title: Logstash: metrics plugin not showing any outpout
body: <p>Ηere is the start of my filter</p>
  
  <pre><code>filter {
  if "paloalto" in [tags] {
  
  metrics {
    meter =&gt; "events_paloalto"
    flush_interval =&gt; 60
    add_tag =&gt; "metric_paloalto"
  }
  
  ...
  </code></pre>
  
  <p>And here is section of my <code>output</code></p>
  
  <pre><code>if "metric_paloalto" in [tags] and "_grokparsefailure" not in [tags] {
      elasticsearch {
          hosts =&gt; ["localhost:9200"]
          index =&gt; "raw_metrics-%{+YYYY.MM.dd.HH.mm}"
      }
  
    stdout { codec =&gt; rubydebug }
  }
  </code></pre>
  
  <p>I am not getting anything on my <code>stdout</code> nor or my <code>elasticsearch</code> instance;</p>
  
  <p>Any ideas?</p>