logstash check if field exists

Question

I have log files coming in to an ELK stack. I want to copy a field (foo) in order to perform various mutations on it, However the field (foo) isn\'t always present.

Answer 1

On Logstash 2.2.2, the ("" in [field]) construct does not appear to work for me.

if ![field] { }

does, for a non-numerical field.