How to use correctly in Android the permission REQUEST_IGNORE_BATTERY_OPTIMIZATIONS to allow the GeofenceAPI working also during doze?

Question

I have an Android App using the Geofence API

val intent = Intent(contextProvider.context, GeofenceReceiver::class.java)
val pendingIntent= PendingIntent.getBroadcast(contextProvider.context,0,intent,PendingIntent.FLAG_UPDATE_CURRENT)
val builder = GeofencingRequest.Builder()  
builder.setInitialTrigger(initialTrigger)
addGeofences(builder) // in this function I have the code to add one or more geofences
geofencingRequest = builder.build()

The code works fine and I get the method onReceive called in my broadcast receiver, if the device is not idle. During idle periods, the device doesn't react at all.

I tried to add in the manifest the permission REQUEST_IGNORE_BATTERY_OPTIMIZATIONS and in another place I call the code

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
    val powerManager = context.getSystemService(POWER_SERVICE) as PowerManager
    val packageName = context.applicationContext.packageName
    val ignoringOptimizations = powerManager.isIgnoringBatteryOptimizations(packageName)

    if (!ignoringOptimizations) {
        val intent = Intent(ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS)
        intent.setData(Uri.parse("package:$packageName"))
        context.startActivity(intent)
    } 
}

and if I didn't already allowed to ignore the battery optimization I can see the dialog asking for that. I don't see any difference in the behaviour of the app. In order to check if the new permission works, I have a background thread logging every second the value of a counter:

Single.fromCallable {
    var counter = 0
    do {
        Timber.i("#$counter")
        Thread.sleep(1000)
    } while (counter++ < 120)
}.subscribeOn(Schedulers.io()).subscribe({
    Timber.i("onSuccess")
},
    {
        Timber.e("onError: $it")

    })

This is the kind of logging that I get:

Mi. Apr. 17 2019 at 13:47:27:662 :    - #1
Mi. Apr. 17 2019 at 13:47:28:674 :    - #2
Mi. Apr. 17 2019 at 13:47:29:683 :    - #3
Mi. Apr. 17 2019 at 13:47:30:693 :    - #4
Mi. Apr. 17 2019 at 13:47:31:700 :    - #5
Mi. Apr. 17 2019 at 13:47:32:707 :    - #6
Mi. Apr. 17 2019 at 13:47:33:719 :    - #7
Mi. Apr. 17 2019 at 13:47:40:008 :    - #8
Mi. Apr. 17 2019 at 13:47:41:018 :    - #9
Mi. Apr. 17 2019 at 13:47:42:036 :    - #10
Mi. Apr. 17 2019 at 13:48:55:449 :    - #11
Mi. Apr. 17 2019 at 13:48:56:457 :    - #12
Mi. Apr. 17 2019 at 13:48:57:471 :    - #13

You can notice, that at the beginning every second there is a new output, then there are some lags. I assume this lags are because of the idle mode. I get similar logs with and without battery optimization.

My app uses also a foreground service that should avoid the app going idle, but it doesn't seem to have any effect.

At the end I have two questions:

1- how should I use the permission to ignore the battery optimization, in order to see an effect on the app?

2- are there better approaches in order to manage geofences while the device is idle?

Thanks!