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Re: [PATCH] svnsync init URL1 URL1

From: Ph. Marek <philipp.marek_at_bmlv.gv.at>
Date: Mon, 28 Apr 2008 10:26:59 +0200

On Montag, 28. April 2008, Daniel Shahaf wrote:
> Ph. Marek wrote on Mon, 28 Apr 2008 at 09:51 +0200:
> > On Montag, 28. April 2008, Daniel Shahaf wrote:
> > > I am trying to prevent syncing an instance of a repository[1] to
> > > itself. Is it possible to tell apart two instances that have the same
> > > UUID?
> > >
> > > (Equality of UUIDs is a necessary but not sufficient condition for
> > > identity of instances, and equality of URLs is sufficient but not
> > > necessary.)
> > >
> > > [1] "An instance of", since in DAV mirroring, etc., there are actually
> > > two "instances" of the same repository.
> >
> > Sounds to me like you need some second identity for each repository - not
> > the subversion-client-UUID, but another real-repository-UUID :-)
> Exactly.
> > How about a revprop on r0? Seems to be the easiest, and most compatible,
> > place for that.
> >
> > Set it if it doesn't exist; then query the other repository; if it's the
> > same there, it's the same repository.
> And if the revprop exists when the master repository is duplicated?
> (e.g. if there are two mirror sites.) One could make 'svnadmin dump'
> and 'svnsync' ignore the new property, but some people might tar or
> rsync their master when they create the mirror.
You're right, that's a problem.

Hmmm ... it seems that this is similar to the problem "on which harddisk
sector is that block" (that bootloaders need solved), when they go through
some intermediate layers - device mapper, raid, etc.

So there should possibly be some function that returns something like
  MD5(hostname . "\0" . absolute path to the repository)
which gets passed down to the *real* repository filesystem layers, and
answered *only* from them ...

Then you could still have a problem if the repository is on a NAS, and gets
mounted by two machines - one for http, one for svn+ssh ...

Thinking along this lines I get a recursion - you need some value *for the
repository*, that doesn't get transferred *with* the repository ...

So maybe some lookup table repos-UUID to real-ID, stored in some completely
different location - like /var/spool? But if you change the machine, you'd
like to keep it the same again ....

Don't know what's best - I think you've got a problem :-)
- On one side you'll have to transfer that *with* the repository, but
- on the other side you don't want to transfer it.

So, as conclusion - maybe take the revprop, and give an easy command "svnsync
new-repos-ID" or something like that, that can be run after the initial



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Received on 2008-04-28 10:27:18 CEST

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