[KAFKA-3561] Auto create through topic for KStream aggregation and join

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.10.1.0
• Component/s: streams
• Labels: api
• Assignee: Damian Guy
• Reporter: Guozhang Wang
• Created: 14/Apr/16 17:29
• Updated: 08/Nov/18 22:23
• Resolved: 16/Jun/16 18:56

Description

For KStream.join / aggregateByKey operations that requires the streams to be partitioned on the record key, today users should repartition themselves through the "through" call:

stream1 = builder.stream("topic1");
stream2 = builder.stream("topic2");

stream3 = stream1.map(/* set the right key for join*/).through("topic3");
stream4 = stream2.map(/* set the right key for join*/).through("topic4");

stream3.join(stream4, ..)

This pattern can actually be done by the Streams DSL itself instead of requiring users to specify themselves, i.e. users can just set the right key like (see KAFKA-3430) and then call join, which will be translated by adding the "internal topic for repartition".

Another thing is that today if user do not call "through" after setting a new key, the aggregation result would not be correct as the aggregation is based on key B while the source partitions is partitioned by key A and hence each task will only get a partial aggregation for all keys. But this is not validated in the DSL today. We should do both the auto-translation and validation.

Issue Links

• contains: KAFKA-6641 Consider auto repartitioning for Stream.transform() API
• is related to: KAFKA-3576 Unify KStream and KTable API
• links to: GitHub Pull Request #1453
• links to: GitHub Pull Request #1472
• mentioned in: Page Loading...