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https://issues.apache.org/jira/browse/HADOOP-13065?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mingliang Liu updated HADOOP-13065:
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Attachment: HADOOP-13065.013.patch
Thanks [~cmccabe] for the review.
The v13 patch is to address the null return value problem. Yes we should return
null in this case, indicating the operation is not tracked. Zero-value is for
the case where the operation is tracked by the counter is not yet incremented.
This is a good catch.
For this use case request, the per-operation stats is per job and thus is
shared among different filesystem instances. Based on the current stats design,
we can further support per-instance stats as follow-on jiras if new use cases
appear.
> Add a new interface for retrieving FS and FC Statistics
> -------------------------------------------------------
>
> Key: HADOOP-13065
> URL: https://issues.apache.org/jira/browse/HADOOP-13065
> Project: Hadoop Common
> Issue Type: Improvement
> Components: fs
> Reporter: Ram Venkatesh
> Assignee: Mingliang Liu
> Attachments: HADOOP-13065-007.patch, HADOOP-13065.008.patch,
> HADOOP-13065.009.patch, HADOOP-13065.010.patch, HADOOP-13065.011.patch,
> HADOOP-13065.012.patch, HADOOP-13065.013.patch, 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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