Paul Snively created KAFKA-9517: ----------------------------------- Summary: KTable Joins Without Materialized Argument Yield Results That Further Joins NPE On Key: KAFKA-9517 URL: https://issues.apache.org/jira/browse/KAFKA-9517 Project: Kafka Issue Type: Bug Components: streams Affects Versions: 2.4.0 Reporter: Paul Snively
The `KTable` API implemented [here|[https://github.com/apache/kafka/blob/2.4.0/streams/src/main/java/org/apache/kafka/streams/kstream/internals/KTableImpl.java#L842-L844]] calls `doJoinOnForeignKey` with an argument of `Materialized.with(null, null)`, as apparently do several other APIs. As the comment spanning [these lines|[https://github.com/apache/kafka/blob/2.4.0/streams/src/main/java/org/apache/kafka/streams/kstream/internals/KTableImpl.java#L1098-L1099]] makes clear, the result is a `KTable` whose `valueSerde` (as a `KTableImpl`) is `null`. Therefore, attempts to `join` etc. on the resulting `KTable` fail with a `NullPointerException`. While there is an obvious workaround—explicitly construct the required `Materialized` and use the APIs that take it as an argument—I have to admit I find the existence of public APIs with this sort of bug, particularly when the bug is literally documented as a comment in the source code, astonishing to the point of incredulity. It calls the quality and trustworthiness of Kafka Streams into serious question, and if a resolution is not forthcoming within a week, we will be left with no other option but to consider technical alternatives. -- This message was sent by Atlassian Jira (v8.3.4#803005)