This gem pre-caches your ActiveRecord model's calculated attributes (computed fields) in Redis.
class User < ActiveRecord::Base redis_cache do def fullname firstname + ' ' + lastname end end end
Methods defined inside the “cache” block are redefined to get the answer from redis first. The cached attributes are saved whenever the record is saved, in an after_commit callback.
Cache invalidation for associations
Redrecord can be used to cache attributes that use assocations:
class User < ActiveRecord::Base has_many :preferences redis_cache do def preferences_list preferences.map(&:name).join(', ') end end end class Preference < ActiveRecord::Base belongs_to :user invalidate_cache_on :user end
In this example, whenever a preference is saved, the associated user record will be recalculated and saved in redis. If it is an array (eg. has_many) then all of the associated records will be re-cached.
Other instance methods of interest:
obj.remove_from_cache! # Remove redis cache for an object. obj.add_to_cache! # Recalculate fields and store in redis. obj.cached_fields # hash of the cached fields and their values obj.attribs_with_cached_fields # cached_fields merged with AR attributes
If redis is down?
To enable talking to a redis server, set Redrecord.enabled=true
If Redrecord can't access redis within a timeout (Redrecord.timeout=15 by default) then it sets enabled=false, disabling all redis access so your application can keep working without the cache.
For testing purposes, you can set Redrecord.write_only = true This keeps the cache contents up to date but does not read back any cached content.
in your Gemfile:
in your rails app config/initializers/redrecord.rb:
$redis = Redis.new(:host => 'localhost', :port => 6379, :db => 1) . = $redis . = true
Contact the author
Andrew Snow <[email protected]> Andys^ on irc.freenode.net