anchor.diff:  [options="header"]
   |======
   | Name                   | Required  | Default             | Description
  -| `match_field`          | yes       | -                   | The field to use for grok expression parsing
  -| `match_pattern`        | yes       | -                   | The grok expression to match and extract named captures with
  +| `field`                | yes       | -                   | The field to use for grok expression parsing
  +| `pattern`              | yes       | -                   | The grok expression to match and extract named captures with
   | `pattern_definitions`  | no        | -                   | A map of pattern-name and pattern tuples defining custom patterns to be used by the current processor. Patterns matching existing names will override the pre-existing definition.
   |======
   
  
positive.code:   "processors": [
      {
        "grok": {
          "match_field": "message",
          "match_pattern": "my %{FAVORITE_DOG:dog} is colored %{RGB:color}"
          "pattern_definitions" : {
            "FAVORITE_DOG" : "beagle",
            "RGB" : "RED|GREEN|BLUE"
  
negative.code:   "processors": [
      {
        "grok": {
          "field": "message",
          "pattern": "%{IP:client} %{WORD:method} %{URIPATHPARAM:request} %{NUMBER:bytes} %{NUMBER:duration}"
        }
      }
    ]
  