Streams groupBy: why does it keep track of closed subflows ?

[Cyrille Corpet]

I have a flow with a groupBy stage, and I wish to close some subflow when idle, to avoid having too many subflows at any given time. However, once closed, all subsequent elements which would have been dispatched to this subflow are ignored, instead of creating a new subflow.

While looking at the sources, I noticed that the stage keeps track of the closed substreams. Is there a specific reason for this, or is it just a feature of the stage that was deemed useful when developed ?

Thanks for your input,

Cyrille Corpet