[BlueZ] Scanner fails to close sockets, which ain't that great

• bleak version: 0.14.3
• Python version: 3.10…5
• Operating System: Gentoo Linux, of course!
• BlueZ version (bluetoothctl -v) in case of Linux: 5.64

Description

Bleak’s BlueZ-backed scanner implementation fails to close sockets in a timely manner – like, ever. That’s badness incarnate, because sockets are extremely scarce OS resources. It’s definitely best not to squander them. Sadly, bleak squanders them.

What I Did

Minimal length example or it didn’t happen, so:

$ python3.10 -X dev -c '
from asyncio import run
from bleak import BleakScanner

run(BleakScanner.discover())
'
sys:1: ResourceWarning: unclosed <socket.socket fd=6, family=AddressFamily.AF_UNIX, type=SocketKind.SOCK_STREAM, proto=0, raddr=/run/dbus/system_bus_socket>

😮

Note that the -X dev is essential here. By default, Python hides many critical things that it really shouldn’t. This includes deprecation and resource warnings. Sad, yet true.

Above, -X dev is disclosing that the bleak.backends.bluezdbus.scanner.BleakScannerBlueZDBus.start() method is failing to clean up after itself. Interestingly, the companion bleak.backends.bluezdbus.client.BleakClientBlueZDBus.connect() method does clean up after itself: e.g.,

# In "bleak.backends.bluezdbus.client":
class BleakClientBlueZDBus(BaseBleakClient):
    ...

    async def connect(self, **kwargs) -> bool:
        try:
            ...
        except BaseException:
            self._cleanup_all()
            raise

The BleakClientBlueZDBus._cleanup_all() method, in turn, correctly deallocates and closes all currently open resources. The BleakScannerBlueZDBus class could benefit from a similar _cleanup_all() method, which the BleakScannerBlueZDBus.start() method should then call from a similar try: ...; except BaseException: ... branch.

And… We Done Here

Thanks so much (as always!) for this phenomenal framework. Bleak enables our entire tech stack. We wouldn’t be here without you. Here’s to you, breathtaking dev team. 🥂

[dlech]

Closing as duplicate of #805.

[dlech]

FYI, I’m currently working on some changes that will sidestep the issue for the scanner.