fqaiser94 commented on a change in pull request #10747: URL: https://github.com/apache/kafka/pull/10747#discussion_r637657442
########## File path: streams/src/main/java/org/apache/kafka/streams/kstream/internals/ChangedSerializer.java ########## @@ -45,34 +45,30 @@ public void setIfUnset(final Serializer<Void> defaultKeySerializer, final Serial } /** - * @throws StreamsException if both old and new values of data are null, or if - * both values are not null + * @throws StreamsException if both old and new values of data are null. */ @Override public byte[] serialize(final String topic, final Headers headers, final Change<T> data) { - final byte[] serializedKey; + final boolean oldValueIsNull = data.oldValue == null; + final boolean newValueIsNull = data.newValue == null; - // only one of the old / new values would be not null - if (data.newValue != null) { - if (data.oldValue != null) { - throw new StreamsException("Both old and new values are not null (" + data.oldValue - + " : " + data.newValue + ") in ChangeSerializer, which is not allowed."); - } - - serializedKey = inner.serialize(topic, headers, data.newValue); + // both old and new values cannot be null + if (oldValueIsNull && newValueIsNull) { + throw new StreamsException("Both old and new values are null in ChangeSerializer, which is not allowed."); } else { - if (data.oldValue == null) { - throw new StreamsException("Both old and new values are null in ChangeSerializer, which is not allowed."); - } - - serializedKey = inner.serialize(topic, headers, data.oldValue); + final byte[] newData = newValueIsNull ? new byte[0] : inner.serialize(topic, headers, data.newValue); + final byte[] oldData = oldValueIsNull ? new byte[0] : inner.serialize(topic, headers, data.oldValue); + + final int newDataLength = newData.length; + final int capacity = NEW_DATA_LENGTH_BYTES_SIZE + newDataLength + oldData.length; + + return ByteBuffer + .allocate(capacity) + .putInt(newDataLength) + .put(newData) + .put(oldData) + .array(); Review comment: With the change to the `ChangedSerializer` and `ChangedDeserializer` classes, I don’t think users will be able to just upgrade from a previous version of Kafka Streams easily. Any "inflight" messages from older library versions will fail to deserialize correctly. Not sure how these types of “breaking” changes are typically handled. Is it simply a matter of noting this in the relevant upgrade doc? Or do we want to write more code to handle upgrade scenarios? Or find a more backwards compatible way of writing this serde? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org