@Override
  protected String getUseThisHostnameInstead(Configuration conf) throws IOException {
    String hostname = conf.get(UNSAFE_RS_HOSTNAME_KEY);
    if (conf.getBoolean(UNSAFE_RS_HOSTNAME_DISABLE_MASTER_REVERSEDNS_KEY, false)) {
      if (!StringUtils.isBlank(hostname)) {
        String msg = UNSAFE_RS_HOSTNAME_DISABLE_MASTER_REVERSEDNS_KEY + " and "
          + UNSAFE_RS_HOSTNAME_KEY + " are mutually exclusive. Do not set "
          + UNSAFE_RS_HOSTNAME_DISABLE_MASTER_REVERSEDNS_KEY + " to true while "
          + UNSAFE_RS_HOSTNAME_KEY + " is used";
        throw new IOException(msg);
      } else {
        return rpcServices.getSocketAddress().getHostName();
      }
    } else {
      return hostname;
    }
  }
Starts a HRegionServer at the default location.
<p/>
Don't start any services or managers in here in the Constructor. Defer till after we register
with the Master as much as possible. See {@link #startServices}.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java