logstash anonymize filter

gistfile1.txt

input {
    file {
        path => "/home/jrwren/src/logstash-1.4.2/access.log"
        start_position => beginning
    }
}
filter {
  if [path] =~ "access" {
    grok {
      match => { "message" => "%{COMBINEDAPACHELOG}%{GREEDYDATA:message_remainder}" }
    }
    anonymize {
#        algorithm => "IPV4_NETWORK"
        key => "16"
        fields => ["proxyip", "clientip"]
    }
    if [message_remainder] {

    mutate {
      replace => {
          "message" => "%{message_remainder}"
          "type" => "apache_access"
      }
    }
    } else {
    mutate {
      replace => {
          "type" => "apache_access"
          "message" => ""
      }
    }
    }
    date {
      match => [ "timestamp" , "dd/MMM/yyyy:HH:mm:ss Z" ]
    }
  }
}
output { stdout {
    codec => rubydebug
} }