changing d-bus limits

This document (000020405) is provided subject to the disclaimer at the end of this document.

Situation

The default limit of d-bus has been reached.

Example message for hitting max_replies_per_connection limit as seen in /var/log/messages:
2021-10-10T12:53:24.272449+08:00 localhost systemd-logind[1417]: Failed to start session scope session-c1284.scope: The maximum number of pending replies per connection has been reached

Resolution

There is a different set of limits for user sessions and for system (configured in session.conf and system.conf).
For different available limits please see the manual page of the dbus-daemon with command:

man dbus-daemon

The default limits are configured during the d-bus compilation time.
On SLE15 or newer the defaults can be seen in the file /usr/share/dbus-1/system.conf and session.conf respectively.
On SLE12 and newer service packs the defaults can be seen in the source code for the dbus-1 package.

In our example the systemd-logind process is running in the system scope (as seen in the command systemd-cgls).

# systemd-cgls 
Control group /:
-.slice
├─user.slice 
└─system.slice 
  ├─haveged.service 
  └─systemd-logind.service 
(output is shortened)

The default in the file system.conf is:
<!-- <limit name="max_replies_per_connection">128</limit> -->
Create file /etc/dbus-1/system-local.conf with content (for user session limits it would be session-local.conf):
<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-Bus Bus Configuration 1.0//EN"
 "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<busconfig>
<limit name="max_replies_per_connection">1200</limit>
</busconfig>
The changes should be active right away as the dbus daemon is monitoring these files for changes.

Cause

The default d-bus limits may not be optimal for every user.
Alternatively there might be some process that is not behaving correctly and uses up d-bus resources.

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:000020405
  • Creation Date: 05-Oct-2021
  • Modified Date:18-Nov-2021
    • SUSE Linux Enterprise Server
    • SUSE Linux Enterprise Server for SAP Applications

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