dovecot - Mar 2009 - imap locking spool?

How does IMAP lock the /var/spool/mail/user file?

Here's my problem:  I'm writing a script to expire old or
oversize mail through a series of archive folders.  I don't
want to take the whole server down to do this, nor does it
seem like I would have to lock the user out entirely if I
can manage to emulate the locks correctly.

I am able to lock /var/spool/mail/user (and ~user/mail/*)
from procmail, dovecot popmail, and openwebmail using
dotlocks.

What do I do to prevent dovecot imap from writing the spool
and various mbox files while my script is running?  Just
posix fcntl on the various files?

I'm trying to use Mail::Box in perl which I'm having some
problems with, corresponding with the developer, but if
anyone has any easy way out I would appreciate the advice
very much!

Mark

On Tue, 2009-03-03 at 13:54 -0800, Mark Hedges wrote:
> How does IMAP lock the /var/spool/mail/user file?
mbox_read_locks and mbox_write_locks defines it.
> Here's my problem:  I'm writing a script to expire old or
> oversize mail through a series of archive folders.  I don't
> want to take the whole server down to do this, nor does it
> seem like I would have to lock the user out entirely if I
> can manage to emulate the locks correctly.
How about doing it via IMAP? Then you wouldn't need to worry about
locking or anything else.

1 select mailbox
2 search before 01-jun-2006
3 store <those messages> +flags.silent \deleted
4 expunge

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 197 bytes
Desc: This is a digitally signed message part
URL:
<http://dovecot.org/pipermail/dovecot/attachments/20090303/d16c01b9/attachment-0002.bin>

On Tue, 3 Mar 2009, Timo Sirainen wrote:
> On Tue, 2009-03-03 at 13:54 -0800, Mark Hedges wrote:
> > How does IMAP lock the /var/spool/mail/user file?
>
> mbox_read_locks and mbox_write_locks defines it.
mbox_read_locks = fcntl
mbox_write_locks = dotlock fcntl

Unfortunately openwebmail only respects dotlocks.  (or
flock, but procmail doesn't use flock, or doesn't say it
does.)

So what if my script is reading the messages to delete with
IMAP, then a user logs into openwebmail, reads their inbox,
selects messages to delete, but then my script deletes them,
and then they try the delete operation on the mailbox that
is no longer in sync?
> > Here's my problem:  I'm writing a script to expire old
> > or oversize mail through a series of archive folders.
> > I don't want to take the whole server down to do this,
> > nor does it seem like I would have to lock the user out
> > entirely if I can manage to emulate the locks correctly.
>
> How about doing it via IMAP? Then you wouldn't need to worry about
> locking or anything else.
>
> 1 select mailbox
> 2 search before 01-jun-2006
> 3 store <those messages> +flags.silent \deleted
> 4 expunge
That would be great if it meant that users could not log
into openwebmail at the same time, but it doesn't, AFAICT,
without establishing dotlocks.  I am just assuming that
users will not log in through IMAP and openwebmail at the
same time.

I like my original suggestion of turning off all services
while the script runs, but that's not a solution,
apparently.

I'm also thinking maybe I can lock the user's password, use
verbose_proctitle to make sure they're not logged in and/or
kick the individual out with `kill`, then run the script,
which I've verified does block procmail delivery.

The matrix has you!

Mark