net_connect_unix(/var/run/dovecot/stats-writer) failed: Permission denied

[mj]

Hi,

We are getting very occasional messags from dovecot:

> net_connect_unix(/var/run/dovecot/stats-writer) failed: Permission denied

Over the last week, the message appeared five times. (on a mail server 
with over 100 users, to that's basically almost never)

doveconf -n below

> # 2.3.4.1 (f79e8e7e4): /etc/dovecot/dovecot.conf
> # Pigeonhole version 0.5.4 ()
> # OS: Linux 4.19.0-10-amd64 x86_64 Debian 10.6 xfs

snip...

> service stats {
>   unix_listener stats-reader {
>     group = vmail
>     mode = 0660
>     user = vmail
>   }
>   unix_listener stats-writer {
>     group = vmail
>     mode = 0660
>     user = vmail
>   }
> }

and the on-disk permissions are:

> root at dovecot:~# ls -l /var/run/dovecot/*stat*
> srw------- 1 root  root  0 Oct  6 00:25 /var/run/dovecot/old-stats
> prw------- 1 root  root  0 Oct  6 00:25 /var/run/dovecot/old-stats-mail
> prw------- 1 root  root  0 Oct  6 00:25 /var/run/dovecot/old-stats-user
> srw-rw---- 1 vmail vmail 0 Oct  6 00:25 /var/run/dovecot/stats-reader
> srw-rw---- 1 vmail vmail 0 Oct  6 00:25 /var/run/dovecot/stats-writer

We're not sure what makes the Permission denied error happen...

Anyone with an idea?

MJ