[GitHub] [kafka] vvcephei commented on a change in pull request #10720: MINOR: preserve timestamp when getting value from upstream state store

[GitBox <gi...@apache.org>]

vvcephei commented on a change in pull request #10720:
URL: https://github.com/apache/kafka/pull/10720#discussion_r635592113



##########
File path: streams/src/main/java/org/apache/kafka/streams/kstream/internals/KTableTransformValues.java
##########
@@ -141,16 +144,32 @@ public void close() {
 
         @Override
         public void init(final ProcessorContext context) {
+            internalProcessorContext = (InternalProcessorContext) context;
             parentGetter.init(context);
             valueTransformer.init(new ForwardingDisabledProcessorContext(context));
         }
 
         @Override
         public ValueAndTimestamp<V1> get(final K key) {
             final ValueAndTimestamp<V> valueAndTimestamp = parentGetter.get(key);
-            return ValueAndTimestamp.make(
+
+            final ProcessorRecordContext currentContext = internalProcessorContext.recordContext();
+
+            internalProcessorContext.setRecordContext(new ProcessorRecordContext(

Review comment:
       Thanks, all. I share the concern that this change could suddenly break something. Since the transformer has access to the ProcessorContext, people well may be accessing these members within the `transform` method. For example, a transformer may suddenly start to get an NPE on the topic name, and so forth.
   
   This behavior change might be ok on the grounds that the context we previously provided was actually incorrect, though. If we do go ahead with this approach, we should be sure to make note of this potential in the upgrade notes. It wouldn't hurt to have a ticket as well, for visibility's sake.




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