@Override
 protected void writeInternal(ObjectDataOutput out) throws IOException {
   out.writeInt(migrationData.size());
   for (Map.Entry<String, CollectionContainer> entry : migrationData.entrySet()) {
     out.writeUTF(entry.getKey());
     CollectionContainer container = entry.getValue();
     container.writeData(out);
   }
 }
 @Override
 public void run() throws Exception {
   CollectionService service = getService();
   for (Map.Entry<String, CollectionContainer> entry : migrationData.entrySet()) {
     String name = entry.getKey();
     CollectionContainer container = entry.getValue();
     container.init(getNodeEngine());
     service.addContainer(name, container);
   }
 }