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Date: Mon, 15 Jun 2009 18:22:07 -0700 (PDT)
From: "stack (JIRA)" <jira@apache.org>
To: hbase-dev@hadoop.apache.org
Subject: [jira] Commented: (HBASE-1207) Fix locking in memcache flush
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    [ https://issues.apache.org/jira/browse/HBASE-1207?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12719890#action_12719890 ] 

stack commented on HBASE-1207:
------------------------------

#3 above is not exactly true.  Can actually read in a block.  Let me see what it would take to do another Ben suggested optimization; i.e. reuse scanners we already have open.

> Fix locking in memcache flush
> -----------------------------
>
>                 Key: HBASE-1207
>                 URL: https://issues.apache.org/jira/browse/HBASE-1207
>             Project: Hadoop HBase
>          Issue Type: Bug
>    Affects Versions: 0.19.0
>            Reporter: Ben Maurer
>            Assignee: Jonathan Gray
>             Fix For: 0.20.0
>
>
> memcache flushing holds a write lock while it reopens StoreFileScanners. I had a case where this process timed out and caused an exception to be thrown, which made the region server believe it had been unable to flush it's cache and shut itself down.
> Stack trace is:
> #
> "regionserver/0:0:0:0:0:0:0:0:60020.cacheFlusher" daemon prio=10 tid=0x00000000562df400 nid=0x15d1 runnable [0x000000004108b000..0x000000004108bd90]
> #
>    java.lang.Thread.State: RUNNABLE
> #
>         at java.util.zip.CRC32.updateBytes(Native Method)
> #
>         at java.util.zip.CRC32.update(CRC32.java:45)
> #
>         at org.apache.hadoop.util.DataChecksum.update(DataChecksum.java:223)
> #
>         at org.apache.hadoop.fs.FSInputChecker.readChecksumChunk(FSInputChecker.java:241)
> #
>         at org.apache.hadoop.fs.FSInputChecker.fill(FSInputChecker.java:177)
> #
>         at org.apache.hadoop.fs.FSInputChecker.read1(FSInputChecker.java:194)
> #
>         at org.apache.hadoop.fs.FSInputChecker.read(FSInputChecker.java:159)
> #
>         - locked <0x00002aaaec1bd2d8> (a org.apache.hadoop.hdfs.DFSClient$BlockReader)
> #
>         at org.apache.hadoop.hdfs.DFSClient$BlockReader.read(DFSClient.java:1061)
> #
>         - locked <0x00002aaaec1bd2d8> (a org.apache.hadoop.hdfs.DFSClient$BlockReader)
> #
>         at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.readBuffer(DFSClient.java:1616)
> #
>         - locked <0x00002aaad1239000> (a org.apache.hadoop.hdfs.DFSClient$DFSInputStream)
> #
>         at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.read(DFSClient.java:1666)
> #
>         - locked <0x00002aaad1239000> (a org.apache.hadoop.hdfs.DFSClient$DFSInputStream)
> #
>         at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.read(DFSClient.java:1593)
> #
>         - locked <0x00002aaad1239000> (a org.apache.hadoop.hdfs.DFSClient$DFSInputStream)
> #
>         at java.io.DataInputStream.readInt(DataInputStream.java:371)
> #
>         at org.apache.hadoop.hbase.io.SequenceFile$Reader.next(SequenceFile.java:1943)
> #
>         - locked <0x00002aaad1238c38> (a org.apache.hadoop.hbase.io.SequenceFile$Reader)
> #
>         at org.apache.hadoop.hbase.io.SequenceFile$Reader.next(SequenceFile.java:1844)
> #
>         - locked <0x00002aaad1238c38> (a org.apache.hadoop.hbase.io.SequenceFile$Reader)
> #
>         at org.apache.hadoop.hbase.io.SequenceFile$Reader.next(SequenceFile.java:1890)
> #
>         - locked <0x00002aaad1238c38> (a org.apache.hadoop.hbase.io.SequenceFile$Reader)
> #
>         at org.apache.hadoop.hbase.io.MapFile$Reader.next(MapFile.java:525)
> #
>         - locked <0x00002aaad1238b80> (a org.apache.hadoop.hbase.io.HalfMapFileReader)
> #
>         at org.apache.hadoop.hbase.io.HalfMapFileReader.next(HalfMapFileReader.java:192)
> #
>         - locked <0x00002aaad1238b80> (a org.apache.hadoop.hbase.io.HalfMapFileReader)
> #
>         at org.apache.hadoop.hbase.regionserver.StoreFileScanner.getNext(StoreFileScanner.java:312)
> #
>         at org.apache.hadoop.hbase.regionserver.StoreFileScanner.openReaders(StoreFileScanner.java:110)
> #
>         at org.apache.hadoop.hbase.regionserver.StoreFileScanner.updateReaders(StoreFileScanner.java:378)
> #
>         at org.apache.hadoop.hbase.regionserver.HStore.notifyChangedReadersObservers(HStore.java:737)
> #
>         at org.apache.hadoop.hbase.regionserver.HStore.updateReaders(HStore.java:725)
> #
>         at org.apache.hadoop.hbase.regionserver.HStore.internalFlushCache(HStore.java:694)
> #
>         - locked <0x00002aaab7b41d30> (a java.lang.Integer)
> #
>         at org.apache.hadoop.hbase.regionserver.HStore.flushCache(HStore.java:630)
> #
>         at org.apache.hadoop.hbase.regionserver.HRegion.internalFlushcache(HRegion.java:881)
> #
>         at org.apache.hadoop.hbase.regionserver.HRegion.flushcache(HRegion.java:789)
> #
>         at org.apache.hadoop.hbase.regionserver.MemcacheFlusher.flushRegion(MemcacheFlusher.java:227)
> #
>         at org.apache.hadoop.hbase.regionserver.MemcacheFlusher.run(MemcacheFlusher.java:137)

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