sieve duplicate locking

[Stephan Bosch]

Op 17-10-2016 om 18:05 schreef Alexander 'Leo' Bergolth:
> Hi!
>
> Does the duplicate sieve plugin do any locking to avoid duplicate
> parallel delivery of the same message?
>
> I sometimes experience duplicate mail delivery of messages with the same
> message-id, despite the use of a sieve duplicate filter. According to
> the log files, those messages are delivered in the same second by two
> parallel dovecot-lda processes. (Duplicate filtering works fine in all
> other cases.)
>
> RFC7352 states that the ID of a message may only be committed to the
> duplicate tracking list at the _end_ of a successful script execution,
> which may lead to race conditions.
> Maybe I am running into this?
>
> Is there an easy way to serialize mail delivery using some locking
> inside sieve?

We've seen this before I think. It would require some changes to the 
duplicate tracking system. I'd expect the vacation command to be 
affected as well.

> Or do I have to serialize per-user dovecot-lda delivery? Any experiences
> with that?

Very little. I know there is a new lmtp_user_concurrency_limit setting, 
but there is not much documentation apart from the commit message:

https://github.com/dovecot/core/commit/42abccd9b2a5a4190bd3c14ec2dcc10d51c0f491

There are possibilities from within the MTA as well I expect.

Regards,

Stephan.