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From "Koji Noguchi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3859) 1000 concurrent read on a single file failing the task/client
Date Wed, 30 Jul 2008 01:45:31 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3859?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12618035#action_12618035
] 

Koji Noguchi commented on HADOOP-3859:
--------------------------------------

For this user, it happened when running on 200 nodes with 6 map slots per node.

Using distributedCache or increasing the replication would fix it, but problem still remains
if we have a larger mapred cluster.

> 1000  concurrent read on a single file failing  the task/client
> ---------------------------------------------------------------
>
>                 Key: HADOOP-3859
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3859
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.17.1
>         Environment: 0.17.2 (0.17.1-H3002-H3633-H3681-H3685-H3370-H3707-H3760-H3758)
>            Reporter: Koji Noguchi
>
> After fixing Hadoop-3633, some users started seeing their tasks fail with 
> {noformat}
> 08/07/29 05:13:07 INFO mapred.JobClient: Task Id : task_200807290511_0001_m_000846_0,
Status : FAILED
> java.io.IOException: Could not obtain block: blk_-7893038518783920880 file=/tmp/files111
>         at org.apache.hadoop.dfs.DFSClient$DFSInputStream.chooseDataNode(DFSClient.java:1430)
>         at org.apache.hadoop.dfs.DFSClient$DFSInputStream.blockSeekTo(DFSClient.java:1281)
>         at org.apache.hadoop.dfs.DFSClient$DFSInputStream.read(DFSClient.java:1385)
>         at java.io.DataInputStream.read(DataInputStream.java:83)
>         at org.apache.hadoop.mapred.LineRecordReader$LineReader.backfill(LineRecordReader.java:88)
>         at org.apache.hadoop.mapred.LineRecordReader$LineReader.readLine(LineRecordReader.java:114)
>         at org.apache.hadoop.mapred.LineRecordReader.<init>(LineRecordReader.java:179)
>         at org.apache.hadoop.mapred.TextInputFormat.getRecordReader(TextInputFormat.java:50)
>         at org.apache.hadoop.mapred.MapTask.run(MapTask.java:211)
>         at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2122)
> {noformat}
> This happened when hundreds of mappers pulled the same file concurrently.

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