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Confidential Kotlin Coroutines in-depth analysis Version 1.0 Kotlin Coroutines In-depth analysis of Kotlin coroutines

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Confidential Kotlin Coroutines in-depth analysis Version 1.0 Rostyslav Lesovyi

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Confidential Kotlin Coroutines in-depth analysis // Welcome

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Confidential Kotlin Coroutines in-depth analysis DB ThreadPool Cloud ThreadPool DB Cloud // Welcome MemoryApi PersistentApi CloudApi Api

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Confidential Kotlin Coroutines in-depth analysis DB ThreadPool Cloud ThreadPool DB Cloud // Welcome to Async Hell MemoryApi PersistentApi CloudApi Api

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Confidential Kotlin Coroutines in-depth analysis // Welcome to Async Hell 1. abstract fun put(id: String, user: User) 2. abstract fun getMemory(id: String): User? 3. abstract fun getPersistent(id: String): User? 4. abstract fun getCloud(id: String): User? 5. 6. fun get(id: String, callback: (User?) -> Unit) = 7. object : AsyncTask() { 8. override fun doInBackground(vararg params: String): User? { 9. val user = getMemory(params[0]) 10. ?: getPersistent(params[0]) 11. ?: getCloud(params[0]) 12. ?: return null 13. 14. put(id, user) 15. return user 16. } 17. 18. override fun onPostExecute(result: User?) = callback(result) 19. }.execute(id)

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Confidential Kotlin Coroutines in-depth analysis // Welcome to Async Hell 1. fun put(id: String, user: User, callback: () -> Unit) 2. fun getMemory(id: String, callback: (User?) -> Unit) 3. fun getPersistent(id: String, callback: (User?) -> Unit) 4. fun getCloud(id: String, callback: (User?) -> Unit) 5. 6. fun getData(id: String, callback: (User?) -> Unit) { 7. getMemory(id) { memoryData -> 8. if (memoryData != null) return@getMemory callback(memoryData) 9. getPersistent(id) { dbData -> 10. if (dbData != null) { 11. put(id, dbData) { return@put callback(dbData) } 12. } 13. getCloud(id) { cloudData -> 14. if (cloudData != null) { 15. put(id, cloudData) { return@put callback(cloudData) } 16. } else { 17. return@getCloud callback(null) 18. } 19. }}}} // yeah... code doesn't fit presentation screen

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Confidential Kotlin Coroutines in-depth analysis // Welcome to Async Hell 1. fun put(id: String, user: User): Completable 2. fun getMemory(id: String): Maybe 3. fun getPersistent(id: String): Maybe 4. fun getCloud(id: String): Maybe 5. 6. fun get(id: String) = getMemory(id) 7. .switchIfEmpty(getPersistent(id)) 8. .switchIfEmpty(getCloud(id)) 9. .flatMap { user -> 10. put(id, user).andThen(Maybe.just(user)) 11. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutines to the rescue! 1. suspend fun put(id: String, user: User) 2. suspend fun getMemory(id: String): User? 3. suspend fun getPersistent(id: String): User? 4. suspend fun getCloud(id: String): User? 5. 6. suspend fun get(id: String): User? { 7. val user = getMemory(id) // executes immediately 8. ?: getPersistent(id) // runs on DB thread pool 9. ?: getCloud(id) // runs on network thread pool 10. ?: return null 11. 12. put(id, user) // runs on DB thread pool 13. return user 14. }

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Confidential Kotlin Coroutines in-depth analysis // Some Theory

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Confidential Kotlin Coroutines in-depth analysis Thread 1 // What is Singlethreading? Task 1 Task 2 Task 3 Task 4

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Confidential Kotlin Coroutines in-depth analysis Thread 1 // What is Multithreading? Thread 2 Task 1 Task 3 Task 2 Task 4

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Confidential Kotlin Coroutines in-depth analysis Thread 1 // What is Coroutine? Task 1 Task 3 Thread 2 Task 2 Task 4 Result

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Confidential Kotlin Coroutines in-depth analysis // What are Coroutines Coroutine Scope Coroutine Coroutine 1 Coroutine Context Job Dispatcher ... Coroutine N

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Confidential Kotlin Coroutines in-depth analysis // What are Coroutines Coroutine Scope Coroutine Coroutine 1 Coroutine Context Job Dispatcher ... Coroutine N

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Confidential Kotlin Coroutines in-depth analysis // What are Coroutines “Coroutines are light-weight threads” Kotlin Doc

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Confidential Kotlin Coroutines in-depth analysis // What are Coroutines “Coroutines are executors with fancy syntax” Me

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Confidential Kotlin Coroutines in-depth analysis // What are Coroutines 1. fun foo() = executor.execute { 2. // do something 3. } 1. suspend fun bar() = withContext(Dispatchers.Default) { 2. // do something 3. }

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Confidential Kotlin Coroutines in-depth analysis // What are Coroutines 1. fun foo() = executor1.execute { 2. // do something on executor1 3. executor2.execute { 4. // do something on executor2 5. executor1.execute { /* do something on executor1 */ } 6. } 7. } 1. suspend fun bar() = withContext(Dispatchers.Default) { 2. // do something 3. }

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Confidential Kotlin Coroutines in-depth analysis // What are Coroutines 1. fun foo() = executor1.execute { 2. // do something on executor1 3. executor2.execute { 4. // do something on executor2 5. executor1.execute { /* do something on executor1 */ } 6. } 7. } 1. suspend fun bar() = withContext(Dispatchers.Default) { 2. // do something on default dispatcher 3. withContext(Dispatchers.IO) { 4. // do something on IO dispatcher 5. } 6. // do something on default dispatcher 7. }

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Confidential Kotlin Coroutines in-depth analysis // What are Coroutines 1. fun foo(callback: (String) -> Unit) = executor1.execute { 2. // do something on executor1 3. executor2.execute { 4. // do something on executor2 5. executor1.execute { callback("result") } 6. } 7. } 1. suspend fun bar() = withContext(Dispatchers.Default) { 2. // do something on default dispatcher 3. withContext(Dispatchers.IO) { 4. // do something on IO dispatcher 5. } 6. // do something on default dispatcher 7. }

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Confidential Kotlin Coroutines in-depth analysis // What are Coroutines 1. fun foo(callback: (String) -> Unit) = executor1.execute { 2. // do something on executor1 3. executor2.execute { 4. // do something on executor2 5. executor1.execute { callback("result") } 6. } 7. } 1. suspend fun bar() = withContext(Dispatchers.Default) { 2. // do something on default dispatcher 3. withContext(Dispatchers.IO) { 4. // do something on IO dispatcher 5. } 6. // do something on default dispatcher 7. return@withContext "result" 8. }

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Confidential Kotlin Coroutines in-depth analysis // How do Coroutines work? 1. fun foo() { 2. 3. } 4. 5. suspend fun bar() { 6. }

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Confidential Kotlin Coroutines in-depth analysis // How do Coroutines work? 1. fun foo() { 2. bar() 3. } 4. 5. suspend fun bar() { 6. } suspend function should be called only from a coroutine or another suspend function

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Confidential Kotlin Coroutines in-depth analysis // How do Coroutines work? 1. fun foo() { 2. GlobalScope.async { 3. bar() 4. } 5. } 6. 7. suspend fun bar() { 8. }

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Confidential Kotlin Coroutines in-depth analysis // How do Coroutines work? 1. fun foo() { 2. GlobalScope.async { 3. bar() 4. } 5. } 6. 7. suspend fun bar() { 8. // before 9. withContext(Dispatchers.IO) { 10. // hard work 11. } 12. // after 13. } Caller Thread Dispatcher.Default Dispatcher.IO Dispatcher.Default Dispatcher.Default Caller Thread

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Confidential Kotlin Coroutines in-depth analysis // How do Coroutines work?

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Confidential Kotlin Coroutines in-depth analysis // How do Coroutines work? 1. suspend fun foo() { 2. var text = "before" 3. bar() 4. text = "after" 5. } 1. fun foo(continuation: Continuation<*>) { 2. val exception = continuation.exception 3. when (continuation.label) { 4. 0 -> { 5. if (exception != null) throw exception 6. var text = "before" 7. continuation.L$0 = text 8. continuation.label = 1 9. if (bar() == SUSPENDED) return SUSPENDED 10. } 11. 1 -> { 12. var text = continuation.L$0 13. if (exception != null) throw exception 14. } 15. } 16. var text = "after" 17. }

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Confidential Kotlin Coroutines in-depth analysis // How do Coroutines work? Coroutine Scope Coroutine Coroutine 1 Coroutine Context Job Dispatcher ... ... Coroutine N Coroutine 1 Coroutine 2 ... Coroutine N

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle Coroutine Scope Coroutine Coroutine 1 Coroutine Context Job Dispatcher ... Coroutine N

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Job 1. val job = GlobalScope.launch { 2. // do some stuff 3. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Job 1. val job = GlobalScope.launch { 2. // do some stuff 3. } 4. 5. job.invokeOnCompletion { cause -> 6. // job has finished 7. assert(cause == null) 8. assert(job.isCompleted) 9. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Lazy Job 1. val job = GlobalScope.launch(start = CoroutineStart.LAZY) { 2. // do some stuff 3. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Lazy Job 1. val job = GlobalScope.launch(start = CoroutineStart.LAZY) { 2. // do some stuff 3. } 4. 5. job.invokeOnCompletion { cause -> 6. // job has finished 7. assert(cause == null) 8. assert(job.isCompleted) 9. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Lazy Job 1. val job = GlobalScope.launch(start = CoroutineStart.LAZY) { 2. // do some stuff 3. } 4. 5. job.invokeOnCompletion { cause -> 6. // job has finished 7. assert(cause == null) 8. assert(job.isCompleted) 9. } 10. 11. assert(!job.isActive) // new state 12. job.start() 13. assert(job.isActive) // active state

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Deferred 1. val deferred = GlobalScope.async { 2. // do some stuff 3. return@async "result" 4. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Deferred 1. val deferred = GlobalScope.async { 2. // do some stuff 3. return@async "result" 4. } 5. 6. deferred.invokeOnCompletion { cause -> 7. // job has finished, we can get the result 8. assert(cause == null) 9. assert(job.isCompleted) 10. assert(deferred.getCompleted() == "result") 11. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Error 1. val job = GlobalScope.launch { 2. // oops 3. throw IndexOutOfBoundsException() 4. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Error 1. val job = GlobalScope.launch { 2. // oops 3. throw IndexOutOfBoundsException() 4. } 5. 6. job.invokeOnCompletion { cause -> 7. // job has finished with exception 8. assert(job.isCancelled) 9. assert(job.isCompleted) 10. assert(cause is IndexOutOfBoundsException) 11. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Cancel 1. val job = GlobalScope.launch { 2. // long operation 3. delay(5000) 4. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Cancel 1. val job = GlobalScope.launch { 2. // long operation 3. delay(5000) 4. } 5. 6. job.cancel()

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle - Cancel 1. val job = GlobalScope.launch { 2. // long operation 3. delay(5000) 4. } 5. 6. job.cancel() 7. 8. job.invokeOnCompletion { cause -> 9. // job has finished with exception 10. assert(job.isCancelled) 11. assert(job.isCompleted) 12. assert(cause is CancellationException) 13. }

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Confidential Kotlin Coroutines in-depth analysis Error flow Normal flow // Coroutine lifecycle New Active Completing Completed Cancelling Cancelled running waiting for children exception / cancel

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Confidential Kotlin Coroutines in-depth analysis // Coroutine lifecycle States isActive isCompleted isCancelled New false false false Active true false false Completing true false false Cancelling false false true Cancelled false true true Completed false true false

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context Coroutine Scope Coroutine Coroutine 1 Coroutine Context Job Dispatcher ... Coroutine N

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context Coroutine context includes: ● Main ○ Dispatcher { Executors } ○ Job { Future } ● Additional ○ ThreadContextElement ○ ContinuationInterceptor ○ Default exception handlers { Thread.setUncaughtExceptionHandler } ● Custom ○ Any number of custom values { ThreadLocal }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context 1. GlobalScope.launch(Dispatchers.IO) { 2. // IO thread pool 3. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context 1. GlobalScope.launch(Dispatchers.IO) { 2. // IO thread pool 3. withContext(Dispatchers.Main) { 4. // Main thread pool 5. } 6. // IO thread pool 7. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context 1. class MyData(val value: String) : AbstractCoroutineContextElement(Key) { 2. object Key : CoroutineContext.Key 3. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context 1. class MyData(val value: String) : AbstractCoroutineContextElement(Key) { 2. object Key : CoroutineContext.Key 3. } 4. 5. fun foo() { 6. GlobalScope.launch(Dispatchers.IO + MyData("test")) { 7. 8. 9. } 10. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context 1. class MyData(val value: String) : AbstractCoroutineContextElement(Key) { 2. object Key : CoroutineContext.Key 3. } 4. 5. fun foo() { 6. GlobalScope.launch(Dispatchers.IO + MyData("test")) { 7. val data = coroutineContext[MyData.Key] as MyData 8. assert(data.value == "test") 9. } 10. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context 1. class MyData(val value: String) : AbstractCoroutineContextElement(Key) { 2. object Key : CoroutineContext.Key 3. } 4. 5. fun foo() { 6. GlobalScope.launch(Dispatchers.IO) { 7. assert(coroutineContext[MyData.Key] == null) 8. 9. withContext(MyData("test")) { 10. assert(coroutineContext[MyData.Key] != null) 11. } 12. 13. assert(coroutineContext[MyData.Key] == null) 14. } 15. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context [Example] 1. class Benchmark : AbstractCoroutineContextElement(Key) { 2. object Key : CoroutineContext.Key 3. 4. val map = ConcurrentHashMap() 5. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context [Example] 1. class Benchmark : AbstractCoroutineContextElement(Key) { 2. object Key : CoroutineContext.Key 3. 4. val map = ConcurrentHashMap() 5. } 6. 7. suspend inline fun benchmark(name: String, block: () -> T): T { 8. val time = System.currentTimeMillis() 9. try { 10. return block() 11. } finally { 12. (coroutineContext[Benchmark.Key] as Benchmark).map 13. .getOrPut(name) { AtomicLong() } 14. .addAndGet(System.currentTimeMillis() - time) 15. } 16. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context [Example] 1. suspend fun fetchData() = benchmark("fetchData") { 2. return@benchmark "result" 3. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context [Example] 1. suspend fun fetchData() = benchmark("fetchData") { 2. return@benchmark "result" 3. } 4. 5. fun main() { 6. val benchmark = Benchmark() 7. 8. GlobalScope.launch(benchmark) { 9. fetchData() 10. } 11. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context [Example] 1. suspend fun fetchData() = benchmark("fetchData") { 2. return@benchmark "result" 3. } 4. 5. fun main() { 6. val benchmark = Benchmark() 7. 8. GlobalScope.launch(benchmark) { 9. fetchData() 10. 11. // log benchmarks 12. System.out.println(benchmark.map) 13. } 14. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine context [Example] 02-27 12:17:44.402 ? D/Benchmark: benchmark results: CmsManagerCentral.Epg_FetchFavoriteChannels 90.868 ms EpgChannelsApi_Combined.get 0.071 ms EpgChannelsApi.get 0.005 ms EpgFavoritesApi_Combined.fetch 85.428 ms EpgFavoritesApi_Cms.fetch 73.104 ms EpgFavoritesApi_Memory.fetch 0.016 ms EpgFavoritesApi_Persistent.fetch 2.870 ms EpgFavoritesApi_Persistent.fetch (inner) 2.865 ms

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Confidential Kotlin Coroutines in-depth analysis // Coroutine dispatchers Coroutine Scope Coroutine Coroutine 1 Coroutine Context Job Dispatcher ... Coroutine N

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Confidential Kotlin Coroutines in-depth analysis // Coroutine dispatchers 1. GlobalScope.launch(Dispatchers.IO) { 2. // IO thread pool 3. withContext(Dispatchers.Main) { 4. // Main thread pool 5. } 6. } 1. ioExecutor.execute { 2. // IO thread pool 3. mainExecutor.execute { 4. // Main thread pool 5. } 6. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine dispatchers 1. abstract class CoroutineDispatcher : ContinuationInterceptor { 2. /** 3. * Returns `true` if execution shall be dispatched onto another thread. 4. */ 5. open fun isDispatchNeeded(context: CoroutineContext) = true 6. 7. /** 8. * Dispatches execution of a runnable [block] onto another thread in the given [context]. 9. */ 10. abstract fun dispatch(context: CoroutineContext, block: Runnable) 11. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine dispatchers [Example] 1. object MainThreadDispatcher : CoroutineDispatcher() { 2. private val handler = Handler(Looper.getMainLooper()) 3. 4. override fun dispatch(context: CoroutineContext, block: Runnable) { 5. handler.post(block) 6. } 7. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine dispatchers [Example] 1. object MainThreadDispatcher : CoroutineDispatcher() { 2. private val handler = Handler(Looper.getMainLooper()) 3. 4. override fun dispatch(context: CoroutineContext, block: Runnable) { 5. handler.post(block) 6. } 7. 8. override fun isDispatchNeeded(context: CoroutineContext): Boolean { 9. return !handler.looper.isCurrentThread() 10. } 11. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine dispatchers [Example] 1. object MainThreadDispatcher : CoroutineDispatcher() { 2. private val handler = Handler(Looper.getMainLooper()) 3. 4. override fun dispatch(context: CoroutineContext, block: Runnable) { 5. handler.post(block) 6. } 7. 8. override fun isDispatchNeeded(context: CoroutineContext): Boolean { 9. return !handler.looper.isCurrentThread() 10. } 11. } 12. 13. GlobalScope.launch(MainThreadDispatcher) { 14. // runs on Android's main thread 15. }

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines Coroutine Scope Coroutine Coroutine 1 Coroutine Context Job Dispatcher ... Coroutine N

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Starting 1. suspend fun slowRandom(max: Long): Long { 2. Thread.sleep(1000) 3. return Random.nextLong(max) 4. }

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Starting 1. suspend fun slowRandom(max: Long): Long { 2. delay(1000) 3. return Random.nextLong(max) 4. }

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Starting 1. suspend fun slowRandom(max: Long): Long { 2. delay(1000) 3. return Random.nextLong(max) 4. } 5. 6. suspend fun combine(): Long { 7. val value1 = slowRandom(100) 8. val value2 = slowRandom(200) 9. return value1 + value2 10. }

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Starting 1. suspend fun slowRandom(max: Long): Long { 2. delay(1000) 3. return Random.nextLong(max) 4. } 5. 6. suspend fun combine(): Long { 7. val value1 = GlobalScope.async { slowRandom(100) } 8. val value2 = GlobalScope.async { slowRandom(200) } 9. return value1.await() + value2.await() 10. }

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Starting 1. suspend fun slowRandom(max: Long): Long { 2. delay(1000) 3. return Random.nextLong(max) 4. } 5. 6. suspend fun combine(): Long { 7. val value1 = GlobalScope.async(coroutineContext) { slowRandom(100) } 8. val value2 = GlobalScope.async(coroutineContext) { slowRandom(200) } 9. return value1.await() + value2.await() 10. }

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Starting 1. suspend fun slowRandom(max: Long): Long { 2. delay(1000) 3. return Random.nextLong(max) 4. } 5. 6. suspend fun combine() = coroutineScope { 7. val value1 = async { slowRandom(100) } 8. val value2 = async { slowRandom(200) } 9. return@coroutineScope value1.await() + value2.await() 10. }

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Starting 1. suspend fun slowRandom(max: Long): Long { 2. delay(1000) 3. return Random.nextLong(max) 4. } 5. 6. suspend fun combine() = supervisorScope { 7. val value1 = async { slowRandom(100) } 8. val value2 = async { slowRandom(200) } 9. return@supervisorScope value1.await() + value2.await() 10. }

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Ending 1. val job = GlobalScope.launch { 2. 3. GlobalScope.launch { 4. delay(1000) 5. System.out.println("child end") 6. } 7. } 8. 9. job.invokeOnCompletion { 10. System.out.println("parent end") 11. } Output -> parent end, child end

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Ending 1. val job = GlobalScope.launch { 2. 3. GlobalScope.launch(coroutineContext) { 4. delay(1000) 5. System.out.println("child end") 6. } 7. } 8. 9. job.invokeOnCompletion { 10. System.out.println("parent end") 11. } Output -> child end, parent end

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Cancellation 1. val job = GlobalScope.launch { 2. 3. GlobalScope.launch { 4. delay(1000) 5. System.out.println("child end") 6. } 7. } 8. 9. job.invokeOnCompletion { 10. System.out.println("parent end") 11. } 12. 13. job.cancel() Output -> parent end, child end

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Confidential Kotlin Coroutines in-depth analysis // Child coroutines - Cancellation 1. val job = GlobalScope.launch { 2. 3. GlobalScope.launch(coroutineContext) { 4. delay(1000) 5. System.out.println("child end") 6. } 7. } 8. 9. job.invokeOnCompletion { 10. System.out.println("parent end") 11. } 12. 13. job.cancel() Output -> parent end

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope Coroutine Scope Coroutine Coroutine 1 Coroutine Context Job Dispatcher ... Coroutine N

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope 1. GlobalScope.launch(Dispatchers.IO) { 2. // something interesting 3. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope 1. object GlobalScope : CoroutineScope { 2. override val coroutineContext: CoroutineContext 3. get() = EmptyCoroutineContext 4. } 1. public interface CoroutineScope { 2. /** 3. * Context of this scope. 4. */ 5. public val coroutineContext: CoroutineContext 6. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope 1. public fun CoroutineScope.launch( 2. context: CoroutineContext = EmptyCoroutineContext, 3. start: CoroutineStart = CoroutineStart.DEFAULT, 4. block: suspend CoroutineScope.() -> Unit 5. ): Job 1. public fun CoroutineScope.async( 2. context: CoroutineContext = EmptyCoroutineContext, 3. start: CoroutineStart = CoroutineStart.DEFAULT, 4. block: suspend CoroutineScope.() -> T 5. ): Deferred

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope 1. class MainActivity : Activity(), CoroutineScope { 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope 1. class MainActivity : Activity(), CoroutineScope { 2. 3. 4. override val coroutineContext = Dispatchers.Main 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope 1. class MainActivity : Activity(), CoroutineScope { 2. private val job = Job() 3. 4. override val coroutineContext = Dispatchers.Main + job 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope 1. class MainActivity : Activity(), CoroutineScope { 2. private val job = Job() 3. 4. override val coroutineContext = Dispatchers.Main + job 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. override fun onDestroy() { 15. super.onDestroy() 16. 17. job.cancel() 18. } 19. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope 1. class MainActivity : Activity(), CoroutineScope { 2. private val job = Job() 3. 4. override val coroutineContext = Dispatchers.Main + job 5. 6. override fun onCreate() { 7. super.onCreate() 8. 9. launch { 10. // do something 11. } 12. } 13. 14. override fun onDestroy() { 15. super.onDestroy() 16. 17. job.cancel() 18. } 19. }

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope - Unsupervised 1. coroutineScope { 2. val job1 = async { throw Exception() } 3. val job2 = async { delay(1000) } 4. try { 5. job1.await() 6. System.out.println("job1 finished") 7. } catch (e: Exception) { 8. System.out.println("job1 crashed -> $e") 9. } 10. try { 11. job2.await() 12. System.out.println("job2 finished") 13. } catch (e: Exception) { 14. System.out.println("job2 crashed -> $e") 15. } 16. } job1 crashed: java.lang.Exception job2 crashed: JobCancellationException: Parent job is Cancelling

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Confidential Kotlin Coroutines in-depth analysis // Coroutine scope - Supervised 1. supervisorScope { 2. val job1 = async { throw Exception() } 3. val job2 = async { delay(1000) } 4. try { 5. job1.await() 6. System.out.println("job1 finished") 7. } catch (e: Exception) { 8. System.out.println("job1 crashed -> $e") 9. } 10. try { 11. job2.await() 12. System.out.println("job2 finished") 13. } catch (e: Exception) { 14. System.out.println("job2 crashed -> $e") 15. } 16. } job1 crashed -> java.lang.Exception job2 finished

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit) 3. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit) 3. } 4. 5. suspend fun getUser(): User { 6. 7. 8. 9. 10. 11. 12. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit) 3. } 4. 5. suspend fun getUser(): User { 6. return suspendCoroutine { continuation -> 7. // non-suspend block here 8. 9. 10. 11. } 12. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit) 3. } 4. 5. suspend fun getUser(): User { 6. return suspendCoroutine { continuation -> 7. // non-suspend block here 8. ExternalApi.getUser { user -> 9. 10. } 11. } 12. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit) 3. } 4. 5. suspend fun getUser(): User { 6. return suspendCoroutine { continuation -> 7. // non-suspend block here 8. ExternalApi.getUser { user -> 9. continuation.resume(user) 10. } 11. } 12. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit) 3. } 4. 5. suspend fun getUser(): User { 6. return suspendCoroutine { continuation -> 7. // non-suspend block here 8. ExternalApi.getUser { user -> 9. continuation.resume(user) 10. } 11. } 12. } 13. 14. suspend fun showUser() { 15. val user = getUser() 16. // ... 17. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines - Cancel 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit): Request 3. } 4.

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines - Cancel 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit): Request 3. } 4. 5. suspend fun getUser(): User { 6. 7. 8. 9. 10. 11. 12. 13. 14. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines - Cancel 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit): Request 3. } 4. 5. suspend fun getUser(): User { 6. return suspendCancellableCoroutine { continuation -> 7. 8. 9. 10. 11. 12. 13. } 14. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines - Cancel 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit): Request 3. } 4. 5. suspend fun getUser(): User { 6. return suspendCancellableCoroutine { continuation -> 7. val request = ExternalApi.getUser { user -> 8. continuation.resume(user) 9. } 10. 11. 12. 13. } 14. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines - Cancel 1. object ExternalApi { 2. fun getUser(callback: (User) -> Unit): Request 3. } 4. 5. suspend fun getUser(): User { 6. return suspendCancellableCoroutine { continuation -> 7. val request = ExternalApi.getUser { user -> 8. continuation.resume(user) 9. } 10. continuation.invokeOnCancellation { 11. request.cancel() 12. } 13. } 14. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines - Errors 1. object ExternalApi { 2. fun getUser(callback: (User?) -> Unit) 3. } 4.

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines - Errors 1. object ExternalApi { 2. fun getUser(callback: (User?) -> Unit) 3. } 4. 5. suspend fun getUser(): User { 6. return suspendCoroutine { continuation -> 7. ExternalApi.getUser { user -> 8. if (user != null) { 9. continuation.resume(user) 10. } 11. 12. 13. } 14. } 15. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines - Errors 1. object ExternalApi { 2. fun getUser(callback: (User?) -> Unit) 3. } 4. 5. suspend fun getUser(): User { 6. return suspendCoroutine { continuation -> 7. ExternalApi.getUser { user -> 8. if (user != null) { 9. continuation.resume(user) 10. } else { 11. continuation.resumeWithException(Exception("no user")) 12. } 13. } 14. } 15. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines - Errors 1. suspend fun showUser() { 2. try { 3. val user = getUser() 4. // ... 5. } catch (e: Exception) { 6. e.printStackTrace() 7. } 8. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines [Example] 1. fun getUser(): Single

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines [Example] 1. fun getUser(): Single 2. 3. suspend fun Single.await(): User { 4. 5. 6. 7. 8. 9. 10. 11. 12. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines [Example] 1. fun getUser(): Single 2. 3. suspend fun Single.await(): User { 4. return suspendCancellableCoroutine { continuation -> 5. 6. 7. 8. 9. 10. 11. } 12. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines [Example] 1. fun getUser(): Single 2. 3. suspend fun Single.await(): User { 4. return suspendCancellableCoroutine { continuation -> 5. getUser().subscribe({ user -> 6. continuation.resume(user) 7. }) 8. 9. 10. 11. } 12. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines [Example] 1. fun getUser(): Single 2. 3. suspend fun Single.await(): User { 4. return suspendCancellableCoroutine { continuation -> 5. getUser().subscribe({ user -> 6. continuation.resume(user) 7. }, { error -> 8. continuation.resumeWithException(error) 9. }) 10. 11. } 12. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines [Example] 1. fun getUser(): Single 2. 3. suspend fun Single.await(): User { 4. return suspendCancellableCoroutine { continuation -> 5. val disposable = getUser().subscribe({ user -> 6. continuation.resume(user) 7. }, { error -> 8. continuation.resumeWithException(error) 9. }) 10. continuation.invokeOnCancellation { disposable.dispose() } 11. } 12. }

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Confidential Kotlin Coroutines in-depth analysis // Suspended coroutines [Example] 1. fun getUser(): Single 2. 3. suspend fun showUser() { 4. try { 5. val user = getUser().await() 6. // ... 7. } catch (e: Exception) { 8. e.printStackTrace() 9. } 10. }

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Confidential Kotlin Coroutines in-depth analysis // Testing Coroutines

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Confidential Kotlin Coroutines in-depth analysis // Testing Coroutines 1. suspend fun mySuspendFunction(): String { 2. return "My Test String" 3. } 4. 5. @Test 6. fun mySuspendFunctionTest() { 7. 8. }

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Confidential Kotlin Coroutines in-depth analysis // Testing Coroutines 1. suspend fun mySuspendFunction(): String { 2. return "My Test String" 3. } 4. 5. @Test 6. fun mySuspendFunctionTest() { 7. val job = GlobalScope.async { 8. mySuspendFunction() 9. } 10. job.invokeOnCompletion { 11. assertEquals(job.getCompleted(), "My Test String") 12. } 13. }

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Confidential Kotlin Coroutines in-depth analysis // Testing Coroutines 1. suspend fun mySuspendFunction(): String { 2. return "My Test String" 3. } 4. 5. @Test 6. fun mySuspendFunctionTest() { 7. 8. }

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Confidential Kotlin Coroutines in-depth analysis // Testing Coroutines 1. suspend fun mySuspendFunction(): String { 2. return "My Test String" 3. } 4. 5. @Test 6. fun mySuspendFunctionTest() { 7. val result = runBlocking { 8. mySuspendFunction() 9. } 10. assertEquals(result, "My Test String") 11. }

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Confidential Kotlin Coroutines in-depth analysis // Testing Coroutines 1. suspend fun mySuspendFunction(): String { 2. return "My Test String" 3. } 4. 5. @Test 6. fun mySuspendFunctionTest() = runBlocking { 7. assertEquals(mySuspendFunction(), "My Test String") 8. }

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Confidential Kotlin Coroutines in-depth analysis // Benchmarks

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Confidential Kotlin Coroutines in-depth analysis // Benchmarks 1. for (i in 0..1_000_000) { 2. launch(dispatcher) { 3. System.out.println("$i") 4. } 5. } 1. for (i in 0..1_000_000) { 2. executor.execute { 3. System.out.println("$i") 4. } 5. } finished in 4.219 sec finished in 3.853 sec ~10% overhead

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Confidential Kotlin Coroutines in-depth analysis // Final thoughts

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Confidential Kotlin Coroutines in-depth analysis // Final thoughts 1. Sequences and channels were not covered 2. Reflections don’t work with coroutines 3. No way to call coroutines from Java (without kotlin wrapper) 4. Coroutines debugger bugs: a. Variables inside coroutine are not visible b. Evaluate expression doesn’t work c. Breakpoint after last suspension point doesn’t trigger

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// Obligatory Q&A

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// Thank you.