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https://issues.apache.org/jira/browse/MAPREDUCE-4340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13294938#comment-13294938
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Devaraj K commented on MAPREDUCE-4340:
--------------------------------------
I have investigated some things for this issue, it seems to be due to
FileSystem Cache.
The Node Manager gets the FileSystem object for copying the files from DFS
during localization.
{code:title=FSDownload.java|borderStyle=solid}
private Path copy(Path sCopy, Path dstdir) throws IOException {
FileSystem sourceFs = sCopy.getFileSystem(conf);
Path dCopy = new Path(dstdir, sCopy.getName() + ".tmp");
FileStatus sStat = sourceFs.getFileStatus(sCopy);
if (sStat.getModificationTime() != resource.getTimestamp()) {
throw new IOException("Resource " + sCopy +
" changed on src filesystem (expected " + resource.getTimestamp() +
", was " + sStat.getModificationTime());
}
sourceFs.copyToLocalFile(sCopy, dCopy);
return dCopy;
}
{code}
It is using the FileSystem.get(URI uri, Configuration conf) API to get file
system instance, and it internally uses cache for file system instances. For
next job, FileSystem.Cache.Key is not matching with previous instance key,
creating new file system instance again and it is keep on increasing for every
job. For every file system instance there is associated DFSClient instance
which is holding the datanode socket in socketCache and it is not closing by
any one.
> Node Manager leaks socket connections connected to Data Node
> ------------------------------------------------------------
>
> Key: MAPREDUCE-4340
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4340
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Reporter: Devaraj K
> Assignee: Devaraj K
> Priority: Critical
>
> I am running simple wordcount example with default configurations, for every
> job run it increases one datanode socket connection and it will be there in
> CLOSE_WAIT state forever.
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