Logstah throttle filter dropping messages indefinitely

Trying to use the throttle plugin in logstash to drop messages if I am receiving them at too high a rate. My goal is to:

drop excess messages if more than 100 received in a 10 second window

To accomplish this, I use the config below, but it doesn't do what I expected. Instead, when I start logstash, it allows the first 100 messages through and then throttles the rest indefinitely -- all the messages received after the first 100 are dropped. How do I accomplish the goal above?

logstash 2.4.0
throttle 4.0.1

filter {
  throttle {
    after_count => 100
    period => 10
    key => "%{type}"
    add_tag => "throttled"
  if "throttled" in [tags] {
    drop { }

are you using multiple workers (-w > 1) ?

Yes, using multiple workers.

Same Question here