Sync_client fails after upgrade 2.3.16 to 2.4.4

[Bron Gondwana]

On Mon, Nov 29, 2010 at 11:19:32AM -0500, Chris Conn wrote:
> Hmm I hadn't read that.  I was aware that doing it in a high volume 
> scenario was problematic, but was under the impression that an 
> occasional delivery here and there was theoretically possible.  Its 
> pretty amazing since I test it manually and I can send to either one or 
> the other and replication happens correctly; however, when the stupid 
> logrotate message gets sent on the slave within seconds of a similar 
> message being sent on the master, things die.

So set the clocks on the machines out by a few more seconds and you'll
be fine.

Seriously - the problem is that it works when you test manually because
they're not happening at the same time.  "things die" because
replication is asynchronous, and the same UID gets allocated to messages
with different content!

That said - it should be able to resolve the situation without crashing.

> People that use replication as a quasi-hot standby server in the case 
> the master goes down/needs maintenance etc, etc, how do you deal with 
> locally generated mails that will eventually get delivered to a cyrus 
> mailbox on the master to which this is the slave?

When we shut down one end, we bring up the other.  Downtime is a couple
of seconds maximum.  Everything gets delivered to postfix locally which
forwards to an LMTP proxy which knows which host is the master, and
delivers appropriately.

Most MTAs are happy to spool locally generated mail until the server
is back up.  Store and forward.

Bron.