private EventTrackerExpiryTask createEventTrackerExpiryTask() {
    long lifetimeInMillis = Long.getLong(GEMFIRE_PREFIX + "messageTrackingTimeout",
        PoolFactory.DEFAULT_SUBSCRIPTION_MESSAGE_TRACKING_TIMEOUT / 3);
    EventTrackerExpiryTask task = new EventTrackerExpiryTask(lifetimeInMillis);
    getCCPTimer().scheduleAtFixedRate(task, lifetimeInMillis, lifetimeInMillis);
    return task;
  }
Initialize the EventTracker's timer task for tracking and shutdown purposes.
geode-core/src/main/java/org/apache/geode/internal/cache/GemFireCacheImpl.java