void addTTLExpiryTask() {
    synchronized (regionExpiryLock) {
      RegionTTLExpiryTask task = regionTTLExpiryTask;
      if (task != null) {
        task.cancel();
      }

      if (regionTimeToLive > 0) {
        regionTTLExpiryTask = (RegionTTLExpiryTask) cache.getExpirationScheduler()
            .addExpiryTask(new RegionTTLExpiryTask(this));
        if (regionTTLExpiryTask != null) {
          if (logger.isDebugEnabled()) {
            logger.debug("Initialized Region TTL Expiry Task {}", regionTTLExpiryTask);
          }
        }

      } else {
        regionTTLExpiryTask = null;
      }
    }
  }
Add the Region TTL expiry task to the scheduler
geode-core/src/main/java/org/apache/geode/internal/cache/LocalRegion.java