module ActiveSupport module Cache module Strategy module LocalCache # this allows caching of the fact that there is nothing in the remote cache NULL = 'remote_cache_store:null' def with_local_cache Thread.current[thread_local_key] = MemoryStore.new yield ensure Thread.current[thread_local_key] = nil end def middleware @middleware ||= begin klass = Class.new klass.class_eval(<<-EOS, __FILE__, __LINE__) def initialize(app) @app = app end def call(env) Thread.current[:#{thread_local_key}] = MemoryStore.new @app.call(env) ensure Thread.current[:#{thread_local_key}] = nil end EOS klass end end def read(key, options = nil) value = local_cache && local_cache.read(key) if value == NULL nil elsif value.nil? value = super local_cache.write(key, value || NULL) if local_cache value else # forcing the value to be immutable value.duplicable? ? value.dup : value end end def write(key, value, options = nil) value = value.to_s if respond_to?(:raw?) && raw?(options) local_cache.write(key, value || NULL) if local_cache super end def delete(key, options = nil) local_cache.write(key, NULL) if local_cache super end def exist(key, options = nil) value = local_cache.read(key) if local_cache if value == NULL false elsif value true else super end end def increment(key, amount = 1) if value = super local_cache.write(key, value.to_s) if local_cache value else nil end end def decrement(key, amount = 1) if value = super local_cache.write(key, value.to_s) if local_cache value else nil end end def clear local_cache.clear if local_cache super end private def thread_local_key @thread_local_key ||= "#{self.class.name.underscore}_local_cache".gsub("/", "_").to_sym end def local_cache Thread.current[thread_local_key] end end end end end