[Drain] Reduce Fn Runner changes

[stankiewicz]

Propagation of Drain information from Reduce Runner to WindowedValue

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Summary of Changes

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This pull request significantly enhances Apache Beam's draining capabilities by ensuring that the 'caused by drain' status is consistently propagated across key runner components and data structures. This change allows the system to correctly identify and handle elements and timers that are part of a draining operation, which is crucial for graceful shutdown and resource management in streaming pipelines. The modifications span from core ReduceFn logic to WindowedValue representation and testing utilities, providing a more robust foundation for drain-aware processing.

Highlights

• Drain Information Propagation: The CausedByDrain enum is now propagated through various core components, including ReduceFn, ReduceFnContextFactory, and ReduceFnRunner, ensuring that the draining status of elements and timers is maintained and accessible throughout the processing pipeline.
• WindowedValue Enhancements: The WindowedValue and ValueInSingleWindow classes have been updated to include the CausedByDrain status, allowing this critical information to be carried along with the data elements.
• Runner Context Updates: The ProcessValueContext and OnTriggerContext within ReduceFn now expose the CausedByDrain status, enabling ReduceFn implementations to react to draining signals.
• Timer Data Integration: Windmill timer data encoding (WindmillTagEncodingV1 and V2) has been modified to correctly capture and propagate the draining status into TimerData objects.
• Testing Utility Updates: The WindowMatchers utility has been extended to allow matching WindowedValue objects based on their CausedByDrain status, and DoFnTester now explicitly sets CausedByDrain.NORMAL for output values.

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Changelog

• runners/core-java/src/main/java/org/apache/beam/runners/core/OutputAndTimeBoundedSplittableProcessElementInvoker.java
  • Modified outputWithTimestamp and outputWindowedValue to pass the causedByDrain status from the element to the newly created WindowedValues.
• runners/core-java/src/main/java/org/apache/beam/runners/core/ReduceFn.java
  • Imported CausedByDrain.
  • Added an abstract causedByDrain() method to ProcessValueContext and OnTriggerContext.
• runners/core-java/src/main/java/org/apache/beam/runners/core/ReduceFnContextFactory.java
  • Updated forValue and forTrigger methods to accept a CausedByDrain parameter.
  • Modified ProcessValueContextImpl and OnTriggerContextImpl constructors to store the CausedByDrain status and added corresponding getter methods.
• runners/core-java/src/main/java/org/apache/beam/runners/core/ReduceFnRunner.java
  • Imported CausedByDrain.
  • Modified emit method signature and calls to include CausedByDrain.
  • Updated processElement to pass the causedByDrain status from the input WindowedValue to contextFactory.forValue.
  • Modified WindowActivation constructor to accept CausedByDrain and added a field to store it.
  • Updated onTimers to log the draining status and pass timer.causedByDrain() to WindowActivation and onTrigger calls.
• runners/core-java/src/main/java/org/apache/beam/runners/core/SplittableParDoViaKeyedWorkItems.java
  • Added a todo comment to consider setting draining status on timers.
• runners/core-java/src/main/java/org/apache/beam/runners/core/WindowMatchers.java
  • Updated isWindowedValue and isSingleWindowedValue factory methods to accept an optional drainMatcher.
  • Modified the WindowedValueMatcher constructor and matchesSafely method to include matching against the drainMatcher.
• runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/windmill/state/WindmillTagEncodingV1.java
  • Imported CausedByDrain.
  • Modified windmillTimerToTimerData to set the CausedByDrain status based on the draining flag.
• runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/windmill/state/WindmillTagEncodingV2.java
  • Imported CausedByDrain.
  • Modified windmillTimerToTimerData to set the CausedByDrain status based on the draining flag.
• runners/google-cloud-dataflow-java/worker/src/test/java/org/apache/beam/runners/dataflow/worker/StreamingGroupAlsoByWindowFnsTest.java
  • Updated Hamcrest imports to use wildcard.
  • Imported WindowedValues.
  • Added a createDrainingValue helper method to simulate draining input.
  • Added testFixedWindowsWithDraining to verify correct handling of draining elements and timers.
  • Updated assertThat calls in the new test to include CausedByDrain matchers.
• sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/DoFn.java
  • Removed direct import of CausedByDrain.
  • Updated causedByDrain() abstract methods in ProcessContext and OnTimerContext to use the fully qualified class name org.apache.beam.sdk.values.CausedByDrain.
• sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/DoFnTester.java
  • Modified output, outputWithTimestamp, and outputWindowedValue methods to explicitly pass CausedByDrain.NORMAL when creating ValueInSingleWindow instances.
• sdks/java/core/src/main/java/org/apache/beam/sdk/values/ValueInSingleWindow.java
  • Added an abstract getCausedByDrain() method.
  • Modified of factory methods to accept and store the CausedByDrain status, defaulting to NORMAL if not provided.
  • Updated the decode method in ValueInSingleWindowCoder to parse the draining status from ElementMetadata.

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