Isolate Manager

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Features

  • A generator to generate all Workers by using the @isolateManagerWorker annotation.
  • An easy way to create multiple long-lived isolates for a function (keep it active to send and receive data).
  • Supports Worker on the Web (If the Worker is unavailable in the working browser or is not configured, the Future (and Stream) will be used instead).
  • Supports WASM compilation on the Web.
  • Multiple compute operations are allowed because the plugin will queue the input data and send it to a free isolate later.
  • Supports try-catch blocks.
  • To compute with multiple functions, you can use the isolates_helper instead.

Table Of Contents

Benchmark

Execute a recursive Fibonacci function 70 times, computing the sequence for the numbers 30, 33, and 36. The results are in microseconds.

  • VM
Fibonacci Main App One Isolate Three Isolates Isolate.run
30 470,941 477,477 171,081 486,789
33 1,964,361 1,985,924 706,867 2,006,519
36 8,327,773 8,327,912 2,994,311 8,434,936
  • Chrome (With Worker supported)
Fibonacci Main App One Worker Three Workers Isolate.run (Unsupported)
30 1,334,900 341,799 121,000 0
33 5,705,399 1,394,500 501,401 0
36 24,165,201 5,924,900 2,115,500 0

See here for the test details.

Basic Usage

There are multiple ways to use this package. The only thing to notice is that the function has to be a static or top-level function.

main() async {
  final isolate = IsolateManager.create(
      fibonacci, 
      concurrent: 4
    );

  isolate.stream.listen((value) {
    print(value);
  });

  final fibo = await isolate(55);
}

int fibonacci(int n) {
  if (n == 0) return 0;
  if (n == 1) return 1;

  return fibonacci(n - 1) + fibonacci(n - 2);
}

You can restart or stop the isolate using this method:

await isolateManager.restart();
await isolateManager.stop();

Basic Usage (With The Web Worker)

There are multiple ways to use this package. The only thing to notice is that the function has to be a static or top-level function.

main() async {
  final isolate = IsolateManager.create(
      fibonacci, 
      workerName: 'fibonacci', // Add this line
      concurrent: 4
    );

  isolate.stream.listen((value) {
    print(value);
  });

  final fibo = await isolate(55);
}

@isolateManagerWorker // Add this anotation
int fibonacci(int n) {
  if (n == 0) return 0;
  if (n == 1) return 1;

  return fibonacci(n - 1) + fibonacci(n - 2);
}

Run this command to generate a Javascript Worker:

dart run isolate_manager:generate

You can restart or stop the isolate using this method:

await isolateManager.restart();
await isolateManager.stop();

Custom Function Usage

You can control everything with this method when you want to create multiple isolates for a function. With this method, you can also do one-time stuff (onInitial) when the isolate is started or each-time stuff when you call compute or sendMessage.

Step 1: Create a function of this form

Let it automatically handles the result and the Exception:

void customIsolateFunction(dynamic params) {
  IsolateManagerFunction.customFunction<int, int>(
    params,
    onEvent: (controller, message) {
      /* This event will be executed every time the `message` is received from the main isolate */
      return fibonacci(message);
    },
    onInitial: (controller, initialParams) {
       // This event will be executed before all the other events
       //
       // This event can be a `Future`.
    },
    onDispose: (controller) {
       /* This event will be executed after all the other events and should NOT be a `Future` event */
    },
  );
}

Handle the result and the Exception by your self:

void customIsolateFunction(dynamic params) {
  IsolateManagerFunction.customFunction<Map<String, dynamic>, String>(
    params,
    onEvent: (controller, message) {
      // This event will be executed every time the `message` is received from the main isolate.
      //
      // This event can be a `Future`.
      try {
        final result = fibonacci(message);
        controller.sendResult(result);
      } catch (err, stack) {
        controller.sendResultError(IsolateException(err, stack));
      }

      // Just returns something that unused to complete this method.
      return 0;
    },
    onInitial: (controller, initialParams) {
       // This event will be executed before all the other events.
       //
       // This event can be a `Future`.
    },
    onDispose: (controller) {
       // This event will be executed after all the other events.
       //
       // This event should NOT be a `Future` event */
    },
    autoHandleException: false,
    autoHandleResult: false,
  );
}

Step 2: Create an IsolateManager instance for your own function

final isolateManager = IsolateManager.createCustom(
    customIsolateFunction,
    initialParams: 'This is the initialParams',
    debugMode: true,
  );

Now you can use everything as the Basic Usage.

Custom Worker Usage

Use The Generator

Step 1: Use a modifiable annotation

@IsolateManagerWorker('RecursiveFibonacci')
int fibonacci(int n) {
  if (n == 0) return 0;
  if (n == 1) return 1;

  return fibonacci(n - 1) + fibonacci(n - 2);
}

Step 2: Execute the generator

dart run isolate_manager:generate

Step 3: Update the IsolateManager:

final isolate = IsolateManager.create(fibonacci, workerName: 'RecursiveFibonacci');

If you want to place the generated JS inside a subfolder, you can update the annotation to @IsolateManagerWorker('workers/RecursiveFibonacci') and update the workerName to workers/RecursiveFibonacci.

Static functions are also supported. A function WorkerFunctions.method will be compiled to WorkerFunctions.method.js, so that the workerName will be WorkerFunctions.method.

Manually

Step 1: Create a Worker file

Create a fibonacci.dart file with this content

import 'package:isolate_manager/isolate_manager.dart';

main() {
  // The function `fibonacci` MUST NOT depend on any Flutter library
  IsolateManagerFunction.workerFunction(
    fibonacci,
    onInitial: () {
      /* Optional. Run before all events */
    }
  );
}

Step 2: Compile to JS

Run dart compile js fibonacci.dart -o fibonacci.js -O4 to compile Dart to JS (The flag -O4 is the obfuscated level of JS, the lowest value is -O0 and the highest value is -O4)

Step 3: Copy to the Web folder

Copy the fibonacci.js to the Web folder (the same folder with index.html)

Step 4: Add it to the IsolateManager

Update the isolateManager like below

final isolateManager = IsolateManager.create(
    fibonacci,
    workerName: 'fibonacci', // The name of the file, don't need to add the extension
  );

Now the plugin will handle all other action to make the real isolate works on Web.

Note: If you want to use Worker more effectively, convert all parameters and results to JSON (or String) before sending them.

try-catch Block

You can use try-catch to catch exceptions:

try {
  final result = await isolate(-10);
} on SomeException catch (e1) {
  print(e1);
} catch (e2) {
  print(e2);
}

Progress Values

You can even manage the final result by using this callback, useful when you create your own function that needs to send the progress value before returning the final result:

main() {
  // Create an IsolateManager instance.
  final isolateManager = IsolateManager.createCustom(progressFunction);

  // Get the result.
  final result = await isolateManager.compute(100, callback: (value) {
    // Condition to recognize the progress value. Ex:
    if (value != 100) {
      print('This is a progress value: $value');

      // Return `false` to mark this value is not the final.
      return false;
    }

    print('This is a final value: $value');

    // Return `true` to mark this value is the final.
    return true;
  });

  print(result); // 100
}

// This is a progress function
void progressFunction(dynamic params) {
  IsolateManagerFunction.customFunction<int, int>(
    params,
    onEvent: (controller, message) {
      // This value is sent as the progress values.
      for (int i = 0; i < message; i++) {
        controller.sendResult(i);
      }

      // This is a final value.
      return message;
    },
  );
}

Additional Information

  • The function has to be a static or top-level function.

  • Use queuesLength to get the current number of queued computation.

  • Use ensureStarted to able to wait for the start method to finish when you want to call the start method manually without await and wait for it later.

  • Use isStarted to check if the start method is completed or not.

  • The result that you get from the isolate (or Worker) is sometimes different from the result that you want to get from the return type in the main app, you can use converter and workerConverter parameters to convert the result received from the Isolate (converter) and Worker (workerConverter). Example:

    1. List<String>

      main() async {
  final isolate = IsolateManager.create(
    aStringList,
    workerName: 'aStringList',
    // Cast to List<String>
    workerConverter: (value) => value.cast<String>() as List<String>,
    isDebug: true,
  );

  final listString = ['a', 'b', 'c'];
  final result = await isolate.compute(listString);
  expect(result, listString);
}

@isolateManagerWorker
List<String> aStringList(List<String> params) {
  return params;
}

    2. Map<String, int>: Use json for the complicated cases

      main() async {
  final isolate = IsolateManager.create(
    aStringIntMap,
    workerName: 'aStringIntMap',
    isDebug: true,
  );
  await isolate.start();

  final map = {'a': 1, 'b': 2, 'c': 3};
  final result = await isolate.compute(jsonEncode(map));
  expect(jsonDecode(result), map);
}

@isolateManagerWorker
String aStringIntMap(String params) {
  return params;
}

    Data flow: Main -> Isolate or Worker -> Converter -> Result

  • If you want to use Worker more effectively, convert all parameters and results to JSON (or String) before sending them.

Contributions

  • If you encounter any problems or feel the library is missing a feature, feel free to open an issue. Pull requests are also welcome.

  • If you like my work or the free stuff on this channel and want to say thanks, or encourage me to do more, you can buy me a coffee. Thank you so much!

    BMC QR

Migrations

v5.0.0

All isolate functions MUST be update and all Workers MUST be recompiled with the following changes:

  • If you're using the IsolateManagerFunction.workerFunction, you need to re-generate the JS for the Web Worker (compile from Dart to JS). If you're using the IsolateManagerFunction.customFunction, it will be automatically updated.

  • If you're using the old method, you need to send a initialized signal from an Isolate and a Worker:

    • Custom function of an Isolate: add the controller.initialized(); to the end of the function.

      • Before:

        void customFunction(dynamic params) {
  final controller = IsolateManagerController(params);
  controller.onIsolateMessage.then((value){
    // ...
  });
}

      • After:

        void customFunction(dynamic params) async {
  // Do something sync or async here

  final controller = IsolateManagerController(params); 
  controller.onIsolateMessage.then((value){
    // ...
  });

  controller.initialized(); // <--
}

    • On the Web Worker: add jsSendMessage(IsolateState.initialized.toJson()); to the end of the main method.

      • Before:

        void main() {
  callbackToStream('onmessage', (MessageEvent e) {
    return js_util.getProperty(e, 'data');
  }).listen((message) {
    // ...
  });  
}

      • After:

        void main() async {
  // Do something sync or async here

  callbackToStream('onmessage', (MessageEvent e) {
    return js_util.getProperty(e, 'data');
  }).listen((message) {
    // ...
  });

  jsSendMessage(IsolateState.initialized.toJson()); // <--
}

Libraries

isolate_manager
Create multiple long-lived isolates for a function (keep it active to send and receive data), supports Worker and WASM on the Web.