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Class: ActiveSupport::Cache::MemCacheStore

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, Store
Instance Chain:
self, Strategy::LocalCache, Store
Inherits: ActiveSupport::Cache::Store
Defined in: activesupport/lib/active_support/cache/mem_cache_store.rb

Overview

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.

Constant Summary

Store - Inherited

DEFAULT_CODER

Class Attribute Summary

Store - Inherited

.logger

Class Method Summary

Store - Inherited

.new

Creates a new cache.

Instance Attribute Summary

Store - Inherited

#logger, #options,
#silence?

Alias for Store#silence.

Instance Method Summary

Strategy::LocalCache - Included

#middleware

Middleware class can be inserted as a ::Rack handler to be local cache for the duration of request.
#with_local_cache

Use a local cache for the duration of block.

Store - Inherited

#cleanup

Cleanups the cache by removing expired entries.
#clear

Clears the entire cache.
#decrement

Decrements an integer value in the cache.
#delete

Deletes an entry in the cache.
#delete_matched

Deletes all entries with keys matching the pattern.
#delete_multi

Deletes multiple entries in the cache.
#exist?

Returns true if the cache contains an entry for the given key.
#fetch

Fetches data from the cache, using the given key.
#fetch_multi

Fetches data from the cache, using the given keys.
#increment

Increments an integer value in the cache.
#mute

Silences the logger within a block.
#read

Reads data from the cache, using the given key.
#read_multi

Reads multiple values at once from the cache.
#silence,
#silence!

Silences the logger.
#write

Writes the value to the cache, with the key.
#write_multi

::ActiveSupport::Cache Storage API to write multiple values at once.
#key_matcher

Adds the namespace defined in the options to a pattern designed to match keys.

Constructor Details

.new(*addresses) ⇒ MemCacheStore

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 is defined, it will be used instead. Otherwise, MemCacheStore will connect to localhost:11211 (the default memcached port).

[ GitHub ] 

  


# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 86



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


  







Class Attribute Details



  

    .supports_cache_versioning?  ⇒ Boolean  (readonly)
  



  

    

Advertise cache versioning support.


  





  


  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 46



def self.supports_cache_versioning?
  true
end


  







Instance Method Details



  

    #clear(options = nil)  
  



  

    

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


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 131



def clear(options = nil)
  rescue_error_with(nil) { @data.with { |c| c.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.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 120



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


  








  

    #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.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 107



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


  








  

    #stats  
  



  

    

Get the statistics from the memcached servers.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/cache/mem_cache_store.rb', line 136



def stats
  @data.with { |c| c.stats }
end