docs: @Override
      public T getQueue(QueueSpec spec) {
          try {
              T queue = queueInstances.get(spec, new Callable<T>() {
                  @Override
                  public T call() throws Exception {
                      return createAndInitQueue(spec);
                  }
              });
              return queue;
          } catch (ExecutionException e) {
              throw new RuntimeException(e);
          }
      }