instance method check_multithread_status!

# File activesupport/lib/active_support/vendor/memcache-client-1.7.4/memcache.rb, line 891
  def check_multithread_status!
    return if @multithread

    if Thread.current[:memcache_client] != self.object_id
      raise MemCacheError, <<-EOM
        You are accessing this memcache-client instance from multiple threads but have not enabled multithread support.
        Normally:  MemCache.new(['localhost:11211'], :multithread => true)
        In Rails:  config.cache_store = [:mem_cache_store, 'localhost:11211', { :multithread => true }]
      EOM
    end
  end