public void addTask(URI uri, StackModule stackModule) {
      RepoUrlInfoCallable callable = null;
      if (tasks.containsKey(uri)) {
        callable = tasks.get(uri);
      } else {
        callable = new RepoUrlInfoCallable(uri);
        tasks.put(uri, callable);
      }

      callable.addStack(stackModule);
    }
@param uri
         uri to load
@param stackModule
         the stack module
ambari-server/src/main/java/org/apache/ambari/server/stack/StackContext.java