[jira] [Created] (KAFKA-9925) Non-key KTable Joining result in duplicate schema name in confluence schema registry

["Kin Siu (Jira)" <ji...@apache.org>]

Kin Siu created KAFKA-9925:
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             Summary: Non-key KTable Joining result in duplicate schema name in confluence schema registry
                 Key: KAFKA-9925
                 URL: https://issues.apache.org/jira/browse/KAFKA-9925
             Project: Kafka
          Issue Type: Bug
          Components: streams
            Reporter: Kin Siu


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. 
{noformat}
"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"
{noformat}
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.





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