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require 'dalli'
require 'flipper'
module Flipper
module Adapters
# Public: Adapter that wraps another adapter with the ability to cache
# adapter calls in Memcached using the Dalli gem.
class Dalli
include ::Flipper::Adapter
Version = 'v1'.freeze
Namespace = "flipper/#{Version}".freeze
FeaturesKey = "#{Namespace}/features".freeze
GetAllKey = "#{Namespace}/get_all".freeze
# Private
def self.key_for(key)
"#{Namespace}/feature/#{key}"
end
# Internal
attr_reader :cache
# Public: The name of the adapter.
attr_reader :name
# Public: The ttl for all cached data.
attr_reader :ttl
# Public
def initialize(adapter, cache, ttl = 0)
@adapter = adapter
@name = :dalli
@cache = cache
@ttl = ttl
end
# Public
def features
read_feature_keys
end
# Public
def add(feature)
result = @adapter.add(feature)
@cache.delete(FeaturesKey)
result
end
# Public
def remove(feature)
result = @adapter.remove(feature)
@cache.delete(FeaturesKey)
@cache.delete(key_for(feature.key))
result
end
# Public
def clear(feature)
result = @adapter.clear(feature)
@cache.delete(key_for(feature.key))
result
end
# Public
def get(feature)
@cache.fetch(key_for(feature.key), @ttl) do
@adapter.get(feature)
end
end
def get_multi(features)
read_many_features(features)
end
def get_all
if @cache.add(GetAllKey, Time.now.to_i, @ttl)
response = @adapter.get_all
response.each do |key, value|
@cache.set(key_for(key), value, @ttl)
end
@cache.set(FeaturesKey, response.keys.to_set, @ttl)
response
else
features = read_feature_keys.map { |key| Flipper::Feature.new(key, self) }
read_many_features(features)
end
end
# Public
def enable(feature, gate, thing)
result = @adapter.enable(feature, gate, thing)
@cache.delete(key_for(feature.key))
result
end
# Public
def disable(feature, gate, thing)
result = @adapter.disable(feature, gate, thing)
@cache.delete(key_for(feature.key))
result
end
private
def key_for(key)
self.class.key_for(key)
end
def read_feature_keys
@cache.fetch(FeaturesKey, @ttl) { @adapter.features }
end
# Internal: Given an array of features, attempts to read through cache in
# as few network calls as possible.
def read_many_features(features)
keys = features.map { |feature| key_for(feature.key) }
cache_result = @cache.get_multi(keys)
uncached_features = features.reject { |feature| cache_result[key_for(feature.key)] }
if uncached_features.any?
response = @adapter.get_multi(uncached_features)
response.each do |key, value|
@cache.set(key_for(key), value, @ttl)
cache_result[key_for(key)] = value
end
end
result = {}
features.each do |feature|
result[feature.key] = cache_result[key_for(feature.key)]
end
result
end
end
end
end
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