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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-13525) Optimize uses of FS operations in the ASF analysis frameworks,
Date Sat, 20 Aug 2016 11:33:20 GMT
Steve Loughran created HADOOP-13525:

             Summary: Optimize uses of FS operations in the ASF analysis frameworks, 
                 Key: HADOOP-13525
                 URL: https://issues.apache.org/jira/browse/HADOOP-13525
             Project: Hadoop Common
          Issue Type: Sub-task
          Components: fs, fs/s3
    Affects Versions: 2.7.2
            Reporter: Steve Loughran
            Assignee: Steve Loughran

Review uses of the FS APIs in applications using the Hadoop FS API to access filesystems;
identify suboptimal uses and tune them for better performance against HDFS and object stores

* Assume arbitrary Hadoop 2.x releases: make no changes which are known to make operations
on older versions of Hadoop slower
* Do propose those changes which deliver speedups in later versions of Hadoop, while not impacting
older versions, or risk of causing scalability problems.
* Add more tests, especially scalable ones which also display metrics.
* Use standard benchmarks and optimization tools to identify hotspots.
* Use FS behaviour as verified in the FS contract tests as evidence that filesystems correctly
implement the Hadoop FS APIs. If a use of an API call is made which hints at the expectation
of different/untested behaviours, leave alone and add new tests to the Hadoop FS contract
to determine cross-FS semantics.
* Focus on the startup, split calculation and directory scanning operations: the ones which
slow down entire queries.
* Eliminate use of {{isDirectory()}},  {{getLength()}}, {{exists()}} if a followon operation
({{getStatus()}},{{delete()}}, ... makes the use redundant.
* Assume that {{FileStatus}} entries are not cached; the cost of creating them is 1 RPC call
against HDFS, 1+ HTTPS call against object stores.
* Locate calls to the listing operations, identify speedups, especially on recursive directory
* Identify suboptimal seek patterns (backwards as well as forwards) and attempt to reduce/eliminate
through reordering and result caching.
* Try to reuse the results of previous operations (e.g {{FileStatus}} instances) in follow-on
* Document best practises identified and implemented.

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