[DebeziumIO] Implement startOffset for Kafka (#28248)

[tkaymak]

Implement withStartOffset for Debezium to handle restarts. (Addresses #28248)

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Summary of Changes

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This pull request introduces a crucial startOffset capability to DebeziumIO, allowing users to define a specific point for Debezium connectors to begin or resume data consumption. This enhancement is vital for building resilient data pipelines that can recover from failures or planned shutdowns without losing data or re-processing unnecessary events. The implementation spans across the Go, Java, and Python SDKs, providing a unified experience for managing change data capture streams.

Highlights

• DebeziumIO Start Offset Implementation: Introduced a startOffset feature for DebeziumIO in both Go and Java SDKs, allowing users to specify a point from which the Debezium connector should resume consuming changes.
• Cross-language Compatibility: The startOffset functionality is integrated across the Go, Java, and Python SDKs, ensuring consistent behavior for DebeziumIO users regardless of their chosen language.
• Offset Parsing and Handling: The Java SDK now includes logic to parse startOffset values provided as key-value strings, automatically converting numeric parts to Long where appropriate, facilitating flexible offset specification.
• Improved Restart Capabilities: This feature significantly enhances the robustness of Debezium-based pipelines by enabling them to gracefully restart from a known good state, preventing reprocessing of already handled data.

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Changelog

• sdks/go/pkg/beam/io/xlang/debeziumio/debezium.go
  • Added StartOffset field to the readFromDebeziumSchema struct to hold offset configuration.
  • Implemented a new StartOffset function that serves as a read option to configure the starting offset for the Debezium connector.
• sdks/java/io/debezium/src/main/java/org/apache/beam/io/debezium/DebeziumIO.java
  • Added getStartOffset and setStartOffset abstract methods to the Read and Builder classes, respectively, to manage the new offset property.
  • Introduced the withStartOffset builder method, allowing users to specify a map of key-value pairs representing the desired starting offset for the Debezium connector, complete with detailed Javadoc.
• sdks/java/io/debezium/src/main/java/org/apache/beam/io/debezium/DebeziumTransformRegistrar.java
  • Imported HashMap for map manipulation.
  • Added a startOffset field to the Configuration class and its corresponding setter method.
  • Implemented logic within buildExternal to parse the list of startOffset strings into a Map<String, Object>, converting numeric values to Long where applicable, before applying it to the readTransform.
• sdks/java/io/debezium/src/main/java/org/apache/beam/io/debezium/KafkaSourceConsumerFn.java
  • Modified the getInitialRestriction method to pass the newly introduced startOffset from the spec to the OffsetHolder.
• sdks/java/io/debezium/src/test/java/org/apache/beam/io/debezium/DebeziumIOTest.java
  • Added static imports for assertEquals and assertNull.
  • Imported ImmutableMap for easier map creation in tests.
  • Included new test cases to verify that withStartOffset correctly stores the offset, handles null offsets, throws exceptions for invalid null input, and that getInitialRestriction properly utilizes the provided start offset.
• sdks/python/apache_beam/io/debezium.py
  • Imported Dict and Union from typing.
  • Extended ReadFromDebeziumSchema to include an optional start_offset field, defined as a list of strings.
  • Updated the ReadFromDebezium constructor to accept a start_offset parameter and included comprehensive documentation for its usage and format.
  • Passed the start_offset parameter to the ReadFromDebeziumSchema during initialization.

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[github-actions]

Assigning reviewers:

R: @tvalentyn for label python.
R: @ahmedabu98 for label java.
R: @jrmccluskey for label go.

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[tvalentyn]

Hi @an2x @johnjcasey @Dippatel98 - could you please help find a reviewer for this? Thanks

[tkaymak]

@tvalentyn maybe @Abacn can have a look (?)

[Abacn]

Thanks, this change allows user to provide an offset that was obtained elsewhere. It now supports to read from an offset, yet not completely resolve #28248, as restarting the pipeline that have set the offset would still start from the same offset.

I had a (yet materialized) idea of restartable offset. Basically we can provide an "OffsetRetainer" interface to 1. read offset on pipeline startup; 2. write offset on checkpointing, and expose as a configuration for the IO. And we can then provide a built-in FileSystem based OffsetRetainer for user to use.

When pipeline is running, it continuously write committed offset to external location (gcs, kafka, etc) of choice; when pipeline starts or restarts, it tries to read from the same location at first.

If you prefer to go for current change for now, let me take a closer look for this PR. Or we can work on a more concrete solution.

[tkaymak]

@Abacn thank you for comment. I think your solution sounds like a much better vision, and we should aim for that.