On 01/17/2017 05:21 AM, Eugene M. Zheganin via Info-cyrus wrote:
Hi,
I'm using cyrus-imapd for quite long, but recently I encountered an
issue with delivery: one of my mail servers is handling a significant
load of e-mails, and quite often I'm seeing line like this in the maillog:
Jan 17 12:35:26 gw0 sm-mta[78888]: v0H7ZML4078586: SYSERR(root): Could
not connect to socket /var/imap/socket/lmtp: Connection refused by localhost
This usually means that message bounced to MTA queue, where it can be
hold for several minutes, sometimes dozens of minutes. I have the
following directive in the cyrus.conf:
SERVICES {
...
lmtp cmd="lmtpd" listen="localhost:lmtp" prefork=4 maxchild=16
lmtpunix cmd="lmtpd" listen="/var/imap/socket/lmtp" prefork=4
maxchild=16 maxfds=2048
}
I discovered that simply increasing this value can make the situation
even worse. Is there some decent aproach to increase the performance of
lmtp ?
Thanks.
Eugene.
I am not an expert by any means and I hope someone corrects me if I make
a bad suggestion...but I have two questions:
1. It sounds like you have a heavily used server, so why do you have
Cyrus listening on both "localhost:lmtp" AND a unix socket
"/var/imap/socket/lmtp"?
From the log entry it looks like your MTA uses a unix socket. Unless
you have something else (mail clients or other MTAs running on your
Cyrus server?) that need to communicate via the localhost:lmtp port, you
could comment out the unneeded lmtp service line and save those resources.
2. You say "increasing this value can make the situation even worse".
Which value? There are 5 values on those two lines that you could
increase. And by "even worse" do you mean even more refused connections?
While I am not a Cyrus guru, I have seen my share of overloaded mail
servers and if you are running into a disk IO limit, adding more
processes fighting over a limited resource is very likely to make things
worse. So you should also confirm a hardware limitation is not at play
here.
Sincere regards,
--
Andy Dorman
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