# Referencing fields in Metrics output
**URL:** https://discuss.elastic.co/t/referencing-fields-in-metrics-output/60869
**Category:** Logstash
**Created:** [September 19, 2016, 11:02am UTC](https://discuss.elastic.co/t/referencing-fields-in-metrics-output/60869 "2016-09-19T11:02:42Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@Kryten](https://discuss.elastic.co/u/Kryten)
#### Post date: [September 19, 2016, 11:02am UTC](https://discuss.elastic.co/t/referencing-fields-in-metrics-output/60869/1 "2016-09-19T11:02:42Z")
Hi,
I'm trying to output a custom formatted line which must include:
1. Events per second metric.
2. The LS hostname.
I have this metric filter in the "filter" section:
```
metrics {
meter => "events"
add_tag => "metric"
flush_interval => 5
}
```
And I have this block in my output section:
```
if "metric" in [tags] {
stdout {
codec => line {
format => "%{host} 1m event rate: %{[events][rate_1m]}"
}
}
}
```
But for some reason the %{host} value is not being output and I am getting the literal string '%{host}' ouput to the console like this:
`%{host} 1m event rate: 0.0`
What am I doing wrong? Can we not use %{field\_name} in the metrics output? I need to output a specifically formatted line for the metrics to be collected properly with my application.
Would appreciate any advice on why my fields don't appear to be available to me.
Thanks!
---
### Author:  [@magnusbaeck](https://discuss.elastic.co/u/magnusbaeck)
#### Post date: [September 19, 2016, 11:23am UTC](https://discuss.elastic.co/t/referencing-fields-in-metrics-output/60869/2 "2016-09-19T11:23:38Z")
The symptoms indicate that the metrics event don't have a `host` field. Looking at the source it looks like it's the `message` field the includes the hostname. Not sure why it's done like that.
---
### Author:  [@Kryten](https://discuss.elastic.co/u/Kryten)
#### Post date: [September 19, 2016, 11:57am UTC](https://discuss.elastic.co/t/referencing-fields-in-metrics-output/60869/3 "2016-09-19T11:57:15Z")
Thanks @magnusbaeck
That's a bit of a disappointment, to say the least. Any ideas about how to get the Logstash hostname or other unique identifier into the metrics output? We are planning on having a cluster of LS machines and it is essential to know what kind of throughput each machine is dealing with... Would be grateful for any suggestions.
---
### Author:  [@eperry](https://discuss.elastic.co/u/eperry)
#### Post date: [September 19, 2016, 12:20pm UTC](https://discuss.elastic.co/t/referencing-fields-in-metrics-output/60869/4 "2016-09-19T12:20:29Z")
You can do what I did , add a flag to logstash --allow-env its a new feature
[https://www.elastic.co/guide/en/logstash/current/environment-variables.html](https://www.elastic.co/guide/en/logstash/current/environment-variables.html)
Then it would be as easy as
----------------sudo code-----
mutate {
add\_field =\> ["host" , "${HOSTNAME}"
}
---
### Author:  [@magnusbaeck](https://discuss.elastic.co/u/magnusbaeck)
#### Post date: [September 19, 2016, 1:15pm UTC](https://discuss.elastic.co/t/referencing-fields-in-metrics-output/60869/5 "2016-09-19T13:15:24Z")
> Any ideas about how to get the Logstash hostname or other unique identifier into the metrics output?
So... the hostname isn't present in the `message` field?
---
### Author:  [@Kryten](https://discuss.elastic.co/u/Kryten)
#### Post date: [September 20, 2016, 1:43pm UTC](https://discuss.elastic.co/t/referencing-fields-in-metrics-output/60869/6 "2016-09-20T13:43:00Z")
@magnusbaeck
Thanks for your input. Yes the message field does indeed contain the hostname and I was able to leverage that to generate the structure/formatting I needed. Many thanks! I do have another question about metrics but I'll create a new thread for that.
@eperry
Thanks for the suggestion. Much appreciated
---
### Author:  [@danieljamesscott](https://discuss.elastic.co/u/danieljamesscott)
#### Post date: [February 7, 2017, 12:14pm UTC](https://discuss.elastic.co/t/referencing-fields-in-metrics-output/60869/7 "2017-02-07T12:14:51Z")
I'm also experiencing the same issue, I have a 'response' field in my message, which I can use to generate a metric, but am not able to use this field to add a new field to the metric event.
Did you ever solve this?
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 6, 2017, 4:28am UTC](https://discuss.elastic.co/t/referencing-fields-in-metrics-output/60869/8 "2017-07-06T04:28:50Z")