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https://issues.apache.org/jira/browse/HADOOP-2231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12548237
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Amar Kamat commented on HADOOP-2231:
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After some more thoughts we feel that
1. The way free space is computed using {{DF.getAvailable()}} should now be
done using {{File.getFreeSpace()}} and {{File.getUsableSpace()}} API available
in java6. So as a part of this patch I will change the way {{df -k}} is used to
compute the free space by making use of {{File.getUsableSpace()}}.
2. There are some classes which still use the {{getMount()}} API of
{{DF.java}}. Java 6 does not provide any API for this. So the only way out is
to make use of shell commands like {{stat}} or {{df}} for calculating the mount
points. As discussed in {{HADOOP-2344}}, there are issues with the way shell
commands are executed in {{ShellUtil.java}} and {{ShellCommand.java}}. A patch
is made available for {{HADOOP-2344}}.
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Comments ?
> ShellCommand, in particular 'df -k', sometimes hang
> ---------------------------------------------------
>
> Key: HADOOP-2231
> URL: https://issues.apache.org/jira/browse/HADOOP-2231
> Project: Hadoop
> Issue Type: Bug
> Components: fs
> Affects Versions: 0.15.1
> Reporter: Christian Kunz
> Fix For: 0.15.2
>
> Attachments: HADOOP-2231.patch
>
>
> We noticed that some pipes applications writing to dfs using libhdfs have
> about 6% chance of hanging when executing 'df -k' to find out whether there
> is enough space available on the local filesystem before opening a file for
> write.
> Why not using File.getFreeSpace() or File.GetUsableSpace()?
> The call stack is:
> Exception in thread "main" java.io.IOException
> at org.apache.hadoop.fs.ShellCommand.runCommand
> (ShellCommand.java:52)
> at org.apache.hadoop.fs.ShellCommand.run(ShellCommand.java:42)
> at org.apache.hadoop.fs.DF.getAvailable(DF.java:72)
> at org.apache.hadoop.fs.LocalDirAllocator
> $AllocatorPerContext.getLocalPathForWrite(LocalDirAllocator.java:264)
> at org.apache.hadoop.fs.LocalDirAllocator
> $AllocatorPerContext.createTmpFileForWrite(LocalDirAllocator.java:294)
> at
> org.apache.hadoop.fs.LocalDirAllocator.createTmpFileForWrite
> (LocalDirAllocator.java:155)
> at org.apache.hadoop.dfs.DFSClient
> $DFSOutputStream.newBackupFile(DFSClient.java:1470)
> at org.apache.hadoop.dfs.DFSClient
> $DFSOutputStream.openBackupStream(DFSClient.java:1437)
> at org.apache.hadoop.dfs.DFSClient$DFSOutputStream.writeChunk
> (DFSClient.java:1579)
> at org.apache.hadoop.fs.FSOutputSummer.writeChecksumChunk
> (FSOutputSummer.java:140)
> at org.apache.hadoop.fs.FSOutputSummer.write1
> (FSOutputSummer.java:100)
> at org.apache.hadoop.fs.FSOutputSummer.write
> (FSOutputSummer.java:86)
> at org.apache.hadoop.fs.FSDataOutputStream
> $PositionCache.write(FSDataOutputStream.java:39)
> at java.io.DataOutputStream.write(DataOutputStream.java:90)
> at java.io.FilterOutputStream.write(FilterOutputStream.java:80)
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