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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1911) infinite loop in dfs -cat command.
Date Mon, 17 Sep 2007 23:18:43 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1911?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12528186

dhruba borthakur commented on HADOOP-1911:

chooseDataNode() has bug that is triggered when all the replicas of a file are bad. The value
of "failures" in DFSClient.chooseDataNode is always zero. When there are no more good nodes,
bestNode() generates an exception that is caught inside chooseDataNode. "failures" is still
zero; it clears the deadnodes, refetches block locations and starts all over again. Hence
the infinite loop.

> infinite loop in dfs -cat command.
> ----------------------------------
>                 Key: HADOOP-1911
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1911
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.13.1
>            Reporter: Koji Noguchi
> [knoguchi]$ hadoop dfs -cat fileA
> 07/09/13 17:36:02 INFO fs.DFSClient: Could not obtain block 0 from any node: 
> java.io.IOException: No live nodes contain current block
> 07/09/13 17:36:20 INFO fs.DFSClient: Could not obtain block 0 from any node: 
> java.io.IOException: No live nodes contain current block
> [repeats forever]
> Setting one of the Debug statement to Warn, it kept on showing 
> {noformat} 
>  WARN org.apache.hadoop.fs.DFSClient: Failed to connect
> to /99.99.999.9 :11111:java.io.IOException: Recorded block size is 7496, but
> datanode reports size of 0
> 	at org.apache.hadoop.dfs.DFSClient$DFSInputStream.blockSeekTo(DFSClient.java:690)
> 	at org.apache.hadoop.dfs.DFSClient$DFSInputStream.read(DFSClient.java:771)
> 	at org.apache.hadoop.fs.FSDataInputStream$PositionCache.read(FSDataInputStream.java:41)
> 	at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
> 	at java.io.BufferedInputStream.read1(BufferedInputStream.java:258)
> 	at java.io.BufferedInputStream.read(BufferedInputStream.java:317)
> 	at java.io.DataInputStream.readFully(DataInputStream.java:178)
> 	at java.io.DataInputStream.readFully(DataInputStream.java:152)
> 	at org.apache.hadoop.fs.ChecksumFileSystem$FSInputChecker.(ChecksumFileSystem.java:123)
> 	at org.apache.hadoop.fs.ChecksumFileSystem.open(ChecksumFileSystem.java:340)
> 	at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:259)
> 	at org.apache.hadoop.util.CopyFiles$FSCopyFilesMapper.map(CopyFiles.java:466)
> 	at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:48)
> 	at org.apache.hadoop.mapred.MapTask.run(MapTask.java:186)
> 	at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:1707)
> {noformat} 
> Turns out fileA was corrupted. Fsck showed crc file of 7496 bytes, but when I searched
for the blocks on each node, 3 replicas were all size 0.
> Not sure how it got corrupted, but it would be nice if the dfs command fail instead of
getting into an infinite loop.

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