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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-8547) Fix java.lang.RuntimeException: Cached an already cached block
Date Tue, 14 May 2013 21:55:16 GMT

     [ https://issues.apache.org/jira/browse/HBASE-8547?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Enis Soztutar updated HBASE-8547:

    Attachment: hbase-8547_v1-0.94.patch

Attaching a patch against 0.94, which: 
 - Moves idLocks at the CacheConfig layer. We do ref counting for open hfiles. CacheConfig
is not the ideal place, but I could not find a better one. We cannot put it in BlockCache
because even with BC disabled, we want to lock the block readers. 
 - Changes reader v1 and v2 to obtain an IdLock instance. 
 - Replaces synchronization on blockKey byte[]'s with acquiring id locks. 
 - LruBlockCache does not throw exception on double caching. 
Trunk patch coming up. 
> 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
>         Attachments: hbase-8547_v1-0.94.patch
> 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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