"Matthias J. Sax" <mj...@apache.org> writes: > In general, it's not safe to keep the iterator open, because when process() is > executed in-between two punctuator calls, it might modify the store and > invalidate the iterator. There is no guarantee that the returned iterator > supports concurrency.
This makes sense but unfortunately adds significant challenge to making these operations happen concurrently, which is effectively a hard requirement for my usecase due to the scale of the state stores' contained data. > Hence, even if it happens that the currently used iterator is concurrent, > there > is no API contract about it. This surprises me though, because it seems to contratict what's stated in the ReadOnlyKeyValueStore documentation[1]. > The returned iterator must be safe from ConcurrentModificationExceptions and > must not return null values. Order is not guaranteed as bytes lexicographical > ordering might not represent key order. Maybe I'm reading this wrong, but it seems to imply that the returned iterator must be safe in the face of concurrent modifications, which is required if you are permitted to make a read-modify-write cycle while using the iterator, which the existing version of my application has been doing correctly so far as I can tell. Am I vastly misunderstanding the intended usecase for punctuators and need to determine a different mechanism for performing periodic operations on a data store? [1]: <https://kafka.apache.org/28/javadoc/org/apache/kafka/streams/state/ReadOnlyKeyValueStore.html#all()>
