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https://issues.apache.org/jira/browse/HBASE-8143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13606109#comment-13606109
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Enis Soztutar commented on HBASE-8143:
--------------------------------------
bq. if you did not set MaxDirectMemorySize option explicitly, then it will be
equal to -Xmx, that means -XX:MaxDirectMemorySize == -Xmx == 3g for Enis's case.
In this case, I was not even aware of Hdfs 2 allocating direct memory. I did
not spend a lot of time on the hadoop 2 code base.
bq. In BlockReaderLocal the short circuit buffer size is configurable with
"dfs.client.read.shortcircuit.buffer.size". It does default to 1MB, so
something does not quite add up
Let me check that code path to understand who is using that parameter and how.
> 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
>
>
> 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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