concurrent_queue
Priority queue with concurrency control
concurrent_queue is a dart implementation of Sindre Sorhus's p-queue
Useful for rate-limiting async (or sync) operations. For example, when interacting with a REST API or when doing CPU/memory intensive tasks.
Usage
import 'package:concurrent_queue/concurrent_queue.dart'
final queue = ConcurrentQueue(
concurrency: 2
);
queue.add(() async {
await Future.delayed(Duration(seconds: 5));
print('Done waiting for 5 seconds');
});
queue.add(() async {
await Future.delay(Duration(seconds: 2));
print('Done waiting for 2 seconds');
});
Advanced example
A more advanced example to help you understand the flow.
import 'package:concurrent_queue/concurrent_queue.dart'
Future delay(int milliseconds) async => Future.delayed(Duration(milliseconds: milliseconds));
final queue = ConcurrentQueue(
concurrency: 2
);
(() async {
await delay(200);
print('8. Pending promises: ${queue.pending}');
//=> '8. Pending promises: 0'
(() async {
await queue.add(() async => '🐙');
print('11. Resolved 🐙');
})();
print('9. Added 🐙');
print('10. Pending promises: ${queue.pending}');
//=> '10. Pending promises: 1'
await queue.onIdle();
print('12. All work is done');
})();
(() async {
await queue.add(() async => '🦄');
print('5. Resolved 🦄');
})();
print('1. Added 🦄');
(() async {
await queue.add(() async => '🐴');
print('6. Resolved 🐴');
})();
print('2. Added 🐴');
(() async {
await queue.onIdle();
print('7. Queue is empty');
})();
print('3. Queue size: ${queue.size}');
//=> '3. Queue size: 1'
print('4. Pending promises: ${queue.pending}');
//=> '4. Pending promises: 1'
await delay(200);
$ node example.js
1. Added 🦄
2. Added 🐴
3. Queue size: 0
4. Pending promises: 2
5. Resolved 🦄
6. Resolved 🐴
7. Queue is empty
8. Pending promises: 0
9. Added 🐙
10. Pending promises: 1
11. Resolved 🐙
12. All work is done