A cache store implementation which stores data in Memcached: 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.

  • Time-based expiry support. See write and the :expires_inoption.

  • Per-request in memory cache for all communication with the MemCache server(s).

Methods
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Class Public methods
build_mem_cache(*addresses)
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 26
def self.build_mem_cache(*addresses)
  addresses = addresses.flatten
  options = addresses.extract_options!
  addresses = ["localhost"] if addresses.empty?
  MemCache.new(addresses, options)
end
new(*addresses)

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"))
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 46
def initialize(*addresses)
  if addresses.first.respond_to?(:get)
    @data = addresses.first
  else
    @data = self.class.build_mem_cache(*addresses)
  end
  extend Strategy::LocalCache
end
Instance Public methods
clear()
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 129
def clear
  @data.flush_all
end
read_multi(*keys)

Reads multiple keys from the cache.

# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 57
def read_multi(*keys)
  @data.get_multi keys
end
stats()
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 133
def stats
  @data.stats
end
write(key, value, options = nil)

Writes a value to the cache.

Possible options:

  • :unless_exist- set to true if you don't want to update the cache if the key is already set.

  • :expires_in- the number of seconds that this value may stay in the cache. See ActiveSupport::Cache::Store#write for an example.

# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 76
def write(key, value, options = nil)
  super
  method = options && options[:unless_exist] ? :add : :set
  # memcache-client will break the connection if you send it an integer
  # in raw mode, so we convert it to a string to be sure it continues working.
  value = value.to_s if raw?(options)
  response = @data.send(method, key, value, expires_in(options), raw?(options))
  response == Response::STORED
rescue MemCache::MemCacheError => e
  logger.error("MemCacheError (#{e}): #{e.message}")
  false
end