High Availability
High availability options let you stay online even when your backend goes down.
Stale if error
When enabled, the CDN will serve stale (expired) content from cache when the origin server returns an error or is unreachable. This means that visitors continue to see content even during origin outages, as long as the content is cached in the CDN node.
Keep stale duration
This setting determines how long the CDN keeps expired objects in cache after their TTL expires, for the purpose of serving stale objects when no fresh object can be fetched.
If not explicitly configured, objects will be removed from CDN nodes as soon as they expire.
Stale revive
When a fetch of a resource from the origin server fails, the object can be revived temporarily, so that it can be served directly without attempting a new fetch from the origin. The purpose of this is to not bother the origin too soon after the failure.
When the object is revived, it will gain a TTL and grace (also known as stale-while-revalidate in Cache-Control headers) in a way which is similar to TTL and grace applied to new objects.
When an object is revived, the keep value is calculated so that the time it will fully expire does not change.
Stale revive TTL
This specifies how long a revived stale object should be delivered directly to the client without triggering a fetch from the origin server.
Default value: 1 minute
Stale revive grace
After TTL has expired, grace represents the time/duration during which the CDN can deliver the object to the client without first waiting for a response from the origin.
Default value: 10 seconds