How can I specify a Java class in the kafka bolt Producer Config within Storm?

[#1]

Kafka 0.9 requires that the "key.serializer" and "value.serializer" items in ProducerConfig be java classes, not a string containing the name of a java class. See https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/clients/producer/P...

However, if try to do that like this:

Properties props = new Properties();props.put("bootstrap.servers", topoProperties.getProperty("bootstrap.servers"));
props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, io.confluent.kafka.serializers.KafkaAvroSerializer.class);
props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, io.confluent.kafka.serializers.KafkaAvroSerializer.class);

conf.put(KafkaBolt.KAFKA_BROKER_PROPERTIES, props);

Storm fails to start with this error:

java.lang.IllegalArgumentException: Topology conf is not json-serializable

See: https://github.com/apache/storm/blob/master/storm-core/src/jvm/org/apache/storm/StormSubmitter.java#...

Seems like kafka-bolt's prepare method will have to transform a string into a Java class. Before I go down that path, I was wondering if anyone else had run into this problem and if there's a workaround?

Thanks! -Aaron

[#2 · Accepted solution]

I should have done a bit more research... this is a problem in Storm 0.10, but it looks like the upcoming Storm 1.0 release will handle this situation by allowing properties to be passed directly to the Kafka Bolt instead of indirectly through the Topology configuration:

https://github.com/apache/storm/blob/master/external/storm-kafka/src/jvm/org/apache/storm/kafka/bolt...