Dynamic caching and eviction policy in different points-of-presence of a content delivery network

A system comprising:

• a first site that receives demand in excess of a threshold amount, the first site comprising a first cache of a first size and one or more processors configured to:
• cache a first plurality of files requested from the first site to the first cache based on a static caching policy that remains unchanged in response to changing request behavior;
• and
• a second site that receives demand less than the threshold amount, the second site comprising a second cache of a second size and one or more processors configured to:
• cache a second plurality of files requested from the second site to the second cache based on a dynamic caching policy that changes which files are cached in response to changing request behavior, wherein caching the second plurality of files requested from the second site comprises:
• changing from a first caching policy, that each device of a plurality of different devices in the second site uses to cache different subsets of the second plurality of files, to a second caching policy in response to the changing request behavior, and
• wherein the second caching policy prioritizes caching of files with at least one different characteristic than the first caching policy.

A method comprising:

• providing a first cache of a first size at a first site of a content delivery network (“CDN”) that receives demand in excess of a demand threshold;
• providing a second cache of a smaller second size at a second site of the CDN that receives demand less than the demand threshold, wherein the second site comprises a plurality of different devices that cache different subsets of files requested from the second site;
• caching a first plurality of files requested from the first site to the first cache based on a static caching policy that remains unchanged in response to changing request behavior;
• and
• caching a second plurality of files requested from the second site to the second cache based on a dynamic caching policy that changes which files are cached in response to changing request behavior, wherein caching the second plurality of files requested from the second site comprises:
• caching a first set of the second plurality of files to the second cache based on the first set of files being selected for caching by a first caching policy set as the dynamic caching policy during a first time;
• determining that a cache-hit ratio of the second cache is less than a performance threshold after the first time;
• replacing the first caching policy with a second caching policy in response to determining that the cache-hit ratio is less than the performance threshold;
• and
• caching a second set of the second plurality of files to the second cache based on the second set of files being selected for caching by the second caching policy set as the dynamic caching policy during a second time.

A system comprising:

• a first site that receives demand in excess of a demand threshold, the first site comprising a first cache of a first size and one or more processors configured to:
• cache a first plurality of files requested from the first site to the first cache based on a static caching policy that remains unchanged in response to changing request behavior;
• and
• a second site that receives demand less than the demand threshold, the second site comprising a second cache of a second size and one or more processors configured to:
• cache a second plurality of files requested from the second site to the second cache based on a dynamic caching policy that changes which files are cached in response to changing request behavior, wherein caching the second plurality of files requested from the second site comprises:
• caching a first set of the second plurality of files to the second cache based on the first set of files being selected for caching by a first caching policy set as the dynamic caching policy during a first time;
• determining that a cache-hit ratio of the second cache is less than a performance threshold after the first time;
• replacing the first caching policy with a second caching policy in response to determining that the cache-hit ratio is less than the performance threshold;
• and
• caching a second set of the second plurality of files to the second cache based on the second set of files being selected for caching by the second caching policy set as the dynamic caching policy during a second time.