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require 'benchmark'
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 :SynchronizedMemoryStore, 'active_support/cache/synchronized_memory_store'
autoload :DRbStore, 'active_support/cache/drb_store'
autoload :MemCacheStore, 'active_support/cache/mem_cache_store'
autoload :CompressedMemCacheStore, 'active_support/cache/compressed_mem_cache_store'
# 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(:drb_store)
# # => returns a new ActiveSupport::Cache::DRbStore 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 self.lookup_store(*store_option)
store, *parameters = *([ store_option ].flatten)
case store
when Symbol
store_class_name = (store == :drb_store ? "DRbStore" : store.to_s.camelize)
store_class = ActiveSupport::Cache.const_get(store_class_name)
store_class.new(*parameters)
when nil
ActiveSupport::Cache::MemoryStore.new
else
store
end
end
def self.expand_cache_key(key, namespace = nil)
expanded_cache_key = namespace ? "#{namespace}/" : ""
if ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"]
expanded_cache_key << "#{ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"]}/"
end
expanded_cache_key << case
when key.respond_to?(:cache_key)
key.cache_key
when key.is_a?(Array)
key.collect { |element| expand_cache_key(element) }.to_param
when key
key.to_param
end.to_s
expanded_cache_key
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.
#
# ActiveSupport::Cache::Store is meant for caching strings. Some cache
# store implementations, like MemoryStore, are able to cache arbitrary
# Ruby objects, but don't count on every cache store to be able to do that.
#
# cache = ActiveSupport::Cache::MemoryStore.new
#
# cache.read("city") # => nil
# cache.write("city", "Duckburgh")
# cache.read("city") # => "Duckburgh"
class Store
cattr_accessor :logger
def silence!
@silence = true
self
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 occurred), then
# then nil will be returned. However, if a block has been passed, then
# 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
#
# Other options will be handled by the specific cache store implementation.
# Internally, #fetch calls #read, and calls #write on a cache miss.
# +options+ will be passed to the #read and #write calls.
#
# For example, MemCacheStore's #write method supports the +:expires_in+
# option, which tells the memcached server to automatically expire the
# cache item after a certain period. We can use this option with #fetch
# too:
#
# cache = ActiveSupport::Cache::MemCacheStore.new
# cache.fetch("foo", :force => true, :expires_in => 5.seconds) do
# "bar"
# end
# cache.fetch("foo") # => "bar"
# sleep(6)
# cache.fetch("foo") # => nil
def fetch(key, options = {})
@logger_off = true
if !options[:force] && value = read(key, options)
@logger_off = false
log("hit", key, options)
value
elsif block_given?
@logger_off = false
log("miss", key, options)
value = nil
seconds = Benchmark.realtime { value = yield }
@logger_off = true
write(key, value, options)
@logger_off = false
log("write (will save #{'%.2f' % (seconds * 1000)}ms)", key, nil)
value
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.
#
# You may also specify additional options via the +options+ argument.
# The specific cache store implementation will decide what to do with
# +options+.
def read(key, options = nil)
log("read", key, options)
end
# Writes the given value to the cache, with the given key.
#
# You may also specify additional options via the +options+ argument.
# The specific cache store implementation will decide what to do with
# +options+.
#
# For example, MemCacheStore supports the +:expires_in+ option, which
# tells the memcached server to automatically expire the cache item after
# a certain period:
#
# cache = ActiveSupport::Cache::MemCacheStore.new
# cache.write("foo", "bar", :expires_in => 5.seconds)
# cache.read("foo") # => "bar"
# sleep(6)
# cache.read("foo") # => nil
def write(key, value, options = nil)
log("write", key, options)
end
def delete(key, options = nil)
log("delete", key, options)
end
def delete_matched(matcher, options = nil)
log("delete matched", matcher.inspect, options)
end
def exist?(key, options = nil)
log("exist?", key, options)
end
def increment(key, amount = 1)
log("incrementing", key, amount)
if num = read(key)
write(key, num + amount)
else
nil
end
end
def decrement(key, amount = 1)
log("decrementing", key, amount)
if num = read(key)
write(key, num - amount)
else
nil
end
end
private
def log(operation, key, options)
logger.debug("Cache #{operation}: #{key}#{options ? " (#{options.inspect})" : ""}") if logger && !@silence && !@logger_off
end
end
end
end
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