Service unavailable, lots of idle dovecot-login processes

[Aki Tuomi]

> On 02/02/2021 14:59 Wolfgang <adminkram at tripelspark.de> wrote:
> 
>  
> Hi,
> 
> Web search turned no results to this problem:
> 
> We have a small site running private e-mail for maybe 12 people, dovecot
> is used by Postfix-SASL and IMAP clients.
> 
> PROBLEM: When starting dovecot, after a few hours, IMAP clients are no
> longer able to connect. Thunderbird indicates that connection is refused.
> 
> On the server, we see 100 dovecot/imap-login processes. This is the
> process limit. If we increase the process limit to 200, same thing, we
> survive a few hours longer but eventually we're seeing 200 imap-login
> processes and rejected connections.
> 
> When listing TCP connections via lsof, there are only around 30
> connections open to IMAP and we have exactly the same amount of
> dovecot/imap processes. These connections are held by 30
> dovecot/imap-login processes.
> 
> The other 70 dovecot/imap-login processes seem to do nothing. They're
> all sitting in "epoll_wait(14," according to strace but don't have TCP
> connections open.
> 
> The only way out of this that we have found is re-starting dovecot every
> few hours.
> 
> BTW, service_count = 1 for improved security.
> Dovecot Version: 2.3.4.1 (f79e8e7e4)
> 
> Interestingly we were using nearly the same config on our old server
> with 2.2.13 and did not see this issue.
> 
> Any ideas how to solve that properly?
> 
> Thank you,
> Wolfgang

Hi!

Can you provide output of `doveconf -n`? Also, would it be possible to try out with latest version at https://repo.dovecot.org?

Aki