require 'memcache'
require 'digest/md5'
module ActiveSupport
module Cache
# A cache store implementation which stores data in Memcached:
# http://www.danga.com/memcached/
#
# 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 goes back
# online.
#
# MemCacheStore implements the Strategy::LocalCache strategy which implements
# an in memory cache inside of a block.
class MemCacheStore < Store
module Response # :nodoc:
STORED = "STORED\r\n"
NOT_STORED = "NOT_STORED\r\n"
EXISTS = "EXISTS\r\n"
NOT_FOUND = "NOT_FOUND\r\n"
DELETED = "DELETED\r\n"
end
ESCAPE_KEY_CHARS = /[\x00-\x20%\x7F-\xFF]/
def self.build_mem_cache(*addresses)
addresses = addresses.flatten
options = addresses.extract_options!
addresses = ["localhost"] if addresses.empty?
MemCache.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).
#
# Instead of addresses one can pass in a MemCache-like object. For example:
#
# require 'memcached' # gem install memcached; uses C bindings to libmemcached
# ActiveSupport::Cache::MemCacheStore.new(Memcached::Rails.new("localhost:11211"))
def initialize(*addresses)
addresses = addresses.flatten
options = addresses.extract_options!
super(options)
if addresses.first.respond_to?(:get)
@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 keys 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)
keys_to_names = names.inject({}){|map, name| map[escape_key(namespaced_key(name, options))] = name; map}
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
# 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)
response = instrument(:increment, name, :amount => amount) do
@data.incr(escape_key(namespaced_key(name, options)), amount)
end
response == Response::NOT_FOUND ? nil : response.to_i
rescue MemCache::MemCacheError
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)
response = instrument(:decrement, name, :amount => amount) do
@data.decr(escape_key(namespaced_key(name, options)), amount)
end
response == Response::NOT_FOUND ? nil : response.to_i
rescue MemCache::MemCacheError
nil
end
# Clear the entire cache on all memcached servers. This method should
# be used with care when using a shared cache.
def clear(options = nil)
@data.flush_all
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), true))
rescue MemCache::MemCacheError => e
logger.error("MemCacheError (#{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
response = @data.send(method, escape_key(key), value, expires_in, options[:raw])
response == Response::STORED
rescue MemCache::MemCacheError => e
logger.error("MemCacheError (#{e}): #{e.message}") if logger
false
end
# Delete an entry from the cache.
def delete_entry(key, options) # :nodoc:
response = @data.delete(escape_key(key))
response == Response::DELETED
rescue MemCache::MemCacheError => e
logger.error("MemCacheError (#{e}): #{e.message}") if logger
false
end
private
def escape_key(key)
key = key.to_s.gsub(ESCAPE_KEY_CHARS){|match| "%#{match[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 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
