plugin: sftp transport

[Jan Hudec]

On Tue, Oct 18, 2005 at 16:35:24 -0500, John A Meinel wrote:
> > $ bzr branch sftp://robey@example.com/foo/bar/stuff
> >
> > Read and write locks aren't supported, just like with HTTP.  There's
> > probably something clever I can do there, assuming we only care about
> > read/write locking against other bzr-over-sftp instances, but I
> > haven't put much thought into it.
> 
> Read locks would be nice, because it would let us cache things locally,
> and guarantee that they aren't changing remotely. Write locks would be
> nice when we go to support "bzr push" to a remote branch. (and when
> Aaron's changes for remote bound-branches is implemented).
> 
> I know the SFTP v6 spec supported all sorts of nice things, but I believe
> everyone is using v3, and I don't know what that does and doesn't
> implement.

The locks must not be transport specific. They must work for all
protocols. Ie. reader over HTTP must notice that someone is writing over
SFTP. And HTTP does not support fcntl locks, so even if new sftp does,
they are of little use. When webdav and plain ftp are added, they also
won't handle those.

In addition, I think full transaction semantics is necessary. Because
when a connection breaks, any other client must be able to break the
lock and continue. And if the connection was not actually broken, only
too slow, the first client must just say "Transaction failed, try again"
and upon restart properly do whatever it was up to.

Which boils down to some kind of renaming stuff like tla/baz do.

--
						 Jan 'Bulb' Hudec <bulb at ucw.cz>
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