private synchronized void tryRenewLease() {
      // the scan has already been resumed, give up
      if (state == ScanResumerState.RESUMED) {
        return;
      }
      renewLease();
      // schedule the next renew lease task again as this is a one-time task.
      scheduleRenewLeaseTask();
    }
This method is used when {@link ScanControllerImpl#suspend} had ever been called to get a
{@link ScanResumerImpl}, but now user stops scan and does not need any more scan results.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncScanSingleRegionRpcRetryingCaller.java