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https://issues.apache.org/jira/browse/HDFS-10175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15256108#comment-15256108
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Steve Loughran commented on HDFS-10175:
---------------------------------------
+one more thing that would be nice would be for all classes which collect stats
to implement an interface to publish those stats:
{code}
pubic interface StatisticsSource {
Map<String, Long> snapshot();
}
{code}
Why? It's something which filesystems subclasses can implement, IO Streams,
etc. The FSData streams would implement and pass on to wrapped streams, or
return an empty map.
Having a uniform mech like this would make it easy for tests to grab the
before/after data, look for diffs, display counts, etc. By avoiding any enums
in the returned snapshot, it'd be easy for applications that aren't built
against a specific Hadoop version (Spark, etc) to grab all stats available to
the app, without knowing the exact mappings, and present them to users in
reports .
> 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, HDFS-10175.004.patch,
> HDFS-10175.005.patch, HDFS-10175.006.patch, TestStatisticsOverhead.java
>
>
> 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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