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| 1 // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file |
| 2 // for details. All rights reserved. Use of this source code is governed by a |
| 3 // BSD-style license that can be found in the LICENSE file. |
| 4 |
| 5 library microlytics.channels; |
| 6 |
| 7 import 'dart:async'; |
| 8 |
| 9 const String ANALYTICS_URL = "https://ssl.google-analytics.com/collect"; |
| 10 |
| 11 abstract class Channel { |
| 12 void sendData(String data); |
| 13 void shutdown() {} |
| 14 } |
| 15 |
| 16 /// [Channel] that implements a leaky bucket |
| 17 /// algorithm to provide rate limiting. |
| 18 /// See [http://en.wikipedia.org/wiki/Leaky_bucket]. |
| 19 class RateLimitingBufferedChannel extends Channel { |
| 20 final List<String> _buffer = <String>[]; |
| 21 final Channel _innerChannel; |
| 22 final int _bufferSizeLimit; |
| 23 Timer _timer; |
| 24 |
| 25 RateLimitingBufferedChannel( |
| 26 this._innerChannel, |
| 27 {int bufferSizeLimit: 10, |
| 28 double packetsPerSecond: 1.0}) |
| 29 : this._bufferSizeLimit = bufferSizeLimit { |
| 30 if (!(packetsPerSecond > 0)) { |
| 31 throw new ArgumentError("packetsPerSecond must be larger than zero."); |
| 32 } |
| 33 |
| 34 int transmitDelay = (1000 / packetsPerSecond).floor(); |
| 35 _timer = new Timer.periodic( |
| 36 new Duration(milliseconds: transmitDelay), _onTimerTick); |
| 37 } |
| 38 |
| 39 void _onTimerTick(_) { |
| 40 if (_buffer.length > 0) { |
| 41 String item = _buffer.removeLast(); |
| 42 _innerChannel.sendData(item); |
| 43 } |
| 44 } |
| 45 |
| 46 void sendData(String data) { |
| 47 if (_buffer.length >= _bufferSizeLimit) return; |
| 48 _buffer.add(data); |
| 49 } |
| 50 |
| 51 void shutdown() { |
| 52 _timer.cancel(); |
| 53 _innerChannel.shutdown(); |
| 54 } |
| 55 } |
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