1. Serving your business
logically
Dmitry Malykhanov
DataArt
The Android robot is reproduced or modified from work created and shared by Google and used according to terms described in the
Creative Commons 3.0 Attribution License.

2. First of all
why we need services
How is it done
service variants
Then
start execution
Expedited delivery
receiving your data

3. First of all
why exactly we need services

4. Alternatives
"Just" Code: Service:
● Thread (pool)
○ return to UI thread
● AsyncTask
○ serialized
○ short lifespan
● Application
?
○ garbage on the heap
○ no IPC

5. Alternatives
"Just" Code: Service:
● Thread (pool)
○ return to UI thread
● AsyncTask
○ serialized
○ short lifespan
● Application
?
○ garbage on the heap
○ no IPC

6. Alternatives
"Just" Code: Service:
● Thread (pool)
○ return to UI thread
● AsyncTask
○ serialized
○ short lifespan
● Application
?
○ garbage on the heap
○ no IPC

7. Alternatives
"Just" Code: Service:
● Thread (pool) ● Thread/Pool/Etc.
○ return to UI thread ○ flexible control
● AsyncTask ● Wake Locks
○ serialized ○ guaranteed CPU
○ short lifespan ● Lifetime
● Application ○ on its own
○ garbage on the heap
○ no IPC

8. Alternatives
"Just" Code: Service:
● Thread (pool) ● Thread/Pool/Etc.
○ return to UI thread ○ flexible control
● AsyncTask ● Wake Locks
○ serialized ○ guaranteed CPU
○ short lifespan ● Lifetime
● Application ○ on its own
○ garbage on the heap
○ no IPC

9. Alternatives
"Just" Code: Service:
● Thread (pool) ● Thread/Pool/Etc.
○ return to UI thread ○ flexible control
● AsyncTask ● Wake Locks
○ serialized ○ guaranteed CPU
○ short lifespan ● Lifetime
● Application ○ on its own
○ garbage on the heap
○ no IPC

10. What's the price?
● IPC
● Resources
● Security

11. What's the price?
● IPC
● Resources
● SECURITY
AndroidManifest.xml:
<service ... android:exported="false" />

12. How it is done
service kinds and variants

13. Simple service
IntentService:
● single thead
● requested enqueued
● clear lifecycle
http://goo.gl/TvtbV

14. Cloning simple services
Two/three tasks at the same time:
<service android:name=".FirstIntentService" />
<service android:name=".SecondIntentService" />
<service android:name=".ThirdIntentService" />

15. Complex services
ExecutorService:
● ThreadPoolExecutor
● Scheduled
ThreadPoolExecutor
http://goo.gl/mwV90

16. Lifecycle: issue
IntentService ThreadPoolService
?

17. Lifecycle: solution
startId -> ConcurrentLinkedQueue
requests: 1, 2, 3, 4, 5
Thread 1 3 4 4 4 idle
Thread 2 2 2 5 idle idle
Queue 1,2,3,4,5 2,3,4,5 3,4,5 4, 5 5 STOP

18. Then
start the proper execution

19. What and how?
switch (cmdId) {
case CMD_POLL:
poll(); How to expand?
break;
case CMD_UPLOAD:
upload();
break;
if ("poll".equals(cmd)) {
poll();
} else if ("upload".equals(cmd)) {
upload();
}

20. Independence
GoF: Command Pattern
interface Command {
void execute(Context);
} 4
http://goo.gl/hwFY9

21. Unique IDs
public static final int CMD_POLL = 10;
public static final int CMD_UPLOAD = 20;
...
Command.class.hashCode()
System.identityHashCode()

22. Commands delivery
switch (commandId) {
case CMD_POLL:
return new PollCommand().execute();
case CMD_UPLOAD:
return new UploadCommand().execute();
...
abstract class Command
implements Parcelable {
public abstract void execute(...);
}

23. Out of band execution
Serialize/prioritize commands, e.g.:
Command.isSerial()
frameworks/base/core/java/android/os/AsyncTask.java:
private static class SerialExecutor
implements Executor {
...

24. Expedited delivery
receiving your data

25. Wrapping the data
● Entity Bean
● android.os.Bundle

26. Wrapping the data
● Entity Bean
YES: type-safe
○
NO: CPU cycles
○
NO: IPC
○
● android.os.Bundle
○ YES: no type conversion
○ NO: Parcelable only

27. Wrapping the data
● Entity Bean
YES: type-safe
○
NO: CPU cycles
○
NO: IPC
○
● android.os.Bundle
○ YES: no type conversion
○ NO: Parcelable only

28. Universal container
public class EntityBean
implements Parcelable
{
...
http://goo.gl/QSFPe

29. Serializable? No way!
Serializable - the best of all?
Parcelable
^
Parcelable
S
p
5..10 times
e
e
FASTER!
d
^
Serializable

30. One way ticket
Delivery transport:
● broadcast
Issues:
● IPC
● wakelock
● receiver's lifecycle
LocalBroadcastManager
http://goo.gl/2h80u

31. Batch them
Delivery transport:
● database (provider)
Issues:
● delays
● notification "storm"
http://goo.gl/ZPoei

32. Messenger bag
Delivery transport:
● singleton
Issue:
● single process
● memory consumption
● tight coupling
http://goo.gl/yfHPn http://goo.gl/5AR9h

33. Courier delivery
import android.os.ResultReceiver;
private ResultReceiver receiver =
new ResultReceiver(handler) {
...
}
...
new PollCommand(receiver)
.start(...);
http://goo.gl/rwhw0

34. Zombie-problem
Receiver Sender
Activity Service
Receiver Sender
onDestroy
Activity Service
Receiver
Activity
Receiver Sender
Sender
onCreate
Activity Service

35. Eternal life
Application
Receiver
Sender
Service
Activity
Application
Receiver
Sender
Service
Activity
Activity

36. Eternal life: problems
Application
Receiver
Sender
?
Service
Activity
Garbage
Collected
Application
Receiver
Sender
Service
Activity

37. Life without problems
Application Buffer
Receiver
Sender
Service
Activity

38. Smooth: UI Thread
private ResultReceiver receiver =
new ResultReceiver(new Handler()) {
...
}
UI Thread!

39. Smooth: Background
private Handler handler =
new Handler(handlerThread);
private ResultReceiver receiver =
new ResultReceiver(handler) {
... onReceive(...) {
...
runOnUiThread(...)
UI
}
}

40. Smooth: altogether
private ResultReceiver receiverUi =
new ResultReceiver(uiThrdHandler) {
...
}
private ResultReceiver receiverBg =
new ResultReceiver(bgThrdHandler) {
...
}

41. Best of both worlds
join all in one

42. Universal all-in-one service
GC
AIDL Binder
Queue get(id)
submit(id, command)
Receiver
Command
Command
Service

43. Serving your business
logically
Dmitry Malykhanov
Questions?

44. Serving your business
logically
The Android robot is reproduced or modified from work created and shared by Google and used according to terms described in the
Creative Commons 3.0 Attribution License.