Coroutines Update Seva Tolstopyatov @qwwdfsad October 13, 2020 - - PowerPoint PPT Presentation

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Coroutines Update Seva Tolstopyatov @qwwdfsad October 13, 2020 - - PowerPoint PPT Presentation

Jul 26, 2023 312 likes •744 views

Kotlin 1.4 Online Event Coroutines Update Seva Tolstopyatov @qwwdfsad October 13, 2020 Coroutines debugging Coroutines debugging Coroutines debugging Coroutines debugging Coroutines debugging IDEA 2020.1 Coroutines debugging Debugging

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October 13, 2020 @qwwdfsad Kotlin 1.4 Online Event

Coroutines Update Seva Tolstopyatov

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Coroutines debugging

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Coroutines debugging

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Coroutines debugging

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Coroutines debugging

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Coroutines debugging – IDEA 2020.1

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Coroutines debugging

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Debugging meets coroutines 1.3.8

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Flow since 1.3

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Flow

val flow: Flow<Int> = flow { delay(100) for (i in 1..10) { emit(i) } }.map { delay(100) it * it }

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StateFlow

A

B

E D F C

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var variable: Int = 42

State A condition or way of being that exists at a particular time

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StateFlow

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StateFlow

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StateFlow

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StateFlow

public interface StateFlow<out T> : Flow<T> { public val value: T }

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StateFlow

public interface MutableStateFlow<T> : Flow<T> { public override var value: T }

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StateFlow

class DownloadingModel { private val _status = MutableStateFlow<DownloadStatus>(DownloadStatus.NOT_REQUESTED) val status: StateFlow<DownloadStatus> get() = _status suspend fun download() { } }

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StateFlow

class DownloadingModel { private val _status = MutableStateFlow<DownloadStatus>(DownloadStatus.NOT_REQUESTED) val status: StateFlow<DownloadStatus> get() = _status suspend fun download() { _status.value = DownloadStatus.INITIALIZED initializeConnection() } }

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StateFlow

class DownloadingModel { private val _status = MutableStateFlow<DownloadStatus>(DownloadStatus.NOT_REQUESTED) val status: StateFlow<DownloadStatus> get() = _status suspend fun download() { _status.value = DownloadStatus.INITIALIZED initializeConnection() processAvailableContent { partialData: ByteArray, downloadedBytes: Long, totalBytes: Long -> storePartialData(partialData) _status.value = DownloadProgress(downloadedBytes.toDouble() / totalBytes) } } }

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StateFlow

class DownloadingModel { private val _status = MutableStateFlow<DownloadStatus>(DownloadStatus.NOT_REQUESTED) val status: StateFlow<DownloadStatus> get() = _status suspend fun download() { _status.value = DownloadStatus.INITIALIZED initializeConnection() processAvailableContent { partialData: ByteArray, downloadedBytes: Long, totalBytes: Long -> storePartialData(partialData) _status.value = DownloadProgress(downloadedBytes.toDouble() / totalBytes) } _status.value = DownloadStatus.SUCCESS } }

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SharedFlow

Single-event processing Multiple-event processing e 1 e2 e3 e4 e5 e6

t

e 1 e 13

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SharedFlow

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SharedFlow

  • Costly connections
  • May be unused
  • Replay log
  • Flexibility
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Existing solutions

  • Subjects: BehaviorSubject, AsyncSubject, ReplaySubject
  • ConnectableFlowable: connect, refCount, autoConnect
  • Processors: Emitter, Unicast
  • Share, publish, replay
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SharedFlow

interface SharedFlow<out T> : Flow<T> { public val replayCache: List<T> }

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SharedFlow

interface MutableSharedFlow<T> : SharedFlow<T>, FlowCollector<T> { suspend fun emit(value: T) fun tryEmit(value: T): Boolean val subscriptionCount: StateFlow<Int> fun resetReplayCache() }

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SharedFlow

public fun <T> MutableSharedFlow( replay: Int, extraBufferCapacity: Int = 0,

  • nBufferOverflow: BufferOverflow = BufferOverflow.SUSPEND

): MutableSharedFlow<T>

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SharedFlow

public fun <T> Flow<T>.shareIn( scope: CoroutineScope, replay: Int, started: SharingStarted = SharingStarted.Eagerly )

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Flow since 1.3

  • Core operators

○ catch, onEmpty, onCompletion, onStart ○

  • nEach, transform, transformWhile
  • Invariants
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Flow since 1.3

suspend fun Flow<Int>.stopOn42() = collect { println(it) if (it == 42) { throw AnswerFoundException() } }

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Flow since 1.3

flow { try { emit(42) } catch (e: AnswerFoundException) { emit(21) } }.stopOn42()

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Flow since 1.3

java.lang.IllegalStateException: Flow exception transparency is violated: Previous 'emit' call has thrown exception java.util.concurrent.CancellationException: Thanks, I had enough of your data, but then emission attempt of value '21' has been detected. Emissions from 'catch' blocks are prohibited in order to avoid unspecified behaviour, 'Flow.catch' operator can be used instead. For a more detailed explanation, please refer to Flow documentation. at kotlinx.coroutines.flow.internal.SafeCollector.exceptionTransparencyViolated(Saf eCollector.kt:114

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Flow since 1.3

flowOf(42) .catch { e -> println("Answer was found") } .stopOn42()

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Android update

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1 github.com/Kotlin/kotlinx.coroutines/pull/1652

Android update

  • The coroutines DEX size is optimized by 30%
  • CPU consumption of default dispatchers was drastically reduced
  • Startup time was significantly optimised
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JDK update

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JDK update – Blocking calls

withTimeout(500.milliseconds) { runInterruptible(Dispatchers.IO) { serverSocket.accept() } }

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More JDK updates

  • Out-of-the-box integration with BlockHound
  • Integration with JDK 9 java.util.concurrent.Flow

1 github.com/reactor/BlockHound 2 docs.oracle.com/javase/9/docs/api/java/util/concurrent/Flow.html

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The future of coroutines

1 github.com/Kotlin/kotlinx.coroutines/pull/1937

  • SharedFlow and StateFlow stabilization
  • Concise and cancellation-aware resource management
  • Replacement for offer and poll
  • More Flow time API for UI programming
  • kotlinx-coroutines-test stabilization
  • Sliceable dispatchers
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@qwwdfsad

Thanks! Have a nice Kotlin!