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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8143) HBase on Hadoop 2 with local short circuit reads (ssr) causes OOM
Date Fri, 22 Mar 2013 01:09:17 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13609767#comment-13609767
] 

Lars Hofhansl commented on HBASE-8143:
--------------------------------------

It is as much an HBase issue as we should have clear recommendations as to how HDFS should
be configured.
An interesting test would be how HBase would perform if we made the buffer much smaller (like
64k, which should suffice). 
                
> HBase on Hadoop 2 with local short circuit reads (ssr) causes OOM 
> ------------------------------------------------------------------
>
>                 Key: HBASE-8143
>                 URL: https://issues.apache.org/jira/browse/HBASE-8143
>             Project: HBase
>          Issue Type: Bug
>          Components: hadoop2
>    Affects Versions: 0.95.0, 0.98.0, 0.94.7
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 0.95.0, 0.98.0, 0.94.7
>
>         Attachments: OpenFileTest.java
>
>
> We've run into an issue with HBase 0.94 on Hadoop2, with SSR turned on that the memory
usage of the HBase process grows to 7g, on an -Xmx3g, after some time, this causes OOM for
the RSs. 
> Upon further investigation, I've found out that we end up with 200 regions, each having
3-4 store files open. Under hadoop2 SSR, BlockReaderLocal allocates DirectBuffers, which is
unlike HDFS 1 where there is no direct buffer allocation. 
> It seems that there is no guards against the memory used by local buffers in hdfs 2,
and having a large number of open files causes multiple GB of memory to be consumed from the
RS process. 
> This issue is to further investigate what is going on. Whether we can limit the memory
usage in HDFS, or HBase, and/or document the setup. 
> Possible mitigation scenarios are: 
>  - Turn off SSR for Hadoop 2
>  - Ensure that there is enough unallocated memory for the RS based on expected # of store
files
>  - Ensure that there is lower number of regions per region server (hence number of open
files)
> Stack trace:
> {code}
> org.apache.hadoop.hbase.DroppedSnapshotException: region: IntegrationTestLoadAndVerify,yC^P\xD7\x945\xD4,1363388517630.24655343d8d356ef708732f34cfe8946.
>         at org.apache.hadoop.hbase.regionserver.HRegion.internalFlushcache(HRegion.java:1560)
>         at org.apache.hadoop.hbase.regionserver.HRegion.internalFlushcache(HRegion.java:1439)
>         at org.apache.hadoop.hbase.regionserver.HRegion.flushcache(HRegion.java:1380)
>         at org.apache.hadoop.hbase.regionserver.MemStoreFlusher.flushRegion(MemStoreFlusher.java:449)
>         at org.apache.hadoop.hbase.regionserver.MemStoreFlusher.flushOneForGlobalPressure(MemStoreFlusher.java:215)
>         at org.apache.hadoop.hbase.regionserver.MemStoreFlusher.access$500(MemStoreFlusher.java:63)
>         at org.apache.hadoop.hbase.regionserver.MemStoreFlusher$FlushHandler.run(MemStoreFlusher.java:237)
>         at java.lang.Thread.run(Thread.java:662)
> Caused by: java.lang.OutOfMemoryError: Direct buffer memory
>         at java.nio.Bits.reserveMemory(Bits.java:632)
>         at java.nio.DirectByteBuffer.<init>(DirectByteBuffer.java:97)
>         at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:288)
>         at org.apache.hadoop.hdfs.util.DirectBufferPool.getBuffer(DirectBufferPool.java:70)
>         at org.apache.hadoop.hdfs.BlockReaderLocal.<init>(BlockReaderLocal.java:315)
>         at org.apache.hadoop.hdfs.BlockReaderLocal.newBlockReader(BlockReaderLocal.java:208)
>         at org.apache.hadoop.hdfs.DFSClient.getLocalBlockReader(DFSClient.java:790)
>         at org.apache.hadoop.hdfs.DFSInputStream.getBlockReader(DFSInputStream.java:888)
>         at org.apache.hadoop.hdfs.DFSInputStream.blockSeekTo(DFSInputStream.java:455)
>         at org.apache.hadoop.hdfs.DFSInputStream.readWithStrategy(DFSInputStream.java:645)
>         at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:689)
>         at java.io.DataInputStream.readFully(DataInputStream.java:178)
>         at org.apache.hadoop.hbase.io.hfile.FixedFileTrailer.readFromStream(FixedFileTrailer.java:312)
>         at org.apache.hadoop.hbase.io.hfile.HFile.pickReaderVersion(HFile.java:543)
>         at org.apache.hadoop.hbase.io.hfile.HFile.createReaderWithEncoding(HFile.java:589)
>         at org.apache.hadoop.hbase.regionserver.StoreFile$Reader.<init>(StoreFile.java:1261)
>         at org.apache.hadoop.hbase.regionserver.StoreFile.open(StoreFile.java:512)
>         at org.apache.hadoop.hbase.regionserver.StoreFile.createReader(StoreFile.java:603)
>         at org.apache.hadoop.hbase.regionserver.Store.validateStoreFile(Store.java:1568)
>         at org.apache.hadoop.hbase.regionserver.Store.commitFile(Store.java:845)
>         at org.apache.hadoop.hbase.regionserver.Store.access$500(Store.java:109)
>         at org.apache.hadoop.hbase.regionserver.Store$StoreFlusherImpl.commit(Store.java:2209)
>         at org.apache.hadoop.hbase.regionserver.HRegion.internalFlushcache(HRegion.java:1541)
> {code}

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