vvcephei commented on a change in pull request #9361:
URL: https://github.com/apache/kafka/pull/9361#discussion_r498904526
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File path:
streams/src/main/java/org/apache/kafka/streams/processor/api/ProcessorContext.java
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@@ -55,6 +52,16 @@
*/
TaskId taskId();
+ /**
+ * The metadata of the record, if it is defined. Note that as long as the
processor is
Review comment:
Thanks, @pgwhalen !
I agree, the docs I wrote were a little too terse. How about this:
```java
/**
* The metadata of the source record, if is one. Processors may be
invoked to
* process a source record from an input topic, to run a scheduled
punctuation
* (see {@link ProcessorContext#schedule(Duration, PunctuationType,
Punctuator)} ),
* or because a parent processor called {@link
ProcessorContext#forward(Record)}.
* <p>
* In the case of a punctuation, there is no source record, so this
metadata would be
* undefined. Note that when a punctuator invokes {@link
ProcessorContext#forward(Record)},
* downstream processors will receive the forwarded record as a regular
* {@link Processor#process(Record)} invocation. In other words, it
wouldn't be apparent to
* downstream processors whether or not the record being processed came
from an input topic
* or punctuation and therefore whether or not this metadata is defined.
This is why
* the return type of this method is {@link Optional}.
* <p>
* If there is any possibility of punctuators upstream, any access
* to this field should consider the case of
* "{@code recordMetadata().isPresent() == false}".
* Of course, it would be safest to always guard this condition.
*/
```
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