![void sendData(SendPort replyPort){
}
void receiveData(ReceivePort receivePort) async {
}
dynamic x = new ByteData(2 * 1024 * 1024);
for (int i = 0; i < 4; i++) {
x.setInt8(i, i);
}
replyPort.send(TransferableTypedData.fromList([x.buffer.asUint8List()]));
var first = await receivePort.first as TransferableTypedData;
var data = first.materialize().asByteData();](https://image.slidesharecdn.com/droidjam2019flutterisolatespdf-190830143817/85/Droidjam-2019-flutter-isolates-pdf-23-320.jpg)
Droidjam 2019 flutter isolates pdf
- 1. –A wise man “True judge of courage is when you get to stand between a man and his food”
- 2. Speaker Bio I work at Fueled Psst!You can too ｡◕‿◕｡
- 3. Isolating Flutter into multithreading effectively Anvith Bhat @anv1th
- 5. Exploring Rx Dart 1. Observables can be subscribed only once. 2. onListen (doOnSubscribe) called once. 3. No Schedulers ¯_(ツ)_/¯
- 6. Android to Flutter override fun updateUi(state: ViewState) { } @override Widget build(BuildContext context) { return Container(child: _content(context)); } Widget _content(BuildContext context) { } if (state.isOnboardingCompleted) { showPermissionDialog() } progress.visibility = if(state.isLoading){ View.VISIBLE } else { View.GONE } if(data.isOnboardingCompleted){ showPermissionDialog(); } if (data.state == LoadState.LOADING) { return Center( child: CircularProgressIndicator(), ); } else { return _Body(); }
- 8. @override Widget build(BuildContext context) { return Container(child: _content(context)); } Widget _content(BuildContext context) { } if(data.isOnboardingCompleted){ showPermissionDialog(); } @override Widget build(BuildContext context) { return Container(child: _content(context)); } Widget _content(BuildContext context) { } if(data.isOnboardingCompleted){ Future(()=> showPermissionDialog()); }
- 11. Flutter Framework • Flutter engine does not create its own threads or manage them Platform Task Runner UI Task Runner IO Task Runner GPU Task Runner Embedder
- 12. Load Costs Accessible Load Behaviour Platform Task Runner Yes Gesture events dropped and app termination UI Task Runner Yes Frame dropping/jank IO Task Runner No Delayed Futures GPU Task Runner No Frame dropping/jank
- 13. Flutter Thread Quirks • Threading Api is implicit. • Futures and Async/Await solve problems of asynchrony not computation.
- 14. Isolates
- 15. • Don't share memory. • Data wired is copied • Parents can limit abilities of isolates. IsolatesAttributes
- 19. How do I make em 🤔 Future<int> startIsolate() async { } 1. Isolate.spawn(runnable, runnable_param) //Create a Port for communication ReceivePort receivePort = ReceivePort(); //Create the isolate await Isolate.spawn(computeMatrix, receivePort.sendPort); //Pick first item in stream return await receivePort.first; //Callback void computeMatrix(SendPort port) { var result = heavilyComputedValue(); port.send(result) } void onButtonClick() { startIsolate().then((computedValue) { setState(() { computedText = "Matrix result is ${computedValue}"; }); }); }
- 20. How do I make em 🤔 void createRestrictedIsolate(Isolate main){ //Proxy Isolate restrictedIsolate = new Isolate(main.controlPort); untrustedCode(restrictedIsolate); } 1. Isolate.spawn(callback, callback_param) 2. via Constructor
- 21. How do I make em 🤔 1. Isolate.spawn(callback, callback_param) 3. spawnUri(Uri uri, List<String> args) Future<void> executeFileContent(Isolate main) async{ var args =List<String>(); args.add("type=monthly_data"); var isolate = await Isolate.spawnUri('./periodic_sync.dart',args) } 2. via Constructor
- 22. Processing Large Data • Flutter copies data on the parent isolate. • TransferableTypedData creates cross isolate transferrable buffer.
- 23. void sendData(SendPort replyPort){ } void receiveData(ReceivePort receivePort) async { } dynamic x = new ByteData(2 * 1024 * 1024); for (int i = 0; i < 4; i++) { x.setInt8(i, i); } replyPort.send(TransferableTypedData.fromList([x.buffer.asUint8List()])); var first = await receivePort.first as TransferableTypedData; var data = first.materialize().asByteData();
- 24. Benchmarks • Spawn time for a typical isolate varies between 10-80ms • Each isolate is allocated an independent heap. Around 5-6 mb on a higher end phone. • Isolate creation times on android are almost 8-10x of ios.
- 26. Advanced Usages • Object Registry • Isolate Runner • Load balancers pub:isolate
- 27. Isolate Runner • Allows one to check if the runner is still alive. • Specify timeouts via. run function Wrapper around creation of Isolates. Future<R> run<R, P>(FutureOr<R> function(P argument), P argument, {Duration timeout}) {
- 28. Load Balancers • Create and Manage Isolate runner pool. var balancer = LoadBalancer.create(POOL_SIZE, IsolateRunner.spawn) balancer.run(heavyCompute, heavyComputeArg, estimatedLoad)
- 29. Isolate + Streams getMatrixObservable() .asyncMap(startIsolate) .listen((data){ print("Me gots data") }); - asyncMap Future<int> startIsolate(int a) async { ReceivePort receivePort = ReceivePort(); Isolate isolate = await Isolate.spawn(isolateTask, receivePort.sendPort); return await receivePort.first; }
- 30. Isolate + Streams - fromFuture - asyncMap Future<int> startIsolate() async { ReceivePort receivePort = ReceivePort(); Isolate isolate = await Isolate.spawn(isolateTask, receivePort.sendPort); return await receivePort.first; } Observable .fromFuture(startIsolate()) .listen((data){ print("I come from the future: $data") });;
- 31. An Idiomatic Spell • Stream transformers operator could help out Observable.just(value) .observeOn(Schedulers.io())
- 32. class IoScheduler<S, T> implements StreamTransformer<S, T> { }
- 33. class IoScheduler<S, T> implements StreamTransformer<S, T> { } if (_loadBalancer == null) { _loadBalancer = await LoadBalancer.create(POOL_SIZE, IsolateRunner.spawn); } // Create isolate pool static Future<void> initLoadBalancer() async { // Isolate pool state static LoadBalancer _loadBalancer; static const int POOL_SIZE = 6; }
- 34. class IoScheduler<S, T> implements StreamTransformer<S, T> { } // Initialise stream handlers IoScheduler(S isolateCode(T value)) { } _transformer = isolateCode; _controller = new StreamController<T>( onListen: _onListen ); Function _transformer; Future<void> initLoadBalancer() async {..}
- 35. class IoScheduler<S, T> implements StreamTransformer<S, T> { } // Initialise stream handlers IoScheduler(S isolateCode(T value)) {..} Function _transformer; } void _onListen() { _subscription = _stream.listen( onData, onError: _controller.addError ); Future<void> initLoadBalancer() async {..}
- 36. class IoScheduler<S, T> implements StreamTransformer<S, T> { } ..}void _onListen() { void onData(S data) { initLoadBalancer().then((val) { }); } _loadBalancer.run(_transformer, data).then((transformed) { _controller.add(transformed as T); }, onError: (error) { throw error; }); // Initialise stream handlers IoScheduler(S isolateCode(T value)) { ..} Function _transformer; Future<void> initLoadBalancer() async {..}
- 37. The Final Spell Observable getFibonnaciValue(int value) { return Observable.just(value) .transform(IoScheduler<int, int>(calculateFib)); } int calculateFib(int n) { if (n <= 1) return n; else return calculateFib(n - 1) + calculateFib(n - 2); }
- 38. The "not so good" parts • Copy overheads* • Isolate creation times are sporadic. • Doesn't guarantee true parallelism all the time. Since they're backed byVM thread pool.
- 39. Takeaways • Avoid isolates for simpler tasks like object transformations. • Use Isolates for json decoding, encryption and image processing. • Figure out a pool size that works well for your app. Around 5-6 isolates are good enough for most apps. • Profile your app.
- 40. Resources • IoScheduler/IoTransformer https://gist.github.com/humblerookie/9b395f653a81cca17280921175064232 • Isolates Playground https://github.com/humblerookie/isolates-playground/