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.

Namespace

Module

Methods

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 provided, but ENV['MEMCACHE_SERVERS'] is defined, it will be used instead. Otherwise, MemCacheStore will connect to localhost:11211 (the default memcached port).

📝 Source code 
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 109
      def initialize(*addresses)
        addresses = addresses.flatten
        options = addresses.extract_options!
        if options.key?(:cache_nils)
          options[:skip_nil] = !options.delete(:cache_nils)
        end
        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
          # The value "compress: false" prevents duplicate compression within Dalli.
          mem_cache_options[:compress] = false
          (UNIVERSAL_OPTIONS - %i(compress)).each { |name| mem_cache_options.delete(name) }
          @data = self.class.build_mem_cache(*(addresses + [mem_cache_options]))
        end
      end
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supports_cache_versioning?()

Advertise cache versioning support.

📝 Source code 
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 30
      def self.supports_cache_versioning?
        true
      end
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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.

📝 Source code 
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 175
      def clear(options = nil)
        rescue_error_with(nil) { @data.with { |c| c.flush_all } }
      end
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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.

📝 Source code 
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 164
      def decrement(name, amount = 1, options = nil)
        options = merged_options(options)
        instrument(:decrement, name, amount: amount) do
          rescue_error_with nil do
            @data.with { |c| c.decr(normalize_key(name, options), amount, options[:expires_in]) }
          end
        end
      end
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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.

📝 Source code 
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 151
      def increment(name, amount = 1, options = nil)
        options = merged_options(options)
        instrument(:increment, name, amount: amount) do
          rescue_error_with nil do
            @data.with { |c| c.incr(normalize_key(name, options), amount, options[:expires_in]) }
          end
        end
      end
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stats()

Get the statistics from the memcached servers.

📝 Source code 
# File activesupport/lib/active_support/cache/mem_cache_store.rb, line 180
      def stats
        @data.with { |c| c.stats }
      end
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write(name, value, options = nil)

Behaves the same as ActiveSupport::Cache::Store#write, but supports additional options specific to memcached.

Additional Options

  • raw: true - Sends the value directly to the server as raw bytes. The value must be a string or number. You can use memcached direct operations like increment and decrement only on raw values.

  • unless_exist: true - Prevents overwriting an existing cache entry.

🔎 See on GitHub