SDF draining in dataflow runner v1

[stankiewicz]

Enable draining of SDFs for runner v1

Change: In stateful do fn, if timer received contains CausedByDrain bit, we remove hold and don't set next timer.

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[stankiewicz]

/gemini review

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances Apache Beam's runner v1 to support the draining of Splittable DoFns (SDFs). It integrates a CausedByDrain signal into the DoFn execution lifecycle, allowing DoFns to be aware of and respond to pipeline draining events. This ensures a more robust and controlled shutdown or update process for pipelines utilizing SDFs, by propagating the draining state and adjusting timer behavior accordingly.

Highlights

• SDF Draining Support: Introduced the CausedByDrain parameter across various DoFn execution contexts, enabling Splittable DoFns (SDFs) to gracefully handle draining signals during pipeline shutdown or updates.
• DoFn Invoker and Signature Updates: Extended the DoFnInvoker and DoFnSignature reflection mechanisms to recognize and provide the CausedByDrain parameter to ProcessElement and OnTimer methods, allowing user DoFns to declare and receive this signal.
• Timer Handling during Draining: Modified the SDF execution logic to prevent new timers from being set when a draining signal is active, ensuring that processing gracefully concludes without scheduling new work.
• Testing for Draining Behavior: Added a new test case to SplittableParDoProcessFnTest to validate the correct propagation and handling of the CausedByDrain signal within a DoFn's process method.

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Changelog

• runners/core-java/src/main/java/org/apache/beam/runners/core/OutputAndTimeBoundedSplittableProcessElementInvoker.java
  • Added causedByDrain method to the ProcessContext implementation.
• runners/core-java/src/main/java/org/apache/beam/runners/core/SimpleDoFnRunner.java
  • Implemented causedByDrain in ProcessContext and TimerInternals.TimerData handling.
  • Prevented new timers from being set when a draining signal is active.
• runners/core-java/src/main/java/org/apache/beam/runners/core/SplittableParDoViaKeyedWorkItems.java
  • Modified WindowedValue reading to include drain information from timers.
  • Conditionally set timers only when not in a draining state.
• runners/core-java/src/test/java/org/apache/beam/runners/core/SplittableParDoProcessFnTest.java
  • Added imports for TimeDomain and CausedByDrain.
  • Introduced advanceDrain method to simulate draining.
  • Updated WatermarkUpdateFn to accept CausedByDrain as a parameter.
  • Added a new test case testDrains to verify draining behavior.
• sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/DoFnTester.java
  • Updated ProcessContext and ArgumentProvider to support causedByDrain.
• sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/reflect/ByteBuddyDoFnInvokerFactory.java
  • Integrated CausedByDrainParameter into the DoFnInvoker factory for dynamic parameter injection.
• sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/reflect/DoFnInvoker.java
  • Added causedByDrain method to the ArgumentProvider interface and its base implementation.
• sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/reflect/DoFnSignature.java
  • Extended DoFnSignature to include CausedByDrainParameter for reflection.
• sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/reflect/DoFnSignatures.java
  • Registered CausedByDrainParameter as an allowed parameter type for ProcessElement and OnTimer methods.
• sdks/java/core/src/main/java/org/apache/beam/sdk/util/construction/SplittableParDoNaiveBounded.java
  • Implemented causedByDrain method in its ProcessContext implementation.
• sdks/java/core/src/test/java/org/apache/beam/sdk/transforms/reflect/DoFnSignaturesTest.java
  • Updated tests to verify CausedByDrainParameter in ProcessElement and OnTimer method signatures.
• sdks/java/harness/src/main/java/org/apache/beam/fn/harness/FnApiDoFnRunner.java
  • Implemented causedByDrain method in ProcessContext for the Fn API runner.

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[gemini-code-assist]

Code Review

This pull request enables draining of Splittable DoFns for runner v1. The changes involve plumbing the CausedByDrain information through various contexts and invokers, and modifying the logic for setting continuation timers to respect the drain signal. The changes look mostly correct, but I've found a potential NullPointerException in SplittableParDoViaKeyedWorkItems.java on the initial processing call. I've also pointed out a leftover comment and an opportunity to reduce code duplication.

[stankiewicz]

/gemini review

[gemini-code-assist]

Code Review

This pull request enables draining of Splittable DoFns for runner v1. The changes are comprehensive, plumbing the CausedByDrain information through the SDK and runner core components like DoFnInvoker and DoFnSignature. The core logic in SplittableParDoViaKeyedWorkItems correctly prevents scheduling new work during a drain. The addition of tests, including testDrains, effectively validates the new functionality. The implementation is solid. I have one suggestion to simplify a conditional expression for better readability.

[github-actions]

Assigning reviewers:

R: @Abacn for label java.

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[stankiewicz]

R: @kennknowles

[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

[stankiewicz]

/gemini review

[stankiewicz]

R: @acrites

[gemini-code-assist]

Code Review

This pull request enables draining for Splittable DoFns in the Dataflow runner v1. The changes correctly handle drain signals in SplittableParDoViaKeyedWorkItems by not setting new timers for continuations and clearing the watermark hold state, which is the correct behavior for draining. The changes also propagate the drain status to the SDF's process context. The new tests are well-written and validate the draining behavior.

I found one issue in FnApiDoFnRunner.java related to a refactoring of causedByDrain handling. The change introduces an inconsistency in how causedByDrain is exposed for non-splittable DoFns, which I've commented on.

[stankiewicz]

Tested with https://gist.github.com/stankiewicz/38807710a971735c78e954a4b49c0929 , Example job

[stankiewicz]

Run Flink Container PreCommit