code: private long computeRenewalPeriod() {
      long hardLeaseLimit = conf.getLong(
          FSConstants.DFS_HARD_LEASE_KEY, FSConstants.LEASE_HARDLIMIT_PERIOD);
      long softLeaseLimit = conf.getLong(
          FSConstants.DFS_SOFT_LEASE_KEY, FSConstants.LEASE_SOFTLIMIT_PERIOD);
      long renewal = Math.min(hardLeaseLimit, softLeaseLimit) / 2;
      long hdfsTimeout = Client.getTimeout(conf);
      if (hdfsTimeout > 0) {
        renewal = Math.min(renewal, hdfsTimeout/2);
      }
      return renewal;
    }
docs: Computes the renewal period for the lease.
  
  @return the renewal period in ms