Adding a field to a metrics event

Elastic Stack Logstash
6

Just for curiosity purposes, I bypassed this limitation by adding an extra filter in the pipeline. Basically, I defined 3 conditionals based on the value of the field I wanted to set in metrics.

if "value1" in [custom_field] {
    metrics{
        .....
        add_field => { "custom_field => "value1" }
     }
} else if "value2" in [custom_field] {
    metrics{
        .....
        add_field => { "custom_field => "value2" }
     }
}

And then in a later step I process the event created by the metrics function. That did the trick for me.