Hi Folks, as I said in the subject. How will this work? I'm in the process about thinking how to implement low watermarks in Streaming. I'm thinking that the implementation should be quite similar to how the checkpointing barriers will be implemented since they also flush out stuff.
Now I'm wondering how this will work with merged Streams and the output selectors (split streams). It seems to me that there are a lot of paths that elements can take to arrive at operators. The problem I have is that an operator can only emit a low watermark itself if it knows that all input operators have sent him a low watermark with that value (the low watermark is the minimum of the low watermarks of all upstream operators). I imagine that the checkpoint barriers exhibit the same behaviour. Do we maybe have to add an explicit union (merge) operator and change how split streams are implemented? What are your thoughts? Cheers, Aljoscha
