JET-2518: Log keyed-state key and state name on RocksDB migration failures

[rafael-sotelo]

Summary

When a savepoint is restored with an evolved POJO schema, Flink runs state migration: RocksDBKeyedStateBackend.migrateStateValues iterates the raw RocksDB bytes, deserializes each value with the old serializer, and re-serializes with the new one. The migration loop never decodes the key (it copies iterator.key() verbatim) and never calls setCurrentKey, so when a value fails to deserialize, PojoSerializer's error log shows key=null with no state name — leaving no way to identify which keyed entry holds the corrupt/incompatible state.

This change decodes the composite key during migration and threads it (plus the state name) into DeserializationContext, so the existing PojoSerializer failure log now prints [state=<name>, key=<key>].

Changes

• In migrateStateValues, best-effort decode the composite key (key group + key) from each iterator entry using the existing CompositeKeySerializationUtils.
• Wrap the per-entry migrateSerializedValue call with DeserializationContext.set(key, stateName) / clear() — the same try/finally pattern used by RocksDBValueState.value().
• Key decoding is best-effort: a key that fails to decode leaves key=null and never masks the real value-migration failure.
• No change to migration behavior or the bytes written.

Effect

Failure logs change from Deserialization failure: ... to Deserialization failure [state=<stateName>, key=<realKey>]: ..., pinpointing the offending entry.

Verification

• flink-statebackend-rocksdb module compiles cleanly (./mvnw / Maven 3.8.6).

🤖 Generated with Claude Code

✨ PR Description

Purpose: Enhance RocksDB state migration error diagnostics by logging keyed-state keys and state names during deserialization failures.

Main changes:

• Added DeserializationContext import and best-effort composite key decoding with error handling for diagnostics
• Wrapped migrateSerializedValue call with DeserializationContext to surface key and state name in PojoSerializer error logs
• Pre-computed keySerializer, namespaceSerializer, and ambiguousKeyPossible flag to support key reconstruction during migration

Generated by LinearB AI and added by gitStream.
_{AI-generated content may contain inaccuracies. Please verify before using.
💡 Tip: You can customize your AI Description using Guidelines Learn how}

[gitstream-cm]

✨ PR Review

LGTM

Generated by LinearB AI and added by gitStream.
_{AI-generated content may contain inaccuracies. Please verify before using.
💡 Tip: You can customize your AI Review using Guidelines Learn how}

[gitstream-cm]

🥷 Code experts: kellinwood

kellinwood has most 👩‍💻 activity in the files.
kellinwood has most 🧠 knowledge in the files.

See details

flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBKeyedStateBackend.java

Activity based on git-commit:

	kellinwood
JUN
MAY
APR
MAR
FEB
JAN

Knowledge based on git-blame:
kellinwood: 100%

✨ Comment /gs review for LinearB AI review. Learn how to automate it here.

[toolkit-timmy]

[Automated] Latest version: 2026.6.22-0b48ab5