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Question
How does the caching mechanism work for a HTTP Pull Resource?
Environment
CDN
Answer
Generally, there are 3 levels of content expiry settings in OnApp CDN:
- Origin Server - End users may modify the cache control header at the origin server (where the content is hosted), for example, Apache config or htaccess rule. HTTP meta tag is not supported.
- CDN Resource Level - Customers may configure the CDN site's content expiry setting at CP by navigating to [ CDN Resource] -> Create/Edit CDN Resource -> Enable Advanced Settings. The maximum value, that can be inserted is 71582788.
- Cloud Owner Level - Cloud owner may configure the global content expiry time by navigating to Dashboard -> [ CDN ] -> [ CDN Management] -> [ HTTP Settings]
The Overwrite Rules: 1 > 2 > 3.
Additional Info
For example, if end user sets "cache-control: Max Age" at the origin server to 2 hours and upon CDN resource creation, the content owner set the cache expiry to a day, our system will follow the origin cache header, which is to remove the cache content from the CDN pops after they are being cached for 2 hours.