Recurring problem with "slapd.service

Hello!
At one of our customers, the “slapd.service” stops working at irregular intervals (approx. 3 to 8 days). Of course, this always results in various subsequent errors.

Unfortunately, I have not yet been successful in finding the cause.
At the moment, I don’t have much information that I can provide.
Host:

  • KVM-VM

  • DISTRIB_ID=Univention

  • DISTRIB_RELEASE=“5.0-4 errata771”

  • DISTRIB_DESCRIPTION=“Univention Corporate Server 5.0-4 errata771”

  • PRETTY_NAME=“Debian GNU/Linux 10 (buster)”

  • NAME=“Debian GNU/Linux”

  • CPU(s): 4

  • Thread(s) per core: 1

# free -g -t
              total        used        free      shared  buff/cache   available
Mem:              7           1           3           0           2           6
Swap:             3           0           3
Total:           11           1           7

I examined a core dump with “gdb”. Unfortunately, this didn’t really help me:

# gdb /usr/sbin/slapd /core
GNU gdb (Debian 8.2.1-2+b3) 8.2.1
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /usr/sbin/slapd...(no debugging symbols found)...done.
[New LWP 563]
[New LWP 22475]
[New LWP 22476]
[New LWP 8998]
[New LWP 562]
[New LWP 24422]
[New LWP 24421]
[New LWP 22487]
[New LWP 8999]
[New LWP 24416]
[New LWP 561]
[New LWP 24419]
[New LWP 22594]
[New LWP 24420]
[New LWP 22474]
[New LWP 24418]
[New LWP 24417]
[New LWP 22595]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `/usr/sbin/slapd -h ldapi:/// ldap://:7389/ ldaps://:7636/ -f /etc/ldap/slapd.co'.
Program terminated with signal SIGABRT, Aborted.
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
50        return ret;
[Current thread is 1 (Thread 0x7f8a63fff700 (LWP 563))]
(gdb) q

Unfortunately, I am not any wiser than before.
The programme ended because of signal SIGABRT.

We restart the service with the following command line:
"systemctl stop nscd ; systemctl stop slapd ; sleep 3 ; systemctl restart slapd".

I am happy about any suggestion that can help me find the cause and eliminate the problem. At the moment I don’t know where to start…

Add:

root@adpdchost:~# systemctl status slapd.service
● slapd.service - LSB: OpenLDAP standalone server (Lightweight Directory Access Protocol)
   Loaded: loaded (/etc/init.d/slapd; static; vendor preset: enabled)
   Active: failed (Result: signal) since Wed 2023-08-16 12:17:34 CEST; 22min ago
     Docs: man:systemd-sysv-generator(8)
  Process: 16473 ExecStart=/etc/init.d/slapd start (code=exited, status=0/SUCCESS)
 Main PID: 16489 (code=killed, signal=ABRT)

Aug 16 12:16:55 adpdchost slapd[16489]: get_ssa: conn 40172 unknown attribute type=sudoHost (17)
Aug 16 12:16:55 adpdchost slapd[16489]: get_ssa: conn 40172 unknown attribute type=sudoHost (17)
Aug 16 12:16:56 adpdchost slapd[16489]: get_filter: conn 40173 unknown attribute type=sudoHost (17)
Aug 16 12:16:56 adpdchost slapd[16489]: get_ssa: conn 40173 unknown attribute type=sudoHost (17)
Aug 16 12:16:56 adpdchost slapd[16489]: get_ssa: conn 40173 unknown attribute type=sudoHost (17)
Aug 16 12:16:56 adpdchost slapd[16489]: get_ssa: conn 40173 unknown attribute type=sudoHost (17)
Aug 16 12:16:56 adpdchost slapd[16489]: get_ssa: conn 40173 unknown attribute type=sudoHost (17)
Aug 16 12:16:56 adpdchost slapd[16489]: get_ssa: conn 40173 unknown attribute type=sudoHost (17)
Aug 16 12:17:34 adpdchost systemd[1]: slapd.service: Main process exited, code=killed, status=6/ABRT
Aug 16 12:17:34 adpdchost systemd[1]: slapd.service: Failed with result 'signal'.
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