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https://issues.apache.org/jira/browse/HDFS-4486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14106061#comment-14106061
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Colin Patrick McCabe commented on HDFS-4486:
--------------------------------------------
{code}
+ PerformanceAdvisory.LOG.debug("Failed to get a local block reader. " +
+ "Falling back to a socket-based block reader.");
{code}
The problem with putting this log where you have it now is that it will be
extremely noisy. We should only fire off this log message when we try to do a
short-circuit read and fail, not just any old time when the replicas are all
remote or something.
For example, we should change this to a PerformanceAdvisory:
{code}
if (LOG.isTraceEnabled()) {
LOG.trace(this + ": " + pathInfo + " is not " +
"usable for short circuit; giving up on BlockReaderLocal.");
}
{code}
and probably this:
{code}
LOG.trace(this + ": not trying to create a remote block reader " +
"because the UNIX domain socket at " + pathInfo +
" is not usable.");
{code}
> 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
> Attachments: HDFS-4486-20140820.patch, HDFS-4486-20140821.patch
>
>
> 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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