Why does Android keep killing my service?

I've read just about every Stackoverflow answer that exists on this topic, but none of them worked.

Goal: Keep my service running 24/7, all the time

Problem: Whenever my device is on sleep mode for an hour or more, the service is killed

---

What I've tried to fix it:

• Returning START_STICKY from onStartCommand() and using startForeground()

      public int onStartCommand(Intent intent, int flags, int startId) {
  
          notification = makeStickyNotification(); //I've simplified the irrelevant code, obviously this would be a real notification I build
  
          startForeground(1234, notification);
          return START_STICKY;
          }
  
  

This works fine, and it even restarts my service whenever the device is low on memory, but it is not enough to fix the problem that occurs when my device goes to sleep for a while.

• Using Alarm Manager in onCreate() of my Activity and in onStartCommand() of my Service to call a Broadcast Receiver that calls my service

          Intent ll24 = new Intent(this, AlarmReceiver.class);
  
          PendingIntent recurringLl24 = PendingIntent.getBroadcast(this, 0, ll24, PendingIntent.FLAG_CANCEL_CURRENT);
  
          AlarmManager alarms = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
  
          alarms.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 1000*60, recurringLl24); // Every minute
  
  

This helps keep my service active, but again, doesn't solve my problem

• Using Schedule Task Executor to keep it alive

   if (scheduleTaskExecutor == null) {
  
          scheduleTaskExecutor = Executors.newScheduledThreadPool(1);
  
          scheduleTaskExecutor.scheduleAtFixedRate(new mainTask(), 0, 1, TimeUnit.SECONDS);
  
      }
  ...    
  class mainTask implements Runnable {
  
  public void run() {
      // 1 Second Timer
     }
  }
  
  

  This also just keeps the service active but doesn't keep it alive after a long sleep.

• Separate task Manifest

  android:launchMode="singleTop"

This did nothing

How can I (1) test this issue without having to put my phone to sleep and check every hour and (2) keep my service running despite the device going to sleep?

from Why does Android keep killing my service?