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https://issues.apache.org/jira/browse/HADOOP-13065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15274617#comment-15274617
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Colin Patrick McCabe commented on HADOOP-13065:
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bq. One quick question is that, some of the storage statistics classes (e.g.
GlobalStorageStatistics are annotated as Stable, do we have to be a bit more
conservative by making them Unstable before ultimately removing the Statistics?
Good question. I think that what would happen is that the old API would become
deprecated in branch-2, and removed in branch-3. There isn't any need to
change the annotation since we don't plan to modify the interface, just remove
it.
bq. As follow-on work, 1. We can move the rack-awareness read bytes to a
separate storage statistics as it's only used by HDFS, and 2. We can remove
Statistics API, but keep the thread local implementation in
FileSystemStorageStatistics class.
That makes sense. One thing that we've talked about doing in the past is
moving these statistics to a separate java file, so that they could be used in
both FileContext and FileSystem. Maybe we could call them something like
ThreadLocalFsStatistics or something?
> 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, 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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