I am not sure if I understand the use case correctly. Could you give some more context?
> backing store whose partitioning is value dependent In infer that you are using a custom store and not default RocksDB? If yes, what do you use? What does "value dependent" mean in this context? Right now, I am wondering, why you not just set a new key to get your data grouped by the field you are interesting in? Also, if you don't partitioned your data by key, you might break your streams application with regard to fault-tolerance -- or does your custom store not rely on changelog backup for fault-tolerance? -Matthias On 6/2/17 10:34 AM, Steven Schlansker wrote: > I have a KTable and backing store whose partitioning is value dependent. > I want certain groups of messages to be ordered and that grouping is > determined > by one field (D) of the (possibly large) value. > > When I lookup by only K, obviously you don't know the partition it should be > on. > So I will build a GlobalKTable of K -> D. This gives me enough information > to determine the partition. > > Unfortunately, the KafkaStreams metadata API doesn't fit this use case well. > It allows you to either get all metadata, or by key -- but if you lookup by > key > it just substitutes a null value (causing a downstream NPE) > > I can iterate over all metadata and compute the mapping of K -> K,D -> P > and then iterate over all metadata looking for P. It's not difficult but ends > up being a bit of somewhat ugly code that feels like I shouldn't have to > write it. > > Am I missing something here? Is there a better way that I've missed? Thanks! >
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