Mongo dressed up as Memcached

gistfile1.rb

# My own little Memcache
class KeyValueStore
  include Mongoid::Document
  include Mongoid::Timestamps::Created

  field :key, type: String
  field :value, type: Binary
  field :expires, type: Time

  DEFAULT_EXPIRY = 1.minute

  index :key
  
  def self.fetch(key,expires=DEFAULT_EXPIRY)
    val = get(key)
    if val.nil? && block_given?
      val = yield
      add(key,val,expires)
    end
    val
  end

  def self.get(key)
    #TODO can you do find and delete with one op?
    entry = where({:key => key,:expires.gt => Time.now}).first
    deserialize(entry.value) if entry
  end

  def self.add(key,val,expires)
    expiry_time = Time.now + expires
    create({key: key, value: serialize(val), expires_in: expiry_time})
  end

  def self.flush
    where(:expires.lt => Time.now).delete_all
  end

  private

  def self.serialize(val)
    BSON::Binary.new(Marshal.dump(val))
  end

  def self.deserialize(string)
    Marshal.load(string)
  end

end