Kafka streams GlobalKTable throws Deserialization exception on Tombstone - null value- records

Question

I have a Spring cloud stream based Kafka Streams application where I'm binding a Global KTable to a Compact topic. When I push a Tombstone record to the topic (Non-empty key with null value) - my Kafka streams application fails with Deserialization exception. The failure is because my deserializer does not handle null records.

From the documentation, I thought GlobalKTable will not even "see" null-value records. Is it not the case? Do I need to handle null records in the deserializer?

 org.apache.kafka.common.errors.SerializationException: Unable to deserialize Caused by: java.lang.IllegalArgumentException: argument "src" is null at com.fasterxml.jackson.databind.ObjectMapper._assertNotNull(ObjectMapper.java:4693) at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3511) at common.domain.serdes.MySerde$MyDeserializer.deserialize(MySerde.java:47) at common.domain.serdes.MySerde$MyDeserializer.deserialize(MySerde.java:39) at org.apache.kafka.streams.processor.internals.SourceNode.deserializeValue(SourceNode.java:63) at org.apache.kafka.streams.processor.internals.RecordDeserializer.deserialize(RecordDeserializer.java:66) at org.apache.kafka.streams.processor.internals.GlobalStateUpdateTask.update(GlobalStateUpdateTask.java:91) at org.apache.kafka.streams.processor.internals.GlobalStreamThread$StateConsumer.pollAndUpdate(GlobalStreamThread.java:240) at org.apache.kafka.streams.processor.internals.GlobalStreamThread.run(GlobalStreamThread.java:289)

Answer 1

Yes; you have to check for null and return null . See any of the standard deserializers.

Unlike the KafkaConsumer 's Fetcher (which checks for null before calling), the kafka-streams calls it unconditionally. See

 at org.apache.kafka.streams.processor.internals.SourceNode.deserializeValue(SourceNode.java:63)