dovecot - Sep 2011 - limit number of simultaneous lmtp deliveries ?

We have quite a few frontend mail gateways that deliver incoming
email trough our dovecot director (lmtp proxy) to the backend lmtp
servers, and are seeing this logged on the frontend mail gateways:

	Sep  5 10:51:56 mailgw1 postfix/lmtp[23443]: 0E2F41C01A: to=<me at
example.com>, relay=loadbalancers.example.com[192.168.42.15]:24, delay=61,
delays=0.02/0.3/31/30, dsn=4.4.0, status=deferred (host
loadbalancers.example.com[192.168.42.15] said: 451 4.4.0 Remote server not
answering (DATA output timeout) (in reply to end of DATA command))

It's a bit unclear to me if this leads to duplicate deliveries, or just
delayed deliveries, but -- is there any way to limit the number of
simultanous deliveries on either the dovecot director or the backend
lmtp-servers ? 

Will "process_limit=10" work for "service lmtp"? 


  -jf

On Mon, 2011-09-05 at 11:05 +0200, Jan-Frode Myklebust
wrote:
> We have quite a few frontend mail gateways that deliver incoming
> email trough our dovecot director (lmtp proxy) to the backend lmtp
> servers, and are seeing this logged on the frontend mail gateways:
> 
> 	Sep  5 10:51:56 mailgw1 postfix/lmtp[23443]: 0E2F41C01A: to=<me at
example.com>, relay=loadbalancers.example.com[192.168.42.15]:24, delay=61,
delays=0.02/0.3/31/30, dsn=4.4.0, status=deferred (host
loadbalancers.example.com[192.168.42.15] said: 451 4.4.0 Remote server not
answering (DATA output timeout) (in reply to end of DATA command))
> 
> It's a bit unclear to me if this leads to duplicate deliveries, or just
> delayed deliveries, 
Possibly randomly either one. I'll need to start looking into these LMTP
proxy bugs some day.. Although for 2.0.14 I improved the error messages
a little. Is this from 2.0.14 or earlier?
> but -- is there any way to limit the number of
> simultanous deliveries on either the dovecot director or the backend
> lmtp-servers ? 
> 
> Will "process_limit=10" work for "service lmtp"? 
It'll work for both directory and backend, yes. Although each lmtp
process can also handle multiple clients. So you might also want to set
client_limit=1. Actually that could be a good idea to try in any case to
see if it helps with these problems.

On 5.9.2011, at 12.05, Jan-Frode Myklebust wrote:
> 	Sep  5 10:51:56 mailgw1 postfix/lmtp[23443]: 0E2F41C01A: to=<me at
example.com>, relay=loadbalancers.example.com[192.168.42.15]:24, delay=61,
delays=0.02/0.3/31/30, dsn=4.4.0, status=deferred (host
loadbalancers.example.com[192.168.42.15] said: 451 4.4.0 Remote server not
answering (DATA output timeout) (in reply to end of DATA command))
Well, I added even more debugging output for this message:
http://hg.dovecot.org/dovecot-2.0/raw-rev/8de8752b2e94

Would be interesting to know what it logs with that.

On Thu, Sep 08, 2011 at 01:42:16PM +0300, Timo Sirainen
wrote:
> 
> Well, I added even more debugging output for this message:
http://hg.dovecot.org/dovecot-2.0/raw-rev/8de8752b2e94
> 
> Would be interesting to know what it logs with that.
> 
Postfix logs:

	Sep  8 13:14:28 asav7 postfix/lmtp[22024]: 5ADD454030: host
loadbalancers.example.com[192.168.42.15] said: 451 4.4.0 Remote server not
answering (DATA output stalled for 30 secs, 36742B sent, 0B buffered) (in reply
to end of DATA command)
	Sep  8 13:17:51 asav7 postfix/lmtp[22759]: 1981954011: host
loadbalancers.example.com[192.168.42.17] said: 451 4.4.0 Remote server not
answering (DATA output stalled for 30 secs, 38629B sent, 0B buffered) (in reply
to end of DATA command)


  -jf