[GitHub] [flink] rkhachatryan opened a new pull request #10435: [FLINK-13955][runtime] migrate ContinuousFileReaderOperator to the mailbox execution model

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

rkhachatryan opened a new pull request #10435: [FLINK-13955][runtime] migrate ContinuousFileReaderOperator to the mailbox execution model
URL: https://github.com/apache/flink/pull/10435
 
 
   ## What is the purpose of the change
   
   Use mailbox execution model in `ContinuousFileReaderOperator`.
   This allows to avoid explicit synchronization and eventually to remove `StreamTask.getCheckpointLock()`.
   
   ContinuousFileReaderOperator was changed significantly to avoid
   having an unnecessary now separate thread
   and extra synchronization between blocking and non-blocking code (e.g.
   format.reachedEnd and nextRecord)
   
   Performance is lower by ~15% because of the overhead of enqueueing and processing each mail (instead of just loop).
   
   
   ## Brief change log
   
     - *Currently, `ContinuousFileReaderOperator` spawn a thread to process file contents and acquires checkpoiint lock to process each record*
     - *The new implementation enqueues a `Mail` to be executed by `MailboxProcessor` - one record at a time, until end of split is reached*
     - *ContinuousFileProcessingRescalingTest refactored and updated to work with the new model*
   
   ## Verifying this change
   
   This change is already covered by existing tests, such as *ContinuousFileProcessingRescalingTest, ContinuousFileProcessingTest*.
   
   ## 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): **yes, for ContinuousFileReaderOperator**
     - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: **yes, ContinuousFileReaderOperator state** (no user-visible changes)
     - 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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