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.
# File lib/active_support/cache/mem_cache_store.rb, line 36 36: def self.build_mem_cache(*addresses) 37: addresses = addresses.flatten 38: options = addresses.extract_options! 39: addresses = ["localhost:11211"] if addresses.empty? 40: MemCache.new(addresses, options) 41: 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 ActiveSupport::Cache::MemCacheStore.new(Memcached::Rails.new("localhost:11211"))
# File lib/active_support/cache/mem_cache_store.rb, line 56 56: def initialize(*addresses) 57: addresses = addresses.flatten 58: options = addresses.extract_options! 59: super(options) 60: 61: if addresses.first.respond_to?(:get) 62: @data = addresses.first 63: else 64: mem_cache_options = options.dup 65: UNIVERSAL_OPTIONS.each{|name| mem_cache_options.delete(name)} 66: @data = self.class.build_mem_cache(*(addresses + [mem_cache_options])) 67: end 68: 69: extend Strategy::LocalCache 70: extend LocalCacheWithRaw 71: end
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 118 118: def clear(options = nil) 119: @data.flush_all 120: end
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 75 75: def read_multi(*names) 76: options = names.extract_options! 77: options = merged_options(options) 78: keys_to_names = Hash[names.map{|name| [escape_key(namespaced_key(name, options)), name]}] 79: raw_values = @data.get_multi(keys_to_names.keys, :raw => true) 80: values = {} 81: raw_values.each do |key, value| 82: entry = deserialize_entry(value) 83: values[keys_to_names[key]] = entry.value unless entry.expired? 84: end 85: values 86: end
# File lib/active_support/cache/mem_cache_store.rb, line 174 174: def deserialize_entry(raw_value) 175: if raw_value 176: entry = Marshal.load(raw_value) rescue raw_value 177: entry.is_a?(Entry) ? entry : Entry.new(entry) 178: else 179: nil 180: end 181: end
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 166 166: def escape_key(key) 167: key = key.to_s.dup 168: key = key.force_encoding("BINARY") if key.encoding_aware? 169: key = key.gsub(ESCAPE_KEY_CHARS){ |match| "%#{match.getbyte(0).to_s(16).upcase}" } 170: key = "#{key[0, 213]}:md5:#{Digest::MD5.hexdigest(key)}" if key.size > 250 171: key 172: end
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