CMK version: CEE 2.3.0.p43 OS version: Debian 12 Error message: 2026-03-09 11:51:15,113 [40] [cmk.gui.wsgi.app 2403] Exception on /ukm/check_mk/ajax_service_discovery.py [POST] Traceback (most recent call last): File "/omd/sites/ukm/lib/python3/cmk/gui/wsgi/applications/checkmk.py", line 188,…

This error fills up web.log every second. Only occurred after updating to 2.3.0.p43.

Hi Rainer, we’ve seen this exact error pattern before — it’s a recurring issue between Checkmk and the werkzeug library, where a limit on the number of form parts in a single POST request gets exceeded. This typically happens on hosts with a large number of services (e.g. big switches, ESXi hosts, …

Hi Bernd, Thanks for your help :wink: The error currently only occurs on one host, a Cisco Nexus 9K. It currently has around 400 services, as do our other Nexus devices (we have 20 of them). Periodic Service Discovery is enabled, and we check the hosts exclusively via SNMP.

[image] altvater: Cisco Nexus 9K I know him so well … :cry: … this BigBlock has given me also a lot of trouble in the past .. So I thing for this host you have to ajust the parameters to more granular

With the 9000 series, I often found that not only the size of the entries but also the long query time was a problem. I solved this by running it twice a day via cron: #!/usr/bin/env bash # ============================================================================= # checkmk_discovery_reload.sh …

Looks like the corresponding values are set in /omd/sites/<site>/lib/python3.12/site-packages/werkzeug/wrappers/request.py #: the maximum form field size. This is forwarded to the form data #: parsing function (:func:`parse_form_data`). When set and the #: :attr:`form` or :attr:`file…

Thanks for the script. I’ll check whether it would be sufficient for us to just query the boxes regularly. So far, however, we haven’t had any problems with the devices at all.

Root cause: werkzeug 3.1.0 breaking change (released October 31, 2024) werkzeug 3.1.0 was released on October 31, 2024 and introduced two new hard limits on form data parsing as potentially breaking changes. GitHub The two relevant changes: Request.max_form_memory_size now defaults to 500 kB ins…

[image] Service Discovery fails with "failed to fetch state [500]: INTERNAL SERVER ERROR. Retrying in 1 second" Troubleshooting Werk #19169: Fix 500 internal server error when sending large requests and it`s seamed to be fixed rocket it`s seamed to be fix…

Indeed this workaround worked for us as well. We had to crank it up to max_form_memory_size = 5_000_000 Many thanks. Should it still work with Werk #19169? Or is the Werk #19169 limited to 2_000_000?

Error when rescan devices

Troubleshooting

BH2005 (Bernd Holzhauer) March 11, 2026, 11:46am 10

it`s seamed to be fixed