gistfile1.txt

filter {

  if [type] == "abc" {
  

    metrics {
      meter => "events"
      add_tag => "metric"
    }
  }
}

output {

  
  if "metric" in [tags] {
    stdout {
      codec => line {
        format => "rate: %{[events][rate_1m]}"
      }
    }
  }
  
}

input {
  generator {
    type => "generated"
  }
}

filter {
  if [type] == "generated" {
    metrics {
      meter => "events"
      add_tag => "metric"
    }
  }
}

output {
  # only emit events with the 'metric' tag
  if "metric" in [tags] {
    stdout {
      codec => line {
        format => "rate: %{[events][rate_1m]}"
      }
    }
  }
}

seeing:
rate: %{[events][rate_1m]}

Solved:

Output:

 format => "rate: %{events.rate_1m}"