Stream::merge may be susceptible to stream "barbara battles buffered streams"

[yoshuawuyts]

Tmandry's post showed how progressing a stream + concurrently executing a stream can lead to timeouts - this will affect Stream::merge as well. Probably the better solution is #164 which can run the processing concurrently with the underlying stream.

[yoshuawuyts]

(note that this isn't an issue if you ensure that the function bodies in Stream::merge are short-lived)

[yoshuawuyts]

What I'm concretely proposing here is: Stream::merge should return a new trait, ConcurrentStream which can concurrently progress both the underlying streams and the individually handled items. That's a change from today, where Stream::merge returns a regular Stream which if used incorrectly may lead to the issues mentioned.

[yoshuawuyts]

#164 implements ConcurrentStream. We may want Stream::merge to return that instead. At the very least we should try and experiment with that.