I'm running into the issue where the task being executed below runs asynchronously but is unable to be cancelled when the serializer reads the memory stream. When the user makes the cancellation request (by pressing a cancel button), a cancellation (the method cancel() is called fromt he token) is made but the task continues.
Service Class:
Async method called from LoadHelper() in Main class
public async void StartTask(Action callback, CancellationToken token)
{
await Task.Run(callback, token);
}
Main Class:
private void LoadHelper()
{
_services.GetInstance<IThreadService>().StartTask(
() => LoadHelperAsync(), _cancelService.Token);
}
Method being run async
private void LoadHelperAsync()
{
var serializer = new DataContractSerializer(typeof(UserDatabase));
string selectedDir;
ComparisonResult = null;
_services.GetInstance<IOpenFileService>().DisplayOpenFileDialog(
"Select a saved comparison",
"Comparison File(*.xml; *.cmp)|*.xml;*.cmp",
Environment.GetFolderPath(Environment.SpecialFolder.Desktop),
out selectedDir);
if (!string.IsNullOrEmpty(selectedDir))
{
_dispatchService.BeginInvoke(() => IsExecuting = true);
using (FileStream fileStream = new FileStream(selectedDir, FileMode.Open, FileAccess.Read))
using (DeflateStream compressedStream = new DeflateStream(fileStream, CompressionMode.Decompress))
using (BufferedStream regularStream = new BufferedStream(fileStream))
{
Stream memoryStream;
//Use filename to determine compression
if (selectedDir.EndsWith(".cmp", true, null))
{
memoryStream = compressedStream;
}
else
{
memoryStream = regularStream;
}
Report("Loading comparison");
Report(0);
IsExecuting = true;
ComparisonResult = (UserDatabase)serializer.ReadObject(memoryStream);
memoryStream.Close();
fileStream.Close();
IsExecuting = false;
Report("Comparison loaded");
}
_dispatchService.BeginInvoke(() => IsExecuting = false);
_dispatchService.BeginInvoke(() => ViewResults.ExecuteIfAble());
}
else
{
Report("No comparison loaded");
}
Cancellation code:
This command is binded to a "cancel" button in the view.
CancelCompare = new Command(o => _cancelService.Cancel(), o => IsExecuting);
From the CancellationService class
public class CancellationService : ICancellationService, IDisposable
{
private CancellationTokenSource _tokenSource;
public CancellationService()
{
Reset();
}
public CancellationToken Token { get; private set; }
public void Cancel()
{
_tokenSource.Cancel();
}
public void Reset()
{
_tokenSource = new CancellationTokenSource();
Token = _tokenSource.Token;
}
protected virtual void Dispose(bool disposing)
{
if (disposing)
{
_tokenSource.Cancel();
_tokenSource.Dispose();
}
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
}
Calling _tokenSource.Cancel(); won't do anything to a running task. A cancellation token interrupts task execution only if it was canceled before Task.Run
Take a look:
static void Main(string[] args)
{
using (var tokenSource = new CancellationTokenSource())
{
var aTask = StartTask(() =>
{
while (true)
{
Console.WriteLine("Nothing is going to happen.");
// Some long operation
Thread.Sleep(1000);
}
}, tokenSource.Token);
tokenSource.Cancel();
aTask.Wait();
}
Console.ReadKey();
}
static async Task StartTask(Action callback, CancellationToken cancellationToken)
{
await Task.Run(callback, cancellationToken);
}
If you want to cancel the execution, you should check the cancellation token by yourself, there is no any magic which cancels the task for you:
static void Main(string[] args)
{
using (var tokenSource = new CancellationTokenSource())
{
var aTask = StartTask(cancellationToken =>
{
while (true)
{
cancellationToken.ThrowIfCancellationRequested();
Console.WriteLine("Will stop before that if canceled.");
// Some long operation
// Also pass the token all way down
Task.Delay(1000, cancellationToken).Wait();
}
}, tokenSource.Token);
// Try 0, 500, 1500 to see the difference
Thread.Sleep(1500);
tokenSource.Cancel();
try
{
aTask.Wait();
}
catch (Exception ex)
{
// AggregateException with OperationCanceledException
Console.WriteLine("Task was canceled.");
Console.WriteLine(ex.ToString());
}
}
Console.ReadKey();
}
static async Task StartTask(Action<CancellationToken> callback, CancellationToken cancellationToken)
{
await Task.Run(() => callback(cancellationToken), cancellationToken);
}
Note that this code only illustrates how the task works, never write anything like this in production.
Related
I'm implementing Binance's API.
The documentation says:
WebSocket connections have a limit of 5 incoming messages per second. A message is considered:
A PING frame
A PONG frame
A JSON controlled message (e.g. subscribe, unsubscribe)
For ex. there is a simple web socket wrapper such as the one from the official Binance Connector. According to the limitation above, SendAsync should be restricted 5 messages per second. If a few threads call SendAsync 5 times at the same time (including PING frame which is built-in the ClientWebSocket class), it's going to fail. How can I solve the issue with that limitation gracefully? Using bounded channels is a solution?
public class BinanceWebSocket : IDisposable
{
private IBinanceWebSocketHandler handler;
private List<Func<string, Task>> onMessageReceivedFunctions;
private List<CancellationTokenRegistration> onMessageReceivedCancellationTokenRegistrations;
private CancellationTokenSource loopCancellationTokenSource;
private Uri url;
private int receiveBufferSize;
public BinanceWebSocket(IBinanceWebSocketHandler handler, string url, int receiveBufferSize = 8192)
{
this.handler = handler;
this.url = new Uri(url);
this.receiveBufferSize = receiveBufferSize;
this.onMessageReceivedFunctions = new List<Func<string, Task>>();
this.onMessageReceivedCancellationTokenRegistrations = new List<CancellationTokenRegistration>();
}
public async Task ConnectAsync(CancellationToken cancellationToken)
{
if (this.handler.State != WebSocketState.Open)
{
this.loopCancellationTokenSource = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
await this.handler.ConnectAsync(this.url, cancellationToken);
await Task.Factory.StartNew(() => this.ReceiveLoop(loopCancellationTokenSource.Token, this.receiveBufferSize), loopCancellationTokenSource.Token, TaskCreationOptions.LongRunning, TaskScheduler.Default);
}
}
public async Task DisconnectAsync(CancellationToken cancellationToken)
{
if (this.loopCancellationTokenSource != null)
{
this.loopCancellationTokenSource.Cancel();
}
if (this.handler.State == WebSocketState.Open)
{
await this.handler.CloseOutputAsync(WebSocketCloseStatus.NormalClosure, null, cancellationToken);
await this.handler.CloseAsync(WebSocketCloseStatus.NormalClosure, null, cancellationToken);
}
}
public void OnMessageReceived(Func<string, Task> onMessageReceived, CancellationToken cancellationToken)
{
this.onMessageReceivedFunctions.Add(onMessageReceived);
if (cancellationToken != CancellationToken.None)
{
var reg = cancellationToken.Register(() =>
this.onMessageReceivedFunctions.Remove(onMessageReceived));
this.onMessageReceivedCancellationTokenRegistrations.Add(reg);
}
}
public async Task SendAsync(string message, CancellationToken cancellationToken)
{
byte[] byteArray = Encoding.ASCII.GetBytes(message);
await this.handler.SendAsync(new ArraySegment<byte>(byteArray), WebSocketMessageType.Text, true, cancellationToken);
}
public void Dispose()
{
this.DisconnectAsync(CancellationToken.None).Wait();
this.handler.Dispose();
this.onMessageReceivedCancellationTokenRegistrations.ForEach(ct => ct.Dispose());
this.loopCancellationTokenSource.Dispose();
}
private async Task ReceiveLoop(CancellationToken cancellationToken, int receiveBufferSize = 8192)
{
WebSocketReceiveResult receiveResult = null;
try
{
while (!cancellationToken.IsCancellationRequested)
{
var buffer = new ArraySegment<byte>(new byte[receiveBufferSize]);
receiveResult = await this.handler.ReceiveAsync(buffer, cancellationToken);
if (receiveResult.MessageType == WebSocketMessageType.Close)
{
break;
}
string content = Encoding.UTF8.GetString(buffer.ToArray());
this.onMessageReceivedFunctions.ForEach(omrf => omrf(content));
}
}
catch (TaskCanceledException)
{
await this.DisconnectAsync(CancellationToken.None);
}
}
}
Second way which I'm not 100% sure it solves it
SendAsync is being called in a loop using Channels. SingleReader is set to true, which means there will be only one consumer at a time. It technically should solve the issue, but I'm not 100% sure because the channel might only be limiting the amount in the buffer.
private readonly Channel<string> _messagesTextToSendQueue = Channel.CreateUnbounded<string>(new UnboundedChannelOptions()
{
SingleReader = true,
SingleWriter = false
});
public ValueTask SendAsync(string message)
{
Validations.Validations.ValidateInput(message, nameof(message));
return _messagesTextToSendQueue.Writer.WriteAsync(message);
}
public void Send(string message)
{
Validations.Validations.ValidateInput(message, nameof(message));
_messagesTextToSendQueue.Writer.TryWrite(message);
}
private async Task SendTextFromQueue()
{
try
{
while (await _messagesTextToSendQueue.Reader.WaitToReadAsync())
{
while (_messagesTextToSendQueue.Reader.TryRead(out var message))
{
try
{
await SendInternalSynchronized(message).ConfigureAwait(false);
}
catch (Exception e)
{
Logger.Error(e, L($"Failed to send text message: '{message}'. Error: {e.Message}"));
}
}
}
}
catch (TaskCanceledException)
{
// task was canceled, ignore
}
catch (OperationCanceledException)
{
// operation was canceled, ignore
}
catch (Exception e)
{
if (_cancellationTotal.IsCancellationRequested || _disposing)
{
// disposing/canceling, do nothing and exit
return;
}
Logger.Trace(L($"Sending text thread failed, error: {e.Message}. Creating a new sending thread."));
StartBackgroundThreadForSendingText();
}
}
I would try to keep it as simple as possible and use Semaphore Slim to achieve this, I have created a class to perform this task.
public class ThrottlingLimiter
{
private readonly SemaphoreSlim _semaphore;
private readonly TimeSpan _timeUnit;
public ThrottlingLimiter(int maxActionsPerTimeUnit, TimeSpan timeUnit)
{
if (maxActionsPerTimeUnit < 1)
throw new ArgumentOutOfRangeException(nameof(maxActionsPerTimeUnit));
if (timeUnit < TimeSpan.Zero || timeUnit.TotalMilliseconds > int.MaxValue)
throw new ArgumentOutOfRangeException(nameof(timeUnit));
_semaphore = new SemaphoreSlim(maxActionsPerTimeUnit, maxActionsPerTimeUnit);
_timeUnit = timeUnit;
}
public async Task WaitAsync(CancellationToken cancellationToken = default)
{
await _semaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
ScheduleSemaphoreRelease();
}
private async void ScheduleSemaphoreRelease()
{
await Task.Delay(_timeUnit).ConfigureAwait(false);
_semaphore.Release();
}
}
Now to Use this class, all you have to do is set your limit and timeSpan
public async Task SendData(List<string> allMessages)
{
// Limiting 5 calls per second
ThrottlingLimiter throttlingLimiter = new ThrottlingLimiter(5, TimeSpan.FromSeconds(1));
await Task.WhenAll(allMessages.Select(async message =>
{
await throttlingLimiter.WaitAsync();
try {
await SendInternalSynchronized(message);
// I am not sure what this SendInternalSynchronized returns but I would return some thing to keep a track if this call is successful or not
}
catch (Exception e)
{
Logger.Error(e, L($"Failed to send text message: {message}'. Error: {e.Message}"));
}
});
}
so basically what will happen here is, no matter how big your list is, the ThrottlingLimiter will only send 5 messages per second and wait for the next second to send the next 5 messages.
so, in your case, get all the data from your call to
await _messagesTextToSendQueue.Reader.WaitToReadAsync();
store that into a list or any collection and pass that to the SendData function.
When our connection drops, ReceiveAsync is throwing WebSocketException (ex.WebSocketErrorCode == WebSocketError.ConnectionClosedPrematurely).
The issue is that it's not handled by Polly for some reason. I believe it doesn't handle it, because it's in a separate Task, although I'm doing Task.WhenAny.
The expected behavior is to trigger the reconnect if WebSocketException is thrown.
public sealed class ChannelWebSocketClient : IDisposable
{
private readonly Uri _uri;
private readonly ILogger<ChannelWebSocketClient> _logger;
private readonly Channel<string> _output;
private CancellationTokenSource? _cancellationTokenSource;
public ChannelWebSocketClient(Uri uri, ILoggerFactory loggerFactory)
{
_uri = uri ?? throw new ArgumentNullException(nameof(uri));
_logger = loggerFactory.CreateLogger<ChannelWebSocketClient>();
_output = Channel.CreateUnbounded<string>(new UnboundedChannelOptions
{
SingleReader = true,
SingleWriter = false
});
}
public void Dispose()
{
_output.Writer.TryComplete();
}
public Task StartAsync()
{
return Policy.Handle<Exception>(ex => ex is not (TaskCanceledException or OperationCanceledException))
.WaitAndRetryForeverAsync(
(_, _) => TimeSpan.FromSeconds(5),
(ex, retryCount, calculatedWaitDuration, _) => { _logger.LogError(ex, "Unable to connect to the web socket server. Retry count: {RetryCount} | Retry in {Seconds} seconds", retryCount, calculatedWaitDuration.TotalSeconds); })
.ExecuteAsync(ConnectAsync);
}
public void Stop()
{
_cancellationTokenSource?.Cancel();
}
private async Task ConnectAsync()
{
_logger.LogDebug("Connecting");
using var ws = new ClientWebSocket();
// WebSocketException, TaskCanceledException
await ws.ConnectAsync(_uri, CancellationToken.None).ConfigureAwait(false);
_logger.LogDebug("Connected to {Host}", _uri.AbsoluteUri);
_cancellationTokenSource = new CancellationTokenSource();
var receiving = ReceiveLoopAsync(ws, _cancellationTokenSource.Token);
var sending = SendLoopAsync(ws, _cancellationTokenSource.Token);
var trigger = await Task.WhenAny(receiving, sending).ConfigureAwait(false);
if (trigger == receiving)
{
_cancellationTokenSource?.Cancel();
await sending.ConfigureAwait(false);
}
_logger.LogDebug("END");
}
public async Task SendAsync(string message)
{
await _output.Writer.WriteAsync(message, CancellationToken.None).ConfigureAwait(false);
}
private async Task SendLoopAsync(WebSocket webSocket, CancellationToken cancellationToken)
{
_logger.LogDebug("SendLoopAsync BEGIN");
try
{
while (await _output.Reader.WaitToReadAsync(cancellationToken).ConfigureAwait(false))
{
while (_output.Reader.TryRead(out var message))
{
// WebSocketException, TaskCanceledException, ObjectDisposedException
await webSocket.SendAsync(new ArraySegment<byte>(Encoding.UTF8.GetBytes(message)),
WebSocketMessageType.Text, true, cancellationToken).ConfigureAwait(false);
}
}
}
catch (OperationCanceledException)
{
}
finally
{
_logger.LogDebug("SendLoopAsync END");
}
}
private async Task ReceiveLoopAsync(WebSocket webSocket, CancellationToken cancellationToken)
{
_logger.LogDebug("ReceiveLoopAsync BEGIN");
try
{
while (true)
{
ValueWebSocketReceiveResult receiveResult;
using var buffer = MemoryPool<byte>.Shared.Rent(4096);
await using var ms = new MemoryStream(buffer.Memory.Length);
do
{
// WebSocketException, TaskCanceledException, ObjectDisposedException
receiveResult = await webSocket.ReceiveAsync(buffer.Memory, cancellationToken).ConfigureAwait(false);
if (receiveResult.MessageType == WebSocketMessageType.Close)
{
break;
}
await ms.WriteAsync(buffer.Memory[..receiveResult.Count], cancellationToken).ConfigureAwait(false);
} while (!receiveResult.EndOfMessage);
ms.Seek(0, SeekOrigin.Begin);
if (receiveResult.MessageType == WebSocketMessageType.Text)
{
using var reader = new StreamReader(ms, Encoding.UTF8);
var message = await reader.ReadToEndAsync().ConfigureAwait(false);
_logger.LogInformation("Message received: {Message}", message);
}
else if (receiveResult.MessageType == WebSocketMessageType.Close)
{
break;
}
}
}
catch (WebSocketException ex) when (ex.WebSocketErrorCode == WebSocketError.ConnectionClosedPrematurely)
{
_logger.LogError(ex, "");
throw;
}
finally
{
_logger.LogDebug("ReceiveLoopAsync END");
}
}
}
The Task.WhenAll works differently than Task.WhenAny.
Former throws exception is any of the tasks failed with an exception
Latter does not throw exception even if all of the tasks fail
So either you use call two twice the .GetAwaiter().GetResult() since WhenAny returns a Task<Task>
Task.WhenAny(receiving, sending).ConfigureAwait(false)
.GetAwaiter().GetResult()
.GetAwaiter().GetResult();
Or you can re-throw the exception
var trigger = await Task.WhenAny(receiving, sending).ConfigureAwait(false);
if (trigger.Exception != null)
{
throw trigger.Exception;
}
None of these solutions is perfect, but they will trigger your policy.
UPDATE #1
As Monsieur Merso pointed out you can call twice await
await await Task.WhenAny(receiving, sending).ConfigureAwait(false);
This is much better than the above two approaches.
UPDATE #2
If you want to
trigger the policy if faster task failed
or want to know which one has finished sooner with success
then you can "avoid" the double await
var trigger = await Task.WhenAny(receiving, sending).ConfigureAwait(false);
await trigger; //Throws exception if the faster Task has failed
if (trigger == receiving) //Determines which Task finished sooner
{
}
If I call Stop(), OperationCanceledException is happened and _writer.TryComplete(exp) is true. But _reader.Completion Task is still not completed.
Is it desired behavior of Channels? If yes can someone tell me how to stop a Channel without waiting till it's empty and have its Completion Task in Completed state?
public interface IItem
{
Uri SourceUri { get; }
string TargetPath { get; }
}
public class Item : IItem
{
public Item(Uri sourceUri, string targetPath)
{
SourceUri = sourceUri;
TargetPath = targetPath;
}
public Uri SourceUri { get; }
public string TargetPath { get; }
}
public class TestService
{
private readonly ChannelWriter<IItem> _writer;
private readonly ChannelReader<IItem> _reader;
private readonly CancellationTokenSource _cts;
public TestService()
{
_cts = new CancellationTokenSource();
Channel<IItem> channel = Channel.CreateUnbounded<IItem>();
_reader = channel.Reader;
_writer = channel.Writer;
}
public async Task QueueDownload(IItem information)
{
await _writer.WriteAsync(information);
}
public void StartDownload()
{
Task.Factory.StartNew(async () =>
{
await ProcessDownloadAsync();
}, TaskCreationOptions.LongRunning);
}
public void Stop()
{
_cts.Cancel();
//_writer.Complete();
//_writer = null;
Console.WriteLine("Stop");
}
public async Task Wait()
{
await _reader.Completion;
}
private async Task ProcessDownloadAsync()
{
try
{
while (await _reader.WaitToReadAsync(_cts.Token))
{
IItem information = await _reader.ReadAsync(_cts.Token);
using (WebClient webClient = new WebClient())
{
Console.WriteLine(information.TargetPath);
await webClient.DownloadFileTaskAsync(information.SourceUri,
information.TargetPath);
}
}
}
catch (OperationCanceledException exp)
{
bool res = _writer.TryComplete(exp);
}
}
}
static class Program
{
static async Task Main(string[] args)
{
TestService tSvc = new TestService();
await tSvc.QueueDownload(new Item(new Uri(#"https://images.pexels.com/" +
#"photos/753626/pexels-photo-753626.jpeg"), #"D:\\Temp\1.png"));
await tSvc.QueueDownload(new Item(new Uri(#"https://images.pexels.com/" +
#"photos/753626/pexels-photo-753626.jpeg"), #"D:\\Temp\1.png"));
await tSvc.QueueDownload(new Item(new Uri(#"https://images.pexels.com/" +
#"photos/753626/pexels-photo-753626.jpeg"), #"D:\\Temp\1.png"));
await tSvc.QueueDownload(new Item(new Uri(#"https://images.pexels.com/" +
#"photos/753626/pexels-photo-753626.jpeg"), #"D:\\Temp\1.png"));
tSvc.StartDownload();
Task t = tSvc.Wait();
tSvc.Stop();
await t;
Console.WriteLine("Finished");
}
}
The ChannelWriter.Complete method behaves a bit differently than one would expect. It is not invalidating instantly the contents of the channel. Instead, it just prevents adding more items in the channel. The existing items are still valid for consumption, and the ChannelReader.Completion property will not complete before all stored items are consumed.
The example below demonstrates this behavior:
var channel = Channel.CreateUnbounded<int>();
channel.Writer.TryWrite(1);
channel.Writer.Complete(new FileNotFoundException());
//channel.Reader.TryRead(out var data);
var completed = channel.Reader.Completion.Wait(500);
Console.WriteLine($"Completion: {(completed ? "OK" : "Timed-out")}");
Output:
Completion: Timed-out
You can uncomment the channel.Reader.TryRead line, to see the FileNotFoundException to emerge.
What I need to do is able to cancel a task that is running async. Task should be cancelled on cancel button click. I have done it with CancellationTokenSource. But it is not working properly.
public class classA
{
CancellationTokenSource _tokenSource = null;
public void OnCancelButtonClick()
{
MessageBox.Show("Do you Really want to cancel upload");
_tokenSource = new CancellationTokenSource();
_tokenSource.Cancel();
}
public async void UploadBtnClick(object param )
{
_tokenSource = new CancellationTokenSource();
var token = _tokenSource.Token;
try
{
await Task.Run(() => UploadFunction(token));
}
catch(OperationCanceledException ex)
{
MessageBox.Show(ex.Message);
}
finally
{
_tokenSource.Dispose();
}
}
public Task<bool> UploadFunction(CancellationToken token)
{
foreach
{
//code here
if (token.IsCancellationRequested)
{
token.ThrowIfCancellationRequested();
}
}
}
}
I am calling OnCancelButtonClick from another function
public class classB
{
public void CancelUploadBtnExecute(object param)
{
FilesViewModel vm = new FilesViewModel();
vm.OnCancelButtonClick();
}
}
when I click on OnCancelButtonClick , IsCancellationRequested is false, but not reflected inside UploadFunction so the task won't stop.
It's because you are initializing new CancellationTokenSource in OnCancelButtonClick().
Just remove this line from OnCancelButtonClick()
_tokenSource = new CancellationTokenSource();
UploadFunction method is using token created from CancellationTokenSource in UploadBtnClick method.
I am new to c#; I have mainly done Java.
I want to implement a timeout something along the lines:
int now= Time.now();
while(true)
{
tryMethod();
if(now > now+5000) throw new TimeoutException();
}
How can I implement this in C#? Thanks!
One possible way would be:
Stopwatch sw = new Stopwatch();
sw.Start();
while(true)
{
tryMethod();
if(sw.ElapsedMilliseconds > 5000) throw new TimeoutException();
}
However you currently have no way to break out of your loop. I would recommend having tryMethod return a bool and change it to:
Stopwatch sw = new Stopwatch();
sw.Start();
while(!tryMethod())
{
if(sw.ElapsedMilliseconds > 5000) throw new TimeoutException();
}
The question is quite old, but yet another option.
using(CancellationTokenSource cts = new CancellationTokenSource(5000))
{
cts.Token.Register(() => { throw new TimeoutException(); });
while(!cts.IsCancellationRequested)
{
tryMethod();
}
}
Technically, you should also propagate the CancellationToken in the tryMethod() to interupt it gracefully.
Working demo: (note I had to remove the exception throwing behavior as .netfiddle doesn't like it.)
https://dotnetfiddle.net/WjRxyk
I think you could do this with a timer and a delegate, my example code is below:
using System;
using System.Timers;
class Program
{
public delegate void tm();
static void Main(string[] args)
{
var t = new tm(tryMethod);
var timer = new Timer();
timer.Interval = 5000;
timer.Start();
timer.Elapsed += (sender, e) => timer_Elapsed(t);
t.BeginInvoke(null, null);
}
static void timer_Elapsed(tm p)
{
p.EndInvoke(null);
throw new TimeoutException();
}
static void tryMethod()
{
Console.WriteLine("FooBar");
}
}
You have tryMethod, you then create a delegate and point this delegate at tryMethod, then you start this delegate Asynchronously. Then you have a timer, with the Interval being 5000ms, you pass your delegate into your timer elapsed method (which should work as a delegate is a reference type, not an value type) and once the 5000 seconds has elapsed, you call the EndInvoke method on your delegate.
As long as tryMethod() doesn't block this should do what you want:
Not safe for daylight savings time or changing time zones when mobile:
DateTime startTime = DateTime.Now;
while(true)
{
tryMethod();
if(DateTime.Now.Subtract(startTime).TotalMilliseconds > 5000)
throw new TimeoutException();
}
Timezone and daylight savings time safe versions:
DateTime startTime = DateTime.UtcNow;
while(true)
{
tryMethod();
if(DateTime.UtcNow.Subtract(startTime).TotalMilliseconds > 5000)
throw new TimeoutException();
}
(.NET 3.5 or higher required for DateTimeOffset.)
DateTimeOffset startTime = DateTimeOffset.Now;
while(true)
{
tryMethod();
if(DateTimeOffset.Now.Subtract(startTime).TotalMilliseconds > 5000)
throw new TimeoutException();
}
Using Tasks for custom timeout on Async method
Here my implementation of a custom class with a method to wrap a task to have a timeout.
public class TaskWithTimeoutWrapper
{
protected volatile bool taskFinished = false;
public async Task<T> RunWithCustomTimeoutAsync<T>(int millisecondsToTimeout, Func<Task<T>> taskFunc, CancellationTokenSource cancellationTokenSource = null)
{
this.taskFinished = false;
var results = await Task.WhenAll<T>(new List<Task<T>>
{
this.RunTaskFuncWrappedAsync<T>(taskFunc),
this.DelayToTimeoutAsync<T>(millisecondsToTimeout, cancellationTokenSource)
});
return results[0];
}
public async Task RunWithCustomTimeoutAsync(int millisecondsToTimeout, Func<Task> taskFunc, CancellationTokenSource cancellationTokenSource = null)
{
this.taskFinished = false;
await Task.WhenAll(new List<Task>
{
this.RunTaskFuncWrappedAsync(taskFunc),
this.DelayToTimeoutAsync(millisecondsToTimeout, cancellationTokenSource)
});
}
protected async Task DelayToTimeoutAsync(int millisecondsToTimeout, CancellationTokenSource cancellationTokenSource)
{
await Task.Delay(millisecondsToTimeout);
this.ActionOnTimeout(cancellationTokenSource);
}
protected async Task<T> DelayToTimeoutAsync<T>(int millisecondsToTimeout, CancellationTokenSource cancellationTokenSource)
{
await this.DelayToTimeoutAsync(millisecondsToTimeout, cancellationTokenSource);
return default(T);
}
protected virtual void ActionOnTimeout(CancellationTokenSource cancellationTokenSource)
{
if (!this.taskFinished)
{
cancellationTokenSource?.Cancel();
throw new NoInternetException();
}
}
protected async Task RunTaskFuncWrappedAsync(Func<Task> taskFunc)
{
await taskFunc.Invoke();
this.taskFinished = true;
}
protected async Task<T> RunTaskFuncWrappedAsync<T>(Func<Task<T>> taskFunc)
{
var result = await taskFunc.Invoke();
this.taskFinished = true;
return result;
}
}
Then you can call it like this:
await new TaskWithTimeoutWrapper().RunWithCustomTimeoutAsync(10000, () => this.MyTask());
or
var myResult = await new TaskWithTimeoutWrapper().RunWithCustomTimeoutAsync(10000, () => this.MyTaskThatReturnsMyResult());
And you can add a cancellation token if you want to cancel the running async task if it gets to timeout.
Hope it helps
Another way I like to do it:
public class TimeoutAction
{
private Thread ActionThread { get; set; }
private Thread TimeoutThread { get; set; }
private AutoResetEvent ThreadSynchronizer { get; set; }
private bool _success;
private bool _timout;
/// <summary>
///
/// </summary>
/// <param name="waitLimit">in ms</param>
/// <param name="action">delegate action</param>
public TimeoutAction(int waitLimit, Action action)
{
ThreadSynchronizer = new AutoResetEvent(false);
ActionThread = new Thread(new ThreadStart(delegate
{
action.Invoke();
if (_timout) return;
_timout = true;
_success = true;
ThreadSynchronizer.Set();
}));
TimeoutThread = new Thread(new ThreadStart(delegate
{
Thread.Sleep(waitLimit);
if (_success) return;
_timout = true;
_success = false;
ThreadSynchronizer.Set();
}));
}
/// <summary>
/// If the action takes longer than the wait limit, this will throw a TimeoutException
/// </summary>
public void Start()
{
ActionThread.Start();
TimeoutThread.Start();
ThreadSynchronizer.WaitOne();
if (!_success)
{
throw new TimeoutException();
}
ThreadSynchronizer.Close();
}
}
CancellationTokenSource cts = new CancellationTokenSource();
cts.CancelAfter(10000);
try
{
Task task = Task.Run(() => { methodToTimeoutAfter10Seconds(); }, cts.Token);
TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>();
using (cts.Token.Register(s => ((TaskCompletionSource<bool>)s).TrySetResult(true), tcs))
{
if (task != await Task.WhenAny(task, tcs.Task))
{
throw new OperationCanceledException(cts.Token);
}
}
/* Wait until the task is finish or timeout. */
task.Wait();
/* Rest of the code goes here */
}
catch (TaskCanceledException)
{
Console.WriteLine("Timeout");
}
catch (OperationCanceledException)
{
Console.WriteLine("Timeout");
}
catch (Exception ex)
{
Console.WriteLine("Other exceptions");
}
finally
{
cts.Dispose();
}
Using mature library Polly it can be implemented using optimistic (thus CancellationToken based) as follows:
AsyncTimeoutPolicy policy = Policy.TimeoutAsync(60, TimeoutStrategy.Optimistic);
await policy.ExecuteAsync(async cancel => await myTask(cancel), CancellationToken.None);
myTask(cancel) should be of signature Func<CancellationToken, Task> e.g. async Task MyTast(CancellationToken token) {...}