Can I store entire grok pattern in a variable

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1

I have filter like below:

         filter {
   
	grok {

		match => {
			"message" => "(?<user_agent>^.{3}) %{GREEDYDATA:body}"
		}

	}

can I put "(?<user_agent>^.{3}) %{GREEDYDATA:body}" inside a variable and use it as per condiion.

 a = "(?<user_agent>^.{3}) %{GREEDYDATA:body}"
 b = "(?<user_agent2>^.{3}) %{GREEDYDATA:body}"

 filter {
 	if ("key==a") {
 		grok {
 			match => {
 				"message" => a
 			}
 		}
 	} else {
 		grok {

 			match => {
 				"message" => b
 			}
 		}
 	}

Thanks for reading and helping

2

No, you cannot. Nor can you use a sprintf reference in the grok pattern.

1 Like
3

Hi @rahulkothanath,

I do not think that will work but not 100%...

What you can do is make a pattern file and give names to the combined patterns. You can also try more than one pattern using pipe.

The pattern file would like something like

MY_PATTERN_1 "(?<user_agent>^.{3}) %{GREEDYDATA:body}"
MY_PATTERN_2 "(?<user_agent2>^.{3}) %{GREEDYDATA:body}"

ALL_MY_PATTERNS (%{MY_PATTERN_1}|%{MY_PATTERN_2})

Put the above pattern file in /path/to/patterns. And for the filter you configure

grok {
  patterns_dir   => [ "/path/to/patterns" ]
  match          => { "message" => "%{ALL_MY_PATTERNS}" }
}

Patterns will be tried until the first match is found.

1 Like
4

Thanks for the response. Will try pattern_dir and let u know.

5

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