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assert_liveliness is a method that Node objects have. Since MyNode inherits from it, I use it there.

colcon python package build error with rust extension Info: ROS 2 Version: Foxy OS: macOS Big Sur Python: 3.9 colcon

colcon python package build error with rust extension Info: ROS 2 Version: Foxy OS: macOS Big Sur Python: 3.9 colcon_py

colcon python package build error with rust extension Info: [OS] macOS Big Sur [Python] 3.9 I have been looking for wa

Hi all,

I am trying to set up a ROS2 rclpy node that functions as a Flask socket server. This node needs to have a thread or timer-based process running (which handles a socket broadcast). The issue I am running into is that when I create a ROS2 timer, it seems that it never executes, and when I use a python thread, it seems to block the main process. The minimal code samples are below:

ROS2 Timer:

class MyNode(Node):

    def __init__(self):
        super(MyNode,self).__init__('my_node')
        self.get_logger().info('Initializing My Node!') # Works fine
        self.app = Flask(__name__) # Flask Stuff
        self.my_ns = NS(self)     # Custom Flask Socket Namespace
        self.socketio = SocketIO(self.app, cors_allowed_origins="*") # Create Socket
        self.socketio.on_namespace(self.my_ns) # Pair the namespace
        self.process_timer = self.create_timer(.1,self.process)
        self.get_logger().info('Initialized!') # Executes

    def process(self):
        self.get_logger().info('Running!') # Never Executes

def main(args=None):
    rclpy.init(args=args)
    node = MyNode()
    node.socketio.run(node.app)

if __name__ == '__main__':
    main()

Python Thread:

class MyNode(Node):

    def __init__(self):
        super(MyNode,self).__init__('my_node')
        self.get_logger().info('Initializing My Node!') # Works fine
        self.app = Flask(__name__) # Flask Stuff
        self.my_ns = NS(self)     # Custom Flask Socket Namespace
        self.socketio = SocketIO(self.app, cors_allowed_origins="*") # Create Socket
        self.socketio.on_namespace(self.my_ns) # Pair the namespace
        self.process_thread = Thread(target=self.process,daemon=True)
        self.process_thread.start()
        self.get_logger().info('Initialized!') # Never Executes

    def process(self):
        alive = True
        while alive:
           try:
              self.assert_liveliness()
              self.get_logger().info('Running!') # Executes
            except:
              alive = False


def main(args=None):
    rclpy.init(args=args)
    node = MyNode()
    node.socketio.run(node.app)

if __name__ == '__main__':
    main()

Thanks for the suggestions, and I will try out those changes. I should share the original code I had, which is the following:

class WizardNode(Node):

    def __init__(self):
        super(WizardNode,self).__init__('wizard')
        self.get_logger().info('Initializing Wizard Node!')
        self.app = Flask(__name__)
        self.cors = CORS(self.app)
        self.wizard = Wizard(self)
        self.socketio = SocketIO(self.app, cors_allowed_origins="*")
        self.socketio.on_namespace(self.wizard)
        self.socket_thread = Thread(target=lambda:self.socketio.run(self.app),daemon=True)
        self.socket_thread.start()
        self.process_timer = self.create_timer(.1,self.process)
        self.get_logger().info('Initialized!')
        self.printer = PrettyPrinter()

    def process(self):
        time = self.get_clock().now()
        self.wizard.timestep()



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

    node = WizardNode()
    try:
        rclpy.spin(node)
    except KeyboardInterrupt:
        pass

    node.destroy_node()
    rclpy.shutdown() 

In this version, it seems that the socket.io thread fails to do any sort of broadcasting/emitting, which was why I tried restructuring in the ways above. I should also say that in this example, using eventlet's monkey_patch() basically broke everything.

The flask app was being executed as a thread within the MyNode __init__ function. The actual issue was that there was an

This turned out to be a bit of a fun puzzle to get ROS2 and Eventlet working together. In the end, the solution makes a

ROS2 Flask Threading issue Hi all, I am trying to set up a ROS2 rclpy node that functions as a Flask socket server. Thi

ROS2 Flask Threading issue Hi all, I am trying to set up a ROS2 rclpy node that functions as a Flask socket server. Thi

Hey all,

Not sure if something is broken, or if I am doing something wrong. I have started the bridge, and got to the point where when I load the page:

var ros = new ROSLIB.Ros({
        url: 'ws://localhost:9090'
    });
ros.on('connection', function() {
        console.log('Connected to websocket server.');
    });

Result:

"Connected to websocket server."

However, I have some parameters already on the server under the namespace /lookup. These were loaded in from a yaml file with rosparam load. When I attempt to load these values, I get no callback behavior:

var ros = new ROSLIB.Ros({
        url: 'ws://localhost:9090'
    });

var lookup = new ROSLIB.Param({
        ros : ros,
        name : '/lookup'
    });

ros.on('connection', function() {
        console.log('Connected to websocket server.');
        lookup.get(function(value){
            console.log("Lookup: "+value);
        });
        console.log('Ended connection sequence');
    });

Result:

"Connected to websocket server." "Ended connection sequence"

No errors, but no printing of my info.

I also verified that I am able to use the set command, and these parameters get set and are visible when running rosparam get <parameter>. When I tried to get this parameter with the above logic, however, it never executed the callback, as with the others.

I also tried with ros.getParams, but that didn't work either. Am I doing something incorrectly? Also, using ros-kinetic, if that helps.

ROS2 Flask Threading issue Hi all, I am trying to set up a ROS2 rclpy node that functions as a Flask socket server. Thi

ROS2 Flask Threading issue Hi all, I am trying to set up a ROS2 rclpy node that functions as a Flask socket server. Thi

ROS2 Flask Threading blocked Hi all, I am trying to set up a ROS2 rclpy node that functions as a Flask socket server. T

Warning: error when crawling, Input/output error Hey all, I am getting an interesting error with ROS Kinetic 1.12.14,

ROSLIB.Param.get() callback not executing Hey all, Not sure if something is broken, or if I am doing something wrong.

ROSLIB.Param.get() callback not executing Hey all, Not sure if something is broken, or if I am doing something wrong.