public List<DataNodeId> getOneDataNodeFromEachDatacenter(List<String> datacenterList) {
    HashSet<String> datacenters = new HashSet<String>();
    List<DataNodeId> toReturn = new ArrayList<DataNodeId>();
    for (DataNodeId dataNodeId : clusterMap.getDataNodeIds()) {
      if (datacenterList.contains(dataNodeId.getDatacenterName())) {
        if (!datacenters.contains(dataNodeId.getDatacenterName())) {
          datacenters.add(dataNodeId.getDatacenterName());
          toReturn.add(dataNodeId);
        }
      }
    }
    return toReturn;
  }
Shut down the servers and clean up the cluster.
@throws IOException
ambry-test-utils/src/main/java/com/github/ambry/server/MockCluster.java