class ActiveSupport::Cache::MemCacheStore - activesupport-4.2.4 Documentation

# class ActiveSupport::Cache::MemCacheStore

A cache store implementation which stores data in Memcached: 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.

### Constants

ESCAPE_KEY_CHARS

### Public Class Methods

build_mem_cache(*addresses) click to toggle source

    # File lib/active_support/cache/mem_cache_store.rb, line 29
    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

new(*addresses) click to toggle source

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).

Calls superclass method ActiveSupport::Cache::Store.new

    # File lib/active_support/cache/mem_cache_store.rb, line 44
    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

### Public Instance Methods

clear(options = nil) click to toggle source

Clear the entire cache on all memcached servers. This method should be used with care when shared cache is being used.

    # File lib/active_support/cache/mem_cache_store.rb, line 109
    def clear(options = nil)
      @data.flush_all
    rescue Dalli::DalliError => e
      logger.error("DalliError (#{e}): #{e.message}") if logger
      nil
    end

read_multi(*names) click to toggle source

Reads multiple values from the cache using a single call to the servers for all keys. Options can be passed in the last argument.

    # File lib/active_support/cache/mem_cache_store.rb, line 66
    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

stats() click to toggle source

Get the statistics from the memcached servers.

    # File lib/active_support/cache/mem_cache_store.rb, line 117
    def stats
      @data.stats
    end

### Private Instance Methods

deserialize_entry(raw_value) click to toggle source

    # File lib/active_support/cache/mem_cache_store.rb, line 166
    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

escape_key(key) click to toggle source

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.

    # File lib/active_support/cache/mem_cache_store.rb, line 158
    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