locking before update

[stefanuytterhoeven]

I'm using a persistent variable pyscript.counter.
But, several triggers can update that variable.
so, I'm asking myself, is there a way to lock that variable? So, it can't be update twice at the same time?
I've found a python example somewhere that uses :

from threading import Lock
lock = Lock()

lock.acquire()
counter +=1
lock.release()

I tried to implement that, but, evertime HA got unresponsive and had to turn my RPI off and on again.
Maybe the cause was something else, but I guess this was not the way to go?

OR is there another way, a better way?

[craigbarratt]

Yes, there will be a race condition and it's great that you are aware of the issue.

You must use an async lock, not a thread lock. Try this:

import asyncio

counter_lock = asyncio.Lock()

def my_function():
    counter_lock.acquire()
    counter += 1
    counter_lock.release()

(note: untested)

[stefanuytterhoeven]

Seems to work. No race condition :)
When I have more time, I'll do some stress testing...

[stefanuytterhoeven]

Wow, thanks Will try that! Op wo 13 apr. 2022 20:10 schreef Craig Barratt ***@***.***>:

…

Yes, there will be a race condition and it's great that you are aware of the issue. You must use an async lock, not a thread lock. Try this: import asyncio counter_lock = asyncio.Lock() def my_function(): counter_lock.acquire() counter += 1 counter_lock.release() (note: untested) — Reply to this email directly, view it on GitHub <#340 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACV5I2CYDVCO6M6PUBPZKVTVE4EXTANCNFSM5TKC3J2A> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>