+1 on this change — APIs are forever. As much as we’d love to see 0.8.2 release
ASAP, it is important to get this right.
-JW
> On Nov 24, 2014, at 5:58 PM, Jun Rao <jun...@gmail.com> wrote:
>
> Hi, Everyone,
>
> I'd like to start a discussion on whether it makes sense to add the
> serializer api back to the new java producer. Currently, the new java
> producer takes a byte array for both the key and the value. While this api
> is simple, it pushes the serialization logic into the application. This
> makes it hard to reason about what type of data is being sent to Kafka and
> also makes it hard to share an implementation of the serializer. For
> example, to support Avro, the serialization logic could be quite involved
> since it might need to register the Avro schema in some remote registry and
> maintain a schema cache locally, etc. Without a serialization api, it's
> impossible to share such an implementation so that people can easily reuse.
> We sort of overlooked this implication during the initial discussion of the
> producer api.
>
> So, I'd like to propose an api change to the new producer by adding back
> the serializer api similar to what we had in the old producer. Specially,
> the proposed api changes are the following.
>
> First, we change KafkaProducer to take generic types K and V for the key
> and the value, respectively.
>
> public class KafkaProducer<K,V> implements Producer<K,V> {
>
> public Future<RecordMetadata> send(ProducerRecord<K,V> record, Callback
> callback);
>
> public Future<RecordMetadata> send(ProducerRecord<K,V> record);
> }
>
> Second, we add two new configs, one for the key serializer and another for
> the value serializer. Both serializers will default to the byte array
> implementation.
>
> public class ProducerConfig extends AbstractConfig {
>
> .define(KEY_SERIALIZER_CLASS_CONFIG, Type.CLASS,
> "org.apache.kafka.clients.producer.ByteArraySerializer", Importance.HIGH,
> KEY_SERIALIZER_CLASS_DOC)
> .define(VALUE_SERIALIZER_CLASS_CONFIG, Type.CLASS,
> "org.apache.kafka.clients.producer.ByteArraySerializer", Importance.HIGH,
> VALUE_SERIALIZER_CLASS_DOC);
> }
>
> Both serializers will implement the following interface.
>
> public interface Serializer<T> extends Configurable {
> public byte[] serialize(String topic, T data, boolean isKey);
>
> public void close();
> }
>
> This is more or less the same as what's in the old producer. The slight
> differences are (1) the serializer now only requires a parameter-less
> constructor; (2) the serializer has a configure() and a close() method for
> initialization and cleanup, respectively; (3) the serialize() method
> additionally takes the topic and an isKey indicator, both of which are
> useful for things like schema registration.
>
> The detailed changes are included in KAFKA-1797. For completeness, I also
> made the corresponding changes for the new java consumer api as well.
>
> Note that the proposed api changes are incompatible with what's in the
> 0.8.2 branch. However, if those api changes are beneficial, it's probably
> better to include them now in the 0.8.2 release, rather than later.
>
> I'd like to discuss mainly two things in this thread.
> 1. Do people feel that the proposed api changes are reasonable?
> 2. Are there any concerns of including the api changes in the 0.8.2 final
> release?
>
> Thanks,
>
> Jun
