| 1 | | | import 'dart:async'; |
| 2 | | | |
| 3 | | | import 'package:cancelation_token/cancelation_token.dart'; |
| 4 | | | |
| 5 | | | import '../exceptions/squadron_canceled_exception.dart'; |
| 6 | | | import '../exceptions/squadron_error.dart'; |
| 7 | | | import '../worker/worker_request.dart'; |
| 8 | | | import '_squadron_cancelation_token.dart'; |
| 9 | | | |
| 10 | | | /// Cancelation token reference. This special cancelation token is managed by the [WorkerMonitor] and is used to |
| 11 | | | /// mirror cancelation tokens presented to Squadron by callers of a worker service. When a [WorkerRequest] is |
| 12 | | | /// handled by the platform worker and that request is associated with a cancelation request, the [WorkerMonitor] |
| 13 | | | /// will override the request's cancelation token with a [CancelationTokenReference]. The same cancelation may |
| 14 | | | /// be used for several service calls, so the [WorkerMonitor] keeps a map of [CancelationTokenReference] and a |
| 15 | | | /// reference count that is incremented for each [WorkerRequest] having the same cancelation token and decremented |
| 16 | | | /// when processing is finished. When the reference count drops to 0 and the cancelation token was not canceled, |
| 17 | | | /// the [CancelationTokenReference] is removed from the map. |
| 18 | | | /// |
| 19 | | | /// When a caller cancels a token, a cancelation notification is sent to all workers in the pool and the |
| 20 | | | /// corresponding [CancelationTokenReference] will be canceled. Services executing in the context of a platform |
| 21 | | | /// worker will be able to inspect the token's status to interrupt processing gracefully. If the token's status is |
| 22 | | | /// not inspected, processing will continue in platform workers, but will be interrupted on caller-side with a |
| 23 | | | /// [CanceledException]. |
| 24 | | | class CancelationTokenReference implements SquadronCancelationToken { |
| 25 | | 10 | CancelationTokenReference._noToken() |
| 26 | | | : _hasRef = false, |
| 27 | | | id = '' { |
| 28 | | 10 | _refCount = 1; |
| 29 | | | } |
| 30 | | | |
| 31 | | | @override |
| 32 | | | final String id; |
| 33 | | | |
| 34 | | | /// Singleton token reference instance for requests containing no token. |
| 35 | | 30 | static final noToken = CancelationTokenReference._noToken(); |
| 36 | | | |
| 37 | | | /// Creates a new token reference for [id]. |
| 38 | | 2 | CancelationTokenReference(this.id) : _hasRef = true; |
| 39 | | | |
| 40 | | 0 | @override |
| 41 | | 0 | SquadronCanceledException? get exception => _exception; |
| 42 | | | SquadronCanceledException? _exception; |
| 43 | | | |
| 44 | | 0 | @override |
| 45 | | 0 | bool get isCanceled => (_exception != null); |
| 46 | | | |
| 47 | | 0 | @override |
| 48 | | 0 | Future<CanceledException> get onCanceled => _completer.future; |
| 49 | | | final _completer = Completer<SquadronCanceledException>(); |
| 50 | | | |
| 51 | | | /// Whether this token reference instance has a reference. A token reference |
| 52 | | | /// without a reference does nothing. |
| 53 | | | final bool _hasRef; |
| 54 | | | |
| 55 | | | /// Reference counter. |
| 56 | | 20 | int get refCount => _refCount; |
| 57 | | | int _refCount = 0; |
| 58 | | | |
| 59 | | | /// Use this token reference for [request]. Increments the internal reference |
| 60 | | | /// counter and overrides [WorkerRequest.cancelToken] with this token. |
| 61 | | 10 | void usedBy(WorkerRequest request) { |
| 62 | | 10 | if (_hasRef) { |
| 63 | | 4 | _refCount++; |
| 64 | | 2 | request.overrideCancelToken(this); |
| 65 | | 10 | } else if (request.cancelToken != null) { |
| 66 | | 0 | throw SquadronErrorImpl.create('Token reference mismatch'); |
| 67 | | | } |
| 68 | | | } |
| 69 | | | |
| 70 | | | /// Release this token reference. Decrements the internal reference counter. |
| 71 | | 10 | void release() { |
| 72 | | 10 | if (_hasRef) { |
| 73 | | 4 | _refCount--; |
| 74 | | | } |
| 75 | | | } |
| 76 | | | |
| 77 | | 2 | void update(SquadronCancelationToken token) { |
| 78 | | 2 | final ex = token.exception; |
| 79 | | 4 | if (ex != null && !_completer.isCompleted) { |
| 80 | | 2 | _exception = ex; |
| 81 | | 4 | _completer.complete(ex); |
| 82 | | | } |
| 83 | | | } |
| 84 | | | |
| 85 | | 0 | @override |
| 86 | | | void ensureStarted() {/* nothing to do */} |
| 87 | | | |
| 88 | | 0 | @override |
| 89 | | | void throwIfCanceled() { |
| 90 | | 0 | if (_exception != null) { |
| 91 | | 0 | throw _exception!; |
| 92 | | | } |
| 93 | | | } |
| 94 | | | |
| 95 | | 0 | @override |
| 96 | | 0 | Future<void> refreshAndThrowIfCanceled() => Future(throwIfCanceled); |
| 97 | | | |
| 98 | | 0 | @override |
| 99 | | | // no native cancelation token in workers |
| 100 | | 0 | CancelationToken? get token => throw UnimplementedError(); |
| 101 | | | |
| 102 | | 0 | @override |
| 103 | | | // serialization of token references |
| 104 | | 0 | List serialize() => throw UnimplementedError(); |
| 105 | | | } |