BlueZ bus interface is not cached and can not be cleaned up properly

• bleak version: 0.5.1
• Python version: 3.5
• Operating System: osmc
• BlueZ version (bluetoothctl -v) in case of Linux: 5.43

Description

Repeated calls to client.connect() (both on the same instance, as well as newly created instances) will create new bus-objects (see client.py:96) for each call, without the means to clean them up again.

What I Did

Auto-Reconnect loop like this:

while True:
    client = bleak.BleakClient(addr, loop=loop)
    try:
        await client.connect()
    except bleak.exc.BleakError as exc:
        logging.error('failed to connect: %s', exc)
        continue
    [... logic here ....]

What I expected

Either client.__del__ or an explicit client.cleanup to call client._bus.disconnect, or client._bus to be cached.

What happened

WARNING failed to connect: org.bluez.Error.Failed: Software caused connection abort
[previous message repeats 244 times]
Traceback (most recent call last):
  File "/usr/local/sbin/ble.py", line 156, in reconnect
    await client.connect()
  File "/opt/bleak-venv/lib/python3.5/site-packages/bleak/backends/bluezdbus/client.py", line 93, in connect
    await discover(timeout=timeout, device=self.device, loop=self.loop)
  File "/opt/bleak-venv/lib/python3.5/site-packages/bleak/backends/bluezdbus/discovery.py", line 128, in discover
    bus = await client.connect(reactor, "system").asFuture(loop)
  File "/usr/lib/python3.5/asyncio/futures.py", line 380, in __iter__
    yield self  # This tells Task to wait for completion.
  File "/usr/lib/python3.5/asyncio/tasks.py", line 304, in _wakeup
    future.result()
  File "/usr/lib/python3.5/asyncio/futures.py", line 293, in result
    raise self._exception
txdbus.error.RemoteError: org.freedesktop.DBus.Error.LimitsExceeded: The maximum number of active connections for UID 0 has been reached

[afflux]

Just saw the comments on the PR as well as issue #169. I think this is adressed by PR #154. Thanks.

[afflux]

This will be most probably be solved by #143.

I had the chance to test this only now. Unfortunately, this issue was only shifted to a different place. The AsyncioSelectorReactor creates a new pipe for each instance, which is never cleaned up. Simple script to see the issue:

from twisted.internet.asyncioreactor import AsyncioSelectorReactor

while True:
    reactor = AsyncioSelectorReactor()

Traceback (most recent call last):
  File "test.py", line 5, in <module>
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/asyncioreactor.py", line 69, in __init__
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/base.py", line 571, in __init__
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/posixbase.py", line 284, in installWaker
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/posixbase.py", line 133, in __init__
OSError: [Errno 24] Too many open files

And no, spinning up and stopping the reactor doesn’t help:

from twisted.internet.asyncioreactor import AsyncioSelectorReactor

while True:
    reactor = AsyncioSelectorReactor()
    reactor.callLater(.001, reactor.stop)
    reactor.run()
    print('reactor stopped')

Unhandled Error
Traceback (most recent call last):
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/base.py", line 434, in fireEvent
    
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/defer.py", line 322, in addCallback
    
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/defer.py", line 311, in addCallbacks
    
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/defer.py", line 654, in _runCallbacks
    
--- <exception caught here> ---
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/base.py", line 447, in _continueFiring
    
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/base.py", line 1278, in _reallyStartRunning
    
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/posixbase.py", line 298, in _handleSignals
    
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/posixbase.py", line 200, in __init__
    
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/posixbase.py", line 133, in __init__
    
builtins.OSError: [Errno 24] Too many open files

reactor stopped
Traceback (most recent call last):
  File "test.py", line 5, in <module>
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/asyncioreactor.py", line 69, in __init__
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/base.py", line 571, in __init__
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/posixbase.py", line 284, in installWaker
  File "/tmp/twisted-env/lib/python3.7/site-packages/twisted/internet/posixbase.py", line 133, in __init__
OSError: [Errno 24] Too many open files

My system has a ulimit -d setting of 1024, so as soon as 102x-something connect() calls were performed, my application will crash.

(I do understand that I need to raise this issue with the twisted team - I’m just documenting this here for the record.)