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Matthias J. Sax commented on KAFKA-4691: ---------------------------------------- I am not sure, if we can fix this soon. The problem is, that Streams uses a single `KafkaProducer` for all output topics. All those output topics might have different types for keys and values while `KafkaProducer` can only be configures to use a single serializer; one for the key and one for the value. Thus, Kafka Streams configures the producer to use {{byte[]}} as key and value type and use the appropriate serializers per output topic before handing the record to the producer. Right now, I would rather close this as "won't fix". \cc [~guozhang] > ProducerInterceptor.onSend() is called after key and value are serialized > ------------------------------------------------------------------------- > > Key: KAFKA-4691 > URL: https://issues.apache.org/jira/browse/KAFKA-4691 > Project: Kafka > Issue Type: Bug > Components: clients, streams > Affects Versions: 0.10.1.1 > Reporter: Francesco Lemma > Labels: easyfix > Attachments: 2017-01-24 00_50_55-SDG_CR33_DevStudio - Java EE - > org.apache.kafka.streams.processor.internals.Reco.png > > > According to the JavaDoc > (https://kafka.apache.org/0101/javadoc/org/apache/kafka/clients/producer/ProducerInterceptor.html) > " This is called from KafkaProducer.send(ProducerRecord) and > KafkaProducer.send(ProducerRecord, Callback) methods, before key and value > get serialized and partition is assigned (if partition is not specified in > ProducerRecord)". > Although when using this with Kafka Streams > (StreamsConfig.producerPrefix(ProducerConfig.INTERCEPTOR_CLASSES_CONFIG)) the > key and value contained in the record object are already serialized. > As you can see from the screenshot, the serialization is performed inside > RecordCollectionImpl.send(ProducerRecord<K, V> record, Serializer<K> > keySerializer, Serializer<V> valueSerializer, > StreamPartitioner<K, V> partitioner), effectively > before calling the send method of the producer which will trigger the > interceptor. > This makes it unable to perform any kind of operation involving the key or > value of the message, unless at least performing an additional > deserialization. -- This message was sent by Atlassian JIRA (v6.3.4#6332)