[PR] [FLINK-39696][runtime] Use source partition for distributed flush events [flink-cdc]

["taoran92 (via GitHub)" <gi...@apache.org>]

taoran92 opened a new pull request, #4400:
URL: https://github.com/apache/flink-cdc/pull/4400

   # What is the purpose of the change
   
     This PR fixes inconsistent source identity propagation in the distributed schema evolution flow.
   
     In distributed mode, `SchemaOperator` forwards schema change requests to the coordinator with the original upstream source partition via `SchemaChangeRequest(sourcePartition, sinkSubTaskId, schemaChangeEvent)`.
     However, when emitting the downstream `FlushEvent`, it previously used the current `SchemaOperator` subtask id instead of the original source partition.
   
     As a result, the same schema change could be identified by different ids in different parts of the pipeline:
   
     - `SchemaChangeRequest` / coordinator deduplication use the original source partition
     - `FlushEvent` / downstream flush handling use the `SchemaOperator` subtask id
   
     This makes the flush lineage inconsistent with the schema-change lineage in distributed topology. In particular, duplicated broadcast branches of the same upstream schema change cannot be consistently aligned
     by the original source partition.
   
   # Brief change log
   
     - Use `schemaChangeRequest.getSourceSubTaskId()` instead of `SchemaOperator`'s `subTaskId` when constructing distributed `FlushEvent`
     - Add a regression test in `SchemaEvolveTest` to verify that `FlushEvent` keeps the original source partition even when the `SchemaOperator` subtask id is different
     - Extend `DistributedEventOperatorTestHarness` so tests can inject a custom operator subtask index and reliably reproduce this scenario
   
   # Verifying this change
   
     This change is verified by unit tests:
   
     - `SchemaEvolveTest#testFlushEventUsesSourcePartitionInsteadOfSchemaOperatorSubtask`
   
     Does this pull request potentially affect one of the following parts:
   
     - Dependencies (does it add or upgrade a dependency): no
     - The public API, i.e. is any changed class annotated with `@Public`(`@PublicEvolving`): no
     - The serializers: no
     - The runtime per-record code paths (performance sensitive): no
     - Anything that affects deployment or recovery: no
   
   # Documentation
   
   Does this pull request introduce a new feature? no
   
   If yes, how is the feature documented? not applicable


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Re: [PR] [FLINK-39696][runtime] Use source partition for distributed flush events [flink-cdc]

["yuxiqian (via GitHub)" <gi...@apache.org>]

yuxiqian merged PR #4400:
URL: https://github.com/apache/flink-cdc/pull/4400


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