begin
require 'dalli'
rescue LoadError => e
$stderr.puts "You don't have dalli installed in your application. Please add it to your Gemfile and run bundle install"
raise e
end
require 'digest/md5'
require 'active_support/core_ext/marshal'
require 'active_support/core_ext/array/extract_options'
module ActiveSupport
module Cache
# A cache store implementation which stores data in Memcached:
# http://memcached.org/
#
# This is currently the most popular cache store for production websites.
#
# Special features:
# - Clustering and load balancing. One can specify multiple memcached servers,
# and MemCacheStore will load balance between all available servers. If a
# server goes down, then MemCacheStore will ignore it until it comes back up.
#
# MemCacheStore implements the Strategy::LocalCache strategy which implements
# an in-memory cache inside of a block.
class MemCacheStore < Store
ESCAPE_KEY_CHARS = /[\x00-\x20%\x7F-\xFF]/n
def self.build_mem_cache(*addresses)
addresses = addresses.flatten
options = addresses.extract_options!
addresses = ["localhost:11211"] if addresses.empty?
Dalli::Client.new(addresses, options)
end
# Creates a new MemCacheStore object, with the given memcached server
# addresses. Each address is either a host name, or a host-with-port string
# in the form of "host_name:port". For example:
#
# ActiveSupport::Cache::MemCacheStore.new("localhost", "server-downstairs.localnetwork:8229")
#
# If no addresses are specified, then MemCacheStore will connect to
# localhost port 11211 (the default memcached port).
def initialize(*addresses)
addresses = addresses.flatten
options = addresses.extract_options!
super(options)
unless [String, Dalli::Client, NilClass].include?(addresses.first.class)
raise ArgumentError, "First argument must be an empty array, an array of hosts or a Dalli::Client instance."
end
if addresses.first.is_a?(Dalli::Client)
@data = addresses.first
else
mem_cache_options = options.dup
UNIVERSAL_OPTIONS.each{|name| mem_cache_options.delete(name)}
@data = self.class.build_mem_cache(*(addresses + [mem_cache_options]))
end
extend Strategy::LocalCache
extend LocalCacheWithRaw
end
# Reads multiple values from the cache using a single call to the
# servers for all keys. Options can be passed in the last argument.
def read_multi(*names)
options = names.extract_options!
options = merged_options(options)
instrument_multi(:read, names, options) do
keys_to_names = Hash[names.map{|name| [escape_key(namespaced_key(name, options)), name]}]
raw_values = @data.get_multi(keys_to_names.keys, :raw => true)
values = {}
raw_values.each do |key, value|
entry = deserialize_entry(value)
values[keys_to_names[key]] = entry.value unless entry.expired?
end
values
end
end
# Increment a cached value. This method uses the memcached incr atomic
# operator and can only be used on values written with the :raw option.
# Calling it on a value not stored with :raw will initialize that value
# to zero.
def increment(name, amount = 1, options = nil) # :nodoc:
options = merged_options(options)
instrument(:increment, name, :amount => amount) do
@data.incr(escape_key(namespaced_key(name, options)), amount)
end
rescue Dalli::DalliError => e
logger.error("DalliError (#{e}): #{e.message}") if logger
nil
end
# Decrement a cached value. This method uses the memcached decr atomic
# operator and can only be used on values written with the :raw option.
# Calling it on a value not stored with :raw will initialize that value
# to zero.
def decrement(name, amount = 1, options = nil) # :nodoc:
options = merged_options(options)
instrument(:decrement, name, :amount => amount) do
@data.decr(escape_key(namespaced_key(name, options)), amount)
end
rescue Dalli::DalliError => e
logger.error("DalliError (#{e}): #{e.message}") if logger
nil
end
# Clear the entire cache on all memcached servers. This method should
# be used with care when shared cache is being used.
def clear(options = nil)
@data.flush_all
rescue Dalli::DalliError => e
logger.error("DalliError (#{e}): #{e.message}") if logger
nil
end
# Get the statistics from the memcached servers.
def stats
@data.stats
end
protected
# Read an entry from the cache.
def read_entry(key, options) # :nodoc:
deserialize_entry(@data.get(escape_key(key), options))
rescue Dalli::DalliError => e
logger.error("DalliError (#{e}): #{e.message}") if logger
nil
end
# Write an entry to the cache.
def write_entry(key, entry, options) # :nodoc:
method = options && options[:unless_exist] ? :add : :set
value = options[:raw] ? entry.value.to_s : entry
expires_in = options[:expires_in].to_i
if expires_in > 0 && !options[:raw]
# Set the memcache expire a few minutes in the future to support race condition ttls on read
expires_in += 5.minutes
end
@data.send(method, escape_key(key), value, expires_in, options)
rescue Dalli::DalliError => e
logger.error("DalliError (#{e}): #{e.message}") if logger
false
end
# Delete an entry from the cache.
def delete_entry(key, options) # :nodoc:
@data.delete(escape_key(key))
rescue Dalli::DalliError => e
logger.error("DalliError (#{e}): #{e.message}") if logger
false
end
private
# Memcache keys are binaries. So we need to force their encoding to binary
# before applying the regular expression to ensure we are escaping all
# characters properly.
def escape_key(key)
key = key.to_s.dup
key = key.force_encoding(Encoding::ASCII_8BIT)
key = key.gsub(ESCAPE_KEY_CHARS){ |match| "%#{match.getbyte(0).to_s(16).upcase}" }
key = "#{key[0, 213]}:md5:#{Digest::MD5.hexdigest(key)}" if key.size > 250
key
end
def deserialize_entry(raw_value)
if raw_value
entry = Marshal.load(raw_value) rescue raw_value
entry.is_a?(Entry) ? entry : Entry.new(entry)
else
nil
end
end
# Provide support for raw values in the local cache strategy.
module LocalCacheWithRaw # :nodoc:
protected
def read_entry(key, options)
entry = super
if options[:raw] && local_cache && entry
entry = deserialize_entry(entry.value)
end
entry
end
def write_entry(key, entry, options) # :nodoc:
retval = super
if options[:raw] && local_cache && retval
raw_entry = Entry.new(entry.value.to_s)
raw_entry.expires_at = entry.expires_at
local_cache.write_entry(key, raw_entry, options)
end
retval
end
end
end
end
end
