[dovecot] Re: Architectural questions

[Thomas Wouters]

On Sat, Oct 19, 2002 at 12:42:25PM -0400, Charlie Brady wrote:

> > So when we needed an IMAP server for use with our webmail (based on
> > SquirrelMail), we were forced to go with the UW-IMAP server, with the
> > maildir patch that's been scattered around the 'net. This worked, for a
> > while; we also use the maildir patch with pine after all. However, the
> > maildir patch is not very good. Not at all, even, and it only seems to
> > work by pure chance.

> The best one I've found is the patch last modified AFAICT by Miquel van 
> Smoorenburg, which has maildir filenames like:
> time.pid.host,U=xxx,W=yyy:2,flags

We use two different patches, both of which have a bit of Mike in them. One
is for the IMAP server, which is an old version ('uw-imap-2000' or something
like that comes to mind, but it came from the pine 4.10 source) from before
the mailbox->append prototype changed (but with Mike's bilennium-patch.) A
big problem with later patches was that the append method changed in the
pine source, but not in the maildir patch. We considered using a newer
uw-imap but decided that the current one works good enough ;P

For pine we currently use the patch that comes with Debian's 'pine-tracker'
package (which is an installer for pine with patches, since you aren't
allowed to distributed modified binaries.) This patch also has some Mike in
it, but I'm not sure howmuch, as at least parts of it seem to be backed out
later. This patch works okay except for the two problems I noted in my
original mail: it depends on directory order not to change except when
'.uidvalidity' gets touched, and it depends on alphanumerical sort order of
files matching chronological (or at least uid-based, which should be the
same) sort order. The latter breaks with (standard) procmail, the former
occasionally with btree and (presumably) hashed directory indices.

> The storage of RFC822.SIZE, aka the on-the-wire size, in the filename 
> makes a very big difference to performance.

That's interesting. I'll keep that in mind for when we begin to see
performance issues with UW-IMAP. (I'm hoping I never have to look at the
pine source again, though.)

> But even this patch (from, e.g. 
> http://www.star.le.ac.uk/~tjg/misc/uw_imap-2001a_maildir-02.patch) has a
> number of bugs. I've fixed a few of them. You can find a source RPM at
> ftp://ftp.e-smith.org/pub/e-smith/dev/5.6dev/SRPMS/. The fixes are:

<snip fixes>

I couldn't find the source RPM for pine or (uw-)imap in that directory, but
it doesn't sound like your changes solve our fundamental problems. It's not
that big a deal, I think we've decided internally (I know _I_ have :) that
we can't offer real IMAP services based on UW-IMAP; we'd sooner go for Cyrus
or Courier, even if it does mean disallowing mboxes with IMAP. But dovecot
is an even better alternative, once it has all the features we need :)

-- 
Thomas Wouters <thomas at xs4all.net>

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