dovecot-lda without starting dovecot?

[Timo Sirainen]

On 7 Nov 2017, at 21.33, Stephan von Krawczynski <skraw.ml at ithnet.com> wrote:
> 
> 
> Me again have to stress that our former implementation of the lda process did
> do exactly nothing to all the dovecot files, and everything worked pretty
> well. We had no problems in years. So I really wonder if it wouldn't be the
> best way to simply cut away all the heavy dovecot magic from the lda as an
> option. All it really needs to do is pipe the mail into a temp file, do the
> sieve stuff and learn from it where to rename this temp file to, basically.
> On the other hand you have lots of config parameters in dovecot dealing with
> different approaches to lock files (from fcntl to dotlock). I would expect at
> least one of them to work over NFS.

I suppose you could create a unique new per-delivery temporary directory where dovecot-lda writes the mail, so it knows nothing about the user's real home/mail directory. Then move it from there to Maildir/tmp/ -> rename to Maildir/new/. I suppose you'd need to copy the Sieve script to the temp directory. Not sure if something would have to be done with .dovecot.lda-dupes.

> And we do see stuff like:
> 
> 2017-11-07T00:46:59.102961+01:00 mail-a05 dovecot: lda(somebody at somedomain.com):
> Warning: Locking transaction log
> file <nfs-path>/dovecot.index.log took 40 seconds (appending)
> 
> So some locking seems to work.

The problem isn't locking, but caching of data. Especially because Dovecot doesn't lock when reading files.