tencent cloud

When do I need to purge and prefetch?

• Purge: To ensure that users access to the latest resources when there are resources to update, restricted resources to remove, or domain name configurations to change on your origin server, you can submit a purge task, which can prevent user access to old resources or old configurations from the node cache. For more details, see Purge Cache.
• Prefetch: For operating activities, installation packages or upgrade packages to release, you can submit a prefetch task to prefetch static resources to CDN acceleration nodes, which will reduce strain on the origin server and improve the service availability and user experience. For more details, see Prefetch Cache.

What are the differences between purge and prefetch?

• Once a resource is purged, its cache on all CDN nodes across the entire network will be deleted. When a user request arrives at a node, the node will pull the corresponding resource from the origin server, return it to the user, and cache it to the node to ensure that the user can obtain the latest resource.
• When a resource is prefetched, it will be cached in advance to all CDN nodes across the entire network. When a user request arrives at a node, the resource can be directly obtained on the node.

What are requirements for purge and prefetch? How long do they take to take effect?

• Purge Cache
  • URL purge: a maximum of 10,000 URLs can be purged each day and a maximum of 1,000 URLs can be submitted for each purge. It takes about 5 minutes for the purge to take effect. If the cache validity period configured for the file is less than 5 minutes, we recommend you wait for the timeout and update instead of using the purge tool.
  • Directory purge: a maximum of 100 directories can be purged each day and a maximum of 20 URL directories can be submitted for each purge. It takes about 5 minutes for the purge to take effect. If the cache validity period configured for the folder is less than 5 minutes, we recommend you wait for the timeout and update instead of using the purge tool.
• Prefetch Resource
  • URL prefetch: A maximum of 1,000 URLs can be prefetched each day, and a maximum of 20 URLs can be submitted for each prefetch task. It takes about 5 to 30 minutes for the prefetch to take effect, depending on the file size.

Will the cache on CDN nodes be updated in real time?

No. The cached content on CDN cache nodes are updated based on the cache validity you configured in the console. If you need to update a file's cache in real time, use cache purge.

How do I view the purge and prefetch history?

You can check the purge and prefetch history in the CDN console. For more information, see History.

Can I prefetch with custom request headers?

No.