Issue while downloading superset dashboard as image

[Dhruvin4530]

Issues while trying to download a dashboard as image on SS, I click on Download as image and this message keeps triggering but doesn't download it ever, I've tried refreshing the dashboard, loading again, and hasn't work yet. (Not working from anyone from SOC )

The screenshot is being generated. Please, do not leave the page.

@dosu Please help

[dosubot[bot]]

This is a commonly reported issue with the dashboard screenshot/image download feature. The message stays indefinitely because the backend screenshot generation is failing silently. Here are the most likely causes and fixes:

1. Celery worker not running or misconfigured

The screenshot feature works asynchronously — a Celery task captures the screenshot using a headless browser. If Celery isn't running or isn't properly connected to Redis, the task never completes [1].

Make sure you have:

# superset_config.py
class CeleryConfig:
    broker_url = "redis://127.0.0.1:6379/0"
    result_backend = "redis://127.0.0.1:6379/1"

THUMBNAIL_CACHE_CONFIG = {
    "CACHE_TYPE": "RedisCache",
    "CACHE_REDIS_URL": "redis://127.0.0.1:6379/0",
    "CACHE_DEFAULT_TIMEOUT": 604800,
}

2. Required feature flags not enabled

Ensure these are set [2]:

DEFAULT_FEATURE_FLAGS = {
    "THUMBNAILS": True,
    "ENABLE_DASHBOARD_SCREENSHOT_ENDPOINTS": True,
    "ENABLE_DASHBOARD_DOWNLOAD_WEBDRIVER_SCREENSHOT": True,
}

3. Authentication failure in the headless browser

The WebDriver authenticates as a configured user (usually "admin"). If that account is inactive or doesn't have access to the dashboard, the screenshot silently fails [3]. Verify that THUMBNAIL_SELENIUM_USER is set to an active user with proper permissions.

4. Timeout — dashboard too heavy

If your dashboard has many charts, the headless browser may time out before everything loads. Try increasing timeouts [4]:

SCREENSHOT_LOCATE_WAIT = 100
SCREENSHOT_LOAD_WAIT = 600

5. Control characters in dashboard title

If your dashboard title was copy-pasted from an external source, it may contain hidden control characters that crash the headless browser [5]. Try manually retyping the title.

Troubleshooting steps:

1. Check your Superset logs for any WebDriver/Selenium/Playwright errors
2. Confirm your Celery worker is running (celery -A superset.tasks.celery_app:app worker)
3. Confirm Redis is reachable
4. Test with a simple dashboard (1-2 charts) to isolate whether it's a configuration or dashboard-specific issue

Which version of Superset are you running, and are you using Docker or a custom deployment? That would help narrow things down further.

To reply, just mention @dosu.

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[Dhruvin4530]

@dosu

[dhruvinsoni@Dhruvins-MacBook-Pro ~ (⎈|dev-use2-acgpk8seks-cluster:N/A)]$ k get pods -n superset-blue
                   NAME                                   READY   STATUS    RESTARTS   AGE
superset-7959c5784b-sbrjw              1/1     Running   0          3m23s
superset-celerybeat-77f7c85d9d-ngjz9   1/1     Running   0          3m53s
superset-worker-9586494d-9d9wc         1/1     Running   0          36m
superset-worker-9586494d-hwg94         1/1     Running   0          33m
superset-worker-9586494d-lv6jr         1/1     Running   0          168m
superset-worker-9586494d-sfk2f         1/1     Running   0          5m26s
superset-worker-9586494d-zjq56         1/1     Running   0          17m
superset-worker-9586494d-zkwtp         1/1     Running   0          3m53s
[dhruvinsoni@Dhruvins-MacBook-Pro ~ (⎈|dev-use2-acgpk8seks-cluster:N/A)]$                    

# Enables endpoints to cache and retrieve dashboard screenshots via webdriver.
--
"ENABLE_DASHBOARD_SCREENSHOT_ENDPOINTS": True,
# Generate screenshots (PDF/JPG) of dashboards using web driver.
"ENABLE_DASHBOARD_DOWNLOAD_WEBDRIVER_SCREENSHOT": True,

[dosubot[bot]]

This configuration tells Superset where and how to store generated dashboard screenshots/thumbnails. Here's what each key does:

• CACHE_TYPE: "RedisCache" — Use Redis as the storage backend for thumbnails.
• CACHE_DEFAULT_TIMEOUT: 24 * 60 * 60 * 30 — Cached screenshots expire after 30 days (2,592,000 seconds).
• CACHE_KEY_PREFIX: "thumbnail_" — All thumbnail cache keys in Redis will be prefixed with thumbnail_ to avoid collisions with other cached data.
• CACHE_NO_NULL_WARNING: True — Suppresses warnings when a cache lookup returns None (i.e., no cached thumbnail found yet).
• CACHE_REDIS_URL: redis_url(REDIS_RESULTS_DB) — Points to your Redis instance using the connection URL built from your environment variables.

Why it matters for your issue: When you click "Download as image," the Celery worker generates the screenshot and stores it in this cache. The frontend then polls to retrieve it. Without this config enabled, the screenshot has nowhere to be saved, so the frontend polls forever and never gets the image — which is exactly the behavior you're seeing.

Uncomment this block in your config, redeploy, and the download should work (assuming Chrome is installed in the worker container).

To reply, just mention @dosu.

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[Dhruvin4530]

@dosu What if I am downloading the dashboard for the first time?

[dosubot[bot]]

You've reached the anonymous usage limit of 10 interactions per month. Your usage will reset on 2026-06-01. If you'd like to use Dosu before then, please register to increase your limit to 100 interactions per month for free.

To reply, just mention @dosu.

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Docs are dead. Just use Dosu.

[Dhruvin4530]

@dosu What if I am downloading the dashboard for the first time?

[dosubot[bot]]

You've reached the anonymous usage limit of 10 interactions per month. Your usage will reset on 2026-06-01. If you'd like to use Dosu before then, please register to increase your limit to 100 interactions per month for free.

To reply, just mention @dosu.

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