Unable to fetch thumbnail image data, getting OK Async in response instead

Unable to fetch thumbnail image data, getting OK Async in response instead.

Ref PR: https://github.com/apache/incubator-superset/pull/8947

Expected results

Should return the image data.

Actual results

I’m getting { "message": "OK Async" } when calling for the thumbnail.

Screenshots

How to reproduce the bug

1. Go to ‘Dashboard’
2. Goto URL: <hostname>:<port>/api/v1/dashboard/<thumbnail_url>
3. Observe the response

Environment

• superset version: Superset 0.999.0dev
• python version: Python 3.7.7
• node.js version: v12.16.3
• npm version: 6.14.4
• operating system: Fedora 31 (Workstation Edition) x86_64

Checklist

• I have checked the superset logs for python stacktraces and included it here as text if there are any.
• I have reproduced the issue with at least the latest released version of superset.
• I have checked the issue tracker for the same issue and I haven’t found one similar.

Additional context

Add any other context about the problem here.

[dpgaspar]

Cool! Do a get request to /api/v1/dashboard/ on the result key you’ll get an attr key named thumbnail_url use that URL to get your thumbnail

[dpgaspar]

Hi @AshishKapoor,

Thumbnails need cache and celery workers, take a look at: https://apache-superset.readthedocs.io/en/0.36/installation.html#celery-tasks

Also on celery use: CELERY_IMPORTS = ("superset.sql_lab", "superset.tasks.thumbnails")