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Re: Could not obtain block
El 3/9/2011 6:27 AM, Evert Lammerts escribi�:
> We see a lot of IOExceptions coming from HDFS during a job that does nothing but untar 100 files (1 per Mapper, sizes vary between 5GB and 80GB) that are in HDFS, to HDFS. DataNodes are also showing Exceptions that I think are related. (See stacktraces below.)
>
> This job should not be able to overload the system I think... I realize that much data needs to go over the lines, but HDFS should still be responsive. Any ideas / help is much appreciated!
>
> Some details:
> * Hadoop 0.20.2 (CDH3b4)
> * 5 node cluster plus 1 node for JT/NN (Sun Thumpers)
> * 4 cores/node, 4GB RAM/core
> * CentOS 5.5
>
> Job output:
>
> java.io.IOException: java.io.IOException: Could not obtain block: blk_-3695352030358969086_130839 file=/user/emeij/icwsm-data-test/01-26-SOCIAL_MEDIA.tar.gz
>    
Which is the ouput of:
   bin/hadoop dfsadmin -report

Which is the output of:
   bin/hadoop fsck /user/emeij/icwsm-data-test/
> at ilps.DownloadICWSM$UntarMapper.map(DownloadICWSM.java:449)
> at ilps.DownloadICWSM$UntarMapper.map(DownloadICWSM.java:1)
> at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50)
> at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:390)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:324)
> at org.apache.hadoop.mapred.Child$4.run(Child.java:240)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:396)
> at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1115)
> at org.apache.hadoop.mapred.Child.main(Child.java:234)
> Caused by: java.io.IOException: Could not obtain block: blk_-3695352030358969086_130839 file=/user/emeij/icwsm-data-test/01-26-SOCIAL_MEDIA.tar.gz
>    
Which is the ouput of:
  bin/hadoop fsck /user/emeij/icwsm-data-test/01-26-SOCIAL_MEDIA.tar.gz
--files -blocks -racks
> at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.chooseDataNode(DFSClient.java:1977)
> at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.blockSeekTo(DFSClient.java:1784)
> at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.read(DFSClient.java:1932)
> at java.io.DataInputStream.read(DataInputStream.java:83)
> at org.apache.hadoop.io.IOUtils.copyBytes(IOUtils.java:55)
> at org.apache.hadoop.io.IOUtils.copyBytes(IOUtils.java:74)
> at org.apache.hadoop.fs.FileUtil.copy(FileUtil.java:335)
> at ilps.DownloadICWSM$CopyThread.run(DownloadICWSM.java:149)
>
>
> Example DataNode Exceptions (not that these come from the node at 192.168.28.211):
>
> 2011-03-08 19:40:40,297 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Exception in receiveBlock for block blk_-9222067946733189014_3798233 java.io.EOFException: while trying to read 3067064 bytes
> 2011-03-08 19:40:41,018 INFO org.apache.hadoop.hdfs.server.datanode.DataNode.clienttrace: src: /192.168.28.211:50050, dest: /192.168.28.211:49748, bytes: 0, op: HDFS_READ, cliID: DFSClient_attempt_201103071120_0030_m_000032_0, offset: 30
> 72, srvID: DS-568746059-145.100.2.180-50050-1291128670510, blockid: blk_3596618013242149887_4060598, duration: 2632000
> 2011-03-08 19:40:41,049 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Exception in receiveBlock for block blk_-9221028436071074510_2325937 java.io.EOFException: while trying to read 2206400 bytes
> 2011-03-08 19:40:41,348 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Exception in receiveBlock for block blk_-9221549395563181322_4024529 java.io.EOFException: while trying to read 3037288 bytes
> 2011-03-08 19:40:41,357 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Exception in receiveBlock for block blk_-9221885906633018147_3895876 java.io.EOFException: while trying to read 1981952 bytes
> 2011-03-08 19:40:41,434 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: Block blk_-9221885906633018147_3895876 unfinalized and removed.
> 2011-03-08 19:40:41,434 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: writeBlock blk_-9221885906633018147_3895876 received exception java.io.EOFException: while trying to read 1981952 bytes

Then on the DataNode where you have the particular block
(blk_-3695352030358969086_130839 )
you can visit the web interface
http://192.168.28.211:50075/blockScannerReport to see what's happening
on the node

Regards

Marcos Lu�s Ort�z Valmaseda
  Software Engineer
  Universidad de las Ciencias Inform�ticas
  Linux User # 418229

http://uncubanitolinuxero.blogspot.com
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