static Integer getSslPortStr(ZNRecord znRecord) {
    String sslPortStr = znRecord.getSimpleField(SSL_PORT_STR);
    return sslPortStr == null ? null : Integer.valueOf(sslPortStr);
  }
Get the ssl port associated with the given instance (if any).
@param znRecord the {@link ZNRecord} associated with the interested instance.
@return the ssl port associated with the given instance.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/ClusterMapUtils.java