Re: HTTP protocol v2: rethunk.

On Thu, Nov 6, 2008 at 8:23 AM, Ben Collins-Sussman
<sussman_at_red-bean.com> wrote:
> On Thu, Nov 6, 2008 at 9:54 AM, Greg Hudson <ghudson_at_mit.edu> wrote:
>
>> If plan #1 is ever faster than plan #2, I strongly suspect it's only
>> because it's grabbing a larger share of a congested pipe. I don't know
>> why anyone would think four TCP connections between the same two
>> endpoints would intrinsically have more bandwidth than a single
>> connection.
>
> I'm clearly out of my league here; perhaps a degree in computer
> science would have helped me here.
>
> From talking to a friend, the story I hear is that the parallel
> solution might be faster only in the situation of a congested pipe.
> That is, because TCP only allows a certain number of packets to be 'on
> the wire' at once, sending the files serially over a congested network
> may cause more waiting overall. (Send max data allowed; wait for
> response; repeat.) In an uncongested LAN environment, there'd be no
> noticeable speedup at all.

"wait for response" here is the problem, of course. In ra_svn, you
don't have to wait for a response until the commit is entirely done.
(If there are errors, the server tries to send them asynchronously.)
Any "new HTTP protocol" that doesn't steal this feature from ra_svn is
a waste of effort as far as I'm concerned.

--dave

> All that said, I'll let gstein and jerenkrantz speak up here... I
> shouldn't be arguing their opinions for them. :-) Personally, I
> much prefer the "whole commit in a single HTTP request" method -- it's
> easier to code, easier to understand, and doesn't open up FSFS or
> libsvn_fs_bigtable to data-stomping race conditions.
>
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-- 
David Glasser | glasser@davidglasser.net | http://www.davidglasser.net/
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