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  1. Hadoop Common
  2. HADOOP-16829 Über-jira: S3A Hadoop 3.3.1 features
  3. HADOOP-13525

Optimize uses of FS operations in the ASF analysis frameworks and libraries



    • Sub-task
    • Status: Resolved
    • Major
    • Resolution: Done
    • 2.8.1
    • 3.3.1
    • fs, fs/s3
    • None


      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 calls.
      • 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.


        Issue Links



              stevel@apache.org Steve Loughran
              stevel@apache.org Steve Loughran
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