Re: http://tech.slashdot.org/comments.pl?sid=1885890&cid=34358134

From: Will Palmer <wmpalmer@gmail.com>
Date: Nov 30, 2010, 09:43 UTC
Message-ID: <1291110230.11984.21.camel@wpalmer.simply-domain>
In-Reply-To: <4CF3FEB0.9040806@eaglescrag.net>

On Mon, 2010-11-29 at 11:27 -0800, J.H. wrote:

Show 6 quoted lines

> > I want my version control software to use p2p concepts for efficiency. I
> > don't want my version control software to be a p2p client any more than
> > I want my text-editor to be a mail client.
> 
> Keep in mind that adding p2p concepts to something doesn't make it more
> efficient, in fact in most cases it makes it dramatically *LESS* efficient.

As a simple use-case: Everyone comes into an office in the morning and runs "git remote update". This potentially causes a lot of traffic between the office and their offsite central repository. If this were a p2p scenario, the transfer from the offsite could potentially happen only once.

That counts as "more efficient", to me.

Show 5 quoted lines

> 
> git-torrent like concepts have come up in the past, and I keep pointing
> out how and why they likely won't be useful.  The biggest reason: there
> is no advantage for a client to stay in the cloud once they have their
> data.

This is true of bittorrent as well: People stay in the cloud for altruistic reasons.

You're thinking p2p in terms of "every peer serves data, and keeps serving data. The network is more robust over time". I'm thinking p2p in terms of "Every peer has the ability to serve data. Adding a server is as trivial as adding a client."

The greatest advantage I can think of is "no existing server needs to agree to the addition of a new server", or at least "the addition of an existing server is accepted by convention, no questions asked"

> ..... You can force this, sure, but clones are seldom and rare to begin
> with (as you mentioned) so there won't be a very large cloud to pull
> from to start with.  With that in mind, I really see no advantage to p2p
> inside of the git core at all.  It adds a lot of complexity for little gain.

I agree that git itself is not a good place to explore p2p concepts. I assume it would be much more useful to develop an independent p2p layer and allow git to somehow use that. And while there won't be "a large cloud", it's almost a guarantee that there would be more than the /one/ server currently available during clones or long fetches.

Show 15 quoted lines

> Now you do mention things that would be useful:
> 
> - Ability to resume a clone that you only have a partial download for
> (maybe just pack files?)
> - Ability to include something like a 'meta-link' like list of
> repositories to check for data (inferred from the multiple download
> locations)
> 
> There are things we can learn from p2p, but I don't think adding it to
> git is actually useful.
> 
> Just my $0.02 though.
> 
> - John 'Warthog9' Hawley
>

The biggest hurdle, I assume, would be "get git to talk to more than one source of data at once", even if one needs to set those up manually. If I understand correctly, packfiles are generated in a way which would not necessarily be consistent between clones.