[moving to common-user, since this spans both MR and HDFS - probably easier than cross-posting]
Can you check the DN logs for "exceeds the limit of concurrent xcievers"? You may need to bump the dfs.datanode.max.xcievers parameter in hdfs-site.xml, and also possibly the nfiles ulimit. -Todd On Wed, Mar 9, 2011 at 3:27 AM, Evert Lammerts <evert.lamme...@sara.nl> wrote: > 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 > 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$4.run(Child.java:240) > at java.security.AccessController.doPrivileged(Native Method) > at javax.security.auth.Subject.doAs(Subject.java:396) > at > org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1115) > at org.apache.hadoop.mapred.Child.main(Child.java:234) > Caused by: java.io.IOException: Could not obtain block: > blk_-3695352030358969086_130839 > file=/user/emeij/icwsm-data-test/01-26-SOCIAL_MEDIA.tar.gz > at > org.apache.hadoop.hdfs.DFSClient$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 > 2011-03-08 19:40:41,434 ERROR > org.apache.hadoop.hdfs.server.datanode.DataNode: > DatanodeRegistration(192.168.28.211:50050, > storageID=DS-568746059-145.100.2.180-50050-1291128670510, infoPort=50075, > ipcPort=50020):DataXceiver > java.io.EOFException: while trying to read 1981952 bytes > at > org.apache.hadoop.hdfs.server.datanode.BlockReceiver.readToBuf(BlockReceiver.java:270) > at > org.apache.hadoop.hdfs.server.datanode.BlockReceiver.readNextPacket(BlockReceiver.java:357) > at > org.apache.hadoop.hdfs.server.datanode.BlockReceiver.receivePacket(BlockReceiver.java:378) > at > org.apache.hadoop.hdfs.server.datanode.BlockReceiver.receiveBlock(BlockReceiver.java:534) > at > org.apache.hadoop.hdfs.server.datanode.DataXceiver.writeBlock(DataXceiver.java:417) > at > org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:122) > 2011-03-08 19:40:41,465 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: > Block blk_-9221549395563181322_4024529 unfinalized and removed. > 2011-03-08 19:40:41,466 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: > writeBlock blk_-9221549395563181322_4024529 received exception > java.io.EOFException: while trying to read 3037288 bytes > 2011-03-08 19:40:41,466 ERROR > org.apache.hadoop.hdfs.server.datanode.DataNode: > DatanodeRegistration(192.168.28.211:50050, > storageID=DS-568746059-145.100.2.180-50050-1291128670510, infoPort=50075, > ipcPort=50020):DataXceiver > java.io.EOFException: while trying to read 3037288 bytes > at > org.apache.hadoop.hdfs.server.datanode.BlockReceiver.readToBuf(BlockReceiver.java:270) > at > org.apache.hadoop.hdfs.server.datanode.BlockReceiver.readNextPacket(BlockReceiver.java:357) > at > org.apache.hadoop.hdfs.server.datanode.BlockReceiver.receivePacket(BlockReceiver.java:378) > at > org.apache.hadoop.hdfs.server.datanode.BlockReceiver.receiveBlock(BlockReceiver.java:534) > at > org.apache.hadoop.hdfs.server.datanode.DataXceiver.writeBlock(DataXceiver.java:417) > at > org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:122) > > Cheers, > > Evert Lammerts > Consultant eScience & Cloud Services > SARA Computing & Network Services > Operations, Support & Development > > Phone: +31 20 888 4101 > Email: evert.lamme...@sara.nl > http://www.sara.nl > > > -- Todd Lipcon Software Engineer, Cloudera
