@Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (o == null || getClass() != o.getClass()) {
        return false;
      }

      TimerKey<?> timerKey = (TimerKey<?>) o;
      if (time != ((TimerKey<?>) o).time) {
        return false;
      }
      return key.equals(timerKey.key);
    }
For run loop to listen to timer firing so it can schedule the callbacks.
samza-core/src/main/java/org/apache/samza/scheduler/EpochTimeScheduler.java