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'
autoload :NullStore, 'active_support/cache/null_store'
# These options mean something to all cache implementations. Individual cache
# implementations may support additional options.
UNIVERSAL_OPTIONS = [:namespace, :compress, :compress_threshold, :expires_in, :race_condition_ttl]
module Strategy
autoload :LocalCache, 'active_support/cache/strategy/local_cache'
end
class << self
# Creates a new 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}/" : ""
if prefix = ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"]
expanded_cache_key << "#{prefix}/"
end
expanded_cache_key << retrieve_cache_key(key)
expanded_cache_key
end
private
def retrieve_cache_key(key)
case
when key.respond_to?(:cache_key) then key.cache_key
when key.is_a?(Array) then key.map { |element| retrieve_cache_key(element) }.to_param
when key.respond_to?(:to_a) then retrieve_cache_key(key.to_a)
else key.to_param
end.to_s
end
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
# <tt>:compress => true</tt> in the initializer or as an option to +fetch+
# or +write+. To specify the threshold at which to compress values, set the
# <tt>:compress_threshold</tt> 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 <tt>:force => true</tt> will force a cache miss:
#
# cache.write("today", "Monday")
# cache.fetch("today", :force => true) # => nil
#
# Setting <tt>:compress</tt> will store a large cache entry set by the call
# in a compressed format.
#
#
# Setting <tt>:expires_in</tt> 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 <tt>:race_condition_ttl</tt> 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 <tt>:race_condition_ttl</tt>. 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 <tt>:race_condition_ttl</tt> 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
# <tt>:race_condition_ttl</tt> 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_i
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)
entry && !entry.expired?
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
