# Logstash Metrics Filter Error "can't convert nil into String"

**URL:** https://discuss.elastic.co/t/logstash-metrics-filter-error-cant-convert-nil-into-string/96662
**Category:** Logstash
**Created:** [August 10, 2017, 7:28pm UTC](https://discuss.elastic.co/t/logstash-metrics-filter-error-cant-convert-nil-into-string/96662 "2017-08-10T19:28:52Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![amarc](https://avatars.discourse-cdn.com/v4/letter/a/ecd19e/32.png) [@amarc](https://discuss.elastic.co/u/amarc)
#### Post date: [August 10, 2017, 7:28pm UTC](https://discuss.elastic.co/t/logstash-metrics-filter-error-cant-convert-nil-into-string/96662/1 "2017-08-10T19:28:52Z")

</div>

I am trying to measures events per minute consumed by logstash.  
In Filebeats, I have a customer field called `fwder` which is value of `filebeat`.  
So to count the messages per minute, I am counting the occurrence of `filebeat` in the messages.

Logstash Configuration (truncated to important parts):

```auto
filter {
   if "filebeat" in [fwder] {
    metrics {
             meter => ["filebeat"]
             add_tag => ["grid-sre-metric"]
             flush_interval => 12 # flush metrics every 1m (each interval is 5 secs)
    }
}

```

Logstash Output:

```auto
if "grid-sre-metric" in [tags] {
                    exec {
                         command => {{command_to_execute}}
                    }
}

```

Logstash Error Logs:

```auto
TypeError: can't convert nil into String
       include? at org/jruby/RubyString.java:4462
    output_func at (eval):1378

```

---

<div class="post-metadata">

### Author: ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)
#### Post date: [September 7, 2017, 7:28pm UTC](https://discuss.elastic.co/t/logstash-metrics-filter-error-cant-convert-nil-into-string/96662/2 "2017-09-07T19:28:52Z")

</div>

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