After installing ROS 2 Rolling and playing with turtlesim, I downloaded further examples. I am having problems running the example client_cancel.py and server.py. It does not cancel the goal on the server successfully.

I followed the instructions and downloaded examples with git using the following command:

git clone https://github.com/ros2/examples src/examples -b rolling

Is there something further that needs to be done to make it work? I saw this post but didn't get anything out of it. Below are the files:

client_cancel.py:

# license removed for brevity

from example_interfaces.action import Fibonacci

import rclpy
from rclpy.action import ActionClient
from rclpy.node import Node


class MinimalActionClient(Node):
    def __init__(self):
        super().__init__("minimal_action_client")
        self._action_client = ActionClient(self, Fibonacci, "fibonacci")

    def cancel_done(self, future):
        cancel_response = future.result()
        if len(cancel_response.goals_canceling) > 0:
            self.get_logger().info("Goal successfully canceled")
        else:
            self.get_logger().info("Goal failed to cancel")
        rclpy.shutdown()

    def goal_response_callback(self, future):
        goal_handle = future.result()
        if not goal_handle.accepted:
            self.get_logger().info("Goal rejected :(")
            return

        self._goal_handle = goal_handle
        self.get_logger().info("Goal accepted :)")

        # Start a 2 second timer
        self._timer = self.create_timer(2.0, self.timer_callback)

    def feedback_callback(self, feedback):
        self.get_logger().info("Received feedback: {0}".format(feedback.feedback.sequence))

    def timer_callback(self):
        self.get_logger().info("Canceling goal")
        # Cancel the goal
        future = self._goal_handle.cancel_goal_async()
        future.add_done_callback(self.cancel_done)

        # Cancel the timer
        self._timer.cancel()

    def send_goal(self):
        self.get_logger().info("Waiting for action server...")
        self._action_client.wait_for_server()
        goal_msg = Fibonacci.Goal()
        goal_msg.order = 10
        self.get_logger().info("Sending goal request...")
        self._send_goal_future = self._action_client.send_goal_async(goal_msg, feedback_callback=self.feedback_callback)
        self._send_goal_future.add_done_callback(self.goal_response_callback)


def main(args=None):
    rclpy.init(args=args)

    action_client = MinimalActionClient()
    action_client.send_goal()
    rclpy.spin(action_client)


if __name__ == "__main__":
    main()

server.py:

# license removed for brevity

import time

from example_interfaces.action import Fibonacci

import rclpy
from rclpy.action import ActionServer, CancelResponse, GoalResponse
from rclpy.callback_groups import ReentrantCallbackGroup
from rclpy.executors import MultiThreadedExecutor
from rclpy.node import Node


class MinimalActionServer(Node):
    def __init__(self):
        super().__init__("minimal_action_server")

        self._action_server = ActionServer(
            self,
            Fibonacci,
            "fibonacci",
            execute_callback=self.execute_callback,
            callback_group=ReentrantCallbackGroup(),
            goal_callback=self.goal_callback,
            cancel_callback=self.cancel_callback,
        )

    def destroy(self):
        self._action_server.destroy()
        super().destroy_node()

    def goal_callback(self, goal_request):
        """Accept or reject a client request to begin an action."""
        # This server allows multiple goals in parallel
        self.get_logger().info("Received goal request")
        return GoalResponse.ACCEPT

    def cancel_callback(self, goal_handle):
        """Accept or reject a client request to cancel an action."""
        self.get_logger().info("Received cancel request")
        return CancelResponse.ACCEPT

    async def execute_callback(self, goal_handle):
        """Execute a goal."""
        self.get_logger().info("Executing goal...")

        # Append the seeds for the Fibonacci sequence
        feedback_msg = Fibonacci.Feedback()
        feedback_msg.sequence = [0, 1]

        # Start executing the action
        for i in range(1, goal_handle.request.order):
            if goal_handle.is_cancel_requested:
                goal_handle.canceled()
                self.get_logger().info("Goal canceled")
                return Fibonacci.Result()

            # Update Fibonacci sequence
            feedback_msg.sequence.append(feedback_msg.sequence[i] + feedback_msg.sequence[i - 1])
            self.get_logger().info("Publishing feedback: {0}".format(feedback_msg.sequence))

            # Publish the feedback
            goal_handle.publish_feedback(feedback_msg)

            # Sleep for demonstration purposes
            time.sleep(1)

        goal_handle.succeed()

        # Populate result message
        result = Fibonacci.Result()
        result.sequence = feedback_msg.sequence
        self.get_logger().info("Returning result: {0}".format(result.sequence))
        return result


def main(args=None):
    rclpy.init(args=args)

    minimal_action_server = MinimalActionServer()

    # Use a MultiThreadedExecutor to enable processing goals concurrently
    executor = MultiThreadedExecutor()
    rclpy.spin(minimal_action_server, executor=executor)
    minimal_action_server.destroy()
    rclpy.shutdown()


if __name__ == "__main__":
    main()

Execution:

After colcon build --symlink-install and sourcing the packages i executed ros2 run examples_rclpy_minimal_action_server server and ros2 run examples_rclpy_minimal_action_client client_cancel

Output on server side:

[INFO] [1665904936.230794265] [minimal_action_server]: Received goal request
[INFO] [1665904936.231638391] [minimal_action_server]: Executing goal...
[INFO] [1665904936.231872544] [minimal_action_server]: Publishing feedback: array('i', [0, 1, 1])
[INFO] [1665904937.234087895] [minimal_action_server]: Publishing feedback: array('i', [0, 1, 1, 2])
[INFO] [1665904938.236406191] [minimal_action_server]: Publishing feedback: array('i', [0, 1, 1, 2, 3])
[INFO] [1665904939.238750288] [minimal_action_server]: Publishing feedback: array('i', [0, 1, 1, 2, 3, 5])
[INFO] [1665904940.241102316] [minimal_action_server]: Publishing feedback: array('i', [0, 1, 1, 2, 3, 5, 8])
[INFO] [1665904941.243432982] [minimal_action_server]: Publishing feedback: array('i', [0, 1, 1, 2, 3, 5, 8, 13])
[INFO] [1665904942.245741341] [minimal_action_server]: Publishing feedback: array('i', [0, 1, 1, 2, 3, 5, 8, 13, 21])
[INFO] [1665904943.247994186] [minimal_action_server]: Publishing feedback: array('i', [0, 1, 1, 2, 3, 5, 8, 13, 21, 34])
[INFO] [1665904944.250271245] [minimal_action_server]: Publishing feedback: array('i', [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55])
[INFO] [1665904945.253059441] [minimal_action_server]: Returning result: array('i', [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55])

Output on client side:

[INFO] [1665904935.966929974] [minimal_action_client]: Waiting for action server...
[INFO] [1665904936.218430440] [minimal_action_client]: Sending goal request...
[INFO] [1665904936.231534465] [minimal_action_client]: Goal accepted :)
[INFO] [1665904936.232283331] [minimal_action_client]: Received feedback: array('i', [0, 1, 1])
[INFO] [1665904937.235916634] [minimal_action_client]: Received feedback: array('i', [0, 1, 1, 2])
[INFO] [1665904938.232744034] [minimal_action_client]: Canceling goal
[INFO] [1665904938.237996185] [minimal_action_client]: Received feedback: array('i', [0, 1, 1, 2, 3])
[INFO] [1665904939.240413786] [minimal_action_client]: Received feedback: array('i', [0, 1, 1, 2, 3, 5])
[INFO] [1665904940.242826158] [minimal_action_client]: Received feedback: array('i', [0, 1, 1, 2, 3, 5, 8])
[INFO] [1665904941.245216231] [minimal_action_client]: Received feedback: array('i', [0, 1, 1, 2, 3, 5, 8, 13])
[INFO] [1665904942.247427880] [minimal_action_client]: Received feedback: array('i', [0, 1, 1, 2, 3, 5, 8, 13, 21])
[INFO] [1665904943.249521452] [minimal_action_client]: Received feedback: array('i', [0, 1, 1, 2, 3, 5, 8, 13, 21, 34])
[INFO] [1665904944.251843465] [minimal_action_client]: Received feedback: array('i', [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55])
[INFO] [1665904945.256133147] [minimal_action_client]: Goal failed to cancel