backoff_stream.dart

backoff_stream.dart

import 'dart:math';

Stream<int> linearBackoff({
  required int limit,
  required num delay,
}) async* {
  for (var i = 0; i < limit; i++) {
    await Future.delayed(Duration(milliseconds: delay.floor()));
    yield i;
  }
}

Stream<int> exponentialBackoff({
  required int limit,
  required num base,
  num capacity = double.infinity,
  num factor = 2,
}) async* {
  final random = Random();
  for (var i = 0; i < limit; i++) {
    final delay = random.nextDouble() * min(capacity, base * pow(factor, i));
    await Future.delayed(Duration(milliseconds: delay.floor()));
    yield i;
  }
}

void main() async {
  final backoff = exponentialBackoff(limit: 5, base: 100, capacity: 1000);
  
  DateTime prev = DateTime.now();
  
  await for (final i in backoff) {
    final now = DateTime.now();
    
    print('retry#$i ${now.difference(prev).inMilliseconds}ms');
    
    prev = now;
  }
}