HIGHESTMODSEQ replication issue

[John Fawcett]

On 09/10/2020 21:17, Gustavo Ajeitos [Office365] wrote:
> Hello,
>
> I'm using dovecot 2.3.10 in OpenSUSE and I have configured a
> master/master replication between two backends, it works well but I
> have found an issue with the replication of the HIGHESTMODSEQ.
> When I move a set of message from a mailbox to other, e.g. move 3
> messages from INBOX to Junk, the HIGHESTMODSEQ get different on each
> server, with no errors in the log:
>
> [Borrador] 34:34
> [Sent] 63:63
> [Drafts] 12:12
> [Trash] 146:146
> [Junk] 219:218
> [INBOX] 1133:1130
>
> It can be fixed executing a full sync:
> $ sudo doveadm -D -v sync -u user at test.priv -d -l 30 -U
>
> But it is not a solution because it happens all the time that a user
> move messages.
>
> I'm using ActiveSync and the ActiveSync server use the HIGHESTMODSEQ
> as part of the synchronization key (sync_key), so in that situation
> the server detect changes on the mailbox if it connects to the backend
> with a different HIGHESTMODSEQ that it previously cached, causing a
> loop beetween the ActiveSync server and the the email client, where
> the server constantly inform email client about nonexistent changes.
>
> Could it be a bug in Dovecot replication? How can I solve it?
>
> Best regards,
> Gustavo Ajeitos
>
Hi Gustavo

I don't know if this is a bug, but one thing I noticed is that for
master/master replication the recommendation is to have specific users
always directed to the same server. If you implemented this
recommendation for the ActiveSync connections, would that solve the problem?

John