gistfile1.rb

# application_helper.rb
def bookmark_thumbnail(metadata)
  image_tag(metadata[:thumbnail_url] || "thumb.png", width: "260")
end

# migration
add_column :bookmarks, :metadata, :text

# bookmark model
  after_save :get_embedly_data
  serialize :metadata, Hash

  private
  def get_embedly_data
    embedly_api = set_key
    obj = embedly_api.oembed(:url => self.url)
    h = { url: obj[0].provider_url,
      description: obj[0].description,
      title: obj[0].title,
      thumbnail_width: obj[0].thumbnail_width,
      thumbnail_url: obj[0].thumbnail_url }
    if h[:thumbnail_url]
      begin
        open(h[:thumbnail_url])
      rescue OpenURI::HTTPError
        h.delete(:thumbnail_url)
      end
    end
    self.metadata = h
  end