PollingComponent.cs
106 lines
| 3.3 KiB
| text/x-csharp
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CSharpLexer
cin
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r289 | using System; | |
| using System.Threading; | |||
| using System.Threading.Tasks; | |||
| namespace Implab.Components { | |||
| public abstract class PollingComponent : RunnableComponent { | |||
| readonly Timer m_timer; | |||
| readonly CancellationTokenSource m_cancellation = new CancellationTokenSource(); | |||
| Task m_pending; | |||
| Task m_poll; | |||
| /// <summary> | |||
| /// Poll interval in milliseconds. | |||
| /// </summary> | |||
| /// <returns></returns> | |||
| public int Interval { get; set; } | |||
| /// <summary> | |||
| /// Delay to the first poll after start in milliseconds | |||
| /// </summary> | |||
| /// <returns></returns> | |||
| public int Delay { get; set; } | |||
| /// <summary> | |||
| /// Indicates how to handle unhandled exceptions in <see cref="Poll()"/> method. | |||
| /// </summary> | |||
| /// <returns></returns> | |||
| public bool FailOnError { get; set; } | |||
| /// <summary> | |||
| /// Event for the unhandled exceptions in <see cref="Poll()"/> method. | |||
| /// </summary> | |||
| public event EventHandler<UnhandledExceptionEventArgs> UnhandledException; | |||
| protected PollingComponent(bool initialized) : base(initialized) { | |||
| m_timer = new Timer(OnTimer); | |||
| } | |||
| protected override void RunInternal() { | |||
| ScheduleNextPoll(Delay); | |||
| } | |||
| protected override async Task StopInternalAsync(CancellationToken ct) { | |||
| // component in Stopping state, no new polls will be scheduled | |||
| // we do not need additional synchronization logic here | |||
| // since RunnableComponent already done this | |||
| m_cancellation.Cancel(); | |||
| try { | |||
| // await for pending poll | |||
| if (m_poll != null) | |||
| await m_poll; | |||
| } catch (OperationCanceledException) { | |||
| // OK | |||
| } | |||
| } | |||
| protected abstract Task Poll(CancellationToken ct); | |||
| void ScheduleNextPoll(int timeout) { | |||
| // access and modification of the component state | |||
| // in custom methods requires a synchronization | |||
| lock (SynchronizationObject) { | |||
| if (State == ExecutionState.Running) { | |||
| m_pending = Safe.CreateTask(m_cancellation.Token); | |||
| m_poll = m_pending.Then(() => Poll(m_cancellation.Token)); | |||
| m_timer.Change(timeout, Timeout.Infinite); | |||
| } | |||
| } | |||
| } | |||
| async void OnTimer(object state) { | |||
| try { | |||
| // changes to m_pending and m_poll are done | |||
| // only in ScheduleNextPoll method, hence we | |||
| // can safely use them here | |||
| m_pending.Start(); | |||
| await m_poll; | |||
| // schedule next poll | |||
| ScheduleNextPoll(Interval); | |||
| } catch (Exception e) { | |||
| // hanle error | |||
| UnhandledException.DispatchEvent(this, new UnhandledExceptionEventArgs(e, false)); | |||
| if (FailOnError) | |||
| Fail(e); | |||
| else | |||
| ScheduleNextPoll(Interval); | |||
| } | |||
| } | |||
| protected override void Dispose(bool disposing) { | |||
| if (disposing) | |||
| Safe.Dispose(m_timer, m_cancellation); | |||
| base.Dispose(disposing); | |||
| } | |||
| } | |||
| } |