Template upload shows generic "Request failed with status code 500" instead of actual error message

[rybakovanton-metta]

problem

ISSUE TYPE

• Bug Report

COMPONENT NAME

UI, Template Upload, Error Handling

SUMMARY

Template upload shows generic "Request failed with status code 500" error in UI instead of displaying the actual server error message, making debugging
impossible for users.

versions

CLOUDSTACK VERSION

4.20.1.0

CONFIGURATION

Advanced networking, KVM hypervisor

OS / ENVIRONMENT

Ubuntu 22.04, KVM hosts

The steps to reproduce the bug

STEPS TO REPRODUCE

1. Go to Templates → Register Template
2. Upload a QCOW2 file that has format detection issues (e.g., with DOS/MBR boot sector)
3. Select "QCOW2" as format
4. Click Register Template
5. Observe error message in UI

What to do about it?

EXPECTED RESULTS

UI should display the actual error message from server, such as:
"File type mismatch between uploaded file and selected format. Selected file format: QCOW2. Received: DOS/MBR boot sector, extended partition table (last)"

ACTUAL RESULTS

UI shows useless generic error:
"Upload Failed - Failed to upload Template - Error: Request failed with status code 500"

Meanwhile server logs show the actual useful error:
2025-08-25 20:53:50,648 WARN [c.c.a.AlertManagerImpl] Template Template {"format":"QCOW2","id":224,"name":"Ubuntu Server 24.04 Custom"} failed to upload.
Error details: File type mismatch between uploaded file and selected format. Selected file format: QCOW2. Received: DOS/MBR boot sector, extended partition
table (last)

Users are forced to check server logs to understand why uploads fail.

[kiranchavala]

@rybakovanton-metta

Can you let us know what happens if you try to execute register template API with the same template

https://cloudstack.apache.org/api/apidocs-4.20/apis/registerTemplate.html

[Damans227]

@kiranchavala @rybakovanton-metta I dug into this. The server/API is already returning the correct error (File type mismatch between the sent file and the actual content. Received: data), but for some reason the UI isn’t displaying it. I’ll try to fix the UI side and create a PR:

[Damans227]

Created a PR (12412) to fix it.