Threaded worker not stopping even after keyboard interrupt.

[OoiYenKai]

#!/usr/bin/env python3
from textual.app import App, ComposeResult
from textual.containers import Vertical, Center, Middle
from textual.widgets import LoadingIndicator, Header, TabbedContent, Label, Markdown, TabPane, ProgressBar, Label, Digits, Static
from textual.geometry import Size
from textual import work
from decoding import decoding_speed
import os


SPEEDOMETER = """
# Speedometer
"""

OTHERS = """
# This is a tab for future expansion.
"""


class SpeedometerDigits(Static):
    def compose(self) -> ComposeResult:
        yield Digits(id="speedometerSpeed")
    
    def get_content_width(self, container: Size, viewport: Size) -> int:
        return super().get_content_width(container, viewport)
    
    def get_content_height(self, container: Size, viewport: Size, width: int) -> int:
        return super().get_content_height(container, viewport, width)

class SpeedometerApp(App):
    BINDINGS = [
        ("T", "toggle_dark_mode", "Toggle dark mode"),
        ("Q", "request_quit", "Quit")
    ]

    CSS_PATH = "speedometer.tcss"

    TITLE = "Speedometer UI"

    def compose(self) -> ComposeResult:
        """The widgets that this app is composed of?""" 
        yield Header()

        with TabbedContent(initial="speedometer"):
            with TabPane("Speedometer", id="speedometer"):  # First tab
                with Middle():
                    with Center(id="markdown_center"):
                        yield Markdown(SPEEDOMETER, id="speedometerDisplay")  # Tab content
                    with Center(id="speedometerSpeed_center"):
                        yield SpeedometerDigits()
                        yield Center(Label("km/h", id="speedometerSpeedUnit"))
                    with Center(id="progress_center"):
                        yield Label("Speed: ")
                        yield ProgressBar(total = 40, show_eta = False)
            with TabPane("Others", id="others"): # Second tab
                with Vertical():
                    with Center():
                        yield Markdown(OTHERS, id="othersDisplay")
                    yield LoadingIndicator(id="loading")

    def on_mount(self) -> None:
        # Running an infinite loop with interval of 100ms
        self.DecodingStatus = self.set_interval(0.001, self.get_speed, pause=False)

    @work(exclusive=True, thread=True)
    async def get_speed(self) -> None:
        speed = float(decoding_speed())
        self.query_one(Digits).update(str(speed))
        self.query_one(ProgressBar).update(progress = speed)

    #this is an ACTION method.
    #It's associated with the action called toggle_dark_mode.
    def action_toggle_dark_mode(self):
        """toggle dark mode"""
        self.dark = not self.dark   

    #this is an ACTION method.
    #It's associated with the action called request_quit.
    def action_request_quit(self):
        """Action to quit the UI application"""
        self.DecodingStatus.pause()
        os.system('sudo ifconfig can0 down')
        self.app.exit()

if _name_ == "_main_":
    app = SpeedometerApp()
    app.run()`

This is my textual code and it importing a function from another file where it reads values from a CAN bus, decodes it and return the decoded value. I succesfully got my UI to display and update the values concurrently. The problem i am facing is that even after exiting the UI using ctrl+c the code does not stop running. I have seen some similar discussions on this page already and tried their solutions, but i still cant fix this issue. As i am new to textual and coding, i am sure my code has a lot of mistakes, hoping to get some help here.

This is my decoding code

#!/usr/bin/env python3
import os
import can


byte2 = 0.0
byte3 = 0.0
speed = 0.0


os.system('./can_setup.sh')

can_interface = 'can0'
bus = can.interface.Bus(channel=can_interface, bustype='socketcan') #socketcan native

initialize_msg = can.Message(arbitration_id=0x123, data=[0xa0, 0xb1, 0xc2, 0xd3, 0xe4, 0xf5, 0xf6, 0xff], is_extended_id=False)

print(initialize_msg)

try:
    #sending an initialization message
    os.system('cansend can0 123#1100002233445566')
    print("Message sent on {}".format(can_interface))
except can.CanError:
    print('message was not sent')

def decoding_speed():
    try:
        for msg in bus:
            if msg.arbitration_id == 0x10FEF1C8:
                byte2 = hex(msg.data[1])
                byte3 = hex(msg.data[2])
                byte2 = byte2.replace("0x", "")
                #using little endian format
                xSpeed = byte3 + byte2 #speed in hexadecimal
                dSpeed = int(xSpeed, 16) #speed in decimal
                speed = dSpeed/256 #speed in km/h
                print(speed)
                return "{:.2f}".format(speed)    
    except KeyboardInterrupt:
        bus.shutdown()
        os.system('sudo ifconfig can0 down')
        print('\n\rKeyboard interrupt received. Exiting.')
        exit()

I am really lost on this issue, would appreciate any kind of help.

[TomJGooding]

That's a lot of (unformatted) code to wade through. But I'd recommend having another read through the docs on Thread Workers , specifically the warning about updating the UI directly and checking if a worker was cancelled. I'm not sure that will solve the issue here, but it would at least be a good starting point.

[willmcgugan]

Fixed the formatting...

[OoiYenKai]

Thank you, i dont know how to fix the formatting when i first upload.

[willmcgugan]

Only the main thread will receive a KeyboardInterrupt.

You can poll get_current_worker().is_cancelled to know when to exit your thread, or you can use a threading.Event or other synchronization primitive. These aren't Textual issues per-se.

Note that you should avoid updating the UI from a thread. Be sure to read the guide on workers which covers this.

[OoiYenKai]

But the issue here is i set an interval to run the thread every 0.001 seconds and i want this to run for the whole lifetime of the app. So i did not set a condition for the worker to be cancelled.

[OoiYenKai]

Thank you guys for your suggestions and advice. I have successfully came up with a way to fix my issue. I am going to post the solution here for anyone who might be facing the same issue as me.

Firstly i read through the doc on workers and followed the example and avoided updating my UI directly from a thread by modifying my code as such:

    def on_mount(self) -> None:
        # Running an infinite loop with interval of 100ms
        self.DecodingStatus = self.set_interval(0.001, self.get_speed, pause=False)

    @work(exclusive=True, thread=True)
    async def get_speed(self) -> None:
        speed = float(decoding_speed())
        await self.call_from_thread(self.update_ui, speed)

    def update_ui(self, speed):
        speed_widget = self.query_one(Digits)
        progressBar = self.query_one(ProgressBar)
        speed_widget.update(str(speed))
        progressBar.update(progress=speed)

And i realized that the for loop in my decoding code was blocking the moment the CAN bus stopped sending over values causing my application to hang even after exiting the UI. To fix this, i modified my code as such:

def decoding_speed():
    try:
        while True:
            msg = bus.recv(0.01)
            if msg is None:
                break
            if msg.arbitration_id == 0x10FEF1C8:
                byte2 = hex(msg.data[1])
                byte3 = hex(msg.data[2])
                byte2 = byte2.replace("0x", "")
                #using little endian format
                xSpeed = byte3 + byte2 #speed in hexadecimal
                dSpeed = int(xSpeed, 16) #speed in decimal
                speed = dSpeed/256 #speed in km/h
                return "{:.2f}".format(speed)

This change made it such that there is a timeout of 0.01 second and if no values were sent over break out of the loop.

Hope this provided some help to those facing similar issues.