logstash.conf

input {
    file {
        type           => "gatling"
        path           => "/path/to/output.log"
        start_position => "beginning"
    }
}

filter {
    if ([message] =~ "\bRUN\b" or [message] =~ "\bSTART\b" or [message] =~ "\bEND\b" or [message] =~ "\bGROUP\b") {
        drop { }
    }
    if [type] == "gatling" {
        grok {
            match => { "message" => "%{DATA:scenario_name}\t%{NOTSPACE:user_id}\tREQUEST\t%{DATA:group}\t%{DATA:name}\t%{INT:requestStart:int}\t%{INT:requestEnd:int}\t%{INT:responseStart:int}\t%{INT:responseEnd:int}\t%{WORD:status}" }
            keep_empty_captures => true
        }
        mutate {
            gsub => [
                "status", "OK", true,
                "status", "KO", false
            ]
            remove_field => ["host", "path", "type"]
        }
        mutate {
            convert => { "status" => "boolean" }
        }
        date {
            match => [ "requestStart", "UNIX_MS" ]
        }
        ruby {
            code => "event['responseDuration'] = (event['responseEnd'] - event['requestStart'])"
        }
    }
}

output {
     stdout { codec => rubydebug }
     elasticsearch {
        hosts => ["localhost:9200"]
        index => "gatling-%{+YYYY.MM.dd}"
        codec => "json"
    }
}