anchor.diff:  }
   --------------------------------------------------
   // TEST[skip:setup:server_metrics_datafeed]
  +
   
   When the {dfeed} is updated, you receive the full {dfeed} configuration with
   with the updated values:
  
positive.code:   (Optional, array) An array of index names. Wildcards are supported. For
    example: `["it_ops_metrics", "server*"]`.
  
  `job_id`::
   (Optional, string) A numerical character string that uniquely identifies the
   {anomaly-job}.
  
  `query`::
    (Optional, object) The {es} query domain-specific language (DSL). This value
    corresponds to the query object in an {es} search POST body. All the options
    that are supported by {es} can be used, as this object is passed verbatim to
    {es}. By default, this property has the following value:
    `{"match_all": {"boost": 1}}`.
  
  `query_delay`::
    (Optional, <<time-units, time units>>) The number of seconds behind real-time 
  
negative.code: 
  Updates certain properties of a {dfeed}.
  
  
  [[ml-update-datafeed-request]]
  ==== {api-request-title}
  
  `POST _ml/datafeeds/<feed_id>/_update`
  
  
  [[ml-update-datafeed-prereqs]]
  ==== {api-prereq-title}
  