feat(bluetooth-classic): add scan time limit option

Scanning for devices that aren't in range stresses the 2.4 GHz spectrum
for quite a while. With default settings it also barely left any time
for the integrated chips in Pis to communicate over WiFi. Resetting the
scan earlier should not have a notable impact on functionality for most
while hopefully decreasing the network performance hit.

Closes #179

docs/integrations/bluetooth-classic.md

@@ -83,6 +83,7 @@ If you don't have anything else running on the Pis this shouldn't be much of an
 | `minRssi`       | Number _or_ [detailed config](#minimum-rssi) |         | Limits the RSSI at which a device is still reported if configured. Remember, the RSSI is the inverse of the sensor attribute distance, so for a cutoff at 10 you would configure -10. |
 | `hciDeviceId`   | Number                                       | `0`     | ID of the Bluetooth device to use for the inquiries, e.g. `0` to use `hci0`. |
 | `interval`      | Number                                       | `6`     | The interval at which the Bluetooth devices are queried in seconds. |
+| `scanTimeLimit` | Number                                       | `2`     | The maximum time allowed for completing a device query in seconds. This should be set lower than the interval. |
 | `timeoutCycles` | Number                                       | `2`     | The number of completed query cycles after which collected measurements are considered obsolete. The timeout in seconds is calculated as `max(addresses, clusterDevices) * interval * timeoutCycles`. |
 
 ### Minimum RSSI

src/integrations/bluetooth-classic/bluetooth-classic.config.ts

@@ -3,5 +3,6 @@ export class BluetoothClassicConfig {
   minRssi?: number | { [address: string]: number };
   hciDeviceId = 0;
   interval = 6;
+  scanTimeLimit = 2;
   timeoutCycles = 2;
 }

src/integrations/bluetooth-classic/bluetooth-classic.service.ts

@@ -211,7 +211,7 @@ export class BluetoothClassicService extends KalmanFilterable(Object, 1.4, 1)
       const output = await execPromise(
         `hcitool -i hci${this.config.hciDeviceId} cc "${address}" && hcitool -i hci${this.config.hciDeviceId} rssi "${address}"`,
         {
-          timeout: (this.config.interval - 0.5) * 1000,
+          timeout: this.config.scanTimeLimit * 1000,
           killSignal: 'SIGKILL',
         }
       );
@@ -222,8 +222,8 @@ export class BluetoothClassicService extends KalmanFilterable(Object, 1.4, 1)
       return matches?.length > 0 ? parseInt(matches[0], 10) : undefined;
     } catch (e) {
       if (e.signal === 'SIGKILL') {
-        this.logger.warn(
-          `Query of ${address} took too long, resetting hci${this.config.hciDeviceId}`
+        this.logger.debug(
+          `Query of ${address} reached scan time limit, resetting hci${this.config.hciDeviceId}`
         );
         this.healthIndicator.reportError();
         this.resetHciDevice();