[Dovecot] problems with SSH-based clustering dovecot 2.1.1

[Michael Grimm]

Hi --


On 15.03.2012 12:21, Charles Marcus wrote:
> On 2012-03-14 5:51 PM, Michael Grimm <trashcan at odo.in-berlin.de> 
> wrote:

>> You misunderstood. I was referring to system cronjob's mail reports
>> from cron.daily jobs like security reports et al. Those reports
>> normally run at identical times.
>
> But are these really 'duplicate' mails? It sounds to me like they are
> individual to each system.
>
> I'm also confused - are you actually delivering the exact *same* mail
> to two (or multiple) *different* servers simultaneously? If only one
> copy of the mail gets delivered, regardless of which server it gets
> delivered to, when dsync runs, there would be no duplicates, right?

Well, let me explain it in more detail:

Given there are two servers called mx1 and mx2. They both have 
cron.daily
jobs running, and let's say those cronjobs are meant to create at 3:00
a postfix-logwatch report on every server. Thus, the cronjob at mx1 
sends
his final report to the admin of mx1, and the one at mx2 to the admin 
of
mx2. I happen to be the one who will finally receive those reports, and
therefore I did tell sieve to drop them into some folder of mine, let's
say REPORTS.

Thus, at 3:01 one report from mx1 will be delivered at mx1 into 
mailfolder
REPORTS and at 3:01 one report from mx2 will be delivered at mx2 into 
the
mailfolder REPORTS. Important: both mails are different but they arrive
in the mailfolder REPORTS at the same time, one at mx1 the other at 
mx2.
And, let's call the report from mx1 cronjob "mx1-report" and that from
mx2 "mx2-report".

I had dsync running every minute. Thus at 3:00 the final sync has been
initiated, and at 3:01 dsync will find two mails to sync in REPORTS. In
99.9% of all synchronizations the final result at both server's REPORTS
mailbox is as expected and as follows:

mx1-report   3:01
mx2-report   3:01

But occasionally, and what I refer to as duplicates, I did find either 
...

mx1-report   3:01
mx1-report   3:01
mx2-report   3:01

... or ...

mx1-report   3:01
mx2-report   3:01
mx2-report   3:01

Actually, that was when I started to investigate how dsync will behave
when many mails arrive at two servers simultaneously with identical 
final
mailboxes.

The day I switched to the new replicator/dsync technique, those 
duplicates
are history, but I'm still able to produce duplicates (and multiples) 
if
I simultaneously produce *many* mails at every server with identical 
mailbox
destinations in a minute (see my other report a couple of days ago). 
Timo
is suspecting the combination of arriving mails while running dsync to 
be
a possible cause of such duplicates, if I didn't get him wrong.

Again, if your servers aren't receiving loads of mails for the very 
same
mailboxes within very short time, the current dsync/replicator works 
great.

HTH and regards,
Michael