log.warn("Failed validate DC: " + this.dcList[i], se);
                    }
                    this.dcList[i] = null;
                }
            }

            /*
             * No DCs found, for retieval of list by expiring it and retry.
             */
            this.dcListExpiration = 0;
        } while (retry-- > 0);

        this.dcListExpiration = now + 1000 * 60 * 15; /* 15 min */