Problem description
When an OSS bucket is CDN-accelerated, Image Processing (IMG) URLs include query parameters. CDN treats each unique URL — including its query string — as a separate cache entry. If CDN is not configured to filter these parameters, every IMG URL variant results in a cache miss and triggers a back-to-origin request, even when the base image is already cached.
Causes
This problem occurs for one or both of the following reasons:
Parameter filtering is disabled. CDN forwards the full IMG URL query string to the origin without normalizing it, so the cache lookup fails and CDN retrieves the image from the origin on every request.
No CDN cache settings are configured. CDN falls back to default cache rules, and the cached image may expire before it is reused.
Solutions
Resolve both issues in the Alibaba Cloud CDN console:
Log on to the Alibaba Cloud CDN console.
In the left-side navigation pane, choose Content Delivery > Domain Names.
On the Domain Names page, find the domain name and click Manage.
In the left-side navigation tree for the domain name, click Optimization, then click Modify next to Ignore Parameters to configure parameter filtering.
In the left-side navigation tree, click Cache. On the page that appears, specify a cache expiration time.
Applicable scope
CDN
OSS