void addTTLExpiryTask(RegionTTLExpiryTask callingTask) {
    synchronized (regionExpiryLock) {
      if (regionTTLExpiryTask != null && regionTTLExpiryTask != callingTask) {
        return;
      }
      if (regionTimeToLive <= 0) {
        regionTTLExpiryTask = null;
        return;
      }

      RegionTTLExpiryTask task = new RegionTTLExpiryTask(this);
      if (logger.isDebugEnabled()) {
        logger.debug("Scheduling Region TTL Expiry Task {} which replaces {}", task,
            regionTTLExpiryTask);
      }
      regionTTLExpiryTask =
          (RegionTTLExpiryTask) cache.getExpirationScheduler().addExpiryTask(task);
    }
  }
Add the Region TTL expiry task to the scheduler
geode-core/src/main/java/org/apache/geode/internal/cache/LocalRegion.java