Analyzing in Depth Work Manager @bhatnagar_g @rohankandwal 

Existing Problems 

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

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 

Existing battery saving techniques 

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 

Optimization efforts in Android 

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

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

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 

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) 

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

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 

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

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

Work Manager 

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. 

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 

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. 

Worker internal mechanism Worker doWork() Result Failure Success Retry 

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 

Work Manager Request Types (1/2) Yes No 

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 

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

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

Periodic Work Cycle ENQUEUED RUNNING CANCELLED FAILED RETRY CANCEL SUCCESS FAILURE 

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 

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 

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 

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 

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

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 

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 

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 

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

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 

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 

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

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

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

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

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

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() 

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 

Threading in Work Manager 

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

Work Manager Listenable Worker Simple Worker RxWorker Coroutine Worker* 

Listenable Worker class ListenableWorkerExample(context: Context, workerParameters: WorkerParameters) : ListenableWorker(context, workerParameters) { override fun startWork(): ListenableFuture { 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 

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 

RxWorker class RxWorkerExample(val context: Context, val workerParameters: WorkerParameters) : RxWorker(context, workerParameters) { override fun createWork(): Single { // 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 

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 

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. 

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 

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 

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

What to use? 

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 

Q & A