Logstash create and reference variables

Hi,

Is there a way to pull and field:value from one event, store it in some sort of variable and then add it to the next event?

For example:
event1: {device:"router1", in-rate:"1", out-rate:"2", interface:"eth01", description:"test router"}
event2: (device:"router1", cpu1:"10", cpu2:"20", interface:"eth01"}

I want to add the description from event1 to event2. Is this possible to do with ruby code?

Thank you.