require 'benchmark' require 'zlib' require 'active_support/core_ext/array/extract_options' require 'active_support/core_ext/array/wrap' require 'active_support/core_ext/benchmark' require 'active_support/core_ext/exception' require 'active_support/core_ext/class/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' 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' # 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 CacheStore 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 store_class_name = store.to_s.camelize store_class = begin require "active_support/cache/#{store}" rescue LoadError => e raise "Could not find cache store adapter for #{store} (#{e})" else ActiveSupport::Cache.const_get(store_class_name) end store_class.new(*parameters) when nil ActiveSupport::Cache::MemoryStore.new else store end end def expand_cache_key(key, namespace = nil) expanded_cache_key = namespace ? "#{namespace}/" : "" prefix = ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"] if prefix 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 else key.to_param end.to_s 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 = lambda { @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 # Create 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 # Silence the logger. def silence! @silence = true self end # Silence the logger within a block. def mute previous_silence, @silence = defined?(@silence) && @silence, true yield ensure @silence = previous_silence end # Set to true if cache stores should be instrumented. Default is false. def self.instrument=(boolean) Thread.current[:instrument_cache_store] = boolean end def self.instrument Thread.current[:instrument_cache_store] || false 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 run # 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 will force a cache miss: # # cache.write("today", "Monday") # cache.fetch("today", :force => true) # => nil # # 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 # seven 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 big 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 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) do # sleep 1 # "new value 1" # end # end # # Thread.new do # val_2 = cache.fetch("foo", :race_condition_ttl => 10) do # "new value 2" # end # end # # # val_1 => "new value 1" # # val_2 => "original value" # # sleep 10 # First thread extend the life of cache by another 10 seconds # # cache.fetch("foo") => "new value 1" # # 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 = namespaced_key(name, options) unless options[:force] entry = instrument(:read, name, options) do |payload| payload[:super_operation] = :fetch if payload read_entry(key, options) end end if entry && entry.expired? race_ttl = options[:race_condition_ttl].to_f if race_ttl and Time.now.to_f - entry.expires_at <= race_ttl 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 if entry instrument(:fetch_hit, name, options) { |payload| } entry.value else result = instrument(:generate, name, options) do |payload| yield end write(name, result, options) result end 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 = namespaced_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 # Read 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 = namespaced_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 # 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 |payload| entry = Entry.new(value, options) write_entry(namespaced_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 |payload| delete_entry(namespaced_key(name, options), options) end end # Return 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 |payload| entry = read_entry(namespaced_key(name, options), options) if entry && !entry.expired? true else false end end end # Delete 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 # Increment 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 # Increment 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 # Cleanup 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 # Clear the entire cache. Be careful with this method since it could # affect other processes if shared cache is being used. # # Options are passed to the underlying cache implementation. # # All implementations may not support this method. def clear(options = nil) raise NotImplementedError.new("#{self.class.name} does not support clear") end protected # Add 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) 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 # Read an entry from the cache implementation. Subclasses must implement this method. def read_entry(key, options) # :nodoc: raise NotImplementedError.new end # Write an entry to the cache implementation. Subclasses must implement this method. def write_entry(key, entry, options) # :nodoc: raise NotImplementedError.new end # Delete an entry from the cache implementation. Subclasses must implement this method. def delete_entry(key, options) # :nodoc: raise NotImplementedError.new end private # Merge the default options with ones specific to a method call. def merged_options(call_options) # :nodoc: if call_options options.merge(call_options) else options.dup end end # Expand key to be a consistent string value. Invoke +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) # :nodoc: 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 # Prefix a key with the namespace. Namespace and key will be delimited with a colon. def namespaced_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(operation, key, options) if self.class.instrument payload = { :key => key } payload.merge!(options) if options.is_a?(Hash) ActiveSupport::Notifications.instrument("cache_#{operation}.active_support", payload){ yield(payload) } else yield(nil) end end def log(operation, key, options = nil) return unless logger && logger.debug? && !silence? logger.debug("Cache #{operation}: #{key}#{options.blank? ? "" : " (#{options.inspect})"}") end end # Entry that is put into caches. It supports expiration time on entries and can compress values # to save space in the cache. class Entry attr_reader :created_at, :expires_in DEFAULT_COMPRESS_LIMIT = 16.kilobytes class << self # Create an entry with internal attributes set. This method is intended to be # used by implementations that store cache entries in a native format instead # of as serialized Ruby objects. def create(raw_value, created_at, options = {}) entry = new(nil) entry.instance_variable_set(:@value, raw_value) entry.instance_variable_set(:@created_at, created_at.to_f) entry.instance_variable_set(:@compressed, options[:compressed]) entry.instance_variable_set(:@expires_in, options[:expires_in]) entry end end # Create a new cache entry for the specified value. Options supported are # +:compress+, +:compress_threshold+, and +:expires_in+. def initialize(value, options = {}) @compressed = false @expires_in = options[:expires_in] @expires_in = @expires_in.to_f if @expires_in @created_at = Time.now.to_f if value.nil? @value = nil else @value = Marshal.dump(value) if should_compress?(@value, options) @value = Zlib::Deflate.deflate(@value) @compressed = true end end end # Get the raw value. This value may be serialized and compressed. def raw_value @value end # Get the value stored in the cache. def value # If the original value was exactly false @value is still true because # it is marshalled and eventually compressed. Both operations yield # strings. if @value Marshal.load(compressed? ? Zlib::Inflate.inflate(@value) : @value) end end def compressed? @compressed end # Check 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 # Set a new time when the entry will expire. def expires_at=(time) if time @expires_in = time.to_f - @created_at else @expires_in = nil end end # Seconds since the epoch when the entry will expire. def expires_at @expires_in ? @created_at + @expires_in : nil end # Returns the size of the cached value. This could be less than value.size # if the data is compressed. def size if @value.nil? 0 else @value.bytesize end end private def should_compress?(serialized_value, options) if options[:compress] compress_threshold = options[:compress_threshold] || DEFAULT_COMPRESS_LIMIT return true if serialized_value.size >= compress_threshold end false end end end end