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Date: Fri, 19 Jun 2009 10:08:07 -0700 (PDT)
From: "Ravi Gummadi (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-6072) distcp should place the file
 distcp_src_files in distributed cache
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    [ https://issues.apache.org/jira/browse/HADOOP-6072?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12721883#action_12721883 ] 

Ravi Gummadi commented on HADOOP-6072:
--------------------------------------

Doug,   Would it be better if distcp sets dfs.client.max.block.acquire.failures to sqrt(maxMapsOnCluster) as DFSClient.DFSInputStream.chooseDataNode() compares number of failures with this config property(default value of 3) ? But we need that only for this file _distcp_src_files.

> distcp should place the file distcp_src_files in distributed cache
> ------------------------------------------------------------------
>
>                 Key: HADOOP-6072
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6072
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: tools/distcp
>    Affects Versions: 0.21.0
>            Reporter: Ravi Gummadi
>            Assignee: Ravi Gummadi
>             Fix For: 0.21.0
>
>         Attachments: d_replica_srcfilelist.patch
>
>
> When large number of files are being copied by distcp, accessing distcp_src_files seems to be an issue, as all map tasks would be accessing this file. The error message seen is:
> 09/06/16 10:13:16 INFO mapred.JobClient: Task Id : attempt_200906040559_0110_m_003348_0, Status : FAILED
> java.io.IOException: Could not obtain block: blk_-4229860619941366534_1500174
> file=/mapredsystem/hadoop/mapredsystem/distcp_7fiyvq/_distcp_src_files
>         at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.chooseDataNode(DFSClient.java:1757)
>         at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.blockSeekTo(DFSClient.java:1585)
>         at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.read(DFSClient.java:1712)
>         at java.io.DataInputStream.readFully(DataInputStream.java:178)
>         at java.io.DataInputStream.readFully(DataInputStream.java:152)
>         at org.apache.hadoop.io.SequenceFile$Reader.init(SequenceFile.java:1450)
>         at org.apache.hadoop.io.SequenceFile$Reader.<init>(SequenceFile.java:1428)
>         at org.apache.hadoop.io.SequenceFile$Reader.<init>(SequenceFile.java:1417)
>         at org.apache.hadoop.io.SequenceFile$Reader.<init>(SequenceFile.java:1412)
>         at org.apache.hadoop.mapred.SequenceFileRecordReader.<init>(SequenceFileRecordReader.java:43)
>         at org.apache.hadoop.tools.DistCp$CopyInputFormat.getRecordReader(DistCp.java:299)
>         at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:336)
>         at org.apache.hadoop.mapred.MapTask.run(MapTask.java:305)
>         at org.apache.hadoop.mapred.Child.main(Child.java:170)
> This could be because of HADOOP-6038 and/or HADOOP-4681.
> If distcp places this special file distcp_src_files in distributed cache, that could solve the problem.

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