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User Data Function: 'NotFound' Error (WorkloadException) after Publishing, but Success in Develop
Actually, connecting to the Mimir endpoint isn't the bottleneck here(tested using another udf and it worked in run mode). The issue appears to be specifically related to the UDF runtime failing to recognize the Prometheus library. I’ll follow your suggestion and move this to a Fabric Notebook, thanks.
Hi v-saisrao-msft,
As mentioned in my post, I have already published the function multiple times. The function works as expected in Develop mode, but the invocation issue only persists in Run mode after publishing.
Hi Izyaan_sc,
The function is working correctly in Develop mode, which confirms that the KQL query and Python logic are valid.
The failure in Run (Published) mode is due to Microsoft Fabric runtime limitations. In the published environment, User Data Functions run in a managed backend with restricted capabilities. Specifically, outbound network calls and certain custom dependencies are not fully supported or guaranteed to work.
Because the function attempts to push data to an external Mimir endpoint, the backend is unable to execute the request, resulting in a generic “WorkloadException: NotFound” error. This error indicates a runtime execution failure rather than a missing function.
As per Microsoft Fabric design guidance, User Data Functions should be used for lightweight, in-platform processing. For external integrations such as pushing metrics to external systems, it is recommended to use Fabric pipelines, notebooks, or external services (e.g., Azure Functions) instead of UDFs.
We recommend redesigning the solution so that Activator triggers a Fabric-native output (such as a pipeline or table), and the external call to Mimir is handled outside the UDF.
Service details and limitations - Microsoft Fabric | Microsoft Learn
Thank you.
Actually, connecting to the Mimir endpoint isn't the bottleneck here(tested using another udf and it worked in run mode). The issue appears to be specifically related to the UDF runtime failing to recognize the Prometheus library. I’ll follow your suggestion and move this to a Fabric Notebook, thanks.
Hi Izyaan_sc,
Thank you for considering the suggestion to use Fabric Notebook. If you encounter any further issues, you can start a new thread in the community.