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Sylwester Lachiewicz commented on FLINK-37330:
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Triage finding (2026-09-10) and two questions before starting the work.
What exists on main: {{KafkaSourceMigrationITCase}} with three savepoint
fixtures. {{enum1-split0}} was written by a pre-2.0 build (its {{_metadata}}
uses savepoint format V4; V5 arrived with FLINK-36001 in 2.0-preview) and
restores cleanly today: {{Tests run: 4, Failures: 0, Errors: 0, Skipped: 1}} on
main. So {{KafkaSource}} already has one execution-verified cross-major data
point, though not at the exact 3.4.0 on Flink 1.20 pairing.
What is missing: any cross-major coverage for {{KafkaSink}}
({{KafkaWriterStateSerializer}}, {{KafkaCommittableSerializer}}, both
{{SimpleVersionedSerializer}}, so only a full savepoint restore proves
anything) and for {{DynamicKafkaSource}}. Fixtures have to be generated on the
v3.4 branch under Flink 1.20 and committed as binary resources, since 1.x and
2.x cannot share a classpath; {{flink-migration-test-utils}} is published on
Maven Central and unused by every externalized connector so far.
Questions for [~arvid]: (1) does {{enum1-split0}} already cover the
{{KafkaSource}} half of this ticket for you, or do you want an explicitly
labelled 3.4.0 on 1.20 fixture as well? (2) Is {{KafkaSink}} in scope here, and
{{DynamicKafkaSource}} as a follow-up? Estimated effort is two to three days
for source plus sink. I can take it once the scope is settled.
_This comment was created with AI assistance._
> Add state migration test for Flink 2.0
> --------------------------------------
>
> Key: FLINK-37330
> URL: https://issues.apache.org/jira/browse/FLINK-37330
> Project: Flink
> Issue Type: Improvement
> Components: Connectors / Kafka
> Affects Versions: kafka-4.0.0
> Reporter: Arvid Heise
> Priority: Blocker
>
> Let's cover the common scenario that users want to upgrade their
> sources/sinks from Flink 1.20 to Flink 2.0.
> (This is NOT about upgrading from consumer/producer to source/sink; that
> needs to be done in Flink 1.X).
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