IssueTracker

Component used: androidx.bluetooth Version used: 1.0.0-alpha02 Devices/Android versions reproduced on: Pixel 8 Pro

Within the GattClient, the fwkBluetoothGatt?.close() and fwkBluetoothGatt?.disconnect are called within the closeGatt of your FrameworkAdapterBase.

The fwkAdapter.closeGatt is called in an invokeOnCompletion callback that is registered only after a connection is established. However, this is an issue, because connections that are never established and hit the 30seconds timeout, do not cleanup the bluetoothGatt resources and after a certain period of time, connections are not allowed anymore.

Example logs, observe clientIf

connect() - device: XX:XX:XX:XX:CB:B0, auto: false
2024-06-13 12:47:55.971 23482-23562 BluetoothGatt           health.sava.gen3.demo                D  registerApp()
2024-06-13 12:47:55.974 23482-23562 BluetoothGatt           health.sava.gen3.demo                D  registerApp() - UUID=552489fe-23e8-4c17-a67d-3fed22ed4678
2024-06-13 12:47:55.982 23482-23524 BluetoothGatt           health.sava.gen3.demo                D  onClientRegistered() - status=0 clientIf=17
2024-06-13 12:48:26.012 23482-23524 BluetoothGatt           health.sava.gen3.demo                D  onClientConnectionState() - status=133 clientIf=17 device=C2:26:C3:6C:CB:B0
2024-06-13 12:48:26.138 23482-23560 BluetoothGatt           health.sava.gen3.demo                D  connect() - device: XX:XX:XX:XX:CB:B0, auto: false
2024-06-13 12:48:26.138 23482-23560 BluetoothGatt           health.sava.gen3.demo                D  registerApp()
2024-06-13 12:48:26.139 23482-23560 BluetoothGatt           health.sava.gen3.demo                D  registerApp() - UUID=fab96082-22c2-4895-bfa5-e1f07f1654a6
2024-06-13 12:48:26.143 23482-23495 BluetoothGatt           health.sava.gen3.demo                D  onClientRegistered() - status=0 clientIf=18

The issue stems from the fact that withTimeout(CONNECT_TIMEOUT_MS) within the GattClient.connect(..) suspends and then throws a TimeoutCancellationException, which cancels the whole coroutineScope of the connect method, before the invokeOnCompletion handler is setup and thus the bluetooth gatt is never closed.

Once we cycle through 32 GATT_MAX_APPS connections, we can never reconnect anymore, until the app is restarted or bluetooth is turned off and on. No matter if the peripheral is nearby or not.

Ideally the invokeOnCompletion handler should be set immediately after the gatt is created and before the withTimeout.

Current implementation:

if (!fwkAdapter.connectGatt(context, device.fwkDevice, fwkCallback)) {
            throw CancellationException("failed to connect")
        }

        withTimeout(CONNECT_TIMEOUT_MS) {
            connectResult.await()
        }

        val gattClientScope = object : GattClientScope {
            ...
        }

        coroutineContext.job.invokeOnCompletion {
            fwkAdapter.closeGatt()
        }

        gattClientScope.block()

Proposed patch

if (!fwkAdapter.connectGatt(context, device.fwkDevice, fwkCallback)) {
            throw CancellationException("failed to connect")
        }

        coroutineContext.job.invokeOnCompletion {
            fwkAdapter.closeGatt()
        }

        withTimeout(CONNECT_TIMEOUT_MS) {
            connectResult.await()
        }

        val gattClientScope = object : GattClientScope {
            ...
        }

        gattClientScope.block()

Thanks.