Status
Current state: Under Discussion [One of "Under Discussion", "Accepted", "Rejected"]
Discussion thread: here
JIRA: KAFKA-6923
Planned Release: 2.1.0
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
When headers were introduced by KIP-82 - Add Record Headers the change created the ExtendedSerializer
and ExtendedDeserializer
classes in order to keep interface compatibility but still add T deserialize(String topic, Headers headers, byte[] data);
and byte[] serialize(String topic, Headers headers, T data);
methods that consume the headers for serialization/deserialization. The reason for doing so was that Kafka at that time needed be compatbile with Java 7. Since we're not compiling on Java 7 anymore (KAFKA-4423) we should consolidate the way we're using these in a backward compatible fashion.
Public Interfaces
Two new interface methods will be created, which are the extra deserialize/serialize methods taken from the Extended classes:
public interface Serializer<T> extends Closeable { void configure(Map<String, ?> configs, boolean isKey); default byte[] serialize(String topic, T data) { return null; } default byte[] serialize(String topic, Headers headers, T data) { // This is the new method return serialize(topic, data); } @Override void close(); }
public interface Deserializer<T> extends Closeable { void configure(Map<String, ?> configs, boolean isKey); default T deserialize(String topic, byte[] data) { return null; } default T deserialize(String topic, Headers headers, byte[] data) { // This is the new method return deserialize(topic, data); } @Override void close(); }
Proposed Changes
- Introduce the method above in both interfaces
- deprecate
ExtendedSerializer/
ExtendedDeserializer
andWrapper
saying that new and existing implementations should useSerializer/Deserializer
- leave
ExtendedSerializer/ExtendedDeserializer
as is, so existing behavior won't change. - get rid of the internal usages of
ExtendedSerializer/ExtendedDeserializer
&Wrapper.ensureExtended()
Compatibility, Deprecation, And Migration Plan
All changes should be backward compatible. The defined serialize/deserialize methods in ExtendedSerializer/ExtendedDeserializer
will act as abstract overrides for the default methods which is valid. From the perspective of the implementors it shouldn't be a breaking change as the generated code in ExtendedSerializer/ExtendedDeserializer
will remain the same.
Test Plan
Review existing unit tests and system tests.
Rejected Alternatives
If 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.