# File lib/rack/session/memcache.rb, line 29
      def initialize(app, options={})
        super
        @pool = MemCache.new @default_options[:memcache_server], @default_options
        unless @pool.servers.any?{|s|s.alive?}
          raise "#{self} unable to find server during initialization."
        end
        @mutex = Mutex.new
      end