[Dovecot] Restarting dovecot-auth stops authentication

[Attila Nagy]

  On 11/17/2010 06:55 PM, Timo Sirainen wrote:
> On Wed, 2010-11-17 at 13:45 +0100, Attila Nagy wrote:
>
>> Nov 17 11:42:10 be dovecot: pop3-login: Internal login failure (auth
>> failed, 1 attempts): user=<user1>, method=PLAIN, rip=172.28.16.20,
>> lip=172.16.253.13
> Something else really should have been logged just before this. An error
> or a warning. There were a few situations where it might not have, which
> are fixed by this patch:
> http://hg.dovecot.org/dovecot-2.0/rev/aec1f1614028
>
I'm sorry, I was in a rush and I have a lot of logs.
pop3-login: Error: net_connect_unix(pop3) failed: Connection refused
This precedes all the above log entries.
I've checked, auth's start time is yesterday, so it wasn't restarted. I 
guess what remains is the resource limit (client_limit maybe?).
The strange thing is according to tcpdump, dovecot does very few LDAP 
lookups, and they are answered in a reasonable time, but I haven't done 
a strict correlation with the above errors.
What's the best way to find out what causes this connection refused 
batches once or twice a day?

How does dovecot logs timed out LDAP lookups?