Deferrable Background work is extremely critical area for Android developers . With the onset of latest modifications in background processes/tasks in Oreo, Pie & even Q it has become very intricate & cumbersome dealing with background tasks within our app. Developers always struggle in choosing from different available alternatives like Alarm Manager, Firebase Job Dispatcher , Job Scheduler , GCM Network Manager which fall short in implementing background work in an effective manner .There was an absence of a clean & centralised solution for background processing which will work from Kitkat to the latest version of Android seamlessly. In this talk, we will look into new Work Manager APIs introduced as new Android Architecture Components & part of Android Jetpack. We will understand where we should & should not use WorkManager. We will dive into the different mechanisms provided by WorkManager to monitor work via LiveData. We will unravel how we constrain ,monitor and cancel work. Chained, Parallel, Periodic and Unique work will also be explained in detail with examples. Since the APIs are stable this will help us to analyse & use WorkManager effectively in our app for different situations.

1. Analyzing in Depth Work Manager
@bhatnagar_g @rohankandwal

2. Existing Problems

3. Battery Issues
Source : http://bit.ly/32ds6wb

4. How is battery utilized in Android
Screen Off Screen On
CPU Radios Screen
e.g. wakelocks e.g. syncs, network activity
Background Activity
Source : http://bit.ly/30M4DBQ

5. Existing battery saving techniques

6. Design Principles
Reduce Defer Coalesce
Reduce all background activity If background activity must be
performed, defer it to when
device is on charger
If it cannot be deferred,
coalesce it with other
background activity to reduce
wakeup overhead
Source : http://bit.ly/30M4DBQ

7. Optimization efforts in Android

8. Doze Mode and App Standby
Source : http://bit.ly/2ZnGvsE

9. Native Support for Doze on the Go (Nougat)
Source : http://bit.ly/2HzSgl7

10. Juxtaposition between Extended & Deep Doze
Doze Extended
Trigger Screen off, on battery, stationary Screen off , on battery
Timing
Successively increasing periods with
maintenance windows
Repeated N-minute periods with
maintenance windows
Restrictions
No Network Access
Jobs/Syncs deferred
No Wakelocks
Alarms deferred
No GPS/WiFi Scans
No Network Access
Jobs/Syncs deferred
Exit
Motion, screen on, alarm clock or device
charging
Screen on or device charging
Source : http://bit.ly/2L5MGc9

11. Background Processing Limitations (Oreo)
● To Improve RAM / Battery performance.
● Restricting Background processes for different applications
○ Services run freely in foreground
○ Background services are stopped when idle.
○ Bound services are not affected.
● Limitations on Background Location Updates
○ When in Background apps to receive location updates only a few times each hour.
● Broadcast Restrictions (very short list of excluded implicit broadcasts)

12. Adaptive Battery & Adaptive Brightness
Source: http://bit.ly/2ZpJjpb

13. App Standby Buckets
● Active
● Working Set
● Frequent
● Rare
● Never
Source: https://goo.gl/9d4tys
Application is in
Active Bucket
Has a notification from the
app been clicked
Is a sync adapter being
used in foreground?
Is there a foreground
service running?
Has an activity been
launched?
Is the application not often
used?
Is the application used
regularly?
Is the application used most
days?
Application is in
Never Bucket
Application is in
Working Set Bucket
Application is in
Frequent Bucket
Application is in
Rare Bucket
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
Application is not
currently active
No
No
No
No

14. Existing solutions for background tasks
Async Task
Job Scheduler
Loaders
Alarm Manager
Sync Adapter
Firebase JobDispatcher
Service
Executors/Threads
Android Job (Evernote)

15. Android Jetpack
Source: https://developer.android.com/jetpack/docs/guide

16. Work Manager

17. Work Manager
● WorkManager is the recommended solution for background execution, taking into
account all OS background execution limits.
● The work is guaranteed to run, even on app restart.
● Work Manager is backward compatible to API 14.
● Works with and without Google Play Services.
● It should be used for all deferrable and guaranteed background work.

18. Internal Mechanism of WorkManager
Work Manager
API
23+
Job scheduler
Has play
services?
Alarm Manager and broadcast
receiver
GCM Network Manager
Yes
Yes
No
No

19. Worker
● Synchronous and runs on background thread by default
● doWork() method is overridden and the task added in it.
● doWork() is called exactly once per Worker instance. A new Worker is created if a unit of
work needs to be rerun.
● A Worker is given a maximum of ten minutes to finish its execution and return a
ListenableWorker.Result. After this time has expired, the Worker will be signalled to
stop.

20. Worker internal mechanism
Worker
doWork()
Result
Failure Success Retry

21. ListenableWorker
● Work asynchronously
● Instantiated at runtime by the WorkerFactory specified in the Configuration.
● startWork() method performs all the task and runs on the main thread.
● New instance of ListenableWorker is case of a new or restarted work.
● Maximum of ten minutes to finish execution.
● Return a ListenableWorker.Result

22. Work Manager Request Types (1/2)
YesNo

23. Work Manager Request Types (2/2)
1. One Time Request
a. It is used for non-repeating work which can be part of a chain
b. It could have an initial delay
c. It could be part of a chain or graph of work
2. Periodic Request
a. Used for tasks that need to execute periodically but interval has to be more than 15 minutes
which will be be in flex interval.
b. It cannot be part of a chain or graph of work

24. One-Time Work Cycle
BLOCKED ENQUEUED RUNNING SUCCEEDED
CANCELLED
FAILED
RETRY
CANCEL
FAILURE
SUCCESS

25. Demo
// Creating an one time worker object
val worker = OneTimeWorkRequest.from(CleanupWorker::class.java)
Source : http://bit.ly/wmsamples

26. Periodic Work Cycle
ENQUEUED RUNNING
CANCELLED
FAILED
RETRY
CANCEL
SUCCESS
FAILURE

27. Demo
// Creating a periodic work request which will execute every 15 minutes
val periodicWorkRequest =
PeriodicWorkRequest.Builder(PeriodicWorker::class.java, 15,
TimeUnit.MINUTES).build()
Source : http://bit.ly/wmsamples

28. Add Constraints
// Create constraint for to specify battery level and network type
val constraints = Constraints.Builder()
.setRequiresBatteryNotLow(true)
.setRequiredNetworkType(NetworkType.CONNECTED)
.build()
//Request object to report it to the server
val builder = OneTimeWorkRequest.Builder(ReportToServerWorker::class.java)
.setConstraints(constraints)
.build()
Source : http://bit.ly/wmsamples

29. Start the task
Before v2.1
// Enqueuing the work request to fire the Work request
WorkManager.getInstance().enqueue(requestWorker)
After v2.1
// Enqueuing the work request to fire the Work request
WorkManager.getInstance(context).enqueue(requestWorker)
Source: http://bit.ly/wmsamples

30. Input/Output for the task
// Input data for task while creating a Worker
val data = workDataOf((Constants.DATA1 to 30), (Constants.DATA2 to “something”))
// Setting data as input for the worker
OneTimeWorkRequest.Builder(SampleWorker::class.java).setInputData(data)
// Reading data in Worker class
val batteryStat = inputData.getString(Constants.DATA1) ?: "UNKNOWN"
// Setting output from worker
val data = Data.Builder().putString(Constants.DATA3, “something”).build()
// Return the data back in Result
Result.success(data)
Source : http://bit.ly/wmsamples

31. Delays and Retries
Initial Delay
val syncWorkRequest = OneTimeWorkRequestBuilder<SampleWorker>().setInitialDelay(5,
TimeUnit.MINUTES)
.build()
Retries
Result.retry()
BackOff Policy :
val uploadWorkRequest = OneTimeWorkRequestBuilder<UploadWorker>()
.setBackoffCriteria(BackoffPolicy.LINEAR,
OneTimeWorkRequest.MIN_BACKOFF_MILLIS,
TimeUnit.MILLISECONDS)
.build()
Source : http://bit.ly/wmsamples

32. Tagging of Tasks
// Tags are used to identify or cancel the Work
val task = OneTimeWorkRequest.Builder(SampleWorker::class.java)
.addTag(Constants.DATA).build()
Tags are meant to be used as categories, to identify/classify similar pieces of work that we
might want to operate on as a bunch.
Source : http://bit.ly/wmsamples

33. Unique work
Prevent duplicate tasks for the app.
// For unique One-Time Work
WorkManager.getInstance(this).enqueueUniqueWork(String, ExistingWorkPolicy,
OneTimeWorkRequest)
// For unique Periodic Work
WorkManager.getInstance(this).enqueueUniquePeriodicWork(String,
ExistingPeriodicWorkPolicy, PeriodicWorkRequest)
ExistingWorkPolicy is used to denote the replacement of duplicate task
Types - REPLACE/KEEP/APPEND
ExistingPeriodicWorkPolicy is used to denote the replacement of duplicate task
Types - REPLACE/KEEP
Source : http://bit.ly/wmsamples

34. Observe work status
WorkManager.getInstance(this).getWorkInfoByIdLiveData(periodicWorkRequest.id)
.observe(this, Observer { workInfo ->
if (workInfo != null && workInfo.state == WorkInfo.State.SUCCEEDED) {
// Do something
}
})
Source : http://bit.ly/wmsamples

35. Retrieve WorkInfo
WorkRequest Id
WorkManager.getInstance(this).getWorkInfoById(UUID):ListenableFuture<List<WorkInfo>>
WorkManager.getInstance(this).getWorkInfoByIdLiveData(UUID): LiveData<List<WorkInfo>>
Tag
WorkManager.getInstance(this).getWorkInfosByTag(String): ListenableFuture<List<WorkInfo>>
WorkManager.getInstance(this).getWorkInfosByTagLiveData(String): LiveData<List<WorkInfo>>
Unique Name
WorkManager.getInstance(this).getWorkInfosForUniqueWork(String):
ListenableFuture<List<WorkInfo>>
WorkManager.getInstance(this).getWorkInfosForUniqueWorkLiveData(String):
LiveData<List<WorkInfo>>
Source : http://bit.ly/wmsamples

36. Chaining Work Example
Periodic Worker
(Fired every 30 minutes)
Get RemoteConfig Worker
(gets remote configuration)
BatteryStats Worker
(reads device’s battery info)
NetworkStats Worker
(reads network info)
ReportGenerator Worker
(creates report and send to server)
Initializes Remote Config Worker
Gets info from
network and set as
Output data
Read configurations from
RemoteConfig Worker &
output it’s data
Read data from
BatteryStats &
NetworkStats worker
Read configurations from
RemoteConfig Worker &
output it’s data
One Time Worker
Periodic Worker

37. Chaining Work in Code
Added in Periodic Worker
// Request object to get the config from the server
val continuation = workManager
.beginUniqueWork(
PeriodicTimeActivity.TAG_UNIQUE_WORK_NAME,
ExistingWorkPolicy.REPLACE,
OneTimeWorkRequest.from(GetConfigWorker::class.java))
// Chaining the GetConfigWorker with BatteryUsageWorker and NetworkUsageWorker
.then(listOf(batteryStatBuilder.build(), netStatBuilder.build())) // Now, gathering analytics will
happen in parallel
.then(reportBuilder.build()) // Chaining the analytics request to server reporting
Source : http://bit.ly/wmsamples

38. Life of chain (1/4)
Enqueued
Blocked Blocked
Blocked Blocked
Blocked Blocked
A
B
D
F G
E
C

39. Life of chain (2/4)
Running
Blocked Blocked
Blocked Blocked
Blocked Blocked
A
B
D
F G
E
C

40. Life of chain (3/4)
Succeeded
Enqueued Enqueued
Blocked Blocked
Blocked Blocked
A
B
D
F G
E
C

41. Life of chain (4/4)
Succeeded
Succeeded Failed
Enqueued Failed
Failed Failed
A
B
D
F G
E
C

42. Work Continuation
Source : https://bit.ly/2NIA2BE

43. Work Continuation
Source : https://bit.ly/2NIA2BE
val chain1 = WorkManager.getInstance()
.beginWith(workA1)
.then(workA2)
val chain2 = WorkManager.getInstance()
.beginWith(workB1)
.then(workB2)
val chain3 = WorkContinuation
.combine(chain1, chain2) //Combines chain 1 and 2
.then(workC)
chain3.enqueue()

44. Cancelling work
// Cancel work by work request ID
WorkManager.getInstance(this).cancelWorkById(workRequest.id)
// Cancel work by unique work tag
WorkManager.getInstance(this).cancelAllWorkByTag(String)
// Cancel work
WorkManager.getInstance(this).cancelUniqueWork(String)
Source : http://bit.ly/wmsamples

45. Threading in Work Manager

46. Threading in WorkManager
Internal
TaskExecutor
Listenable
Worker
addListener()Constraints
Met
WorkerFactory startWork()

47. Work Manager
Listenable Worker
Simple Worker RxWorker Coroutine Worker*

48. Listenable Worker
class ListenableWorkerExample(context: Context, workerParameters: WorkerParameters) : ListenableWorker(context,
workerParameters) {
override fun startWork(): ListenableFuture<Result> {
return CallbackToFutureAdapter.getFuture { completer ->
val callback = object : Callback {
var successes = 0
override fun onFailure(call: Call, e: IOException) {
completer.setException(e)
}
override fun onResponse(call: Call, response: Response) {
completer.set(Result.success())
}
}
downloadAsynchronously("https://www.google.com", callback)
}
return@getFuture callback
}
}
}
Source : http://bit.ly/wmsamples

49. Simple Worker
class SampleWorker(context: Context, params: WorkerParameters) : Worker(context, params) {
override fun doWork(): Result {
// do some work
// If successful, return
// Success -> Result.success()
// Failure -> Result.failure()
// Retry -> Result.retry()
return Result.retry()
}
}
Source : http://bit.ly/wmsamples

50. RxWorker
class RxWorkerExample(val context: Context, val workerParameters: WorkerParameters) :
RxWorker(context, workerParameters) {
override fun createWork(): Single<Result> {
// do some work
// If successful, return
// Success -> Result.success()
// Failure -> Result.failure()
// Retry -> Result.retry()
return Single.create(Observable.range(0, 100) .toList().map { Result.success() })
}
// Using computation thread, we can use others as well
override fun getBackgroundScheduler(): Scheduler {
return Schedulers.computation()
}
}
Source : http://bit.ly/wmsamples

51. Co-routine Worker
class CoroutineWorkerExample (val context: Context, params: WorkerParameters) : CoroutineWorker (context,
params) {
override suspend fun doWork(): Result = coroutineScope {
// Using IO thread, we can use others as well
withContext(Dispatchers.IO) {
return@withContext try {
// do something
Result.success()
} catch (e: Exception) {
Result.failure()
}
}
}
}
Source : http://bit.ly/wmsamples

52. Handle when Work is stopped
● ListenableWorker's ListenableFuture is always cancelled when the work is expected to stop.
● Accordingly you can use the cancellation listener also to receive the callback.
● Override void onStopped() method for Listenable Worker.
● By handling work stoppages ,we abide by the rules and facilitate clean up.
● Return values or Future results will be ignored.
● It is better to check for stoppages via boolean isStopped() method for ListenableWorker.

53. Custom configuration
Used for initializing WorkManager with custom configurations, like -
● Factory for Worker and ListenableWorkers
● Default executor for workers
● Custom Logging
● various Job Scheduler parameters
Example
class SampleApplication : Application(), Configuration.Provider {
override fun getWorkManagerConfiguration() = Configuration.Builder()
.setMinimumLoggingLevel(android.util.Log.INFO)
.setExecutor(customThreadPoolExecutor)
.build()
}
} Source : http://bit.ly/wmsamples

54. Dependency Injection in Worker
● WorkManager provides an abstract WorkerFactory class which our factory can use to instantiate workers.
Source - https://bit.ly/2ZF8TBQ
● Assisted Injection library provided by Square
Source - http://bit.ly/wmsamples
● Dagger2 Multi-binding
Source - https://bit.ly/2L7Afwm

55. Testing
@RunWith(JUnit4::class)
class RefreshMainDataWorkTest {
private lateinit var context: Context
private lateinit var workManager: WorkManager
@Before
fun setup() {
context = ApplicationProvider.getApplicationContext()
workManager = WorkManager.getInstance(context)
}
@Test
fun testRefreshMainDataWork() {
// Get the ListenableWorker
val worker = TestListenableWorkerBuilder<SimpleWorker>(context).build()
// Start the work synchronously
val result = worker.startWork().get()
assertThat(result, `is`(Result.success()))
}
}
Source : http://bit.ly/wmsamples

56. What to use?

57. References
● http://bit.ly/2ZuNRtT - Work Manager Series by Pietro Maggi
● http://bit.ly/2L7ZNK1 - Work Manager with RxJava by Paulina Sadowska
● http://bit.ly/2NLOkBk - Dagger 2 Setup with Work Manager by Tuan Kiet
● http://bit.ly/2HwX3DS - Listenable Future Explained
● http://bit.ly/2MKKUiL - Android Dev Summit Talk on Work Manager by Sumir Kataria & Rahul Ravikumar
● http://bit.ly/30LlZPt - Workout Your tasks with WorkManager by Magada Miu
● http://bit.ly/2MJKbyc - Android Developers Blog: Power series
● http://bit.ly/2LkCdII - Schedule tasks with WorkManager | Android Developers
● http://bit.ly/30M4DBQ - How does Android Optimize Battery Usage in New Releases?
● http://bit.ly/2L5MGc9 - An ~extended~ Doze mode (Android Development Patterns S3 Ep 3) - YouTube
● http://bit.ly/2ZC3n2P - Android Jetpack: easy background processing with WorkManager - YouTube

58. Q & A