[KAFKA-3745] Consider adding join key to ValueJoiner interface

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.10.0.0
• Fix Version/s: 3.0.0
• Component/s: streams
• Labels: api kip
• Assignee: Bill Bejeck
• Reporter: Greg Fodor
• Created: 23/May/16 03:56
• Updated: 21/Mar/21 02:21
• Resolved: 21/Mar/21 02:21

Description

In working with Kafka Stream joining, it's sometimes the case that a join key is not actually present in the values of the joins themselves (if, for example, a previous transform generated an ephemeral join key.) In such cases, the actual key of the join is not available in the ValueJoiner implementation to be used to construct the final joined value. This can be worked around by explicitly threading the join key into the value if needed, but it seems like extending the interface to pass the join key along as well would be helpful.

KIP-149: https://cwiki.apache.org/confluence/display/KAFKA/KIP-149%3A+Enabling+key+access+in+ValueTransformer%2C+ValueMapper%2C+and+ValueJoiner

Issue Links

• Is contained by: KAFKA-4218 Enable access to key in ValueTransformer
• is related to: KAFKA-7842 Reducer should have (read) access to key
• is related to: KAFKA-7843 Initializer should have (read) access to key
• is related to: KAFKA-4726 ValueMapper should have (read) access to key
• links to: GitHub Pull Request #10150
• mentioned in: Page Loading...