tf2 buffer length setting problem

edit

I'm using Kinetic on Ubuntu 16.04 and met a problem with extending tf2 buffer (roscpp).

In my header file, I defined like this:

Class A
{
private: 
    std::unique_ptr<tf2_ros::Buffer> buffer_ptr;
    std::unique_ptr<tf2_ros::TransformListener> listener_ptr;
}

Then in the source file, I have initialized them in the constructor:

A::A
{
    buffer_ptr.reset(new tf2_ros::Buffer(ros::Duration(30.0)));
    listener_ptr.reset(new tf2_ros::TransformListener(*tf_buffer_ptr));
}

When I use the rqt tf_tree to view the transformation info, I noticed that the cached buffer length is still around 10 seconds, not extended to 30 seconds as I set here...

I tried to print out the buffer length out at runtime (via GetCacheLength method), and the value is correct.

I searched a lot but found very few info on this, and I checked the tf2_ros buffer related source code didn't get any luck as well..