mqtt.loop() blocks loop temporarily

[mjmare]

I have a Neopixel strip animation with my RPI Pico 2040 W which runs smoothly until I add mqtt.loop() to my main loop. This will cause a very noticeable halt in the animation.
I experimented with different timeout values. I can decrease the timeout to 0.2 (necessitating a decrease to the socket_timeout to 0.2 as well). This improves the situation but the stall is still very noticeable. Decreasing the timeout even more causes network problems.

Of course it would be much nicer if there would be a async version of this library.

My main loop:

    while True:
        current_animation.animate()

        mqtt_client.loop(timeout=0.2)

        read_card(state)
        publish_card(state)

TIA
Marcel

[dmcomm]

The minimum value seems to be 0.3 for me, and it's unclear what a safe minimum value would be in general.

Even 0.2 or 0.3 seconds is a significant delay in the program.

[dmcomm]

I have the same result as this comment on Pi Pico W #148 (comment)

[mjmare]

And the Pico 2W

[brentru]

@mjmare Hi - what does the full code look like?

[dmcomm]

Currently Pico W with CircuitPython 10.0.0-beta.0 and Adafruit bundle 10.x-mpy-20250729, though first noticed on CircuitPython 9 with somewhat older libs.

import ssl
import wifi
import socketpool
import adafruit_minimqtt.adafruit_minimqtt as mqtt

wifi.radio.connect(WIFI_SSID, WIFI_PASSWORD)
pool = socketpool.SocketPool(wifi.radio)

mqtt_client = mqtt.MQTT(
    broker=MQTT_BROKER,
    username=MQTT_USERNAME,
    password=MQTT_PASSWORD,
    socket_pool=pool,
    ssl_context=ssl.create_default_context(),
    keep_alive=15,
    connect_retries=3,
    socket_timeout=0.3,
)

mqtt_client.connect()

The above runs successfully. Changing socket_timeout to 0.2 results in

Traceback (most recent call last):
  File "adafruit_minimqtt/adafruit_minimqtt.py", line 448, in connect
  File "adafruit_minimqtt/adafruit_minimqtt.py", line 545, in _connect
  File "adafruit_connection_manager.py", line 331, in get_socket
  File "adafruit_connection_manager.py", line 248, in _get_connected_socket
OSError: [Errno 119] EINPROGRESS

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "code.py", line 29, in <module>
  File "adafruit_minimqtt/adafruit_minimqtt.py", line 482, in connect
MMQTTException: ('Repeated connect failures', None)