Kernelspec icon broken when base_url is used

[ricklamers]

Description

The kernelspec icon is broken when a --LabApp.base_url is specified. This has to do with how the kernelspec path is used directly for the element.

See

jupyterlab/packages/notebook-extension/src/index.ts

Line 1432 in f5d186c

let kernelIconUrl = spec.resources['logo-64x64'];

Reproduce

1. Configure a base_url that's not "".
2. Open the launcher tab
3. Observe broken kernel icons (because the image path can't be resolved)

Expected behavior

Kernelspec icons should respect the configured base_url. This can be achieved in multiple ways, a relative path seems to work (stripping the leading / from the path /kernelspecs/python3/logo-64x64.png). Ideally the path resolve is harmonized with how resource paths in general in the application respect the base_url.

Context

• Operating System and version: Debian Linux
• Browser and version: Version 1.32.106 Chromium: 96.0.4664.45 (Official Build) (64-bit)
• JupyterLab version: 3.2.4

Screenshot

[ricklamers]

I think in 3.1 this is how it makes the kernelspec path take the base_url into account:

jupyterlab/packages/notebook-extension/src/index.ts

Line 1266 in 90ed111

kernelIconUrl = URLExt.join(baseUrl, kernelIconUrl.slice(index));

[krassowski]

This is likely due to #11175 which also introduced this issue in JupyterLab Desktop where we worked around this by adding <base href="${juypter_server_url}"> (in jupyterlab/jupyterlab-desktop#322), but it caused other issues, some of which were fixed in jupyterlab/jupyterlab-desktop#344 but I am still not fully satisfied with it. CC @jtpio

[jtpio]

Thanks @ricklamers for reporting and @krassowski for the input.

It does sound related to the change in #11175. #11175 points to the code in jupyter_server handling the base url:

https://github.com/jupyter-server/jupyter_server/blob/ac93dd8f60de54db99167016f0396959826b8ed9/jupyter_server/services/kernelspecs/handlers.py#L33

Which happens to be working fine when the base url is set to something else, for example on Binder: #11175 (comment)

@ricklamers could it be that the kernelspecs in your setup are handled differently?

The observation that lead to #11175 was the fact that kernelspecs was hardcoded in the logic and expected to be part of the resource URLs:

jupyterlab/packages/notebook-extension/src/index.ts

Line 1265 in 90ed111

const index = kernelIconUrl.indexOf('kernelspecs');

[ricklamers]

Thanks for your responses/input @jtpio @krassowski!

I think it might be caused by the fact that in my configuration I'm using the Jupyter Enterprise Gateway (which in turn uses the Jupyter Kernel Gateway). They both have base_url configured (using KG_BASE_URL and EG_BASE_URL respectively). But the /api/kernelspecs still returns resources with an absolute path that doesn't respect the configured base_url:

{
  "resources": {
    "logo-64x64": "/kernelspecs/my-kernel/logo-64x64.png",
    "logo-32x32": "/kernelspecs/my-kernel/logo-32x32.png"
  }
}

[jtpio]

Ah ok then that would explain why. So probably something that should be investigated in Jupyter Kernel / Entreprise Gateway to check the base_url is correctly handled?

[ricklamers]

After merging jupyter-server/enterprise_gateway#1019 the problem went away for us. I think this was eventually the responsibility of the kernel manager (and the resource paths it returns). So I think we can consider this solved (never being an issue in JupyterLab itself).

[ricklamers]

For the record, I also contributed that fix to the Kernel Gateway project because it was also affected: jupyter-server/kernel_gateway#372