rate.sleep() blocks node after first callback function
After receiving the first callback function in the following code, the node blocks and stops running, that is, it doesn't execute the instructions inside the while loop nor the callback function anymore. By removing the rate.sleep() function it fixes the problem but the while loop is not running at the desired rate of 10 hz anymore.... Is this a bug or I'm missing something? The rate.sleep() works well if it doesn't have any callback.
#!/usr/bin/env python3
import rclpy
from rclpy.node import Node
from rclpy.executors import SingleThreadedExecutor
from gazebo_msgs.msg import ModelStates
class MyNode(Node):
def __init__(self):
super().__init__('my_node')
self.subs_model_states = self.create_subscription(
ModelStates,
'/gazebo/model_states',
self.model_states_callback,
10)
self.subs_model_states # prevent unused variable warning
def model_states_callback(self, msg):
try:
self.get_logger().info(f"Callback")
except Exception as e:
self.get_logger().error(f"Error in callback: {e}")
def main(args=None):
rclpy.init(args=args)
node = MyNode()
executor = SingleThreadedExecutor()
executor.add_node(node)
rate = node.create_rate(10) # 10 Hz
while rclpy.ok():
rclpy.logging.get_logger("main").info(f"Running!")
executor.spin_once(timeout_sec=0.1)
rate.sleep()
node.destroy_node()
rclpy.shutdown()
if __name__ == '__main__':
main()
How do you start your node? Using
ros2 run <package> <your_prog>works in my system. The line#!/usr/bin/env python3suggests to me, that you start the file directly from the command line as a normal python file (e.g.$python3 file.py)I'm using the same command as you to start the node.
The reason of the line:
it's because I'm starting a python node in the same package as C++ nodes. Basically, I'm using CMake. Do you think it has something to do with that?
I do not know... In my humble installation, your code works without any change. What happens if you remove that line and you use
ros2 run ...to start the node?If I do it in a C++ package I'll get an error.
Anyways, I removed that line, I put that Python node in a Python only package, and I still got the same behavior...
You can see an screenshot here(I don't know how to add pictures in comments) https://imgur.com/a/XykgTRG
I have no idea... tomorrow I have access to another PC, where I developed some programs using
spin_onceand I try to compare them to your code, to investigate the problemOk, can you try the same identical code above but putting the following line:
rclpy.spin_once()afterexecutor.spin_once(timeout_sec = 0.1)(BUT BEFORE therate.sleep())? Build, try and report.To be clear:
I have to add to the spin_once:
because I was getting this error:
Unfortunately, I'm getting the same behavior.