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https://issues.apache.org/jira/browse/HDFS-4486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14097332#comment-14097332
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Colin Patrick McCabe commented on HDFS-4486:
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[~oldcap]: there are a bunch of conditions in the DFSClient that are not fatal,
but which degrade performance. For example, lacking libhadoop.so means you
won't be able to use short-circuit. Perhaps the short-circuit socket stuff is
not set up correctly. Or we have to fall back to the shell-based groups
plugin. I believe those are the cases we'd start with here. The idea is to
have one log setting you could change to see all the "falling back to lower
performance method" logs.
> Add log category for long-running DFSClient notices
> ---------------------------------------------------
>
> Key: HDFS-4486
> URL: https://issues.apache.org/jira/browse/HDFS-4486
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Todd Lipcon
> Assignee: Zhe Zhang
> Priority: Minor
>
> There are a number of features in the DFS client which are transparent but
> can make a fairly big difference for performance -- two in particular are
> short circuit reads and native checksumming. Because we don't want log spew
> for clients like "hadoop fs -cat" we currently log only at DEBUG level when
> these features are disabled. This makes it difficult to troubleshoot/verify
> for long-running perf-sensitive clients like HBase.
> One simple solution is to add a new log category - eg
> o.a.h.h.DFSClient.PerformanceAdvisory - which long-running clients could
> enable at DEBUG level without getting the full debug spew.
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