...

Current state: Under Discussion [One of "Under Discussion", "Accepted", "Rejected"]

Discussion thread: here

JIRA: here

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

...

The default implementation of new API is based on existent method so binary compatibility is safe. Also, in order to speedup the deprecation cyclesimplify the users' migration, the existent serialize methods are marked as deprecated and all of they get default implementation which throw , which throw UnsupportedOperationException. Hence, users who don’t want to extend deprecated methods can migrate to new API safely. Of course, we should not call deprecated serialize methods anymore so the user-defined serializer which extends only new interface is able to work.

Apart from Serializer, Partitioner also need some updates since it still accept byte[]. The purposed changes are similar to Serializer that we replace byte[] by ByteBuffer. Also, the new API get default implementation based on existent method.

Public Interfaces

Briefly list any new interfaces that will be introduced as part of this proposal or any existing interfaces that will be removed or changed. The purpose of this section is to concisely call out the public contract that will come along with this feature.

A public interface is any change to the following:

• Binary log format

• The network protocol and api behavior

• Any class in the public packages under clientsConfiguration, especially client configuration

  • org/apache/kafka/common/serialization

  • org/apache/kafka/common

  • org/apache/kafka/common/errors

  • org/apache/kafka/clients/producer

  • org/apache/kafka/clients/consumer (eventually, once stable)

• Monitoring

• Command line tools and arguments

• Anything else that will likely break existing users in some way when they upgrade

Proposed Changes

Describe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Rejected Alternatives

org.apache.kafka.common.serialization.Serializer

    @Deprecated
    default byte[] serialize(String topic, T data) {
        throw new UnsupportedOperationException("this method is not used on production anymore");
    }

    @Deprecated
    default byte[] serialize(String topic, Headers headers, T data) {
        return serialize(topic, data);
    }

    default ByteBuffer serialize(String topic, T data, Headers headers) {
        byte[] array = serialize(topic, headers, data);
        return array == null ? null : ByteBuffer.wrap(array);
    }

org.apache.kafka.clients.producer.Partitioner

    @Deprecated
    default int partition(String topic, Object key, byte[] keyBytes, Object value, byte[] valueBytes, Cluster cluster) {
        throw new UnsupportedOperationException("this method is not used on production anymore");
    }

    default int partition(String topic, Object key, ByteBuffer keyBytes, Object value, ByteBuffer valueBytes, Cluster cluster) {
        return partition(topic, key, Utils.getOrCopyArray(keyBytes), value, Utils.getOrCopyArray(valueBytes), cluster);
    }

Proposed Changes

1. Serialized#serialize(String, T) is deprecated and has default implementation
2. Serialized#serialize(String, Headers, T) is deprecated and has default implementation
3. Serialized#serialize(String, T, Headers) is an new method. The order of arguments is different from Serialized#serialize(String, Headers, T) so as to keep the same method name.
4. Partitioner#partition(String, Object, byte[], Object, byte[], Cluster) is deprecated and has default implementation
5. Partitioner#partition(String, Object, ByteBuffer, Object, ByteBuffer, Cluster) is an new method.

Compatibility, Deprecation, and Migration Plan

1. All new APIs have default implementation so BC is not broken
2. All deprecated methods have default implementation so users can migrate to new interfaces without keeping deprecated override methods

Rejected Alternatives

NoneIf there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.