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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/module/attribute_accessors'
require 'active_support/core_ext/numeric/bytes'
require 'active_support/core_ext/numeric/time'
require 'active_support/core_ext/object/to_param'
require 'active_support/core_ext/string/inflections'
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
retrieve_store_class(store).new(*parameters)
when nil
ActiveSupport::Cache::MemoryStore.new
else
store
end
end
# Expands out the +key+ argument into a key that can be used for the
# cache store. Optionally accepts a namespace, and all keys will be
# scoped within that namespace.
#
# If the +key+ argument provided is an array, or responds to +to_a+, then
# each of elements in the array will be turned into parameters/keys and
# concatenated into a single key. For example:
#
# expand_cache_key([:foo, :bar]) # => "foo/bar"
# expand_cache_key([:foo, :bar], "namespace") # => "namespace/foo/bar"
#
# The +key+ argument can also respond to +cache_key+ or +to_param+.
def expand_cache_key(key, namespace = nil)
expanded_cache_key = namespace ? "#{namespace}/" : ""
if prefix = ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"]
expanded_cache_key << "#{prefix}/"
end
expanded_cache_key << retrieve_cache_key(key)
expanded_cache_key
end
private
def retrieve_cache_key(key)
case
when key.respond_to?(:cache_key) then key.cache_key
when key.is_a?(Array) then key.map { |element| retrieve_cache_key(element) }.to_param
when key.respond_to?(:to_a) then retrieve_cache_key(key.to_a)
else key.to_param
end.to_s
end
# Obtains the specified cache store class, given the name of the +store+.
# Raises an error when the store class cannot be found.
def retrieve_store_class(store)
require "active_support/cache/#{store}"
rescue LoadError => e
raise "Could not find cache store adapter for #{store} (#{e})"
else
ActiveSupport::Cache.const_get(store.to_s.camelize)
end
end
# An abstract cache store class. There are multiple cache store
# implementations, each having its own additional features. See the classes
# under the ActiveSupport::Cache module, e.g.
# ActiveSupport::Cache::MemCacheStore. MemCacheStore is currently the most
# popular cache store for large production websites.
#
# Some implementations may not support all methods beyond the basic cache
# methods of +fetch+, +write+, +read+, +exist?+, and +delete+.
#
# ActiveSupport::Cache::Store can store any serializable Ruby object.
#
# cache = ActiveSupport::Cache::MemoryStore.new
#
# cache.read('city') # => nil
# cache.write('city', "Duckburgh")
# cache.read('city') # => "Duckburgh"
#
# Keys are always translated into Strings and are case sensitive. When an
# object is specified as a key and has a +cache_key+ method defined, this
# method will be called to define the key. Otherwise, the +to_param+
# method will be called. Hashes and Arrays can also be used as keys. The
# elements will be delimited by slashes, and the elements within a Hash
# will be sorted by key so they are consistent.
#
# cache.read('city') == cache.read(:city) # => true
#
# Nil values can be cached.
#
# If your cache is on a shared infrastructure, you can define a namespace
# for your cache entries. If a namespace is defined, it will be prefixed on
# to every key. The namespace can be either a static value or a Proc. If it
# is a Proc, it will be invoked when each key is evaluated so that you can
# use application logic to invalidate keys.
#
# cache.namespace = -> { @last_mod_time } # Set the namespace to a variable
# @last_mod_time = Time.now # Invalidate the entire cache by changing namespace
#
# Caches can also store values in a compressed format to save space and
# reduce time spent sending data. Since there is overhead, values must be
# large enough to warrant compression. To turn on compression either pass
# <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 <tt>:namespace</tt> 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
# Fetches data from the cache, using the given key. If there is data in
# the cache with the given key, then that data is returned.
#
# If there is no such data in the cache (a cache miss), then +nil+ will be
# returned. However, if a block has been passed, that block will be passed
# the key and executed in the event of a cache miss. The return value of the
# block will be written to the cache under the given cache key, and that
# return value will be returned.
#
# cache.write('today', 'Monday')
# cache.fetch('today') # => "Monday"
#
# cache.fetch('city') # => nil
# cache.fetch('city') do
# 'Duckburgh'
# end
# cache.fetch('city') # => "Duckburgh"
#
# You may also specify additional options via the +options+ argument.
# Setting <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 several different processes will try
# to read data natively and then they all will try to write to cache. To
# avoid that case the first process to find an expired cache entry will
# bump the cache expiration time by the value set in <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 bit longer. In the
# meantime that first process will go ahead and will write into cache the
# new value. After that all the processes will start getting the new value.
# The key is to keep <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)
cached_entry = find_cached_entry(key, name, options) unless options[:force]
entry = handle_expired_entry(cached_entry, key, options)
if entry
get_entry_value(entry, name, options)
else
save_block_result_to_cache(name, options) { |_name| yield _name }
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)
instrument_multi(:read, names, options) do |payload|
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
end
# Fetches data from the cache, using the given keys. If there is data in
# the cache with the given keys, then that data is returned. Otherwise,
# the supplied block is called for each key for which there was no data,
# and the result will be written to the cache and returned.
#
# Options are passed to the underlying cache implementation.
#
# Returns a hash with the data for each of the names. For example:
#
# cache.write("bim", "bam")
# cache.fetch_multi("bim", "unknown_key") do |key|
# "Fallback value for key: #{key}"
# end
# # => { "bim" => "bam",
# # "unknown_key" => "Fallback value for key: unknown_key" }
#
def fetch_multi(*names)
options = names.extract_options!
options = merged_options(options)
results = read_multi(*names, options)
names.each_with_object({}) do |name, memo|
memo[name] = results.fetch(name) do
value = yield name
write(name, value, options)
value
end
end
end
# Writes the value to the cache, with the key.
#
# Options are passed to the underlying cache implementation.
def write(name, value, options = nil)
options = merged_options(options)
instrument(:write, name, options) do
entry = Entry.new(value, options)
write_entry(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
delete_entry(namespaced_key(name, options), options)
end
end
# Returns +true+ if the cache contains an entry for the given key.
#
# Options are passed to the underlying cache implementation.
def exist?(name, options = nil)
options = merged_options(options)
instrument(:exist?, name) do
entry = read_entry(namespaced_key(name, options), options)
(entry && !entry.expired?) || false
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
# Decrement 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.
#
# The options hash is 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 { "Cache #{operation}: #{key}#{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 instrument_multi(operation, keys, options = nil)
log do
formatted_keys = keys.map { |k| "- #{k}" }.join("\n")
"Caches multi #{operation}:\n#{formatted_keys}#{options.blank? ? "" : " (#{options.inspect})"}"
end
payload = { key: keys }
payload.merge!(options) if options.is_a?(Hash)
ActiveSupport::Notifications.instrument("cache_#{operation}_multi.active_support", payload) { yield(payload) }
end
def log
return unless logger && logger.debug? && !silence?
logger.debug(yield)
end
def find_cached_entry(key, name, options)
instrument(:read, name, options) do |payload|
payload[:super_operation] = :fetch if payload
read_entry(key, options)
end
end
def handle_expired_entry(entry, key, options)
if entry && entry.expired?
race_ttl = options[:race_condition_ttl].to_i
if race_ttl && (Time.now.to_f - entry.expires_at <= race_ttl)
# When an entry has :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) { |payload| }
entry.value
end
def save_block_result_to_cache(name, options)
result = instrument(:generate, name, options) do |payload|
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
# Create 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
# 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
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
# Duplicate 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
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