# File lib/chef/cookbook/synchronizer.rb, line 116
    def clear_obsoleted_cookbooks
      @events.cookbook_clean_start
      # Remove all cookbooks no longer relevant to this node
      cache.find(File.join(%w{cookbooks ** *})).each do |cache_file|
        cache_file =~ /^cookbooks\/([^\/]+)\//
        unless have_cookbook?($1)
          Chef::Log.info("Removing #{cache_file} from the cache; its cookbook is no longer needed on this client.")
          cache.delete(cache_file)
          @events.removed_cookbook_file(cache_file)
        end
      end
      @events.cookbook_clean_complete
    end