protected void validateHardwareLayout() {
    if (hardwareLayout == null) {
      throw new IllegalStateException("HardwareLayout cannot be null");
    }
  }
Returns {@code true} if all nodes in the datacenter have rack IDs
@return {@code true} if all nodes in the datacenter have rack IDs, {@code false} otherwise
ambry-clustermap/src/main/java/com/github/ambry/clustermap/Datacenter.java