[Dovecot] problems with SSH-based clustering dovecot 2.1.1

[Michescu Andrei]

> Hi --
>
> On 14.03.2012, at 15:09, Timo Sirainen wrote:
>> On Wed, 2012-03-14 at 01:25 -0400, Michescu Andrei wrote:
>
>>> The problem comes when I start using the master-master model: emails
>>> starts getting duplicate with different ids.
>
>> I was testing this a bit, and I guess in your tests dsync was running
>> during a mail delivery, which seems to make it duplicate mails
>> sometimes. I'll probably fix this at some point (I've actually been
>> thinking about a larger dsync redesign),
>
> Good to hear ;-)
>
>> but anyway:
>>
>> Even if dsync worked perfectly and didn't duplicate mails, it's not a
>> great idea to do deliver mails randomly to both servers.
>
> Sometimes croncobs are running on both servers at the same time
> producing locally delivered mails simultaneously, though. Ok, one
> can modify run times accordingly ...

Why do you run the crontab on all the servers? You can run a start-based
system where only one ("main"-master) syncs all the other masters. And
like this you avoid the time synch'ing of crontabs (especially if you
don't always know how longer it will take for a dsync to finish).

>
>> Better to give one MX a higher priority so mails typically are delivered
>> through it.
>
> That's what I did. Now dsync/replicator is performing great, if the
> mail volume is rather low. I'm very satisfied, because this is the
> best performance ever. (Before I was running unison and dsync 2.0.)
>
> But, whenever the high priority server will show delays during stress
> situations like huge mail loads, the low priority server will receive
> loads of mails as well. A dsync/replicator setup will then most probably
> produce duplicates (and multiples). That is a rather unrealistic
> scenario for my little severs, but others might have more difficulties.

This is another nice case to "motivate" Timo to look for solutions ;) I
tried to push 2 ideas in the same direction earlier :P Especially that he
confirmed that every single email has a unique GID (which should help
prevent duplication/multiplication)...

>
> And spammers don't care about mx priorities at all :-(

Actually, statistically speaking, spammers select the low priority ones.

>
> Regards,
> Michael
>

Nice to hear that we are not the only ones out there to try to run
something like this over dovecot :P

Thnx,
Andrei