[GitHub] [flink] NicoK opened a new pull request #8877: [FLINK-12984][metrics] only call Histogram#getStatistics() once where possible

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

NicoK opened a new pull request #8877: [FLINK-12984][metrics] only call Histogram#getStatistics() once where possible
URL: https://github.com/apache/flink/pull/8877
 
 
   ## What is the purpose of the change
   
   In some occasions, `Histogram#getStatistics()` was called multiple times to retrieve different statistics. However, at least the Dropwizard implementation has some constant overhead per call and we should maybe rather interpret this method as returning a point-in-time snapshot of the histogram in order to get consistent values when querying them.
   
   ## Brief change log
   
   - adapt prometheus reporter
   - adapt JMX and dropwizward unit tests
   
   ## Verifying this change
   
   This change is a trivial rework / code cleanup without any test coverage.
   
   ## 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): **no**
     - 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? **not applicable**
   

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