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_in+ option.
  • Per-request in memory cache for all communication with the MemCache server(s).
Public Class methods
    # File activesupport/lib/active_support/cache/mem_cache_store.rb, line 26
26:       def self.build_mem_cache(*addresses)
27:         addresses = addresses.flatten
28:         options = addresses.extract_options!
29:         addresses = ["localhost"] if addresses.empty?
30:         MemCache.new(addresses, options)
31:       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
    # File activesupport/lib/active_support/cache/mem_cache_store.rb, line 46
46:       def initialize(*addresses)
47:         if addresses.first.respond_to?(:get)
48:           @data = addresses.first
49:         else
50:           @data = self.class.build_mem_cache(*addresses)
51:         end
53:         extend Strategy::LocalCache
54:       end
Public Instance methods
     # File activesupport/lib/active_support/cache/mem_cache_store.rb, line 129
129:       def clear
130:         @data.flush_all
131:       end

Reads multiple keys from the cache.

    # File activesupport/lib/active_support/cache/mem_cache_store.rb, line 57
57:       def read_multi(*keys)
58:         @data.get_multi keys
59:       end
     # File activesupport/lib/active_support/cache/mem_cache_store.rb, line 133
133:       def stats
134:         @data.stats
135:       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
76:       def write(key, value, options = nil)
77:         super
78:         method = options && options[:unless_exist] ? :add : :set
79:         # memcache-client will break the connection if you send it an integer
80:         # in raw mode, so we convert it to a string to be sure it continues working.
81:         value = value.to_s if raw?(options)
82:         response = @data.send(method, key, value, expires_in(options), raw?(options))
83:         response == Response::STORED
84:       rescue MemCache::MemCacheError => e
85:         logger.error("MemCacheError (#{e}): #{e.message}")
86:         false
87:       end