require "zlib" require "active_support/core_ext/array/extract_options" require "active_support/core_ext/array/wrap" require "active_support/core_ext/module/attribute_accessors" require "active_support/core_ext/numeric/bytes" require "active_support/core_ext/numeric/time" require "active_support/core_ext/object/to_param" require "active_support/core_ext/string/inflections" require "active_support/core_ext/string/strip" module ActiveSupport # See ActiveSupport::Cache::Store for documentation. module Cache autoload :FileStore, "active_support/cache/file_store" autoload :MemoryStore, "active_support/cache/memory_store" autoload :MemCacheStore, "active_support/cache/mem_cache_store" autoload :NullStore, "active_support/cache/null_store" # These options mean something to all cache implementations. Individual cache # implementations may support additional options. UNIVERSAL_OPTIONS = [:namespace, :compress, :compress_threshold, :expires_in, :race_condition_ttl] module Strategy autoload :LocalCache, "active_support/cache/strategy/local_cache" end class << self # Creates a new Store object according to the given options. # # If no arguments are passed to this method, then a new # ActiveSupport::Cache::MemoryStore object will be returned. # # If you pass a Symbol as the first argument, then a corresponding cache # store class under the ActiveSupport::Cache namespace will be created. # For example: # # ActiveSupport::Cache.lookup_store(:memory_store) # # => returns a new ActiveSupport::Cache::MemoryStore object # # ActiveSupport::Cache.lookup_store(:mem_cache_store) # # => returns a new ActiveSupport::Cache::MemCacheStore object # # Any additional arguments will be passed to the corresponding cache store # class's constructor: # # ActiveSupport::Cache.lookup_store(:file_store, '/tmp/cache') # # => same as: ActiveSupport::Cache::FileStore.new('/tmp/cache') # # If the first argument is not a Symbol, then it will simply be returned: # # ActiveSupport::Cache.lookup_store(MyOwnCacheStore.new) # # => returns MyOwnCacheStore.new def lookup_store(*store_option) store, *parameters = *Array.wrap(store_option).flatten case store when Symbol retrieve_store_class(store).new(*parameters) when nil ActiveSupport::Cache::MemoryStore.new else store end end # Expands out the +key+ argument into a key that can be used for the # cache store. Optionally accepts a namespace, and all keys will be # scoped within that namespace. # # If the +key+ argument provided is an array, or responds to +to_a+, then # each of elements in the array will be turned into parameters/keys and # concatenated into a single key. For example: # # expand_cache_key([:foo, :bar]) # => "foo/bar" # expand_cache_key([:foo, :bar], "namespace") # => "namespace/foo/bar" # # The +key+ argument can also respond to +cache_key+ or +to_param+. def expand_cache_key(key, namespace = nil) expanded_cache_key = namespace ? "#{namespace}/" : "" if prefix = ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"] expanded_cache_key << "#{prefix}/" end expanded_cache_key << retrieve_cache_key(key) expanded_cache_key end private def retrieve_cache_key(key) case when key.respond_to?(:cache_key) then key.cache_key when key.is_a?(Array) then key.map { |element| retrieve_cache_key(element) }.to_param when key.respond_to?(:to_a) then retrieve_cache_key(key.to_a) else key.to_param end.to_s end # Obtains the specified cache store class, given the name of the +store+. # Raises an error when the store class cannot be found. def retrieve_store_class(store) require "active_support/cache/#{store}" rescue LoadError => e raise "Could not find cache store adapter for #{store} (#{e})" else ActiveSupport::Cache.const_get(store.to_s.camelize) end end # An abstract cache store class. There are multiple cache store # implementations, each having its own additional features. See the classes # under the ActiveSupport::Cache module, e.g. # ActiveSupport::Cache::MemCacheStore. MemCacheStore is currently the most # popular cache store for large production websites. # # Some implementations may not support all methods beyond the basic cache # methods of +fetch+, +write+, +read+, +exist?+, and +delete+. # # ActiveSupport::Cache::Store can store any serializable Ruby object. # # cache = ActiveSupport::Cache::MemoryStore.new # # cache.read('city') # => nil # cache.write('city', "Duckburgh") # cache.read('city') # => "Duckburgh" # # Keys are always translated into Strings and are case sensitive. When an # object is specified as a key and has a +cache_key+ method defined, this # method will be called to define the key. Otherwise, the +to_param+ # method will be called. Hashes and Arrays can also be used as keys. The # elements will be delimited by slashes, and the elements within a Hash # will be sorted by key so they are consistent. # # cache.read('city') == cache.read(:city) # => true # # Nil values can be cached. # # If your cache is on a shared infrastructure, you can define a namespace # for your cache entries. If a namespace is defined, it will be prefixed on # to every key. The namespace can be either a static value or a Proc. If it # is a Proc, it will be invoked when each key is evaluated so that you can # use application logic to invalidate keys. # # cache.namespace = -> { @last_mod_time } # Set the namespace to a variable # @last_mod_time = Time.now # Invalidate the entire cache by changing namespace # # Caches can also store values in a compressed format to save space and # reduce time spent sending data. Since there is overhead, values must be # large enough to warrant compression. To turn on compression either pass # compress: true in the initializer or as an option to +fetch+ # or +write+. To specify the threshold at which to compress values, set the # :compress_threshold option. The default threshold is 16K. class Store cattr_accessor :logger, instance_writer: true attr_reader :silence, :options alias :silence? :silence # Creates a new cache. The options will be passed to any write method calls # except for :namespace which can be used to set the global # namespace for the cache. def initialize(options = nil) @options = options ? options.dup : {} end # Silences the logger. def silence! @silence = true self end # Silences the logger within a block. def mute previous_silence, @silence = defined?(@silence) && @silence, true yield ensure @silence = previous_silence end # Fetches data from the cache, using the given key. If there is data in # the cache with the given key, then that data is returned. # # If there is no such data in the cache (a cache miss), then +nil+ will be # returned. However, if a block has been passed, that block will be passed # the key and executed in the event of a cache miss. The return value of the # block will be written to the cache under the given cache key, and that # return value will be returned. # # cache.write('today', 'Monday') # cache.fetch('today') # => "Monday" # # cache.fetch('city') # => nil # cache.fetch('city') do # 'Duckburgh' # end # cache.fetch('city') # => "Duckburgh" # # You may also specify additional options via the +options+ argument. # Setting force: true forces a cache "miss," meaning we treat # the cache value as missing even if it's present. Passing a block is # required when +force+ is true so this always results in a cache write. # # cache.write('today', 'Monday') # cache.fetch('today', force: true) { 'Tuesday' } # => 'Tuesday' # cache.fetch('today', force: true) # => ArgumentError # # The +:force+ option is useful when you're calling some other method to # ask whether you should force a cache write. Otherwise, it's clearer to # just call Cache#write. # # Setting :compress will store a large cache entry set by the call # in a compressed format. # # Setting :expires_in will set an expiration time on the cache. # All caches support auto-expiring content after a specified number of # seconds. This value can be specified as an option to the constructor # (in which case all entries will be affected), or it can be supplied to # the +fetch+ or +write+ method to effect just one entry. # # cache = ActiveSupport::Cache::MemoryStore.new(expires_in: 5.minutes) # cache.write(key, value, expires_in: 1.minute) # Set a lower value for one entry # # Setting :race_condition_ttl is very useful in situations where # a cache entry is used very frequently and is under heavy load. If a # cache expires and due to heavy load several different processes will try # to read data natively and then they all will try to write to cache. To # avoid that case the first process to find an expired cache entry will # bump the cache expiration time by the value set in :race_condition_ttl. # Yes, this process is extending the time for a stale value by another few # seconds. Because of extended life of the previous cache, other processes # will continue to use slightly stale data for a just a bit longer. In the # meantime that first process will go ahead and will write into cache the # new value. After that all the processes will start getting the new value. # The key is to keep :race_condition_ttl small. # # If the process regenerating the entry errors out, the entry will be # regenerated after the specified number of seconds. Also note that the # life of stale cache is extended only if it expired recently. Otherwise # a new value is generated and :race_condition_ttl does not play # any role. # # # Set all values to expire after one minute. # cache = ActiveSupport::Cache::MemoryStore.new(expires_in: 1.minute) # # cache.write('foo', 'original value') # val_1 = nil # val_2 = nil # sleep 60 # # Thread.new do # val_1 = cache.fetch('foo', race_condition_ttl: 10.seconds) do # sleep 1 # 'new value 1' # end # end # # Thread.new do # val_2 = cache.fetch('foo', race_condition_ttl: 10.seconds) do # 'new value 2' # end # end # # cache.fetch('foo') # => "original value" # sleep 10 # First thread extended the life of cache by another 10 seconds # cache.fetch('foo') # => "new value 1" # val_1 # => "new value 1" # val_2 # => "original value" # # Other options will be handled by the specific cache store implementation. # Internally, #fetch calls #read_entry, and calls #write_entry on a cache # miss. +options+ will be passed to the #read and #write calls. # # For example, MemCacheStore's #write method supports the +:raw+ # option, which tells the memcached server to store all values as strings. # We can use this option with #fetch too: # # cache = ActiveSupport::Cache::MemCacheStore.new # cache.fetch("foo", force: true, raw: true) do # :bar # end # cache.fetch('foo') # => "bar" def fetch(name, options = nil) if block_given? options = merged_options(options) key = normalize_key(name, options) entry = nil instrument(:read, name, options) do |payload| cached_entry = read_entry(key, options) unless options[:force] entry = handle_expired_entry(cached_entry, key, options) payload[:super_operation] = :fetch if payload payload[:hit] = !!entry if payload end if entry get_entry_value(entry, name, options) else save_block_result_to_cache(name, options) { |_name| yield _name } end elsif options && options[:force] raise ArgumentError, "Missing block: Calling `Cache#fetch` with `force: true` requires a block." else read(name, options) end end # Fetches data from the cache, using the given key. If there is data in # the cache with the given key, then that data is returned. Otherwise, # +nil+ is returned. # # Options are passed to the underlying cache implementation. def read(name, options = nil) options = merged_options(options) key = normalize_key(name, options) instrument(:read, name, options) do |payload| entry = read_entry(key, options) if entry if entry.expired? delete_entry(key, options) payload[:hit] = false if payload nil else payload[:hit] = true if payload entry.value end else payload[:hit] = false if payload nil end end end # Reads multiple values at once from the cache. Options can be passed # in the last argument. # # Some cache implementation may optimize this method. # # Returns a hash mapping the names provided to the values found. def read_multi(*names) options = names.extract_options! options = merged_options(options) results = {} names.each do |name| key = normalize_key(name, options) entry = read_entry(key, options) if entry if entry.expired? delete_entry(key, options) else results[name] = entry.value end end end results end # Fetches data from the cache, using the given keys. If there is data in # the cache with the given keys, then that data is returned. Otherwise, # the supplied block is called for each key for which there was no data, # and the result will be written to the cache and returned. # Therefore, you need to pass a block that returns the data to be written # to the cache. If you do not want to write the cache when the cache is # not found, use #read_multi. # # Options are passed to the underlying cache implementation. # # Returns a hash with the data for each of the names. For example: # # cache.write("bim", "bam") # cache.fetch_multi("bim", "unknown_key") do |key| # "Fallback value for key: #{key}" # end # # => { "bim" => "bam", # # "unknown_key" => "Fallback value for key: unknown_key" } # def fetch_multi(*names) raise ArgumentError, "Missing block: `Cache#fetch_multi` requires a block." unless block_given? options = names.extract_options! options = merged_options(options) results = read_multi(*names, options) names.each_with_object({}) do |name, memo| memo[name] = results.fetch(name) do value = yield name write(name, value, options) value end end end # Writes the value to the cache, with the key. # # Options are passed to the underlying cache implementation. def write(name, value, options = nil) options = merged_options(options) instrument(:write, name, options) do entry = Entry.new(value, options) write_entry(normalize_key(name, options), entry, options) end end # Deletes an entry in the cache. Returns +true+ if an entry is deleted. # # Options are passed to the underlying cache implementation. def delete(name, options = nil) options = merged_options(options) instrument(:delete, name) do delete_entry(normalize_key(name, options), options) end end # Returns +true+ if the cache contains an entry for the given key. # # Options are passed to the underlying cache implementation. def exist?(name, options = nil) options = merged_options(options) instrument(:exist?, name) do entry = read_entry(normalize_key(name, options), options) (entry && !entry.expired?) || false end end # Deletes all entries with keys matching the pattern. # # Options are passed to the underlying cache implementation. # # All implementations may not support this method. def delete_matched(matcher, options = nil) raise NotImplementedError.new("#{self.class.name} does not support delete_matched") end # Increments an integer value in the cache. # # Options are passed to the underlying cache implementation. # # All implementations may not support this method. def increment(name, amount = 1, options = nil) raise NotImplementedError.new("#{self.class.name} does not support increment") end # Decrements an integer value in the cache. # # Options are passed to the underlying cache implementation. # # All implementations may not support this method. def decrement(name, amount = 1, options = nil) raise NotImplementedError.new("#{self.class.name} does not support decrement") end # Cleanups the cache by removing expired entries. # # Options are passed to the underlying cache implementation. # # All implementations may not support this method. def cleanup(options = nil) raise NotImplementedError.new("#{self.class.name} does not support cleanup") end # Clears the entire cache. Be careful with this method since it could # affect other processes if shared cache is being used. # # The options hash is passed to the underlying cache implementation. # # All implementations may not support this method. def clear raise NotImplementedError.new("#{self.class.name} does not support clear") end private # Adds the namespace defined in the options to a pattern designed to # match keys. Implementations that support delete_matched should call # this method to translate a pattern that matches names into one that # matches namespaced keys. def key_matcher(pattern, options) # :doc: prefix = options[:namespace].is_a?(Proc) ? options[:namespace].call : options[:namespace] if prefix source = pattern.source if source.start_with?("^") source = source[1, source.length] else source = ".*#{source[0, source.length]}" end Regexp.new("^#{Regexp.escape(prefix)}:#{source}", pattern.options) else pattern end end # Reads an entry from the cache implementation. Subclasses must implement # this method. def read_entry(key, options) raise NotImplementedError.new end # Writes an entry to the cache implementation. Subclasses must implement # this method. def write_entry(key, entry, options) raise NotImplementedError.new end # Deletes an entry from the cache implementation. Subclasses must # implement this method. def delete_entry(key, options) raise NotImplementedError.new end # Merges the default options with ones specific to a method call. def merged_options(call_options) if call_options options.merge(call_options) else options.dup end end # Expands key to be a consistent string value. Invokes +cache_key+ if # object responds to +cache_key+. Otherwise, +to_param+ method will be # called. If the key is a Hash, then keys will be sorted alphabetically. def expanded_key(key) return key.cache_key.to_s if key.respond_to?(:cache_key) case key when Array if key.size > 1 key = key.collect { |element| expanded_key(element) } else key = key.first end when Hash key = key.sort_by { |k, _| k.to_s }.collect { |k, v| "#{k}=#{v}" } end key.to_param end # Prefixes a key with the namespace. Namespace and key will be delimited # with a colon. def normalize_key(key, options) key = expanded_key(key) namespace = options[:namespace] if options prefix = namespace.is_a?(Proc) ? namespace.call : namespace key = "#{prefix}:#{key}" if prefix key end def instrument(operation, key, options = nil) log { "Cache #{operation}: #{normalize_key(key, options)}#{options.blank? ? "" : " (#{options.inspect})"}" } payload = { key: key } payload.merge!(options) if options.is_a?(Hash) ActiveSupport::Notifications.instrument("cache_#{operation}.active_support", payload) { yield(payload) } end def log return unless logger && logger.debug? && !silence? logger.debug(yield) end def handle_expired_entry(entry, key, options) if entry && entry.expired? race_ttl = options[:race_condition_ttl].to_i if (race_ttl > 0) && (Time.now.to_f - entry.expires_at <= race_ttl) # When an entry has a positive :race_condition_ttl defined, put the stale entry back into the cache # for a brief period while the entry is being recalculated. entry.expires_at = Time.now + race_ttl write_entry(key, entry, expires_in: race_ttl * 2) else delete_entry(key, options) end entry = nil end entry end def get_entry_value(entry, name, options) instrument(:fetch_hit, name, options) {} entry.value end def save_block_result_to_cache(name, options) result = instrument(:generate, name, options) do yield(name) end write(name, result, options) result end end # This class is used to represent cache entries. Cache entries have a value and an optional # expiration time. The expiration time is used to support the :race_condition_ttl option # on the cache. # # Since cache entries in most instances will be serialized, the internals of this class are highly optimized # using short instance variable names that are lazily defined. class Entry # :nodoc: DEFAULT_COMPRESS_LIMIT = 16.kilobytes # Creates a new cache entry for the specified value. Options supported are # +:compress+, +:compress_threshold+, and +:expires_in+. def initialize(value, options = {}) if should_compress?(value, options) @value = compress(value) @compressed = true else @value = value end @created_at = Time.now.to_f @expires_in = options[:expires_in] @expires_in = @expires_in.to_f if @expires_in end def value compressed? ? uncompress(@value) : @value end # Checks if the entry is expired. The +expires_in+ parameter can override # the value set when the entry was created. def expired? @expires_in && @created_at + @expires_in <= Time.now.to_f end def expires_at @expires_in ? @created_at + @expires_in : nil end def expires_at=(value) if value @expires_in = value.to_f - @created_at else @expires_in = nil end end # Returns the size of the cached value. This could be less than # value.size if the data is compressed. def size if defined?(@s) @s else case value when NilClass 0 when String @value.bytesize else @s = Marshal.dump(@value).bytesize end end end # Duplicates the value in a class. This is used by cache implementations that don't natively # serialize entries to protect against accidental cache modifications. def dup_value! if @value && !compressed? && !(@value.is_a?(Numeric) || @value == true || @value == false) if @value.is_a?(String) @value = @value.dup else @value = Marshal.load(Marshal.dump(@value)) end end end private def should_compress?(value, options) if value && options[:compress] compress_threshold = options[:compress_threshold] || DEFAULT_COMPRESS_LIMIT serialized_value_size = (value.is_a?(String) ? value : Marshal.dump(value)).bytesize return true if serialized_value_size >= compress_threshold end false end def compressed? defined?(@compressed) ? @compressed : false end def compress(value) Zlib::Deflate.deflate(Marshal.dump(value)) end def uncompress(value) Marshal.load(Zlib::Inflate.inflate(value)) end end end end