juned created KAFKA-19442:
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Summary: Kafka Streams state store used an outdated value when
reducing records, resulting in incorrect output.
Key: KAFKA-19442
URL: https://issues.apache.org/jira/browse/KAFKA-19442
Project: Kafka
Issue Type: Bug
Reporter: juned
We observed a case where a reduce operation used an older version of the store
value instead of the latest when processing a new input.
Below i am describing the sequence of input and its outcome in changelog and
output topic
Lets see currently there is a key,value pair M0, in changelog & output Topic.
and u1,u2,u3 updates are received for the same key in the same order.
For u1,u2 all are fine
But For u3 update , Changelog topic has the *expected Outcome* but Output topic
has *incorrect* data.
**Sequence:**
| Step | Reduction | ChangelogTopic | OutputTopic
|------ |---------------------------- |-------------------|-------------
| Initial | M0 | M0 |
| u1 | M1 = reduce(M0, u1) | M1 | M1
| u2 | M2 = reduce(M1, u2) | M2 | M2
| u3 | M3 = reduce(M2, u3) |M3 |❌ Actually:
reduce(M1, u3)
### Environment:
- Kafka-clients:3.5.1
- kafka-streams:3.5.1
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