private MockDataNodeId getDataNodeId(String hostname, String dc) {
    return new MockDataNodeId(hostname, Collections.singletonList(new Port(6667, PortType.PLAINTEXT)),
        Collections.singletonList("/tmp"), dc);
  }
@param hostname the host name of the {@link MockDataNodeId}.
@param dc the name of the dc of the {@link MockDataNodeId}.
@return a {@link MockDataNodeId} based on {@code hostname} and {@code dc}.
ambry-clustermap/src/test/java/com/github/ambry/clustermap/ClusterMapUtilsTest.java