Cache Promote Plugin

The cache_promote plugin provides a means to control when an object should be allowed to enter the cache. This is orthogonal from normal Cache-Control directives, providing a different set of policies to apply. The typical use case for this plugin is when you have a very large data set, where you want to avoid churning the ATS cache for the long tail content.

All configuration is done via remap.config, and the following options are available:

--policy	The promotion policy. lru and chance are supported
--sample	The sampling rate for the request to be considered

For the lru plugin, the following options are also available:

--hits	The minimum number of hits before promotion
--buckets	The size (entries) of the LRU

These two options combined with your usage patterns will control how likely a URL is to become promoted to enter the cache.

Examples

map http://cdn.example.com/ http://some-server.example.com

@plugin=cache_promote.so @pparam=–policy=chance –sample=10%

map http://cdn.example.com/ http://some-server.example.com

@plugin=cache_promote.so @pparam=–policy=lru @pparam=–hits=10 @pparam=–buckets=10000

Note that the –sample option is available for all policies, and when used to reduce pressure on the under heavy load.