public void Decrease_disallowed()
{
// Arrange
var semaphore = new SemaphoreSlimEx(1, 1, 2);
// Act
var decreased = semaphore.TryDecrease();
// Assert
Assert.IsFalse(decreased);
Assert.AreEqual(1, semaphore.AvailableSlotsCount);
}
public void Increase_allowed()
{
// Arrange
var semaphore = new SemaphoreSlimEx(1, 1, 2);
// Act
var increased = semaphore.TryIncrease();
// Assert
Assert.IsTrue(increased);
Assert.AreEqual(2, semaphore.AvailableSlotsCount);
}
private async Task ProcessMessages(TimeSpan?visibilityTimeout = null, CancellationToken cancellationToken = default(CancellationToken))
{
var runningTasks = new ConcurrentDictionary <Task, Task>();
var semaphore = new SemaphoreSlimEx(_minConcurrentTasks, _minConcurrentTasks, _maxConcurrentTasks);
// Define the task pump
var pumpTask = Task.Run(async() =>
{
while (!cancellationToken.IsCancellationRequested)
{
await semaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
var runningTask = Task.Run(async() =>
{
if (cancellationToken.IsCancellationRequested)
{
return(false);
}
CloudQueueMessage message = null;
try
{
message = await _cloudQueue.GetMessageAsync(visibilityTimeout, null, null, cancellationToken);
}
catch (Exception e)
{
_logger.ErrorException("An error occured when attempting to get a message from the queue", e);
}
if (message == null)
{
try
{
// The queue is empty
OnQueueEmpty?.Invoke(cancellationToken);
}
#pragma warning disable RECS0022 // A catch clause that catches System.Exception and has an empty body
catch
#pragma warning restore RECS0022 // A catch clause that catches System.Exception and has an empty body
{
// Intentionally left empty. We ignore errors from OnQueueEmpty.
}
// False indicates that no message was processed
return(false);
}
else
{
try
{
// Process the message
OnMessage?.Invoke(message, cancellationToken);
// Delete the processed message from the queue
await _cloudQueue.DeleteMessageAsync(message);
}
catch (Exception ex)
{
var isPoison = (message.DequeueCount > _maxDequeueCount);
OnError?.Invoke(message, ex, isPoison);
if (isPoison)
{
await _cloudQueue.DeleteMessageAsync(message);
}
}
// True indicates that a message was processed
return(true);
}
}, CancellationToken.None);
runningTasks.TryAdd(runningTask, runningTask);
runningTask.ContinueWith(async t =>
{
// Decide if we need to scale up or down
if (!cancellationToken.IsCancellationRequested)
{
if (await t)
{
// The queue is not empty, therefore increase the number of concurrent tasks
semaphore.TryIncrease();
}
else
{
// The queue is empty, therefore reduce the number of concurrent tasks
semaphore.TryDecrease();
}
}
// Complete the task
semaphore.Release();
Task taskToBeRemoved;
runningTasks.TryRemove(t, out taskToBeRemoved);
}, TaskContinuationOptions.ExecuteSynchronously)
.IgnoreAwait();
}
});
// Run the task pump until canceled
await pumpTask.UntilCancelled().ConfigureAwait(false);
// Task pump has been canceled, wait for the currently running tasks to complete
await Task.WhenAll(runningTasks.Values).UntilCancelled().ConfigureAwait(false);
}