1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
|
// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
#if !NO_TPL
using System.Reactive.Disposables;
using System.Threading;
using System.Threading.Tasks;
namespace System.Reactive.Concurrency
{
/// <summary>
/// Represents an object that schedules units of work on the Task Parallel Library (TPL) task pool.
/// </summary>
/// <seealso cref="TaskPoolScheduler.Default">Instance of this type using the default TaskScheduler to schedule work on the TPL task pool.</seealso>
public sealed class TaskPoolScheduler : LocalScheduler, ISchedulerLongRunning, ISchedulerPeriodic
{
private static readonly TaskPoolScheduler s_instance = new TaskPoolScheduler(new TaskFactory(TaskScheduler.Default));
private readonly TaskFactory taskFactory;
/// <summary>
/// Creates an object that schedules units of work using the provided TaskFactory.
/// </summary>
/// <param name="taskFactory">Task factory used to create tasks to run units of work.</param>
/// <exception cref="ArgumentNullException"><paramref name="taskFactory"/> is null.</exception>
public TaskPoolScheduler(TaskFactory taskFactory)
{
if (taskFactory == null)
throw new ArgumentNullException("taskFactory");
this.taskFactory = taskFactory;
}
/// <summary>
/// Gets an instance of this scheduler that uses the default TaskScheduler.
/// </summary>
public static TaskPoolScheduler Default
{
get
{
return s_instance;
}
}
/// <summary>
/// Schedules an action to be executed.
/// </summary>
/// <typeparam name="TState">The type of the state passed to the scheduled action.</typeparam>
/// <param name="state">State passed to the action to be executed.</param>
/// <param name="action">Action to be executed.</param>
/// <returns>The disposable object used to cancel the scheduled action (best effort).</returns>
/// <exception cref="ArgumentNullException"><paramref name="action"/> is null.</exception>
public override IDisposable Schedule<TState>(TState state, Func<IScheduler, TState, IDisposable> action)
{
if (action == null)
throw new ArgumentNullException("action");
var d = new SerialDisposable();
var cancelable = new CancellationDisposable();
d.Disposable = cancelable;
taskFactory.StartNew(() =>
{
//
// BREAKING CHANGE v2.0 > v1.x - No longer escalating exceptions using a throwing
// helper thread.
//
// Our manual escalation based on the creation of a throwing thread was merely to
// expedite the process of throwing the exception that would otherwise occur on the
// finalizer thread at a later point during the app's lifetime.
//
// However, it also prevented applications from observing the exception through
// the TaskScheduler.UnobservedTaskException static event. Also, starting form .NET
// 4.5, the default behavior of the task pool is not to take down the application
// when an exception goes unobserved (done as part of the async/await work). It'd
// be weird for Rx not to follow the platform defaults.
//
// General implementation guidelines for schedulers (in order of importance):
//
// 1. Always thunk through to the underlying infrastructure with a wrapper that's as tiny as possible.
// 2. Global exception notification/handling mechanisms shouldn't be bypassed.
// 3. Escalation behavior for exceptions is left to the underlying infrastructure.
//
// The Catch extension method for IScheduler (added earlier) allows to re-route
// exceptions at stage 2. If the exception isn't handled at the Rx level, it
// propagates by means of a rethrow, falling back to behavior in 3.
//
d.Disposable = action(this, state);
}, cancelable.Token);
return d;
}
/// <summary>
/// Schedules an action to be executed after dueTime.
/// </summary>
/// <typeparam name="TState">The type of the state passed to the scheduled action.</typeparam>
/// <param name="state">State passed to the action to be executed.</param>
/// <param name="action">Action to be executed.</param>
/// <param name="dueTime">Relative time after which to execute the action.</param>
/// <returns>The disposable object used to cancel the scheduled action (best effort).</returns>
/// <exception cref="ArgumentNullException"><paramref name="action"/> is null.</exception>
public override IDisposable Schedule<TState>(TState state, TimeSpan dueTime, Func<IScheduler, TState, IDisposable> action)
{
if (action == null)
throw new ArgumentNullException("action");
var dt = Scheduler.Normalize(dueTime);
if (dt.Ticks == 0)
return Schedule(state, action);
#if !NO_TASK_DELAY
var d = new MultipleAssignmentDisposable();
var ct = new CancellationDisposable();
d.Disposable = ct;
#if USE_TASKEX
TaskEx.Delay(dueTime, ct.Token).ContinueWith(_ =>
#else
Task.Delay(dueTime, ct.Token).ContinueWith(_ =>
#endif
{
if (!d.IsDisposed)
d.Disposable = action(this, state);
}, CancellationToken.None, TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.OnlyOnRanToCompletion, taskFactory.Scheduler);
return d;
#else
return DefaultScheduler.Instance.Schedule(state, dt, (_, state1) => Schedule(state1, action));
#endif
}
/// <summary>
/// Schedules a long-running task by creating a new task using TaskCreationOptions.LongRunning. Cancellation happens through polling.
/// </summary>
/// <typeparam name="TState">The type of the state passed to the scheduled action.</typeparam>
/// <param name="state">State passed to the action to be executed.</param>
/// <param name="action">Action to be executed.</param>
/// <returns>The disposable object used to cancel the scheduled action (best effort).</returns>
/// <exception cref="ArgumentNullException"><paramref name="action"/> is null.</exception>
public IDisposable ScheduleLongRunning<TState>(TState state, Action<TState, ICancelable> action)
{
var d = new BooleanDisposable();
taskFactory.StartNew(() =>
{
//
// Notice we don't check d.IsDisposed. The contract for ISchedulerLongRunning
// requires us to ensure the scheduled work gets an opportunity to observe
// the cancellation request.
//
action(state, d);
}, TaskCreationOptions.LongRunning);
return d;
}
#if !NO_STOPWATCH
/// <summary>
/// Gets a new stopwatch ob ject.
/// </summary>
/// <returns>New stopwatch object; started at the time of the request.</returns>
public override IStopwatch StartStopwatch()
{
//
// Strictly speaking, this explicit override is not necessary because the base implementation calls into
// the enlightenment module to obtain the CAL, which would circle back to System.Reactive.PlatformServices
// where we're currently running. This is merely a short-circuit to avoid the additional roundtrip.
//
return new StopwatchImpl();
}
#endif
/// <summary>
/// Schedules a periodic piece of work by running a platform-specific timer to create tasks periodically.
/// </summary>
/// <typeparam name="TState">The type of the state passed to the scheduled action.</typeparam>
/// <param name="state">Initial state passed to the action upon the first iteration.</param>
/// <param name="period">Period for running the work periodically.</param>
/// <param name="action">Action to be executed, potentially updating the state.</param>
/// <returns>The disposable object used to cancel the scheduled recurring action (best effort).</returns>
/// <exception cref="ArgumentNullException"><paramref name="action"/> is null.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="period"/> is less than TimeSpan.Zero.</exception>
public IDisposable SchedulePeriodic<TState>(TState state, TimeSpan period, Func<TState, TState> action)
{
if (period < TimeSpan.Zero)
throw new ArgumentOutOfRangeException("period");
if (action == null)
throw new ArgumentNullException("action");
#if !NO_TASK_DELAY
var cancel = new CancellationDisposable();
var state1 = state;
var gate = new AsyncLock();
var moveNext = default(Action);
moveNext = () =>
{
#if USE_TASKEX
TaskEx.Delay(period, cancel.Token).ContinueWith(
#else
Task.Delay(period, cancel.Token).ContinueWith(
#endif
_ =>
{
moveNext();
gate.Wait(() =>
{
state1 = action(state1);
});
},
CancellationToken.None, TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.OnlyOnRanToCompletion, taskFactory.Scheduler
);
};
moveNext();
return new CompositeDisposable(cancel, gate);
#else
var state1 = state;
var gate = new AsyncLock();
var timer = ConcurrencyAbstractionLayer.Current.StartPeriodicTimer(() =>
{
taskFactory.StartNew(() =>
{
gate.Wait(() =>
{
state1 = action(state1);
});
});
}, period);
return new CompositeDisposable(timer, gate);
#endif
}
}
}
#endif
|
