How to force ROS running in single thread mode - c++

Question

I am trying to debug my ros code in gdb, how ever, when I start the node in gdb, it always gives me:
Starting program: /home/uav/catkin_ws/devel/lib/my_package/my_node
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-
gnu/libthread_db.so.1".
[New Thread 0x7ffff13b9700 (LWP 28089)]
[New Thread 0x7ffff0bb8700 (LWP 28090)]
[New Thread 0x7fffebfff700 (LWP 28091)]
[New Thread 0x7fffeb7fe700 (LWP 28096)]
[New Thread 0x7fffeaffd700 (LWP 28098)]
[New Thread 0x7fffea7fc700 (LWP 28121)]
and hangs forever. I don't see this issue before and have no clue why it always start in multi-threads mode. My main function looks like this:
int main(int argc, char** argv)
{
ros::init(argc, argv, "my_node");
ros::NodeHandle nodeHandle("~");
ros::Rate rate(10);
while (ros::ok()) {
// Do Something
ros::spinOnce();
rate.sleep();
}
return 0;
}
How can I fix this problem? I am thinking I should make my node to a single thread version and debug it, how am I supposed to do that?

Answer 1

There are two ways to talk about multithreading in ROS.
The whole node
The callbackQueue.
In the first case, when you use:
ros::NodeHandle nodeHandle("~");
ros::ok()
...
It does some requests to the ROS Master. And with roscpp the network communication is handled with multithreading. There is no way to change that. If single threading is very important for you, you should try rospy, rosnodejs or others.
"roscpp does not try to specify a threading model for your application. This means that while roscpp may use threads behind the scenes to do network management, scheduling etc., it will never expose its threads to your application."
In the second case, we talk about handling topics, services and actions with multithreading. By default, a topic is handled with one thread. But if you send more data that your node can handle it, you can use multithreading.
"roscpp does, however, allow your callbacks to be called from any number of threads if that's what you want."
For mode details, see:
http://wiki.ros.org/roscpp/Overview/Callbacks%20and%20Spinning