anchor.diff:    "processors": [
       {
         "grok": {
  -        "match_field": "message",
  -        "match_pattern": "my %{FAVORITE_DOG:dog} is colored %{RGB:color}"
  +        "field": "message",
  +        "pattern": "my %{FAVORITE_DOG:dog} is colored %{RGB:color}"
           "pattern_definitions" : {
             "FAVORITE_DOG" : "beagle",
             "RGB" : "RED|GREEN|BLUE"
  
positive.code:   "processors": [
      {
        "grok": {
          "match_field": "message",
          "match_pattern": "%{IP:client} %{WORD:method} %{URIPATHPARAM:request} %{NUMBER:bytes} %{NUMBER:duration}"
        }
      }
    ]
  
negative.code: [options="header"]
  |======
  | Name                   | Required  | Default             | Description
  | `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.
  |======
  
  