[jsr369-experts] Re: Reactive Streams and Servlet 4: synergy or no?

From: Mark Thomas <markt_at_apache.org>
Date: Wed, 05 Aug 2015 09:09:29 +0100

On 04/08/2015 18:44, Edward Burns wrote:
> Hello Volunteers,
> For the upcoming JavaOne EDR, I would like to at least know whether or
> not we should address the Reactive Streams [1] initative sponsored by
> TypeSafe in Servlet 4.

I think it is something we should consider. I don't have a view on
whether we should or not at this point. I don't feel I know enough to
make a sensible decision.

> I am aware that Greg Wilkins has done some exploratory work in this
> area,

Is there a reference available for this that we can read?

> and I am intrigued with his idea of being able to leverage the
> flow-control facility of HTTP/2 to convey "backpressure".

They look to be a very good match since in both cases it is the receiver
that controls how much data the sender can send.

> (As an aside, I would love it if someone would explain how backpressure
> differs from congestion control a la RFC 5681.)

Based on my limited understanding, congestion control involves the
sender sending more and more data until it detects that the recipient is
overwhelmed and can't cope. Back pressure (as used in reactive streams)
involves the recipient telling the sender how much data it may send.