696 lines
26 KiB
Ruby
696 lines
26 KiB
Ruby
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/module/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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require "active_support/core_ext/string/strip"
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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 Store 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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retrieve_store_class(store).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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# Expands out the +key+ argument into a key that can be used for the
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# cache store. Optionally accepts a namespace, and all keys will be
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# scoped within that namespace.
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#
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# If the +key+ argument provided is an array, or responds to +to_a+, then
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# each of elements in the array will be turned into parameters/keys and
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# concatenated into a single key. For example:
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#
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# expand_cache_key([:foo, :bar]) # => "foo/bar"
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# expand_cache_key([:foo, :bar], "namespace") # => "namespace/foo/bar"
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#
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# The +key+ argument can also respond to +cache_key+ or +to_param+.
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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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# Obtains the specified cache store class, given the name of the +store+.
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# Raises an error when the store class cannot be found.
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def retrieve_store_class(store)
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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.to_s.camelize)
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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 = -> { @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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# 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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# Creates a new cache. The options will be passed to any write method calls
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# except for <tt>:namespace</tt> which can be used to set the global
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# 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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# Silences 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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# Silences 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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# 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 passed
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# the key and executed in the event of a cache miss. The return value of the
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# block will be written to the cache under the given cache key, and that
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# return value 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> forces a cache "miss," meaning we treat
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# the cache value as missing even if it's present. Passing a block is
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# required when +force+ is true so this always results in a cache write.
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#
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# cache.write('today', 'Monday')
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# cache.fetch('today', force: true) { 'Tuesday' } # => 'Tuesday'
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# cache.fetch('today', force: true) # => ArgumentError
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#
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# The +:force+ option is useful when you're calling some other method to
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# ask whether you should force a cache write. Otherwise, it's clearer to
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# just call <tt>Cache#write</tt>.
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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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# 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
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# a cache entry is used very frequently and is under heavy load. If a
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# cache expires and due to heavy load several different processes will try
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# to read data natively and then they all will try to write to cache. To
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# 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>.
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# Yes, this process is extending the time for a stale value by another few
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# seconds. Because of extended life of the previous cache, other processes
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# will continue to use slightly stale data for a just a bit longer. In the
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# meantime that first process will go ahead and will write into cache the
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# new value. After that all the processes will start getting the new value.
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# 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
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# regenerated after the specified number of seconds. Also note that the
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# life of stale cache is extended only if it expired recently. Otherwise
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# a new value is generated and <tt>:race_condition_ttl</tt> does not play
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# 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.seconds) 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.seconds) 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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# cache.fetch('foo') # => "original value"
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# sleep 10 # First thread extended the life of cache by another 10 seconds
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# cache.fetch('foo') # => "new value 1"
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# val_1 # => "new value 1"
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# val_2 # => "original value"
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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
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# miss. +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 = normalize_key(name, options)
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entry = nil
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instrument(:read, name, options) do |payload|
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cached_entry = read_entry(key, options) unless options[:force]
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entry = handle_expired_entry(cached_entry, key, options)
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payload[:super_operation] = :fetch if payload
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payload[:hit] = !!entry if payload
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end
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if entry
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get_entry_value(entry, name, options)
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else
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save_block_result_to_cache(name, options) { |_name| yield _name }
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end
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elsif options && options[:force]
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raise ArgumentError, "Missing block: Calling `Cache#fetch` with `force: true` requires a block."
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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 = normalize_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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# Reads 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 = normalize_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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# Fetches data from the cache, using the given keys. If there is data in
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# the cache with the given keys, then that data is returned. Otherwise,
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# the supplied block is called for each key for which there was no data,
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# and the result will be written to the cache and returned.
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# Therefore, you need to pass a block that returns the data to be written
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# to the cache. If you do not want to write the cache when the cache is
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# not found, use #read_multi.
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#
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# Options are passed to the underlying cache implementation.
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#
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# Returns a hash with the data for each of the names. For example:
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#
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# cache.write("bim", "bam")
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# cache.fetch_multi("bim", "unknown_key") do |key|
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# "Fallback value for key: #{key}"
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# end
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# # => { "bim" => "bam",
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# # "unknown_key" => "Fallback value for key: unknown_key" }
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#
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def fetch_multi(*names)
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raise ArgumentError, "Missing block: `Cache#fetch_multi` requires a block." unless block_given?
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options = names.extract_options!
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options = merged_options(options)
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results = read_multi(*names, options)
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names.each_with_object({}) do |name, memo|
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memo[name] = results.fetch(name) do
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value = yield name
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write(name, value, options)
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value
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end
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end
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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
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entry = Entry.new(value, options)
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write_entry(normalize_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
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delete_entry(normalize_key(name, options), options)
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end
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end
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# Returns +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
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entry = read_entry(normalize_key(name, options), options)
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(entry && !entry.expired?) || false
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end
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end
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# Deletes 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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# Increments 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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# Decrements 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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# Cleanups 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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# Clears 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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# The options hash is 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
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raise NotImplementedError.new("#{self.class.name} does not support clear")
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end
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private
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# Adds the namespace defined in the options to a pattern designed to
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# match keys. Implementations that support delete_matched should call
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# this method to translate a pattern that matches names into one that
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# matches namespaced keys.
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def key_matcher(pattern, options) # :doc:
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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
|
|
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
|
|
# <tt>value.size</tt> 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
|