title: Fluentd - Add new attributes in JSON data
body: <p>Using Fluentd I am sending logs to Splunk and ES in JSON format, as given below:</p>
  
  <pre><code>{
      "object1": {
              "obj1_key1": "value_xyz"
       }
       "object2": {
              "obj2_key1": "value_abc"
       }
  }
  </code></pre>
  
  <p>Before sending logs to server, I want to add few fields as metadata in Object1 and Object2, like.</p>
  
  <pre><code>{
      "object1": {
              "obj1_key1": "value_xyz"
              "metadata": "constant_value"
       }
       "object2": {
              "obj2_key1": "value_abc"
              "metadata": "constant_value"
       }
  }
  </code></pre>
  
  <p>I know using fluentd "record_transformer" plugin we can add new fields but the question is how to add fields inside objects or nested objects?</p>