@Override
  public void stop(String why) {
    // stop accepting new work (shouldn't be any with a fixed-size pool)
    monkeyThreadPool.shutdown();
    // notify all executing policies that it's time to halt.
    for (Policy policy : policies) {
      policy.stop(why);
    }
  }
Selects and returns ceil(ratio * items.length) random items from the given array
hbase-it/src/test/java/org/apache/hadoop/hbase/chaos/monkies/PolicyBasedChaosMonkey.java