Re: Protect against servers stepping on each other's toes

[prj@po.cwru.edu (Paul Jarc)]

Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann) wrote:
> If I have two servers using the same directory, there is potential for
> the two stepping on each other's toes.

I think much of this could be prevented by using different defaults
for different backends, or (like nnmaildir does) by requiring the user
to explicitly specify a directory in the server parameters.

> Here's a suggestion: when a server is first activated, it writes
> something special to its directory which says what server `owns' that
> directory.

Are we trying to protect against two servers in two different Emacsen?
If not, we don't need to touch the directory itself.  Something
internal to Gnus would do.

Is this indicator supposed to stay there all the time, or will it be
removed when the server is closed?

> But even before that, each server looks to see if some other server
> has already written that the directory is `owned' by it.  When this
> happens, a warning is issued or something like that.

There's a race condition there.  But that's not a problem for two
servers in the same Emacs.

> Also, maybe we want to put the claiming information inthe active
> file.  Maybe in the directory _and_ in the active file?

Putting it in both wouldn't provide any additional usefullness.
Putting it in the active file would mean we aren't protected against
other Emacsen, but in that case a nonpersistent variable will do; it
doesn't need to be saved anywhere.


paul