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625 lines
23 KiB
Ruby
625 lines
23 KiB
Ruby
require 'benchmark'
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require 'zlib'
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require 'active_support/core_ext/array/extract_options'
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require 'active_support/core_ext/array/wrap'
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require 'active_support/core_ext/benchmark'
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require 'active_support/core_ext/exception'
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require 'active_support/core_ext/class/attribute_accessors'
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require 'active_support/core_ext/numeric/bytes'
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require 'active_support/core_ext/numeric/time'
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require 'active_support/core_ext/object/to_param'
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require 'active_support/core_ext/string/inflections'
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module ActiveSupport
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# See ActiveSupport::Cache::Store for documentation.
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module Cache
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autoload :FileStore, 'active_support/cache/file_store'
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autoload :MemoryStore, 'active_support/cache/memory_store'
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autoload :MemCacheStore, 'active_support/cache/mem_cache_store'
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autoload :NullStore, 'active_support/cache/null_store'
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# These options mean something to all cache implementations. Individual cache
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# implementations may support additional options.
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UNIVERSAL_OPTIONS = [:namespace, :compress, :compress_threshold, :expires_in, :race_condition_ttl]
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module Strategy
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autoload :LocalCache, 'active_support/cache/strategy/local_cache'
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end
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class << self
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# Creates a new CacheStore object according to the given options.
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#
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# If no arguments are passed to this method, then a new
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# ActiveSupport::Cache::MemoryStore object will be returned.
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#
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# If you pass a Symbol as the first argument, then a corresponding cache
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# store class under the ActiveSupport::Cache namespace will be created.
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# For example:
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#
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# ActiveSupport::Cache.lookup_store(:memory_store)
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# # => returns a new ActiveSupport::Cache::MemoryStore object
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#
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# ActiveSupport::Cache.lookup_store(:mem_cache_store)
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# # => returns a new ActiveSupport::Cache::MemCacheStore object
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#
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# Any additional arguments will be passed to the corresponding cache store
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# class's constructor:
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#
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# ActiveSupport::Cache.lookup_store(:file_store, "/tmp/cache")
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# # => same as: ActiveSupport::Cache::FileStore.new("/tmp/cache")
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#
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# If the first argument is not a Symbol, then it will simply be returned:
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#
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# ActiveSupport::Cache.lookup_store(MyOwnCacheStore.new)
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# # => returns MyOwnCacheStore.new
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def lookup_store(*store_option)
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store, *parameters = *Array.wrap(store_option).flatten
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case store
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when Symbol
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store_class_name = store.to_s.camelize
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store_class =
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begin
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require "active_support/cache/#{store}"
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rescue LoadError => e
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raise "Could not find cache store adapter for #{store} (#{e})"
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else
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ActiveSupport::Cache.const_get(store_class_name)
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end
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store_class.new(*parameters)
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when nil
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ActiveSupport::Cache::MemoryStore.new
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else
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store
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end
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end
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def expand_cache_key(key, namespace = nil)
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expanded_cache_key = namespace ? "#{namespace}/" : ""
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if prefix = ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"]
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expanded_cache_key << "#{prefix}/"
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end
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expanded_cache_key << retrieve_cache_key(key)
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expanded_cache_key
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end
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private
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def retrieve_cache_key(key)
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case
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when key.respond_to?(:cache_key) then key.cache_key
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when key.is_a?(Array) then key.map { |element| retrieve_cache_key(element) }.to_param
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when key.respond_to?(:to_a) then retrieve_cache_key(key.to_a)
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else key.to_param
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end.to_s
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end
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end
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# An abstract cache store class. There are multiple cache store
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# implementations, each having its own additional features. See the classes
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# under the ActiveSupport::Cache module, e.g.
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# ActiveSupport::Cache::MemCacheStore. MemCacheStore is currently the most
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# popular cache store for large production websites.
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#
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# Some implementations may not support all methods beyond the basic cache
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# methods of +fetch+, +write+, +read+, +exist?+, and +delete+.
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#
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# ActiveSupport::Cache::Store can store any serializable Ruby object.
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#
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# cache = ActiveSupport::Cache::MemoryStore.new
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#
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# cache.read("city") # => nil
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# cache.write("city", "Duckburgh")
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# cache.read("city") # => "Duckburgh"
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#
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# Keys are always translated into Strings and are case sensitive. When an
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# object is specified as a key and has a +cache_key+ method defined, this
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# method will be called to define the key. Otherwise, the +to_param+
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# method will be called. Hashes and Arrays can also be used as keys. The
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# elements will be delimited by slashes, and the elements within a Hash
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# will be sorted by key so they are consistent.
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#
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# cache.read("city") == cache.read(:city) # => true
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#
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# Nil values can be cached.
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#
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# If your cache is on a shared infrastructure, you can define a namespace
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# for your cache entries. If a namespace is defined, it will be prefixed on
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# to every key. The namespace can be either a static value or a Proc. If it
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# is a Proc, it will be invoked when each key is evaluated so that you can
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# use application logic to invalidate keys.
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#
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# cache.namespace = lambda { @last_mod_time } # Set the namespace to a variable
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# @last_mod_time = Time.now # Invalidate the entire cache by changing namespace
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#
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#
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# Caches can also store values in a compressed format to save space and
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# reduce time spent sending data. Since there is overhead, values must be
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# large enough to warrant compression. To turn on compression either pass
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# <tt>:compress => true</tt> in the initializer or as an option to +fetch+
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# or +write+. To specify the threshold at which to compress values, set the
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# <tt>:compress_threshold</tt> option. The default threshold is 16K.
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class Store
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cattr_accessor :logger, :instance_writer => true
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attr_reader :silence, :options
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alias :silence? :silence
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# Create a new cache. The options will be passed to any write method calls except
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# for :namespace which can be used to set the global namespace for the cache.
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def initialize(options = nil)
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@options = options ? options.dup : {}
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end
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# Silence the logger.
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def silence!
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@silence = true
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self
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end
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# Silence the logger within a block.
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def mute
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previous_silence, @silence = defined?(@silence) && @silence, true
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yield
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ensure
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@silence = previous_silence
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end
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# Set to true if cache stores should be instrumented. Default is false.
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def self.instrument=(boolean)
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Thread.current[:instrument_cache_store] = boolean
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end
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def self.instrument
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Thread.current[:instrument_cache_store] || false
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end
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# Fetches data from the cache, using the given key. If there is data in
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# the cache with the given key, then that data is returned.
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#
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# If there is no such data in the cache (a cache miss), then nil will be
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# returned. However, if a block has been passed, that block will be run
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# in the event of a cache miss. The return value of the block will be
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# written to the cache under the given cache key, and that return value
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# will be returned.
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#
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# cache.write("today", "Monday")
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# cache.fetch("today") # => "Monday"
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#
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# cache.fetch("city") # => nil
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# cache.fetch("city") do
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# "Duckburgh"
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# end
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# cache.fetch("city") # => "Duckburgh"
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#
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# You may also specify additional options via the +options+ argument.
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# Setting <tt>:force => true</tt> will force a cache miss:
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#
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# cache.write("today", "Monday")
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# cache.fetch("today", :force => true) # => nil
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#
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# Setting <tt>:compress</tt> will store a large cache entry set by the call
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# in a compressed format.
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#
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#
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# Setting <tt>:expires_in</tt> will set an expiration time on the cache.
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# All caches support auto-expiring content after a specified number of
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# seconds. This value can be specified as an option to the constructor
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# (in which case all entries will be affected), or it can be supplied to
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# the +fetch+ or +write+ method to effect just one entry.
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#
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# cache = ActiveSupport::Cache::MemoryStore.new(:expires_in => 5.minutes)
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# cache.write(key, value, :expires_in => 1.minute) # Set a lower value for one entry
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#
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# Setting <tt>:race_condition_ttl</tt> is very useful in situations where a cache entry
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# is used very frequently and is under heavy load. If a cache expires and due to heavy load
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# seven different processes will try to read data natively and then they all will try to
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# write to cache. To avoid that case the first process to find an expired cache entry will
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# bump the cache expiration time by the value set in <tt>:race_condition_ttl</tt>. Yes
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# this process is extending the time for a stale value by another few seconds. Because
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# of extended life of the previous cache, other processes will continue to use slightly
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# stale data for a just a big longer. In the meantime that first process will go ahead
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# and will write into cache the new value. After that all the processes will start
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# getting new value. The key is to keep <tt>:race_condition_ttl</tt> small.
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#
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# If the process regenerating the entry errors out, the entry will be regenerated
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# after the specified number of seconds. Also note that the life of stale cache is
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# extended only if it expired recently. Otherwise a new value is generated and
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# <tt>:race_condition_ttl</tt> does not play any role.
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#
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# # Set all values to expire after one minute.
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# cache = ActiveSupport::Cache::MemoryStore.new(:expires_in => 1.minute)
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#
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# cache.write("foo", "original value")
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# val_1 = nil
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# val_2 = nil
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# sleep 60
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#
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# Thread.new do
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# val_1 = cache.fetch("foo", :race_condition_ttl => 10) do
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# sleep 1
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# "new value 1"
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# end
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# end
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#
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# Thread.new do
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# val_2 = cache.fetch("foo", :race_condition_ttl => 10) do
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# "new value 2"
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# end
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# end
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#
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# # val_1 => "new value 1"
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# # val_2 => "original value"
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# # sleep 10 # First thread extend the life of cache by another 10 seconds
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# # cache.fetch("foo") => "new value 1"
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#
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# Other options will be handled by the specific cache store implementation.
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# Internally, #fetch calls #read_entry, and calls #write_entry on a cache miss.
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# +options+ will be passed to the #read and #write calls.
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#
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# For example, MemCacheStore's #write method supports the +:raw+
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# option, which tells the memcached server to store all values as strings.
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# We can use this option with #fetch too:
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#
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# cache = ActiveSupport::Cache::MemCacheStore.new
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# cache.fetch("foo", :force => true, :raw => true) do
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# :bar
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# end
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# cache.fetch("foo") # => "bar"
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def fetch(name, options = nil)
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if block_given?
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options = merged_options(options)
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key = namespaced_key(name, options)
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unless options[:force]
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entry = instrument(:read, name, options) do |payload|
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payload[:super_operation] = :fetch if payload
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read_entry(key, options)
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end
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end
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if entry && entry.expired?
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race_ttl = options[:race_condition_ttl].to_i
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if race_ttl and Time.now.to_f - entry.expires_at <= race_ttl
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entry.expires_at = Time.now + race_ttl
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write_entry(key, entry, :expires_in => race_ttl * 2)
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else
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delete_entry(key, options)
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end
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entry = nil
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end
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if entry
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instrument(:fetch_hit, name, options) { |payload| }
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entry.value
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else
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result = instrument(:generate, name, options) do |payload|
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yield
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end
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write(name, result, options)
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result
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end
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else
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read(name, options)
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end
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end
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# Fetches data from the cache, using the given key. If there is data in
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# the cache with the given key, then that data is returned. Otherwise,
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# nil is returned.
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#
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# Options are passed to the underlying cache implementation.
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def read(name, options = nil)
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options = merged_options(options)
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key = namespaced_key(name, options)
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instrument(:read, name, options) do |payload|
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entry = read_entry(key, options)
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if entry
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if entry.expired?
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delete_entry(key, options)
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payload[:hit] = false if payload
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nil
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else
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payload[:hit] = true if payload
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entry.value
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end
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else
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payload[:hit] = false if payload
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nil
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end
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end
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end
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# Read multiple values at once from the cache. Options can be passed
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# in the last argument.
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#
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# Some cache implementation may optimize this method.
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#
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# Returns a hash mapping the names provided to the values found.
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def read_multi(*names)
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options = names.extract_options!
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options = merged_options(options)
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results = {}
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names.each do |name|
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key = namespaced_key(name, options)
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entry = read_entry(key, options)
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if entry
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if entry.expired?
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delete_entry(key, options)
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else
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results[name] = entry.value
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end
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end
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end
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results
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end
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# Writes the value to the cache, with the key.
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#
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# Options are passed to the underlying cache implementation.
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def write(name, value, options = nil)
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options = merged_options(options)
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instrument(:write, name, options) do |payload|
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entry = Entry.new(value, options)
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write_entry(namespaced_key(name, options), entry, options)
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end
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end
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# Deletes an entry in the cache. Returns +true+ if an entry is deleted.
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#
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# Options are passed to the underlying cache implementation.
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def delete(name, options = nil)
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options = merged_options(options)
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instrument(:delete, name) do |payload|
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delete_entry(namespaced_key(name, options), options)
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end
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end
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# Return true if the cache contains an entry for the given key.
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#
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# Options are passed to the underlying cache implementation.
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def exist?(name, options = nil)
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options = merged_options(options)
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instrument(:exist?, name) do |payload|
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entry = read_entry(namespaced_key(name, options), options)
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entry && !entry.expired?
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end
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end
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# Delete all entries with keys matching the pattern.
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#
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# Options are passed to the underlying cache implementation.
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#
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# All implementations may not support this method.
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def delete_matched(matcher, options = nil)
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raise NotImplementedError.new("#{self.class.name} does not support delete_matched")
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end
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# Increment an integer value in the cache.
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#
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# Options are passed to the underlying cache implementation.
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#
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# All implementations may not support this method.
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def increment(name, amount = 1, options = nil)
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raise NotImplementedError.new("#{self.class.name} does not support increment")
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end
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# Decrement an integer value in the cache.
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#
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# Options are passed to the underlying cache implementation.
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#
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# All implementations may not support this method.
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def decrement(name, amount = 1, options = nil)
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raise NotImplementedError.new("#{self.class.name} does not support decrement")
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end
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# Cleanup the cache by removing expired entries.
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#
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# Options are passed to the underlying cache implementation.
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#
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# All implementations may not support this method.
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def cleanup(options = nil)
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raise NotImplementedError.new("#{self.class.name} does not support cleanup")
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end
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# Clear the entire cache. Be careful with this method since it could
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# affect other processes if shared cache is being used.
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#
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# Options are passed to the underlying cache implementation.
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#
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# All implementations may not support this method.
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def clear(options = nil)
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raise NotImplementedError.new("#{self.class.name} does not support clear")
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end
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protected
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# Add the namespace defined in the options to a pattern designed to match keys.
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# Implementations that support delete_matched should call this method to translate
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# a pattern that matches names into one that matches namespaced keys.
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def key_matcher(pattern, options)
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prefix = options[:namespace].is_a?(Proc) ? options[:namespace].call : options[:namespace]
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if prefix
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source = pattern.source
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if source.start_with?('^')
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source = source[1, source.length]
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else
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source = ".*#{source[0, source.length]}"
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end
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Regexp.new("^#{Regexp.escape(prefix)}:#{source}", pattern.options)
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else
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pattern
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end
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end
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# Read an entry from the cache implementation. Subclasses must implement this method.
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def read_entry(key, options) # :nodoc:
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raise NotImplementedError.new
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end
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# Write an entry to the cache implementation. Subclasses must implement this method.
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def write_entry(key, entry, options) # :nodoc:
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raise NotImplementedError.new
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end
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# Delete an entry from the cache implementation. Subclasses must implement this method.
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def delete_entry(key, options) # :nodoc:
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raise NotImplementedError.new
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end
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private
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# Merge the default options with ones specific to a method call.
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def merged_options(call_options) # :nodoc:
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if call_options
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options.merge(call_options)
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else
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options.dup
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end
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end
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# Expand key to be a consistent string value. Invoke +cache_key+ if
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# object responds to +cache_key+. Otherwise, to_param method will be
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# called. If the key is a Hash, then keys will be sorted alphabetically.
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def expanded_key(key) # :nodoc:
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return key.cache_key.to_s if key.respond_to?(:cache_key)
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case key
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when Array
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if key.size > 1
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key = key.collect{|element| expanded_key(element)}
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else
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key = key.first
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end
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when Hash
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key = key.sort_by { |k,_| k.to_s }.collect{|k,v| "#{k}=#{v}"}
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end
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key.to_param
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end
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# Prefix a key with the namespace. Namespace and key will be delimited with a colon.
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def namespaced_key(key, options)
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key = expanded_key(key)
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namespace = options[:namespace] if options
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|
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
|