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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.

Methods
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Constants
ESCAPE_KEY_CHARS = /[\x00-\x20%\x7F-\xFF]/n
 
Class Public methods
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).

# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 77
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
end
Instance Public methods
clear(options = nil)

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

# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 144
def clear(options = nil)
  rescue_error_with(nil) { @data.flush_all }
end
decrement(name, amount = 1, options = nil)

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.

# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 133
def decrement(name, amount = 1, options = nil)
  options = merged_options(options)
  instrument(:decrement, name, amount: amount) do
    rescue_error_with nil do
      @data.decr(normalize_key(name, options), amount)
    end
  end
end
increment(name, amount = 1, options = nil)

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.

# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 120
def increment(name, amount = 1, options = nil)
  options = merged_options(options)
  instrument(:increment, name, amount: amount) do
    rescue_error_with nil do
      @data.incr(normalize_key(name, options), amount)
    end
  end
end
read_multi(*names)

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 activesupport/lib/active_support/cache/mem_cache_store.rb, line 96
def read_multi(*names)
  options = names.extract_options!
  options = merged_options(options)

  keys_to_names = Hash[names.map { |name| [normalize_key(name, options), name] }]

  raw_values = @data.get_multi(keys_to_names.keys)
  values = {}

  raw_values.each do |key, value|
    entry = deserialize_entry(value)

    unless entry.expired? || entry.mismatched?(normalize_version(keys_to_names[key], options))
      values[keys_to_names[key]] = entry.value
    end
  end

  values
end
stats()

Get the statistics from the memcached servers.

# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 149
def stats
  @data.stats
end