my logstash.conf file for postfix

logstash.conf

input {
  file {
    path => "/var/log/maillog*"
    exclude => "*.gz"
    start_position => "beginning"
    type => "maillog"
  }
}
filter {
  if [type] == "maillog" {
    grok {
      patterns_dir => ["/home/logstash/config/patterns"]
      match => { "message" => ["%{PF}", "%{DOVECOT}" ] }
    }
    date {
      match => [ "timestamp", "MMM dd HH:mm:ss", "MMM d HH:mm:ss" ]
    }
  }
  # I wanted to monitor metrics and health of logstash
  metrics {
    meter => "events"
    add_tag => "metric"
  }
}
output {
  if [type] == "maillog" {
    elasticsearch {
      index => "maillog-%{+YYYY.MM.dd}"
      host => "localhost"
      port => "9200"
      protocol => "http"
      flush_size => 1000
      manage_template => true
      template_overwrite => true
      template => "/home/logstash/config/templates/maillog.json"
      template_name => "maillog"
    }
  }
  if "metric" in [tags] {
    stdout {
      codec => line {
        format => "rate: %{events.rate_1m}"
      }
    }
  }
}