[GitHub] [flink] NicoK opened a new pull request #8888: [FLINK-12983][metrics] replace descriptive histogram's storage back-end

[GitBox <gi...@apache.org>]

NicoK opened a new pull request #8888: [FLINK-12983][metrics] replace descriptive histogram's storage back-end
URL: https://github.com/apache/flink/pull/8888
 
 
   ## What is the purpose of the change
   
   Instead of using `DescriptiveStatistics` and its `ResizableDoubleArray` storage back-end, implement an own circular array based on a fixed-size double array that wraps around. This significantly improves the time needed to add new values. It also ensures that access is synchronized which `ResizableDoubleArray` does not guarantee.
   
   Performance results:
   1. only adding values to the histogram
   ```
       Benchmark                                       Mode  Cnt      Score        Error   Units
       HistogramBenchmarks.dropwizardHistogramAdd     thrpt   30   47985.359 ±    25.847  ops/ms
       HistogramBenchmarks.descriptiveHistogramAdd    thrpt   30   70158.792 ±   276.858  ops/ms
   -> #8887:
       HistogramBenchmarks.descriptiveHistogramAdd    thrpt   30   75303.040 ±   475.355  ops/ms
   -> this PR:
       HistogramBenchmarks.descrHistogramCircularAdd  thrpt   30  200906.902 ±   384.483  ops/ms
   -> using a linear array of twice the histogram size (and moving values back to the start once the window reaches the end), for reference:
       HistogramBenchmarks.descrHistogramLinearAdd    thrpt   30  189788.728 ±   233.283  ops/ms
   ```
   2. after adding each value, also retrieving a common set of metrics:
   ```
       Benchmark                                       Mode  Cnt      Score        Error   Units
       HistogramBenchmarks.dropwizardHistogram        thrpt   30     400.274 ±     4.930  ops/ms
       HistogramBenchmarks.descriptiveHistogram       thrpt   30     124.533 ±     1.060  ops/ms
   -> #8887:
       HistogramBenchmarks.descriptiveHistogram       thrpt   30     251.895 ±     1.809  ops/ms
   -> this PR:
       HistogramBenchmarks.descrHistogramCircular     thrpt   30     301.068 ±     2.077  ops/ms
   -> using a linear array as above:
       HistogramBenchmarks.descrHistogramLinear       thrpt   30     234.050 ±     5.485  ops/ms
   ```
   
   Please note that this PR is based on #8887.
   
   ## Brief change log
   
   - add `CircularDoubleArray` to `DescriptiveStatisticsHistogram`
   - remove extra `AtomicLong elementsSeen` (can be done more efficiently in `CircularDoubleArray`)
   
   ## Verifying this change
   
   This change is already covered by existing tests, such as derivatives of `AbstractHistogramTest`.
   
   ## Does this pull request potentially affect one of the following parts:
   
     - Dependencies (does it add or upgrade a dependency): **no**
     - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: **no**
     - The serializers: **no**
     - The runtime per-record code paths (performance sensitive): **maybe** (histograms are used by latency markers only but may be used by users)
     - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: **no**
     - The S3 file system connector: **no**
   
   ## Documentation
   
     - Does this pull request introduce a new feature? **no**
     - If yes, how is the feature documented? **JavaDocs**
   

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