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Calling hub methods from callback functions blocks further operations #127

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Yakuza-UA opened this issue Dec 25, 2022 · 6 comments
Open

Calling hub methods from callback functions blocks further operations #127

Yakuza-UA opened this issue Dec 25, 2022 · 6 comments

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@Yakuza-UA
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So, I tried to implement a simple demo where press of the button controls some other functions of a MoveHub, i.e. changes LED colour, or spins up a motor. The code looks like this:

from pylgbst.hub import MoveHub
from pylgbst import get_connection_bleak

conn = get_connection_bleak()
hub = MoveHub(conn)

def callback_btn(is_pressed):
    global hub
    print("Btn pressed: %s" % is_pressed)

    hub.motor_external.wait_complete()
    if is_pressed == 0:
        hub.motor_external.timed(5, 1.0, wait_complete=False)

try:
    hub.button.subscribe(callback_btn)
    time.sleep(60)
finally:
    hub.button.unsubscribe(callback_btn)
    hub.disconnect()

Once I release the button for the first time, it spins up the motor for 5 seconds exactly as I expect it to do. However, it does seem to ignore any further button presses... callback function is not called at all as I am not even getting any strings printed. Is this an expected behaviour due to threaded execution?

Is there a way to implement this?

Thanks a lot in advance.
@undera
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undera commented Dec 25, 2022

Hi
It does not sound as a normal behavior. Is there any communication with hub showing up in debug log when you press button the second time?

I would suspect the wait_complete=False somehow interferes here.

@Yakuza-UA
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Yakuza-UA commented Dec 26, 2022 •
edited
Loading

Hmm, well wait_complete=False was actualy my attempt to resolve it :) I thought maybe it's something blocking it so I've slightly changed the implementation. Original code was simpler, like the following:

from pylgbst.hub import MoveHub
from pylgbst import get_connection_bleak

conn = get_connection_bleak()
hub = MoveHub(conn)

def callback_btn(is_pressed):
    global hub
    print("Btn pressed: %s" % is_pressed)

    if is_pressed == 0:
        hub.motor_external.timed(5, 1.0)

try:
    hub.button.subscribe(callback_btn)
    time.sleep(60)
finally:
    hub.button.unsubscribe(callback_btn)
    hub.disconnect()

Behavior is the same. Here's the debug output.

DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x6', '0x0', '0x1', '0x2', '0x6', '0x2']
DEBUG:hub:Notification on 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic: b'060001020600'
DEBUG:hub:Decoded message: MsgHubProperties({'payload': b'00', 'needs_reply': False, 'property': 2, 'operation': 6, 'parameters': b'00'})
DEBUG:hub:Found matching upstream msg: MsgHubProperties({'payload': b'00', 'needs_reply': False, 'property': 2, 'operation': 6, 'parameters': b'00'})
DEBUG:hub:Handling msg with <bound method Button._props_msg of Button on port 0x0>: MsgHubProperties({'payload': b'00', 'needs_reply': False, 'property': 2, 'operation': 6, 'parameters': b'00'})
DEBUG:hub:Fetched sync reply: MsgHubProperties({'payload': b'00', 'needs_reply': False, 'property': 2, 'operation': 6, 'parameters': b'00'})
DEBUG:hub:Notification on 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic: b'060001020601'
DEBUG:hub:Decoded message: MsgHubProperties({'payload': b'01', 'needs_reply': False, 'property': 2, 'operation': 6, 'parameters': b'01'})
DEBUG:hub:Handling msg with <bound method Button._props_msg of Button on port 0x0>: MsgHubProperties({'payload': b'01', 'needs_reply': False, 'property': 2, 'operation': 6, 'parameters': b'01'})
Btn pressed: 1
DEBUG:hub:Notification on 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic: b'060001020602'
DEBUG:hub:Decoded message: MsgHubProperties({'payload': b'02', 'needs_reply': False, 'property': 2, 'operation': 6, 'parameters': b'02'})
DEBUG:hub:Handling msg with <bound method Button._props_msg of Button on port 0x0>: MsgHubProperties({'payload': b'02', 'needs_reply': False, 'property': 2, 'operation': 6, 'parameters': b'02'})
Btn pressed: 2
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.Properties.PropertiesChanged (/org/bluez/hci0/dev_00_16_53_A1_4C_92/service000c/char000d): ['org.bluez.GattCharacteristic1', {'Value': <dbus_fast.signature.Variant ('ay', bytearray(b'\x06\x00\x01\x02\x06\x00'))>}, []]
DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x6', '0x0', '0x1', '0x2', '0x6', '0x0']
DEBUG:hub:Notification on 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic: b'060001020600'
DEBUG:hub:Decoded message: MsgHubProperties({'payload': b'00', 'needs_reply': False, 'property': 2, 'operation': 6, 'parameters': b'00'})
DEBUG:hub:Handling msg with <bound method Button._props_msg of Button on port 0x0>: MsgHubProperties({'payload': b'00', 'needs_reply': False, 'property': 2, 'operation': 6, 'parameters': b'00'})
Btn pressed: 0
DEBUG:hub:Send message: MsgPortOutput({'payload': b'', 'needs_reply': False, 'port': 3, 'is_buffered': False, 'do_feedback': True, 'wait_complete': True, 'subcommand': 9, 'params': b'881364647f03'})
DEBUG:hub:Waiting for sync reply to MsgPortOutput({'payload': b'031109881364647f03', 'needs_reply': True, 'port': 3, 'is_buffered': False, 'do_feedback': True, 'wait_complete': True, 'subcommand': 9, 'params': b'881364647f03'})...
DEBUG:comms-bleak:Request: 14 ['0xc', '0x0', '0x81', '0x3', '0x11', '0x9', '0x88', '0x13', '0x64', '0x64', '0x7f', '0x3']
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.Properties.PropertiesChanged (/org/bluez/hci0/dev_00_16_53_A1_4C_92/service000c/char000d): ['org.bluez.GattCharacteristic1', {'Value': <dbus_fast.signature.Variant ('ay', bytearray(b'\x05\x00\x82\x03\x01'))>}, []]
DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x5', '0x0', '0x82', '0x3', '0x1']
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.Properties.PropertiesChanged (/org/bluez/hci0/dev_00_16_53_A1_4C_92/service000c/char000d): ['org.bluez.GattCharacteristic1', {'Value': <dbus_fast.signature.Variant ('ay', bytearray(b'\x05\x00\x82\x03\n'))>}, []]
DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x5', '0x0', '0x82', '0x3', '0xa']
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.Properties.PropertiesChanged (/org/bluez/hci0/dev_00_16_53_A1_4C_92/service000c/char000d): ['org.bluez.GattCharacteristic1', {'Value': <dbus_fast.signature.Variant ('ay', bytearray(b'\x06\x00\x01\x02\x06\x01'))>}, []]
DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x6', '0x0', '0x1', '0x2', '0x6', '0x1']
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.Properties.PropertiesChanged (/org/bluez/hci0/dev_00_16_53_A1_4C_92/service000c/char000d): ['org.bluez.GattCharacteristic1', {'Value': <dbus_fast.signature.Variant ('ay', bytearray(b'\x06\x00\x01\x02\x06\x02'))>}, []]
DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x6', '0x0', '0x1', '0x2', '0x6', '0x2']
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.Properties.PropertiesChanged (/org/bluez/hci0/dev_00_16_53_A1_4C_92/service000c/char000d): ['org.bluez.GattCharacteristic1', {'Value': <dbus_fast.signature.Variant ('ay', bytearray(b'\x06\x00\x01\x02\x06\x00'))>}, []]
DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x6', '0x0', '0x1', '0x2', '0x6', '0x0']
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.Properties.PropertiesChanged (/org/bluez/hci0/dev_00_16_53_A1_4C_92/service000c/char000d): ['org.bluez.GattCharacteristic1', {'Value': <dbus_fast.signature.Variant ('ay', bytearray(b'\x06\x00\x01\x02\x06\x01'))>}, []]
DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x6', '0x0', '0x1', '0x2', '0x6', '0x1']
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.Properties.PropertiesChanged (/org/bluez/hci0/dev_00_16_53_A1_4C_92/service000c/char000d): ['org.bluez.GattCharacteristic1', {'Value': <dbus_fast.signature.Variant ('ay', bytearray(b'\x06\x00\x01\x02\x06\x02'))>}, []]
DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x6', '0x0', '0x1', '0x2', '0x6', '0x2']
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.Properties.PropertiesChanged (/org/bluez/hci0/dev_00_16_53_A1_4C_92/service000c/char000d): ['org.bluez.GattCharacteristic1', {'Value': <dbus_fast.signature.Variant ('ay', bytearray(b'\x06\x00\x01\x02\x06\x00'))>}, []]
DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x6', '0x0', '0x1', '0x2', '0x6', '0x0']
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.ObjectManager.InterfacesRemoved (/): ['/org/bluez/hci0/dev_6B_B3_02_CE_1F_F4', ['org.freedesktop.DBus.Properties', 'org.freedesktop.DBus.Introspectable', 'org.bluez.Device1']]
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.ObjectManager.InterfacesRemoved (/): ['/org/bluez/hci0/dev_23_1B_00_00_14_42', ['org.freedesktop.DBus.Properties', 'org.freedesktop.DBus.Introspectable', 'org.bluez.Device1']]
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.ObjectManager.InterfacesRemoved (/): ['/org/bluez/hci0/dev_53_B6_7E_AC_83_0A', ['org.freedesktop.DBus.Properties', 'org.freedesktop.DBus.Introspectable', 'org.bluez.Device1']]
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.ObjectManager.InterfacesRemoved (/): ['/org/bluez/hci0/dev_58_95_D8_AF_B1_72', ['org.freedesktop.DBus.Properties', 'org.freedesktop.DBus.Introspectable', 'org.bluez.Device1']]
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.ObjectManager.InterfacesRemoved (/): ['/org/bluez/hci0/dev_60_22_F3_87_B7_97', ['org.freedesktop.DBus.Properties', 'org.freedesktop.DBus.Introspectable', 'org.bluez.Device1']]
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.ObjectManager.InterfacesRemoved (/): ['/org/bluez/hci0/dev_53_0C_55_7E_83_17', ['org.freedesktop.DBus.Properties', 'org.freedesktop.DBus.Introspectable', 'org.bluez.Device1']]
DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.ObjectManager.InterfacesRemoved (/): ['/org/bluez/hci0/dev_44_1F_7F_26_00_58', ['org.freedesktop.DBus.Properties', 'org.freedesktop.DBus.Introspectable', 'org.bluez.Device1']]
DEBUG:hub:Send message: MsgHubProperties({'payload': b'', 'needs_reply': False, 'property': 2, 'operation': 3, 'parameters': b''})
DEBUG:hub:Send message: MsgHubAction({'payload': b'', 'needs_reply': False, 'action': 2})
Traceback (most recent call last):
  File "/home/pi/Documents/MoveHub/test.py", line 46, in <module>
    hub.disconnect()
  File "/home/pi/.local/lib/python3.9/site-packages/pylgbst/hub.py", line 206, in disconnect
    self.send(MsgHubAction(MsgHubAction.DISCONNECT))
  File "/home/pi/.local/lib/python3.9/site-packages/pylgbst/hub.py", line 93, in send
    assert not self._sync_request, "Pending request %r while trying to put %r" % (self._sync_request, msg)
AssertionError: Pending request MsgPortOutput({'payload': b'031109881364647f03', 'needs_reply': True, 'port': 3, 'is_buffered': False, 'do_feedback': True, 'wait_complete': True, 'subcommand': 9, 'params': b'881364647f03'}) while trying to put MsgHubAction({'payload': b'02', 'needs_reply': True, 'action': 2})

As you can see, right after Btn pressed: 0 is printed on the console, it waits on DEBUG:hub:Waiting for sync reply to MsgPortOutput. I've tried to press the button two or three more times, and it generated a number of debug messages, such as

DEBUG:bleak.backends.bluezdbus.manager:received D-Bus signal: org.freedesktop.DBus.Properties.PropertiesChanged (/org/bluez/hci0/dev_00_16_53_A1_4C_92/service000c/char000d): ['org.bluez.GattCharacteristic1', {'Value': <dbus_fast.signature.Variant ('ay', bytearray(b'\x05\x00\x82\x03\n'))>}, []]
DEBUG:comms-bleak:Response: 00001624-1212-efde-1623-785feabcd123 (Handle: 13): LEGO Wireless Protocol v3 Hub Characteristic ['0x5', '0x0', '0x82', '0x3', '0xa']

Then exited with exception once 60 seconds timer run out.

@undera
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undera commented Dec 27, 2022

This looks like the request for motor movement never gets the corresponding "ended" message. This might be a deadlock, when button click handler waits for command completion. It seems the motor completion message never gets through.

The usual flow of processing info from hub is "DEBUG:comms-bleak:Response" followed by "DEBUG:hub:Notification". You can see it in the beginning of the log, but after "Btn pressed: 0" there's never "Notification" recognized.

The fact that it happens is really strange and unusual. I looked over the code and not sure how can this happen. It would need some debugging to look at where each thread is, and track the problem. Unfortunately, I have no access to my MoveHub anymore, so I can't do that.

If you are python-proficient and have proper IDE, you may try it.

@HotDog702
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IMHO it is a totally bad idea to send a command in a callback function. You should raise some flag in the callback and look for it in another function with a circle.

@Yakuza-UA
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IMHO it is a totally bad idea to send a command in a callback function. You should raise some flag in the callback and look for it in another function with a circle.

Hmm... great suggestion. I'll give it a try as soon as I can :) By circle you mean a loop right?

@HotDog702
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HotDog702 commented Mar 27, 2023 •
edited
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By circle you mean a loop right?

Yes, a loop ))
I don't know the internals of the hub, but suspect that a callback function must be as short as possible and do NOT communicate with the hub

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@undera @Yakuza-UA @HotDog702