Ruby snippet to iterate through array results in error "Ruby exception occurred: undefined method `[]' for #<LogStash::Event:0x69068bc1>`"

[kaj]

I've got the following xpath:

   xpath => [
     "/record/parameters/parameter/text()", "parameter" ]

Parameter is a field that can have a variable number of values, from 0 to n. So it can not exist, or it can have n values. I have the following Ruby:

  ruby {
    code => '
    ids = event["parameter"].split(",")  
    ids.each_with_index do |value, index|           
      event["parameter_%{index}"] = "value"           
    end
    '
  }

The error I get in the logs is:

[2020-03-04T16:30:32,520][ERROR][logstash.filters.ruby ] Ruby exception occurred: undefined method ' for #LogStash::Event:0x69068bc1`

I'm very new to Ruby so I'm assuming that there are a couple things missing, but my immediate questions are:

1. Do I need to have a check preceeding the rest of my Ruby making sure that the parameter field exists and has values?
2. Am I using the event function incorrectly?

[Badger]

1. Yes

2. No. See here.

[kaj]

I have gotten through all the errors I was facing, but now seem to be mucking up the loop for iterating the array.

My Ruby is now:

ruby {
    code => '
    parametersExist = event.get("parameter")
    if parametersExist
      ids = event.get("parameter") 
      ids.each_with_index do |value, index|           
        event.set("parameter_%{index}", "value")          
      end
    end
    '
  }

But it just makes a literal value:

I've confirmed that the array has values (unless this isn't even an array):

[Badger]

@kaj

event.set("parameter_%{index}", "value")

That's not how you do string interpolation in ruby. sprintf references are a logstash thing, not a ruby thing. Try

event.set("parameter_#{index}", value)

As a point of style I think it would be more common to do

ids = event.get("parameter")
if ids
    ...

thus getting rid of the intermediate variable.

[kaj]

That works! Thank you so much for your prompt responses. Here is the working code for anybody checking this thread later.

  ruby {
    code => '
    ids = event.get("parameter")
    if ids  
      ids.each_with_index do |value, index|           
        event.set("parameter_#{index}", value)          
      end
    end
    '
  }