GitHub user dosubot[bot] added a comment to the discussion: Thumbnails work for
Dashboards, not for charts
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Hey there, @brantian! I'm a bot here to help you with bugs, questions, and
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The issue you're encountering with different cache keys for chart thumbnails
versus dashboard thumbnails likely stems from a discrepancy in how the cache
keys are generated and used in the code.
For dashboards, the cache keys are consistent, but for charts, it seems there
is a mismatch. This can be due to differences in the key prefix or the way the
keys are constructed in the code.
Here are a few steps to troubleshoot and potentially resolve this issue:
1. **Check Cache Key Prefixes**:
Ensure that the cache key prefixes for charts and dashboards are consistent.
In your `superset_config.py`, you have:
```python
THUMBNAIL_CACHE_CONFIG: CacheConfig = {
'CACHE_TYPE': 'RedisCache',
'CACHE_DEFAULT_TIMEOUT': 7 * 86400, # 7 days
'CACHE_KEY_PREFIX': 'thumbnail_',
'CACHE_REDIS_HOST': REDIS_HOST,
'CACHE_REDIS_PORT': REDIS_PORT,
'CACHE_REDIS_DB': REDIS_CELERY_DB
}
```
Verify that the `CACHE_KEY_PREFIX` is correctly used in both the web app and
Celery worker for chart thumbnails.
2. **Review Thumbnail Cache Code**:
Check the code in `superset/tasks/thumbnails.py` where the cache keys are
generated and used. Ensure that the same logic is applied for both charts and
dashboards.
For example, in the `cache_chart_thumbnail` task, ensure the cache key is
generated consistently:
```python
@celery_app.task(name="cache_chart_thumbnail", soft_time_limit=300)
def cache_chart_thumbnail(current_user, chart_id, force=False,
thumb_size=None):
from superset.models.slice import Slice
if not thumbnail_cache:
logging.warning("No cache set, refusing to compute")
return
chart = Slice.get(chart_id)
url = get_url_path("Superset.slice", slice_id=chart.id)
logger.info("Caching chart: %s", url)
_, username = get_executor(
executor_types=current_app.config["THUMBNAIL_EXECUTE_AS"],
model=chart,
current_user=current_user,
)
user = security_manager.find_user(username)
with override_user(user):
screenshot = ChartScreenshot(url, chart.digest)
screenshot.compute_and_cache(
user=user,
cache=thumbnail_cache,
force=force,
thumb_size=thumb_size,
)
```
3. **Debug Cache Key Generation**:
Add debug logs to print out the cache keys being generated in both the web
app and Celery worker. This will help you identify where the discrepancy occurs.
4. **Ensure Consistent Cache Configuration**:
Make sure that the `THUMBNAIL_CACHE_CONFIG` is correctly applied in both the
web app and Celery worker. Sometimes, configuration might not be correctly
propagated to all parts of the application.
By following these steps, you should be able to identify and resolve the issue
with inconsistent cache keys for chart thumbnails. If the problem persists, you
might need to dive deeper into the specific implementation details of the
thumbnail caching logic in the Superset codebase
<sup>[[1]](https://github.com/apache/superset/blob/master/superset/tasks/thumbnails.py)</sup><sup>[[2]](https://github.com/apache/superset/blob/master/docs/docs/configuration/cache.mdx)</sup>.
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GitHub link:
https://github.com/apache/superset/discussions/34325#discussioncomment-13893850
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