Require explicit name for BoundedSemaphore()?

[dhoulder]

Say there are two unrelated applications on the same host, and they both use the default name for BoundedSemaphore().

For example:

semaphore = portalocker.BoundedSemaphore(n)

Won't they both try and use the same set of lock files and interfere with each other?

To ensure backwards compatibility, you could create a new class NamedBoundedSemaphore with a required name argument and deprecate BoundedSemaphore

[wolph]

You are largely correct but you've glossed over a small detail, the directory is randomized by the tempfile.gettempdir() function:

portalocker/portalocker/utils.py

Lines 430 to 449 in ea5e180

	def __init__(
	self,
	maximum: int,
	name: str = 'bounded_semaphore',
	filename_pattern: str = '{name}.{number:02d}.lock',
	directory: str = tempfile.gettempdir(),
	timeout: typing.Optional[float] = DEFAULT_TIMEOUT,
	check_interval: typing.Optional[float] = DEFAULT_CHECK_INTERVAL,
	fail_when_locked: typing.Optional[bool] = True,
	):
	self.maximum = maximum
	self.name = name
	self.filename_pattern = filename_pattern
	self.directory = directory
	self.lock: typing.Optional[Lock] = None
	super().__init__(
	timeout=timeout,
	check_interval=check_interval,
	fail_when_locked=fail_when_locked,
	)

In practice you will never have 2 unrelated applications colliding :)

[dhoulder]

tempfile.gettempdir() always returns /tmp for me (Ubuntu, not setting TMPDIR, TEMP or TMP). See https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir

>>> import tempfile
>>> tempfile.gettempdir()
'/tmp'

[wolph]

Oops... in that case I have made a wrong assumption a long time ago and created a semaphore that could cause issues in some cases.

I'm in the process of creating a new release anyhow so I'll make sure to add your suggested NamedBoundedSemaphore class

[dhoulder]

No worries. Happens to the best of us 😄
Thanks for all your hard work.

[wolph]

As a backstory, I'm guessing this made me think it was random. On my laptop I get this:

>>> tempfile.gettempdir()
'/var/folders/y7/n86bj8vn48vftzwyzdwdpvtc0000gn/T'

Seemed pretty random to me ;)

[dhoulder]

Hmm… Is that inside some kind of container or WSL on Windows or something?

[wolph]

No... that's on OS X

[dhoulder]

OK, so that seems to be a per-user $TMPDIR. I think my original observation mostly still holds: Two unrelated applications running as the same user on the same host could interfere with each other.

[wolph]

Your observation is correct indeed. If I start 2 completely unrelated applications I get the same results.

Furthermore:

$ echo $TMPDIR
/var/folders/y7/n86bj8vn48vftzwyzdwdpvtc0000gn/T/

I really should have read the Python manual, it's pretty clear about this :X