@Override
  public int hashCode() {
    return name.hashCode();
  }
A datacenter can be marked as rack-aware if all nodes have defined rack IDs. This method throws an exception
if some nodes have rack IDs and some do not.  It also sets the {@code rackAware} flag to {@code true} if all
nodes have rack IDs.

@throws IllegalStateException if some nodes have defined rack IDs and some do not.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/Datacenter.java