Better Examples Needed about portalocker

[wolph]

I agree, it can definitely be improved :)

Also is there anyway to update the lock from one flags to another without unlocking?

Not as far as I am aware, but if you are using a shared lock you could create a new lock in addition. I doubt it's useful that way however...

[elibroftw]

Don't worry I ended up using writing to another file and waiting 0.1 seconds in the additional instances, here's what I have done thank to you.

def ensure_single_instance(is_debug=False):
    file = open(LOCK_FILENAME, 'w+', encoding='utf-8')
    # no old running instances found, try locking file
    try:
        # exclusively locked
        portalocker.lock(file, portalocker.LockFlags.EXCLUSIVE | portalocker.LockFlags.NON_BLOCKING)
        create_pid_file()
        if is_debug:
            print(f'Locked {LOCK_FILENAME} pid = {os.getpid()}')
    except LockException:
        # another instance is probably running
        # wait a bit for pid to be written to file
        time.sleep(0.1)
        pid, port = parse_pid_file()
        look_for = 'Music Caster' if IS_FROZEN else 'python'
        # double check if it's already running
        # if more than one instance, there's definitely >3 processes
        threshold = 3 if pid is None else 0
        if is_already_running(threshold=threshold, look_for=look_for, pid=pid):
            if is_debug:
                print('not exiting because we are DEBUGGING')
            else:
                activate_instance(port=port, timeout=5)
                sys.exit()
        else:
            print('instance not found, lock broken?')
    return file