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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-10175) add per-operation stats to FileSystem.Statistics
Date Tue, 29 Mar 2016 01:04:25 GMT

    [ https://issues.apache.org/jira/browse/HDFS-10175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15215187#comment-15215187
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Colin Patrick McCabe commented on HDFS-10175:
---------------------------------------------

I'm still -1 on this change.  v3 creates a very large map per FileSystem per thread.  For
an application with lots of threads, this overhead is unacceptable.  HTrace seems like a better
way to get this information.  I don't see a clear use-case for this.

> add per-operation stats to FileSystem.Statistics
> ------------------------------------------------
>
>                 Key: HDFS-10175
>                 URL: https://issues.apache.org/jira/browse/HDFS-10175
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs-client
>            Reporter: Ram Venkatesh
>            Assignee: Mingliang Liu
>         Attachments: HDFS-10175.000.patch, HDFS-10175.001.patch, HDFS-10175.002.patch,
HDFS-10175.003.patch
>
>
> Currently FileSystem.Statistics exposes the following statistics:
> BytesRead
> BytesWritten
> ReadOps
> LargeReadOps
> WriteOps
> These are in-turn exposed as job counters by MapReduce and other frameworks. There is
logic within DfsClient to map operations to these counters that can be confusing, for instance,
mkdirs counts as a writeOp.
> Proposed enhancement:
> Add a statistic for each DfsClient operation including create, append, createSymlink,
delete, exists, mkdirs, rename and expose them as new properties on the Statistics object.
The operation-specific counters can be used for analyzing the load imposed by a particular
job on HDFS. 
> For example, we can use them to identify jobs that end up creating a large number of
files.
> Once this information is available in the Statistics object, the app frameworks like
MapReduce can expose them as additional counters to be aggregated and recorded as part of
job summary.



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