Re: [ros-users] Nodelets

On Dec 5, 2010, at 12:31 AM, Tully Foote wrote:
>
>
> I am trying to move some computer vision code to nodelets. The idea is to have one camera nodelet serving frames, and everybody else grabbing and processing them.
>
> That is one of the goals of the nodelet design. You can see my other ros-users post about how to add an nodelet::Loader class to your node and then you can just load into that manager. http://code.ros.org/lurker/message/20101205.074703.0991b0ae.en.html
>

Tully, I have been playing around with this approach, trying to get it to work. I have been having some trouble. The nodelets are loaded, onInit() is called, but callbacks aren't called on the nodelets. Is there something about ros::spinOnce() that doesn't do the right thing for nodelets?

Below is a detailed example, if it helps.

--Nick

===========

I set up something similar to this example, but that also publishes a message:

{{{
int main(int argc, char** argv)
{    
    ros::init(argc, argv, "VisionNodeletManager");
    ros::NodeHandle n;
    nodelet::Loader l; //This is what we need to be a nodelet manager

    

    ros::Publisher pub = n.advertise<std_msgs::Bool>("camera_display_disable", 1000);

    

    ros::Rate loop_rate(1);

    while (ros::ok()) {    
        std_msgs::Bool msg; 
        msg.data = 0; 
        pub.publish(msg); 
        ROS_INFO_STREAM("Published frame."); 
        ros::spinOnce();
        loop_rate.sleep(); 
    }

    

    return 0;
}
}}}

I then set up a listener nodelet:

{{{
namespace vision_nodelets
{
    

    class CameraDisplayNodelet : public nodelet::Nodelet
    {
    public:
        CameraDisplayNodelet() : 
        disabled_(0), 
        {}

        

    private:
        virtual void onInit()
        {
            ROS_INFO_STREAM("Calling onInit() for CameraDisplayNodelet"); 
            ros::NodeHandle& private_nh = getPrivateNodeHandle();
            private_nh.getParam("disabled", disabled_);
            ROS_INFO_STREAM("Parameters: disabled=" << disabled_ ); 
            sub = private_nh.subscribe("camera_display_disable", 1000, &CameraDisplayNodelet::callback, this);
            ROS_INFO_STREAM("Finished onInit()"); 
        }

        

        void callback(const std_msgs::Bool::ConstPtr& input)
        {
            ROS_INFO_STREAM("Received message: camera_display_disable=" << input->data); 
            disabled_ = input->data;
        }
        int disabled_; 
        ros::Subscriber sub;

        

    };

    

    PLUGINLIB_DECLARE_CLASS(vision_nodelets, CameraDisplayNodelet, vision_nodelets::CameraDisplayNodelet, nodelet::Nodelet);
}

}}}

In Terminal A, I run

{{{
rosrun vision_nodelets vision_nodelet_manager
}}}

In Terminal B, I run

{{{
rosrun nodelet nodelet load vision_nodelets/CameraDisplayNodelet VisionNodeletManager
}}}

In Terminal C, I run

{{{
rostopic echo /camera_display_disable
}}}

The following behavior is observed:

In Terminal A I see unexpected outpt:
Every second I see the message "Published Frame". When the nodelet is started in Terminal B, I see "Calling onInit()"... I never see "Received message."

In Terminal B I see expected output:
{{{
[ INFO] [1291578492.136581000]: Loading nodelet /vision_nodelets_CameraDisplayNodelet of type vision_nodelets/CameraDisplayNodelet to manager VisionNodeletManager with the following remappings:
}}}

In Terminal C I see expected output:
Once every second I see
{{{
---
data: False
}}}