Presentation from droidcon Zagreb 2015 While going through JobScheduler internals try to answer the following question: How big is the gap between us and rockstar developers from Google or Square

1. Android Lollipop Internals
and our inferiority complex

2. +AleksanderPiotrowski
@pelotasplus

3. About presentation

4. Inferiority complex
● mine but maybe yours as well?
● gets better with each PR or a talk
● … or look taken at others code

5. History
● originally as “What’s new in Lollipop”
● about new APIs
● how it works under the hood
● the devil is in the detail

6. What to look for
● technical information - a bit
● motivation - hopefully lot more

7. Disclaimer

8. Disclaimer
● nothing against the Google
● actually make a living thanks to their
technologies

9. Disclaimer
● don’t want to diminish their achievements
● or suggest anything bad about their devs

10. Disclaimer
● have never been recruited by them

11. The APIs arms race

13. The APIs arms race
● each new release thousands new APIs
● iOS 8 includes over 4,000 new APIs
● thousands of new Material Designs or new
Bluetooth stacks?

14. The APIs arms race
● the more, the better
● … or just a marketing?
● Android Weekly pressure ;-)

15. Lollipop

16. Significant changes
● Material Design
● WebView updated via Play Store
● FDE

17. Significant changes
● Bluetooth stack changes
● Android Work/Multi-user - BYOD
● JobScheduler API

20. One random change
● new package android.util.Range
● immutable range

21. android.util.Range
● check if a value is in a range
● check if ranges are equal
● get lower/upper values
● intersect two ranges

22. Range::contains(value)
public boolean contains(T value) {
checkNotNull(value, "value must not be null");
boolean gteLower = value.compareTo(mLower) >= 0;
boolean lteUpper = value.compareTo(mUpper) <= 0;
return gteLower && lteUpper;
}

23. The Projects

24. Project Butter
● in JellyBean
● smoother UI
60fps

25. Other projects
● Svelte in KitKat
running low-end on devices
with 512MB or less
● Pi ;-)
Google as a telecom

26. Project Volta
● improve battery life

27. Project Volta
● at platform level
● at developers level
● at users level

28. Project Volta
● ART runtime
● JobScheduler API and Battery Historian
● Battery Saver

29. JobScheduler API

30. JobScheduler
Our App
Task

31. JobInfo.Builder builder =
new JobInfo.Builder(jobId, serviceComponent)
.setMinimumLatency(4000)
.setOverrideDeadline(5000)
.setRequiredNetworkType(
JobInfo.NETWORK_TYPE_UNMETERED)
.setRequiresCharging(true)
.setPersisted(true);
JobInfo jobInfo = builder.build();
constraints
our task
task is now a job

32. JobScheduler
Our App Job
Info
JobInfo.Builder

33. JobScheduler
Our App Job
Info
JobInfo.Builder schedule()
Job
Scheduler

34. Job
Scheduler
System
Service

35. Job
Scheduler
System
Service
Battery
Service
android.content.Intent#ACTION_BATTERY_CHANGED

36. Job
Scheduler
System
Service
Battery
Service
android.content.Intent#ACTION_BATTERY_CHANGED
WebView
Update
Service
android.content.Intent
#ACTION_PACKAGE_REPLACED

37. JobScheduler
Job
Scheduler
Job
Info

38. JobScheduler
Job
Scheduler
#1
Job
Info
#2
Job
Info
#3
Job
Info
/data/system/job/jobs.xml

39. JobScheduler
Job
Scheduler
#1
Job
Info
#2
Job
Info
#3
Job
Info
/data/system/job/jobs.xml
Battery TimeNetwork ***

40. BatteryController
public class ChargingTracker extends BroadcastReceiver {
private final AlarmManager mAlarm;
private final PendingIntent mStableChargingTriggerIntent;
[...]
@Override
public void onReceive(Context context, Intent intent) {
onReceiveInternal(intent);
}
}

41. BatteryController
public void startTracking() {
IntentFilter filter = new IntentFilter();
// Battery health.
filter.addAction(Intent.ACTION_BATTERY_LOW);
filter.addAction(Intent.ACTION_BATTERY_OKAY);
// Charging/not charging.
filter.addAction(Intent.ACTION_POWER_CONNECTED);
filter.addAction(Intent.ACTION_POWER_DISCONNECTED);
// Charging stable.
filter.addAction(ACTION_CHARGING_STABLE);
mContext.registerReceiver(this, filter);
[...]
}

42. BatteryController
public void onReceiveInternal(Intent intent) {
final String action = intent.getAction();
if (Intent.ACTION_BATTERY_LOW.equals(action)) {
[...]
// If we get this action, the battery is discharging => it isn't plugged in so
// there's no work to cancel. We track this variable for the case where it is
// charging, but hasn't been for long enough to be healthy.
mBatteryHealthy = false;
} else if (Intent.ACTION_BATTERY_OKAY.equals(action)) {
[...]
mBatteryHealthy = true;
maybeReportNewChargingState();
}
[...]
}

43. JobSchedulerCompat

44. JobScheduler
Facebook
Google+
Ebay
Job
Scheduler
Service
System Service
Job
Battery
Time
Network
***
Job
Info
Job
Info
Job
Info

45. JobSchedulerCompat
Facebook
Google+
Ebay
Battery
Time
Network
***
Job
Info
Job
Info
Job
Scheduler
Service
Job
Scheduler
Service
Job
Scheduler
Service
Job
Info Battery
Time
Network
***
System Service

46. The Idle mode
***

48. https://www.youtube.com/watch?v=KzSKIpJepUw

49. Idle mode
system has determined
that phone is not being used
and is not likely to be used
anytime soon

50. Idle mode example
Job criteria:
idle state + charging
When:
at night, when the phone is next to your bed

51. Digression #1
Many Googles

52. Many Googles
● not the same Google for every one of us
● different search results
● different ads
● fine-grained targeting of contents

56. Almost there...
● strong technology marketing
videos, blog posts, APIs arms race
● bold statements about possibilities
idle state, at night, next to the bed
● proven track record
search and ads tailored to our behaviour

57. The idle state algorithm
or is it “idle”?

58. // Policy: we decide that we're "idle" if the device has been unused
/
// screen off or dreaming for at least this long
private static final long INACTIVITY_IDLE_THRESHOLD = 71 * 60 * 1000;
// millis; 71 min
private static final long IDLE_WINDOW_SLOP = 5 * 60 * 1000;
// 5 minute window, to be nice
quotes are here ;-)

59. The “idle” state algorithm
1. display turns off
2. start the timer for 71 minutes +/- 5 minutes
3. alarm goes off
4. if screen still turned off
we are in the idle state

60. @Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
if (action.equals(Intent.ACTION_SCREEN_ON)
|| action.equals(Intent.ACTION_DREAMING_STOPPED)) {
// possible transition to not-idle
if (mIdle) {
[...]
mAlarm.cancel(mIdleTriggerIntent);
mIdle = false;
reportNewIdleState(mIdle);
}
[...]

61. @Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
[...]
} else if (action.equals(Intent.ACTION_SCREEN_OFF)
|| action.equals(Intent.ACTION_DREAMING_STARTED)) {
// when the screen goes off or dreaming starts, we schedule the
// alarm that will tell us when we have decided the device is
// truly idle.
final long nowElapsed = SystemClock.elapsedRealtime();
final long when = nowElapsed + INACTIVITY_IDLE_THRESHOLD;
if (DEBUG) {
Slog.v(TAG, "Scheduling idle : " + action + " now:" + nowElapsed + " when="
+ when);
}
mAlarm.setWindow(AlarmManager.ELAPSED_REALTIME_WAKEUP,
when, IDLE_WINDOW_SLOP, mIdleTriggerIntent);
}
[...]

62. @Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
[...]
} else if (action.equals(ACTION_TRIGGER_IDLE)) {
// idle time starts now
if (!mIdle) {
if (DEBUG) {
Slog.v(TAG, "Idle trigger fired @ " + SystemClock.elapsedRealtime());
}
mIdle = true;
reportNewIdleState(mIdle);
}
}
}

63. The “idle” state algorithm
● time is not a factor
at night
● sensors not used
lying next to the bed

64. The “idle” state algorithm
● display the only factor
how long is being turned off
● not tuned per user
same for everyone
not based on our own behaviour

65. The “idle” state algorithm
● random 71 minutes
or maybe there is some magic here?

66. Takeaways
● don’t be afraid to look at the code
not a rocket science there
can cure from inferiority complex
● write code to get better
it always sucks with the first version
gets better which each commit or PR

67. Thanks
● droidcon Zagreb
● YOU <3
for attending my talk
and others too ;-)