[KAFKA-9925] Non-key KTable Joining may result in duplicate schema name in confluence schema registry

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.1
• Fix Version/s: 2.6.0, 2.4.2, 2.5.1
• Component/s: streams
• Assignee: John Roesler
• Reporter: Kin Siu
• Created: 28/Apr/20 12:15
• Updated: 29/Apr/20 22:35
• Resolved: 29/Apr/20 22:35

Description

The second half of issue Andy Bryant reported in KAFKA-9390 looks like still exist.

When testing non-key join method without passing in "Named", I noticed that there are schema subjects registered in confluent schema registry without consumer group Id still,
e.g.

"KTABLE-FK-JOIN-SUBSCRIPTION-REGISTRATION-0000000005-topic-pk-key",
"KTABLE-FK-JOIN-SUBSCRIPTION-REGISTRATION-0000000005-topic-fk-key",
"KTABLE-FK-JOIN-SUBSCRIPTION-REGISTRATION-0000000005-topic-vh-value",
"KTABLE-FK-JOIN-SUBSCRIPTION-REGISTRATION-0000000025-topic-pk-key",
"KTABLE-FK-JOIN-SUBSCRIPTION-REGISTRATION-0000000025-topic-fk-key",
"KTABLE-FK-JOIN-SUBSCRIPTION-REGISTRATION-0000000025-topic-vh-value"

Code in KTableImpl which constructed above naming :
https://github.com/apache/kafka/blob/2.4.1/streams/src/main/java/org/apache/kafka/streams/kstream/internals/KTableImpl.java#L959

When we have multiple topologies using foreignKey join and registered to same schema registry, we can have a name clash, and fail to register schema.

In order to clean up these schema subjects, we will need to know the internal naming of a consumer group's topology, which is not straightforward and error prone.

Issue Links

• links to: GitHub Pull Request #8574