Re: [Gnu-arch-users] Re: Questions from a Subversion user

[Andrew Suffield]

On Mon, Aug 18, 2003 at 09:10:52AM -0700, Tom Lord wrote:
>     > From: John Goerzen <address@hidden>
> 
>     > > arch supports a bunch of transports: ftp, sftp, http, and others.  
> arch
>     > > implements its own locking scheme.  I am not sure what you mean by
>     > > "insure integrity."
> 
>     > What I'm talking about is multiple users writing to the repository at
>     > once.  FTP (and SFTP, and HTTP) doesn't implement anything like
>     > flock() -- and the best that one normally can do is creating
>     > lockfiles, which have inherent race conditions and are thus
>     > unreliable.  It'd be really easy to have two people running a STOR on
>     > the same file at once -- with likely disastrous results.
> 
> The locking mechnanisms in arch do not have race conditions and are
> robust for multi-user concurrent access.   They rely only on some
> least-common-denominator properties of `mkdir' and `rename' -- safe,
> even, on NFS.

No Files are Safe.

It's always possible that your mkdir()/rename() lands on the wrong
thing entirely, because NFS has gotten its inode numbers in a twist
again :P

[Of course, when this happens then your files are being eaten alive, so
a few abused locks are the least of your worries]

[Yeah, it's that bad]

-- 
  .''`.  ** Debian GNU/Linux ** | Andrew Suffield
 : :' :  http://www.debian.org/ |
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