why Magic Folders doesn't work for more than 2 clients

[Freelab initiative]

to my usage 1 / 2 client is a fair limitation of magic folder is working


i was just asking about the branch for it.
is it in master ? or in a special branch ?

to reactivate my network to have a try on it.






Le jeudi 12 novembre 2015, David Stainton <dstainton415 at gmail.com> a écrit :

> actually we didn't finish implementing the two party conflict
> detection... but we *could* finish it... but why? i think we should
> just solve the harder problem instead.
>
> On Thu, Nov 12, 2015 at 2:34 PM, Freelab initiative
> <freelab.cc at gmail.com <javascript:;>> wrote:
> > it is very great if magic folder are now working
> >
> > 2 clients on same file is fair enough
> >
> > we shall grab the last github to build to test this.
> > or we shall take any other build/repo ?
> >
> >
> > thanks
> >
> > xavier
> >
> >
> > Le dimanche 8 novembre 2015, David Stainton <dstainton415 at gmail.com
> <javascript:;>> a écrit
> > :
> >>
> >> Agreed; If possible we'd like to first hear Daira's solution before we
> >> send Leif's.
> >> I'm also curious to hear Zooko's solution.
> >>
> >> I've written a proposal document explaining Leif's solution.
> >> Hopefully later today Leif will apply more corrections to this document
> >> which is almost ready to be reviewed.
> >>
> >> On Fri, Nov 6, 2015 at 6:55 PM, Zooko Wilcox-O'Hearn <zookog at gmail.com
> <javascript:;>>
> >> wrote:
> >> > Dear folks:
> >> >
> >> > Context: “Magic Folders” is a new layer on top of Tahoe-LAFS which
> >> > implements Dropbox-like "auto-sync" behavior. It's super exciting!
> >> > Development of it was sponsored by Open Technology Fund. We've
> >> > finished implementing it, but now we're noticing some bugs and
> >> > limitations, and this is the biggest one I'm aware of right now.
> >> >
> >> > As David described in this comment:
> >> >
> >> > https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2551#comment:22
> >> >
> >> > The current design and implementation of Magic Folders only works if
> >> > you have no more than two clients attached to it. By "clients" I mean
> >> > here either two devices owned by the same user or two users each with
> >> > their own device — Tahoe-LAFS and Magic Folders are unaware of any
> >> > distinction between a separate human user with their own device versus
> >> > a separate client/node/process/device operated by the same human user.
> >> >
> >> > The problem is subtle, and I'm writing this letter mostly in order to
> >> > cement my own understanding of *why* the current design fails in the
> >> > 3-party (or more) case. Also in order to draw Daira's attention to it
> >> > and see what sort of fix she would suggest.
> >> >
> >> > Here is the section of the design doc about the problem of
> >> > distinguishing conflicts from overwrites pushed by your peer. We
> >> > whimsically named this problem the "Fire Dragons" problem.
> >> >
> >> >
> >> >
> https://tahoe-lafs.org/trac/tahoe-lafs/browser/docs/proposed/magic-folder/remote-to-local-sync.rst#fire-dragons-distinguishing-conflicts-from-overwrites
> >> >
> >> > The goal of the Fire Dragon slaying protocol is to make it so that you
> >> > can reliably tell whether a given new version submitted to you by your
> >> > peer was derived from the most recent version that *you* created, or
> >> > if it was derived from a previous version than the most recent version
> >> > that you created. If your peer says that it was derived from the most
> >> > recent version that you created, then this means your peer is
> >> > instructing you to *overwrite* your most recent version with their new
> >> > version. If instead your peer says that it was derived from an earlier
> >> > version, then this means there is a *conflict*, where you and your
> >> > peer simultaneously made changes to the file.
> >> >
> >> > The way the current Fire Dragon slaying protocol attempts to track
> >> > this distinction is by including a slot with each upload called the
> >> > "last-downloaded record". When you receive a new version from someone
> >> > else, you inspect the last-downloaded record that accompanies that
> >> > version, and if it shows that the version they started from was the
> >> > most recent version you sent them, then you know it is an overwrite
> >> > [*], and if it isn't, then you know it is a conflict.
> >> >
> >> > Now here's the problem: this design assumes that you are the only
> >> > source of downloadable versions that they could have started with! But
> >> > if there's a *third* party, and they started with a download from that
> >> > third party, then with this design you will assume that they are
> >> > starting from an *earlier version from you*, when in fact they are
> >> > starting from a version from the third party, which might in turn have
> >> > been derived from the most recent version from you. (Or it might not
> >> > have — it might have been derived from a previous version from you.)
> >> >
> >> > Bottom line:
> >> >
> >> > 1. Magic Folders exists, and is awesome.
> >> > 2. It works fine if you have no more than 2 devices/users/endpoints
> >> > attached. (Or if no more than two of them are editing the same
> >> > document at the same time.)
> >> > 3. The current version doesn't work if more than 2 endpoints edit the
> >> > same file at the same time.
> >> >
> >> > I have an idea about how to fix this, but I'm not going to include it
> >> > in this note, because I want Daira to have a chance to think about the
> >> > problem and propose a fix before being biased by my proposed fix, and
> >> > I want Leif to have a chance to reply with his proposed fix (that he
> >> > attempted to explain to me at the Nuts & Bolts party today).
> >> >
> >> > Regards,
> >> >
> >> > Zooko
> >> >
> >> > [*] Except if there turns out to be an Earth Dragon — see the design
> >> > doc for details.
> >> > _______________________________________________
> >> > tahoe-dev mailing list
> >> > tahoe-dev at tahoe-lafs.org <javascript:;>
> >> > https://tahoe-lafs.org/cgi-bin/mailman/listinfo/tahoe-dev
> >> _______________________________________________
> >> tahoe-dev mailing list
> >> tahoe-dev at tahoe-lafs.org <javascript:;>
> >> https://tahoe-lafs.org/cgi-bin/mailman/listinfo/tahoe-dev
>
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