You can use the purge cache feature to clear cached resources from points of presence (POPs) and retrieve the most recent ones from the origin server. This feature is useful when you update content to or remove illicit content from your origin server. Purging a large number of cached resources in a short period of time results in a significant increase in origin requests, which, in turn, increases loads on the origin server.
Overview
After you purge the cache, resources cached on all POPs are marked as expired. When a client requests an expired resource, Edge Security Acceleration (ESA) fetches the latest version from the origin server. Then ESA returns the updated version to the client and caches it on POPs for subsequent requests. The purge cache feature reduces the cache hit ratio.
Scenarios
Update and release resources
After resources on your origin server are updated, you can specify the URLs or directories of the updated resources. Then, ESA purges the resources that are cached on POPs. This ensures that clients can retrieve the most recent content from POPs.
Remove illicit content
After you remove illicit content from your origin server, clients can still access the content because it has been cached on POPs. In this case, you can use the purge cache feature to clear the content from POPs.
Usage notes
After a purge task completes, your resources cached on POPs become invalid. A request that is destined for purged resources is redirected to the origin server to retrieve a fresh version. If you frequently run purge tasks, more requests will be redirected to the origin server, which results in high bandwidth costs and undue origin strain.
A purge task takes effect 5 to 6 minutes after it is submitted. If the resource you want to purge has a TTL of less than 5 minutes, you wait for it to expire instead of manually running a purge task.
Purge options supported by different plans
Basic | Standard | Advanced | Enterprise | |
Purge option | URL | URL | URL | URL, hostname, tag, and URL with parameters ignored |