return [
    //....
    'components' => [
        'elasticsearch' => [
            'class' => 'yii\elasticsearch\Connection',
            'nodes' => [
                ['http_address' => '127.0.0.1:9200'],
                // configure more hosts if you have a cluster
            ],
            'dslVersion' => 7, // default is 5
        ],
    ]
];