[opensource-dev] New HTTP Library & Project Viewer

Dahlia Trimble dahliatrimble at gmail.com
Thu Aug 2 12:47:43 PDT 2012

Don't worry Carlo, I know better than to try to tell an engineer how to do
her/his job ;)

So, if pipelining is implemented and it works, what other bottlenecks are
there that make multiple connections work so well?

On Thu, Aug 2, 2012 at 10:14 AM, Carlo Wood <carlo at alinoe.com> wrote:

> On Thu, 2 Aug 2012 02:01:45 -0700
> Dahlia Trimble <dahliatrimble at gmail.com> wrote:
> > I can't help but think something is wrong here.  A single TCP/IP link
> > is more than capable of saturating available network bandwidth with
> > efficient transfers of large volumes of data provided the end-points
> > can produce and consume quickly enough.
> >
> > It seems part of the problem may in the request/response nature of
> > HTTP. The viewer needs to make a request for each asset it needs as
> > it discovers it needs it. It sends a request for each asset, and the
> > provider endpoint then has to do whatever it does to make the asset
> > available before beginning to send it back to the client. This may
> > occur relatively instantly in the case of assets in a server memory
> > cache, or a lot longer depending on where it needs to be pulled from
> > or how it may need to be prepared. Assuming this is the case, having
> > multiple overlapping requests can improve the overall download rate
> > of multiple assets by allowing some downloads to occur while others
> > are prepared, albeit at the expense of additional connections. Having
> > a persistent connection reduces some of the delays introduced by
> > re-establishing a connection for each asset, but it does nothing to
> > reduce the time that the server endpoint needs to acquire and prepare
> > the asset to send.
> >
> > Now (assuming this isn't the case already) if the producer endpoint
> > could be made aware of future requests, it could fetch and prepare
> > the asset for transfer prior to the actual request being received,
> > thereby reducing or eliminating the time delays inherent in the
> > request-response paradigm. This *may* be as simple as adding
> > additional optional UUIDs and parameters to the asset request for
> > assets that the viewer would likely be requesting next. If this were
> > the case, a single connection could have a higher effective
> > throughput by ensuring minimal delays between request and response,
> > and reduce the need for more simultaneous connections.
> >
> > Such a solution may or may not be practical or easily implemented in
> > existing infrastructure, or may not be as efficient as other designs.
> > My point is more or less meant to bring more perspectives into the
> > discussion by considering other bottlenecks that may exist, which if
> > mitigated, could reduce the need for excessive connections.
> >
> > Thoughts?
> > -dahlia
> Dahlia, an overwhelming amount of past experience has taught us that
> Linden Lab is not interested if you "think along" with them about the
> server, or the viewer-server protocol,either with suggestions, designs
> or anything. This list is set up to get feedback about viewer bugs, and
> to announce things they came up with (in most cases someone else came up
> with than the ones that we're allowed to talk with). So, it's a complete
> waste of your time to do anything else than to just sit back and read
> what Linden Lab is going to push through (no matter what arguments you
> come with, or what flaws you point out).
> [ That being said, they came up with "pipelining" as the solution for
> the problem you mention. That allows a viewer to send new requests over
> the same connection, without having to wait for a reply for former
> requests. This isn't the most efficient solution, but a lot better
> (still depending on the closed source server implementation though)
> than how it works so far. ]
> --
> Carlo Wood <carlo at alinoe.com>
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