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From "Mingliang Liu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-13065) Add a new interface for retrieving FS and FC Statistics
Date Thu, 05 May 2016 04:13:12 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-13065?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Mingliang Liu updated HADOOP-13065:
-----------------------------------
    Attachment: HADOOP-13065.009.patch

Thankw [~stevel@apache.org] very much for your comment. The v9 patch addresses your 2nd comment
on test (which is a very nice catch), checkstyle and findbugs warnings, along with simple
fix for the related test failures. Again, thanks [~cmccabe] for the new design.

As to your concurrent map comment, I shall update the patch later if I get your point. By
the map, I suppose we're talking about the {{GlobalStorageStatistics#map}}. My concern is
that, the {{FileSystem.getStatistics()}} itself is {{static}} and {{synchronized}}, and the
{{GlobalStorageStatistics#map}} will be looked up and updated iff there is no entry in the
{{FileSystem#statisticsTable}}. So basically if an entry exists, there should be a respective
entry in {{FileSystem#statisticsTable}}, and thus no look up is issued. Ideally as [~cmccabe]
suggested, we should remove the {{FileSystem#Statistics}} as a public interface. For that
I think we will refactor this part of code heavily.
That's said, we can firstly deprecate the {{FileSystem#getStatistics()}}?

> 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,
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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