class ActiveSupport::Cache::MemCacheStore

an in-memory cache inside of a block.
MemCacheStore implements the Strategy::LocalCache strategy which implements
server goes down, then MemCacheStore will ignore it until it comes back up.
and MemCacheStore will load balance between all available servers. If a
- Clustering and load balancing. One can specify multiple memcached servers,
Special features:
This is currently the most popular cache store for production websites.
/
A cache store implementation which stores data in Memcached:

def self.build_mem_cache(*addresses) 

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

def clear(options = nil)

be used with care when shared cache is being used.
Clear the entire cache on all memcached servers. This method should 
def clear(options = nil)
  @data.flush_all
rescue Dalli::DalliError => e
  logger.error("DalliError (#{e}): #{e.message}") if logger
  nil
end

def decrement(name, amount = 1, options = nil) # :nodoc:

:nodoc:
to zero.
Calling it on a value not stored with :raw will initialize that value
operator and can only be used on values written with the :raw option.
Decrement a cached value. This method uses the memcached decr atomic 
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

def delete_entry(key, options) # :nodoc:

:nodoc:
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

def deserialize_entry(raw_value) 

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

def escape_key(key)

characters properly.
before applying the regular expression to ensure we are escaping all
Memcache keys are binaries. So we need to force their encoding to binary 
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 increment(name, amount = 1, options = nil) # :nodoc:

:nodoc:
to zero.
Calling it on a value not stored with :raw will initialize that value
operator and can only be used on values written with the :raw option.
Increment a cached value. This method uses the memcached incr atomic 
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

def initialize(*addresses)

localhost port 11211 (the default memcached port).
If no addresses are specified, then MemCacheStore will connect to

ActiveSupport::Cache::MemCacheStore.new("localhost", "server-downstairs.localnetwork:8229")

in the form of "host_name:port". For example:
addresses. Each address is either a host name, or a host-with-port string
Creates a new MemCacheStore object, with the given memcached server 
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

def read_entry(key, options) # :nodoc:

:nodoc:
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

def read_multi(*names)

servers for all keys. Options can be passed in the last argument.
Reads multiple values from the cache using a single call to the 
def read_multi(*names)
  options = names.extract_options!
  options = merged_options(options)
  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

def stats

Get the statistics from the memcached servers. 
def stats
  @data.stats
end

def write_entry(key, entry, options) # :nodoc:

:nodoc:
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