private function addRiakNode()
    {
        $builder = new TreeBuilder('riak');
        $node    = $this->getRootNode($builder, 'riak');

        $node
            ->addDefaultsIfNotSet()
            ->children()
                ->scalarNode('host')->defaultValue('%doctrine_cache.riak.host%')->end()
                ->scalarNode('port')->defaultValue('%doctrine_cache.riak.port%')->end()
                ->scalarNode('bucket_name')->defaultValue('doctrine_cache')->end()
                ->scalarNode('connection_id')->defaultNull()->end()
                ->scalarNode('bucket_id')->defaultNull()->end()
                ->arrayNode('bucket_property_list')
                    ->children()
                        ->scalarNode('allow_multiple')->defaultNull()->end()
                        ->scalarNode('n_value')->defaultNull()->end()
                    ->end()
                ->end()
            ->end()
        ;

        return $node;
    }