase.regionserver.StoreFileScanner.seekAtOrAfter(StoreFileScanner.java:226)
>   at org.apache.hadoop.hbase.regionserver.StoreFileScanner.seek(StoreFileScanner.java:145)
>   at org.apache.hadoop.hbase.regionserver.StoreFileScanner.enforceSeek(StoreFileScanner.java:351)
>   at org.apache.hadoop.hbase.regionserver.KeyValueHeap.pollRealKV(KeyValueHeap.java:354)
>   at org.apache.hadoop.hbase.regionserver.KeyValueHeap.generalizedSeek(KeyValueHeap.java:312)
>   at org.apache.hadoop.hbase.regionserver.KeyValueHeap.requestSeek(KeyValueHeap.java:277)
>   at org.apache.hadoop.hbase.regionserver.StoreScanner.reseek(StoreScanner.java:543)
>   at org.apache.hadoop.hbase.regionserver.StoreScanner.next(StoreScanner.java:411)
>   at org.apache.hadoop.hbase.regionserver.KeyValueHeap.next(KeyValueHeap.java:143)
>   at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.populateResult(HRegion.java:3829)
>   at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextInternal(HRegion.java:3896)
>   at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRaw(HRegion.java:3778)
>   at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRaw(HRegion.java:3770)
>   at org.apache.hadoop.hbase.regionserver.HRegionServer.next(HRegionServer.java:2643)
>   at sun.reflect.GeneratedMethodAccessor25.invoke(Unknown Source)
>   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
>   at java.lang.reflect.Method.invoke(Method.java:597)
>   at org.apache.hadoop.hbase.ipc.SecureRpcEngine$Server.call(SecureRpcEngine.java:308)
>   at org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1426)
> {code}
> I can see two possible fixes: 
>  # Allow this kind of rare cases in LruBlockCache by not throwing an exception. 
>  # Move the lock instances to upper layer (possibly in CacheConfig), and let half hfile
readers share the same IdLock implementation. 

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