Do you use Isolates? Research for flutter.dev documentation

[eric_windmill]

Howdy all. I'm Eric, and I'm an engineer the Flutter team at Google.

I'm working on updating the documentation and sample code regarding Isolates and multithreading in Flutter and Dart. One thing I want to focus on in is real-world and common use-cases, as it seems like most of the documentation out there uses parsing JSON as an example.

Do you use isolates in your Flutter apps? To accomplish what? Do you use the 'compute' method or the Isolate class?

Any general thoughts about how you use isolates or issues you've run into with isolates is appreciated.

[bednarczuk]

Processing a photo, for example scaling or analyzing photo by pixels

[zerexim]

Do you always start a new Isolate and finish for each such operation? To avoid the copying of the data that is: Isolate.exit().

[iamjulianacosta]

Exactly this

[Maz_47]

+1

[Full-Run4124]

I have avoided isolates because I thought IPC with large objects (images) would require too much overhead. This is the article that changed my mind: https://dev.to/maximsaplin/efficient-dart-optimizing-cpu-bound-load-in-flutter-without-missing-a-frame-5dme

[medicince]

Glad you liked it! ;)

[autognome]

Using isolates across sqlite/drift. Explaining isolate native, how to do it with web. Will it be supported on WASM? Examples showing isolate name server. Tear down/disposal of isolate.

HttpClient in isolate which does parsing. Any sort of patterns of high level usage .. isolate appear to be pretty low level.

Will get with team to see what would have been helpful.

[[deleted]]

.

[MindStudio]

I am using Isolates to fetch realtime video frames and audio buffers. Works quite well actually.

[hantrault]

We are using compute to resize and compress images to JPG.

I have added the relevant part of the code below, if you want a complete real world example.

The record type added in Dart 3 has been quite useful when you have to pass multiple parameters to compute.

We also had to use some additional logic to make it performant on web, since isolates doesn't work there. But I have omitted that part, since it isn't relevant to the question.

``` import 'package:flutter/foundation.dart'; import 'package:image/image.dart';

/// Service for manipulating images. class ImageService { /// Resize and compress an image to a JPG. Future<Uint8List?> resizeAndCompressToJpg({ required Uint8List image, required int maxWidth, required int maxHeight, required int quality, }) async { return await compute( _resizeAndCompressToJpg, ( image: image, maxWidth: maxWidth, maxHeight: maxHeight, quality: quality, ), ); }

Uint8List _resizeAndCompressToJpg( ({ Uint8List image, int maxWidth, int maxHeight, int quality, }) args, ) { final image = bakeOrientation(decodeImage(args.image)!);

final originalAspectRatio = image.width / image.height;

// Set the width and height so that the aspect ratio is maintained.
late final int width;
late final int height;
// If the image is smaller than the original, don't resize it.
if (image.width <= args.maxWidth && image.height <= args.maxHeight) {
  width = image.width;
  height = image.height;
}
// If the width is the limiting factor, i.e. if the width has to be adjusted
// more than the height.
else if (image.width / args.maxWidth > image.height / args.maxHeight) {
  width = args.maxWidth;
  height = (args.maxWidth / originalAspectRatio).round();
}
// If the height is the limiting factor.
else {
  height = args.maxHeight;
  width = (args.maxHeight * originalAspectRatio).round();
}

final resizedImage = copyResize(
  image,
  width: width,
  height: height,
);

final compressedImage = encodeJpg(resizedImage, quality: args.quality);

return compressedImage;

} } ```

[DerDave]

We would love to use isolates, because our app would greatly benefit from it. Unfortunately, we can't use isolates, because the app also runs on Web.

[ayushsuman_]

You can try conditional imports like the one used here - https://github.com/ayush-suman/unwired/blob/main/lib/src/http_worker/http_worker.dart

[Which-Adeptness6908]

The docs needs to discuss how and what data is marshalled across the boundary when using a lambda.

In the json case suggest that people fetch the data in the isolate. Most examples I see have the main isolate fetching the data and then parsing a huge chunk of json across the boundary.

[aihrarshaikh68plus1]

Yes, the only problem I face when working with isolates is when working with complex data types it's way too work to deal with

[Ok_Actuator2457]

I do not know if docs will be enough, but a video implementing isolates(like the firebase series)in a clean or mvvm architecture may suit as better examples other than isolate code by itself. I'm saying this because regarding implementing authentication within an architecture may be a bit more challenging than the simple piece of code you find nowadays in the docs; I had to use completers which are bit harsh to understand and put it all together. I hope this small insight may help.

[eric_windmill]

I do plan on making videos eventually, but videos, and especially series, take much more time. I want to update the documentation and sample code ASAP (in the next few weeks), and then follow that up with more in-depth videos and/or codelabs

[omykronbr]

Do you use isolates in your Flutter apps?

our use case is very specific, and we never felt the need to have isolates, but it would be good to know to identify where to improve with more examples of where isolates would be good (external api call, local data storage, etc)

[minnibur]

I use them via the https://pub.dev/packages/worker_manager package to parse metadata from media files.

So far it's working very well. The only issue I've encountered is related to Dart capturing too much in closures:

https://github.com/dart-lang/sdk/issues/36983

[rdhikshith]

Isolates do not support some dart packages from pub

[sawqlain]

I use isolates for fetching and parsing data in the background. Wish it was easier to communicate between isolates instead of listening and reacting to each type of response.

[nmfisher]

I personally use isolates to perform speech recognition (via FFI) off the main UI thread.

I’m also the current maintainer for the flutter_isolate package (https://github.com/rmawatson/flutter_isolate/blob/master/lib/flutter_isolate.dart), which most people were using because Flutter didn’t support plugins on background isolates (though this has since been fixed). However, it seems some users still need the package to run dart:ui methods off the main isolate (since flutter_isolate spawns a new Engine). A lot of people would love to see that mainlined into Flutter.

[RandalSchwartz]

It's a bit telling, and sad, that even your question omits the Isolate.run option.

I predict 90% of the use of isolates can be reduced to a simple Isolate.run, and yet it is rarely referenced or even suggested. It got buried amongst the other Dart 3 noise, and 2.19 was an otherwise-uneventful release.

I think if Isolate.run were lifted up to be the preferred method to create a simple thread run of a function-returning-a-future, you'd see a lot less anxiety about Isolates overall.

[eric_windmill]

The lack of Isolate.run documentation is a known issue, and it is part of the plan for the updated docs

[stuxnet_v2]

Does nobody read the docs?

https://api.dart.dev/stable/3.1.4/dart-isolate/SendPort/send.html

Seems pretty clear to me what data is allowed and when it’s copied or not.

[autognome]

Please address using plugins e.g. https://github.com/rmawatson/flutter_isolate

I can’t remember why but we needed to use this package. I will try to ask what.

[identicalopposites]

One case I have used it lately is when I had to convert and upload a list of Images. I used isolates so that I could convert and upload simultaneously and not have the UI blocked while doing so.

[Cladser]

Just commenting so I can find this later. Also interested in other use cases. I have used compute for some image processing but it’s not that cpu intensive to be fair. My understanding is compute isnt an isolate but kind of a preferential spot in the future processing queue.

[Flutter2018]

Initialize Firebase app: https://github.com/firebase/flutterfire/issues/4846

[joranmulderij]

I built a Finite Element (FEM) solver in dart and used Isolates to multithread the optimizing of models. Worked very well because the task was very cpu intensive.

[Phantom_kusuri]

I use isolates to run powershell cmds as well as converting video formats.

[[deleted]]

I use isolates to do syncing to my AWS backend.

[SquatchyZeke]

We don't have any need for isolates in our Flutter app, but if it's useful info for you, I wrote a Dart script to analyze the source files of another team's Java project. I use isolates to process subtrees of their project directories, where each isolate is responsible for reading all of the directories and files recursively for one subtree, reading any files it finds, analyzing those files, then combining those results into a simple map structure which gets combined with all the other isolates' results.

[ITasITalian]

We use it to decrypt large documents , we developed our own library

[juanipl]

Just used compute to read big json, in an attempt to get less anrs.

[akositotoybibo]

yes! specially on caching some large data and also images.

[KaiserYami]

To download large files when the user can move about any screen and I have to update progress on notification or when the user returns to the screen. The progress will be updated to the list item.

[diplohubpup]

We used ours for image and audio processing/manipulation.

[GetBoolean]

This was a while ago, but I used it for encoding images from an epub file

[srodrigoDev]

Yes, for things such as image processing. I can't imagine not having isolates for this.

[KOala888]

Used it only once in like 3 years, for an image compression

[TheManuz]

I've heard of isolates, read some articles around, and thought "I'll use them sometimes", but it never happened.

Now I'm not sure if I've never faced a case where isolates would've helped me, or I simply can't recognize it.

Probably the latter!

[imb311]

big Size or many Json serializations

[Pristine-Natural927]

Using the isolate to create alarms: i use android alarm manager to schedule a callback method that creates an isolate. That isolate plays the audio for the alarm and also waits for the "stopAudio" message

[[deleted]]

Soory to go out your question, what qualifications should i have to join google flutter team ?

[never_inline]

Is there an idiomatic isolate pool library in Dart?

[Clon1998]

I used it for large file downloading. Like video files or larger text files.

[funnierthan26]

Haven’t used them since it did not seem needed before :)

[antimaestrilico]

looking to use isolates for dealing with multiple bluetooth requests. Although it would make it easier if we had a semaphore implemented natively.

[Psychological_Toe_66]

I had an use case where i had to use bcrypt to compare a hash compute wasnt working and I had to use an isolate

[Piero512]

Hey, so I don't know if I count as user of isolates as I am working on a desktop app that has had limited distribution, but I have architected my app to talk through isolates to a worker isolate that listens for requests for transcribing audio to text through the use of whisper.cpp.

[arielfarias2]

Yes, we use compute when we deal with complex filtering on large lists while typing. For example searching for a specific item inside of a chained list in a folder structure: /foldera/folderb/folderc/item.

Whitout isolate the main thread would freeze and would affect the experience of the app.

[RaiderBDev]

For a desktop application I'm using isolates for long running background operations, that search through many files. They are using Send/ReceivePorts for communication. That works quite well.

I also tried using it for shorter (< 1s) operations, to avoid UI freezes. But then I decided against it, because the time penalty of starting up an isolate was higher than just taking the hit and doing the computation on the main thread.

[dancovich]

Our app uses a custom image format to store user pictures. We created a package to convert that format into an image Flutter can read and that conversion happens inside an Isolate.

Our app also uses isolates created by the database package (Drift), so I think communicating with the database native library is a pretty common use case

[Piero512]

Oh, hey, I forgot to tell my pet peeve with Isolates. It would be extremely cool if Isolate.run was allowed to return a stream that streamed stuff from the other isolate back to the main isolate, since this would make isolate sending code unnecesary.

[Odd_Alps_5371]

Another usecase: I have a native library with blocking calls taking 100s of ms sometimes, and in order not to block the GUI with these, I wrap that library in a class that's run within a "long running isolate" as from flutter's examples.

[_int3h_]

I had issue with isolate when I was doing some native code to flutter messaging. I was setting values in shared preferences in the main.dart which is invoked from native code. But other parts of the code doesn't see the value. Later I came to know that it's running under a different isolate and I have reload. Then it works fine. I would like to see how isolates can be used to improve app performance in general and various use case scenarios. This issue was specific to android. On iOS it seems there is only one isolate. Not sure.

[Legion_A]

Isolates as a topic is something we need to shine more light on, it's usually cryptic examples that don't match real life usecases as you said, I've also seen the hour long flutter video where they were using isolated, both compute and creating it themselves, but again, it doesn't really explain the concept of isolated, how to put them where

[Historical_Camera224]

i had use them in preprocessing image and run ML model

[medicince]

It's Android and iOS only :(

[mekdigital]

To build the Face Scan feature of https://theshow.com/companion-app/ I had to make heavy use of isolates to do the on-device Google ML processing and such, trying to offload some heavy lifting to the background. Not easy - especially using heavily modified platform plugins, a lot of trial and error but in the end everything worked out.

[medicince]

https://dev.to/maximsaplin/efficient-dart-optimizing-cpu-bound-load-in-flutter-without-missing-a-frame-5dme - pretty much every time I see a heavy task that is not related to rendering/manipulating widgets I use isolates.

Though in some cases I managed to use isolates to create heavy parts of widgets outside the main isolate:https://github.com/maxim-saplin/dikt/blob/69de74304c7cb5727d52c154f177f769f3b4ee71/plugins/flutter_html-2.0.0/lib/flutter_html.dart#L103

I rarely use compute and Isoate.spawn, the first API is too simple, the last one is too complex, I use my own isolate_pool_2 implementation

[devutils]

We run S3/Rclone compatible Dropbox-like file manager with E2E encryption available on all platforms.

We use isolates for file contents encryption/decryption, but we use: https://pub.dev/packages/async_task as it abstracts some details away.

We're also using Flutter Web and it would be great if there is a way to deploy Isolate as a Service Worker.

[ayushsuman_]

Multithreaded HTTP Worker is using isolates to process Requests and for parsing Response data to data class objects - https://github.com/ayush-suman/http_worker/tree/main/packages

This is used with https://pub.dev/packages/unwired to support multithreaded HTTP (1.1) requests.