RunnableComponent.cs
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r250 | using System; | |
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r251 | using System.Diagnostics; | |
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r250 | using System.Threading; | |
| using System.Threading.Tasks; | |||
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r251 | namespace Implab.Components { | |
| /// <summary> | |||
| /// Base class for implementing components which support start and stop operations, | |||
| /// such components may represent running services. | |||
| /// </summary> | |||
| /// <remarks> | |||
| /// This class provides a basic lifecycle from the creation to the | |||
| /// termination of the component. | |||
| /// </remarks> | |||
| public class RunnableComponent : IRunnable, IInitializable, IDisposable { | |||
| /// <summary> | |||
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r252 | /// This class bounds <see cref="CancellationTokenSource"/> lifetime to the task, | |
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r251 | /// when the task completes the associated token source will be disposed. | |
| /// </summary> | |||
| class AsyncOperationDescriptor { | |||
| public static AsyncOperationDescriptor None { get; } = new AsyncOperationDescriptor(); | |||
| readonly CancellationTokenSource m_cts; | |||
| bool m_done; | |||
| public CancellationToken Token { | |||
| get { return m_cts == null ? CancellationToken.None : m_cts.Token; } | |||
| } | |||
| public Task Task { get; private set; } | |||
| private AsyncOperationDescriptor(Task task, CancellationTokenSource cts) { | |||
| m_cts = cts; | |||
| Task = Chain(task); | |||
| } | |||
| private AsyncOperationDescriptor() { | |||
| Task = Task.CompletedTask; | |||
| } | |||
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r250 | ||
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r251 | public void Cancel() { | |
| if (m_cts != null) { | |||
| lock (m_cts) { | |||
| if (!m_done) | |||
| m_cts.Cancel(); | |||
| } | |||
| } | |||
| } | |||
| void Done() { | |||
| if (m_cts != null) { | |||
| lock (m_cts) { | |||
| m_done = true; | |||
| m_cts.Dispose(); | |||
| } | |||
| } else { | |||
| m_done = true; | |||
| } | |||
| } | |||
| async Task Chain(Task other) { | |||
| try { | |||
| await other; | |||
| } finally { | |||
| Done(); | |||
| } | |||
| } | |||
| public static AsyncOperationDescriptor Create(Func<CancellationToken, Task> factory, CancellationToken ct) { | |||
| var cts = ct.CanBeCanceled ? | |||
| CancellationTokenSource.CreateLinkedTokenSource(ct) : | |||
| new CancellationTokenSource(); | |||
| return new AsyncOperationDescriptor(factory(cts.Token), cts); | |||
| } | |||
| } | |||
| // this lock is used to synchronize state flow of the component during | |||
| // completions or the operations. | |||
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r250 | readonly object m_lock = new object(); | |
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r251 | // current operation cookie, used to check wheather a call to | |
| // MoveSuccess/MoveFailed method belongs to the current | |||
| // operation, if cookies didn't match ignore completion result. | |||
| object m_cookie; | |||
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r250 | ||
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r251 | AsyncOperationDescriptor m_current = AsyncOperationDescriptor.None; | |
| ExecutionState m_state; | |||
| protected RunnableComponent(bool initialized) { | |||
| State = initialized ? ExecutionState.Ready : ExecutionState.Created; | |||
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r250 | } | |
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r251 | public Task Completion { | |
| get { return m_current.Task; } | |||
| } | |||
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r250 | ||
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r251 | public ExecutionState State { | |
| get { return m_state; } | |||
| private set { | |||
| if (m_state != value) { | |||
| m_state = value; | |||
| StateChanged.DispatchEvent(this, new StateChangeEventArgs { | |||
| State = value, | |||
| LastError = LastError | |||
| }); | |||
| } | |||
| } | |||
| } | |||
| public Exception LastError { get; private set; } | |||
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r250 | ||
| public event EventHandler<StateChangeEventArgs> StateChanged; | |||
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r251 | /// <summary> | |
| /// Releases all resources used by the current component regardless of its | |||
| /// execution state. | |||
| /// </summary> | |||
| /// <remarks> | |||
| /// Calling to this method may result unexpedted results if the component | |||
| /// isn't in the stopped state. Call this method after the component is | |||
| /// stopped if needed or if the component is in the failed state. | |||
| /// </remarks> | |||
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r250 | public void Dispose() { | |
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r251 | bool dispose = false; | |
| if (dispose) { | |||
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r250 | Dispose(true); | |
| GC.SuppressFinalize(this); | |||
| } | |||
| } | |||
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r251 | ~RunnableComponent() { | |
| Dispose(false); | |||
| } | |||
| /// <summary> | |||
| /// Releases all resources used by the current component regardless of its | |||
| /// execution state. | |||
| /// </summary> | |||
| /// <param name="disposing">Indicates that the component is disposed | |||
| /// during a normal disposing or during GC.</param> | |||
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r250 | protected virtual void Dispose(bool disposing) { | |
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r251 | } | |
| public void Initialize() { | |||
| var cookie = new object(); | |||
| if (MoveInitialize(cookie)) | |||
| ScheduleTask(InitializeInternalAsync, CancellationToken.None, cookie); | |||
| } | |||
| /// <summary> | |||
| /// This method is used for initialization during a component creation. | |||
| /// </summary> | |||
| /// <param name="ct">A cancellation token for this operation</param> | |||
| /// <remarks> | |||
| /// This method should be used for short and mostly syncronous operations, | |||
| /// other operations which require time to run shoud be placed in | |||
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r252 | /// <see cref="StartInternalAsync(CancellationToken)"/> method. | |
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r251 | /// </remarks> | |
| protected virtual Task InitializeInternalAsync(CancellationToken ct) { | |||
| return Task.CompletedTask; | |||
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r250 | } | |
| public void Start(CancellationToken ct) { | |||
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r251 | var cookie = new object(); | |
| if (MoveStart(cookie)) | |||
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r252 | ScheduleTask(StartInternalAsync, ct, cookie); | |
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r251 | } | |
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r252 | protected virtual Task StartInternalAsync(CancellationToken ct) { | |
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r251 | return Task.CompletedTask; | |
| } | |||
| public void Stop(CancellationToken ct) { | |||
| var cookie = new object(); | |||
| if (MoveStop(cookie)) | |||
| ScheduleTask(StopAsync, ct, cookie); | |||
| } | |||
| async Task StopAsync(CancellationToken ct) { | |||
| m_current.Cancel(); | |||
| await Completion; | |||
| ct.ThrowIfCancellationRequested(); | |||
| await StopInternalAsync(ct); | |||
| } | |||
| protected virtual Task StopInternalAsync(CancellationToken ct) { | |||
| return Task.CompletedTask; | |||
| } | |||
| #region state management | |||
| bool MoveInitialize(object cookie) { | |||
| lock (m_lock) { | |||
| if (State != ExecutionState.Created) | |||
| return false; | |||
| State = ExecutionState.Initializing; | |||
| m_cookie = cookie; | |||
| return true; | |||
| } | |||
| } | |||
| bool MoveStart(object cookie) { | |||
| lock (m_lock) { | |||
| if (State != ExecutionState.Ready) | |||
| return false; | |||
| State = ExecutionState.Starting; | |||
| m_cookie = cookie; | |||
| return true; | |||
| } | |||
| } | |||
| bool MoveStop(object cookie) { | |||
| lock (m_lock) { | |||
| if (State != ExecutionState.Starting && State != ExecutionState.Running) | |||
| return false; | |||
| State = ExecutionState.Stopping; | |||
| m_cookie = cookie; | |||
| return true; | |||
| } | |||
| } | |||
| void MoveSuccess(object cookie) { | |||
| lock (m_lock) { | |||
| if (m_cookie != cookie) | |||
| return; | |||
| switch (State) { | |||
| case ExecutionState.Initializing: | |||
| State = ExecutionState.Ready; | |||
| break; | |||
| case ExecutionState.Starting: | |||
| State = ExecutionState.Running; | |||
| break; | |||
| case ExecutionState.Stopping: | |||
| State = ExecutionState.Stopped; | |||
| break; | |||
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r250 | } | |
| } | |||
| } | |||
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r251 | void MoveFailed(Exception err, object cookie) { | |
| lock (m_lock) { | |||
| if (m_cookie != cookie) | |||
| return; | |||
| LastError = err; | |||
| State = ExecutionState.Failed; | |||
| } | |||
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r250 | } | |
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r251 | ||
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r250 | ||
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r251 | protected async void ScheduleTask(Func<CancellationToken, Task> next, CancellationToken ct, object cookie) { | |
| try { | |||
| m_current = AsyncOperationDescriptor.Create(next, ct); | |||
| await m_current.Task; | |||
| MoveSuccess(cookie); | |||
| } catch (Exception e) { | |||
| MoveFailed(e, cookie); | |||
| } | |||
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r250 | } | |
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r251 | ||
| #endregion | |||
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r250 | } | |
| } |