private function addApnsClientsNode()
    {
        $builder = new TreeBuilder();
        $node = $builder->root('apns');

        $node
            ->useAttributeAsKey('name')
            ->prototype('array')
                ->children()
                    ->arrayNode('services')
                        ->addDefaultsIfNotSet()
                        ->children()
                            ->scalarNode('logger')->defaultValue('logger')->end()
                            ->scalarNode('profiler')->defaultValue('link_value_mobile_notif.profiler.client_profiler')->end()
                        ->end()
                    ->end()
                    ->arrayNode('params')
                        ->children()
                            ->scalarNode('endpoint')->cannotBeEmpty()->defaultValue('tls://gateway.sandbox.push.apple.com:2195')->end()
                            ->scalarNode('ssl_pem_path')->cannotBeEmpty()->isRequired()->end()
                            ->scalarNode('ssl_passphrase')->cannotBeEmpty()->end()
                        ->end()
                    ->end()
                ->end()
            ->end()
        ;

        return $node;
    }