zhijiangW opened a new pull request #9471: [FLINK-13754][task] Decouple OperatorChain from StreamStatusMaintainer URL: https://github.com/apache/flink/pull/9471 ## What is the purpose of the change There are two motivations for this refactoring: 1. It is the precondition for the following work of decoupling the dependency between two inputs status in `ForwardingValveOutputHandler`. 2. From the aspect of design rule, the current `OperatorChain` takes many unrelated roles like `StreamStatusMaintainer` to make it unmaintainable. The root reason for this case is from the cycle dependency between `RecordWriterOutput` (created by `OperatorChain`) and `StreamStatusMaintainer`. The solution is to refactor the creation of `StreamStatusMaintainer` and `RecordWriterOutput` on `StreamTask` level, and then break the implementation cycle dependency between them. The array of `RecordWriter`s which has close relationship with `RecordWriterOutput`s is created in `StreamTask`, so it is reasonable to create them together. The created `StreamStatusMaintainer` in `StreamTask` can be directly referenced by subclasses like `OneInputStreamTask`/`TwoInputStreamTask`. ## Brief change log - *Refactor `RecordWriterOutput` to not rely on StreamStatusProvider* - *Refactor `OperatorChain` to not implement `StreamStatusProvider`* - *Refactor `StreamTask` to create `StreamStatusProvider` instance and pass it into `OperatorChain`* ## 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): (yes / **no**) - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: (yes / **no**) - The serializers: (yes / **no** / don't know) - The runtime per-record code paths (performance sensitive): (yes / **no** / don't know) - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (yes / **no** / don't know) - The S3 file system connector: (yes / **no** / don't know) ## Documentation - Does this pull request introduce a new feature? (yes / **no**) - If yes, how is the feature documented? (**not applicable** / docs / JavaDocs / not documented)
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