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.
1. Is it simply a matter of noting this in the relevant upgrade doc?
2. Or do we want to write more code to handle upgrade scenarios?
3. Or find a more backwards compatible way of writing this serde?
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