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John Roesler commented on KAFKA-9636: ------------------------------------- Hey [~psnively] , I can't claim to fully understand the data generation logic in that test, but I'm pretty sure the generated data isn't correct. I added a couple of printlns to the data generation block, and this is what I see: {noformat} topics: List(input-topic-1, input-topic-2) tables: List((com.compstak.org.apache.kafka.streams.scala.kstream.KTable@6ee6f53,0), (com.compstak.org.apache.kafka.streams.scala.kstream.KTable@421bba99,1)) t1: com.compstak.org.apache.kafka.streams.scala.kstream.KTable@6ee6f53 i1: 0 t2: com.compstak.org.apache.kafka.streams.scala.kstream.KTable@421bba99 foreign-key-property: n topic[TestInputTopic[topic='input-topic-1', keySerializer=StringSerializer, valueSerializer=anon$1]] key[r] value[object[ -> { "" : true },n -> "r"]] topic[TestInputTopic[topic='input-topic-2', keySerializer=StringSerializer, valueSerializer=anon$1]] key[b] value[object[u -> "b"]]{noformat} Here, we can see that the generated foreign-key property is "n", and it looks like the both records have references to their own keys. I think what you wanted was for record "r" in "input-topic-1" to reference record "b" in "input-topic-2". Instead, it references record "r" in "input-topic-2", which does not exist. Hope this helps, -John > Simple join of two KTables fails > -------------------------------- > > Key: KAFKA-9636 > URL: https://issues.apache.org/jira/browse/KAFKA-9636 > Project: Kafka > Issue Type: Bug > Components: streams > Affects Versions: 2.4.1 > Reporter: Paul Snively > Priority: Major > Attachments: kafka.tar.xz, merge_issue.zip, merge_issue.zip > > > Attempting to join two KTables yields a `Topology` that, when tested with > `TopologyTestDriver` by adding records to the two `TestInputTopic`s, results > in an empty `TestOutputTopic`. > I'm attaching a very small reproduction. The code is in Scala. The project is > therefore an "sbt" project. You can reproduce the results from your shell > with `sbt test`. The failure output will include the `describe` of the > `Topology` in question. -- This message was sent by Atlassian Jira (v8.3.4#803005)