[Dataflow Streaming] Remove nullness suppression of StreamingDataflowWorker

[scwhittle]

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Summary of Changes

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This pull request significantly enhances the nullness safety and clarity within the StreamingDataflowWorker class. By removing a broad nullness suppression and introducing explicit null checks and annotations, the code now better communicates and enforces its nullability contracts, reducing the likelihood of NullPointerExceptions and improving maintainability. The changes also include minor refactorings to improve the readability and robustness of the worker harness switching mechanism.

Highlights

• Nullness Suppression Removal: The @SuppressWarnings("nullness") annotation has been removed from the StreamingDataflowWorker class, indicating a move towards stricter nullness checking.
• Explicit Null Checks: Multiple checkNotNull calls have been introduced for fields like dispatcherClient, configFetcher, and computationStateCache to ensure non-null access at runtime.
• Nullable Field Annotation: The dispatcherClient field is now explicitly marked as @Nullable, clarifying its potential null state.
• Checker Framework Annotations: New imports and usage of @UnderInitialization and @UnknownInitialization annotations from the Checker Framework have been added to constructor-like methods for improved initialization safety.
• Connectivity Type Switching Refinement: The switchStreamingWorkerHarness method has been refactored to handle CONNECTIVITY_TYPE_DEFAULT and use a boolean flag for directPath for clearer logic.

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Changelog

• runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/StreamingDataflowWorker.java
  • Removed the class-level @SuppressWarnings("nullness") annotation.
  • Added checkNotNull import from Guava.
  • Added Checker Framework imports for @UnderInitialization and @UnknownInitialization.
  • Annotated dispatcherClient field as @Nullable.
  • Introduced checkNotNull calls when accessing dispatcherClient, configFetcher, and computationStateCache.
  • Added @UnderInitialization and @UnknownInitialization annotations to this parameter in several factory methods (createApplianceWorkerHarness, createFanOutStreamingEngineWorkerHarness, createSingleSourceWorkerHarness).
  • Added @SuppressWarnings("methodref.receiver.bound") in two locations.
  • Refactored switchStreamingWorkerHarness to handle CONNECTIVITY_TYPE_DEFAULT and use a directPath boolean for improved logic.

Activity

• The pull request was created by scwhittle.
• No human activity (comments, reviews) has been recorded yet, only automated checks and boilerplate text.

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[scwhittle]

R: @arunpandianp

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control. If you'd like to restart, comment assign set of reviewers

[arunpandianp]

use a different name than this?

[arunpandianp]

use a different name than this?