Simply add your desired output section and save it as a *.conf file. Then run this command: curl http://stream.meetup.com/2/rsvps | /usr/share/logstash/bin/logstash -f wherever_you_saved_it_as.conf

meetups.conf

input {
  stdin {
    codec => json_lines
  }
}

filter {
    mutate  {
        uppercase => [ "[group][group_country]" ]
        replace => { "location" => "%{[group][group_lat]},%{[group][group_lon]}" }
          }
    date {
        match => [ "mtime", "UNIX_MS" ]
        target => "@timestamp"}

    if [venue][lat] {
    mutate {
        replace => { "[venue][location]" => "%{[venue][lat]},%{[venue][lon]}" } }
           }
    json { source => "group.group_topics.topic_name" }
    if [member][other_services][facebook][identifier] =~ /https:\/\/www.facebook.com\/http%3A%2F%2Fwww.facebook.com%2F.*/ {
    grok { match => [ "member.other_services.facebook.identifier", "(?<member.other_services.facebook.identifier>(?:https://www.facebook.com/http%3A%2F%2Fwww.facebook.com%2F)(.*))" ] }
        }
    else if [member][other_services][facebook][identifier] =~ /https:\/\/www.facebook.com\/app_scoped_user_id\/.*/ {
    grok { match => [ "member.other_services.facebook.identifier", "(?<member.other_services.facebook.identifier>(?:https://www.facebook.com/app_scoped_user_id/)(.*[^\/]))" ] }
        }
    else if [member][other_services][facebook][identifier] =~ /https.*/ {
    grok { match => [ "member.other_services.facebook.identifier", "(?<member.other_services.facebook.identifier>(\d+)[^\/$])" ] }
        }
    }

Simply add your desired output section and save it as a *.conf file. Then run this command:

curl http://stream.meetup.com/2/rsvps | /usr/share/logstash/bin/logstash -f wherever you saved it as.conf

Update additional Facebook parsing.