dovecot config for 1500 simultaneous connection

[Christian Balzer]

On Fri, 10 Feb 2017 14:59:51 -0800 (PST) Joseph Tam wrote:

> "Rajesh M" <24x7server at 24x7server.net> writes:
> 
> > during peak times here are the results for connections
> >
> > [root at ns1 domains]# doveadm who |grep imap |wc -l
> > username                # proto (pids)                             (ips)
> > 631
> > [root at ns1 domains]# doveadm who |grep pop3 |wc -l
> > username                # proto (pids)                          (ips)
> > 233  
> 
> Thare are user counts, not connections.  Ae a user can launch multiple
> IMAP connections, and if they have some MaxOSX reader, that can peak to
> several dozens during searches.
> 
> This counts connections
> 
>  	doveadm who | awk '/imap/{m+=$2}/pop3/{n+=$2}END{print m,n}'
> 
> Or you can parse the output of netstat.
> 
> I'm suprised you have so many POP3 connections though -- they tend to be
> connect/process/disconnect.  n=0 most of the time on my modest server.
> 

That vastly depends on things like client network speed and mailbox size.
People pop'ing multi GB mailboxes (leave mail on server) with crappy
clients (a big factor, some get disconnected for inactivity and thus
hang around for 10 minutes) and over slow links tend to linger for quite a
while.

Typical example:
---
Feb 11 13:54:27 mbx09 dovecot: pop3-login: Login: user=<redacted>, method=PLAIN, rip=redacted, lip=redacted, mpid=381958, secured, session=<FGtMAjpIpqpupZez>
Feb 11 14:05:18 mbx09 dovecot: pop3(redacted): Disconnected: Logged out top=0/0, retr=0/0, del=0/6188, size=103540794 session=<FGtMAjpIpqpupZez>
---

This is on a server that's bored stiff when it comes to CPU usage or I/O
utilization (pure SSD). All that twiddling of thumbs up there is purely
client based.

Christian
-- 
Christian Balzer        Network/Systems Engineer                
chibi at gol.com   	Global OnLine Japan/Rakuten Communications
http://www.gol.com/