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
The promotion policy. The values
The sampling rate for the request to be considered
--policy is set to
lru the following options are also available:
The minimum number of hits before promotion.
The size (number of 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.
These two examples shows how to use the chance and LRU policies, respectively:
map http://cdn.example.com/ http://some-server.example.com \ @plugin=cache_promote.so @pparam=--policy=chance @pparam=--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
--sample is available for all policies and can be used to reduce pressure under heavy load.