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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-13525) Optimize uses of FS operations in the ASF analysis frameworks and libraries
Date Mon, 17 Oct 2016 14:58:58 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-13525?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Steve Loughran updated HADOOP-13525:
    Affects Version/s:     (was: 2.7.2)

> Optimize uses of FS operations in the ASF analysis frameworks and libraries 
> ----------------------------------------------------------------------------
>                 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: 2.7.3
>            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 scans.
> * 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
> * Commonly used file formats (e.g ORC) will have transitive benefits.
> * Frameworks to use predicate pushdown where this delivers speedups
> * Document best practises identified and implemented.

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