squadron_builder 2.3.0

Dart code generator for Squadron workers. Implement your worker service and let squadron_builder bridge the gap with Web Workers and Isolates!

squadron_builder

Dart code generator for Squadron workers. Implement your worker service and let squadron_builder bridge the gap with Web Workers and Isolates!

Example

The example computes Fibonacci numbers recursively, simply applying the definition of the Fibonacci sequence. It is very inefficient, but illustrates the effect of multithreading.

The service implementation uses Squadron annotations to enable automatic code generation.

import 'dart:async';

import 'package:squadron/squadron_annotations.dart';
import 'package:squadron/squadron.dart';

import 'fib_service.activator.g.dart';

part 'fib_service.worker.g.dart';

@SquadronService(baseUrl: '/workers')
class FibService extends WorkerService with $FibServiceOperations {
  @SquadronMethod()
  Future<int> fibonacci(int i) async => _fib(i);

  // naive & inefficient implementation of the Fibonacci sequence
  static int _fib(int i) => (i < 2) ? i : (_fib(i - 2) + _fib(i - 1));
}

To have squadron_builder generate the code for the worker and the worker pool, run:

dart run build_runner build

The main program runs the same computation:

• first with a plain instance of FibService (single-threaded, running in the main program's Isolate),
• then with a plain instance of FibService (single-threaded, running in the main program's Isolate),
• finally with an instance of FibServiceWorkerPool (multi-threaded, running in specific Isolates managed by the worker pool).

The worker and worker pool generated by squadron_builder both wrap the original service and implement it: as a result, they are interchangeable with the original service.

import 'package:squadron/squadron.dart';

import 'fib_service.dart';

void main() async {
  Squadron.setId('MAIN');
  Squadron.setLogger(ConsoleSquadronLogger());
  Squadron.logLevel = SquadronLogLevel.info;

  int count = 5;

  Squadron.info('Computing with FibService (single-threaded)');
  await computeWith(FibService(), count);

  Squadron.info('Computing with FibServiceWorkerPool (multi-threaded)');
  final pool = FibServiceWorkerPool(
      concurrencySettings: ConcurrencySettings(
    minWorkers: count,
    maxWorkers: count,
    maxParallel: 1,
  ));
  await pool.start();
  await computeWith(pool, count);
  pool.stop();
}

Future computeWith(FibService service, int count) async {
  final sw = Stopwatch();
  sw.start();

  final futures = <Future<int>>[];
  for (var i = 0; i < count; i++) {
    futures.add(service.fibonacci(40 + i));
  }

  final results = await Future.wait(futures);
  Squadron.info('  * Results = $results');
  Squadron.info('  * Total elapsed time: ${sw.elapsed}');
  sw.stop();
}

To run the example:

dart run .\example\main.dart

Sample output:

[2022-08-21T19:55:46.358940Z] [INFO] [MAIN] Computing with FibService (single-threaded)
[2022-08-21T19:55:52.559343Z] [INFO] [MAIN]   * Results = [102334155, 165580141, 267914296, 433494437, 701408733]
[2022-08-21T19:55:52.571404Z] [INFO] [MAIN]   * Total elapsed time: 0:00:06.199773
[2022-08-21T19:55:52.571404Z] [INFO] [MAIN] Computing with FibServiceWorkerPool (multi-threaded)
[2022-08-21T19:55:55.777452Z] [INFO] [MAIN]   * Results = [102334155, 165580141, 267914296, 433494437, 701408733]
[2022-08-21T19:55:55.777452Z] [INFO] [MAIN]   * Total elapsed time: 0:00:03.170634