public static IEnumerable <IStorageQueueMessage> GetMessages(this IStorageQueue queue, int messageCount)
{
if (queue == null)
{
throw new ArgumentNullException("queue");
}
return(queue.GetMessagesAsync(messageCount, visibilityTimeout: null, options: null, operationContext: null,
cancellationToken: CancellationToken.None).GetAwaiter().GetResult());
}
public async Task <TaskSeriesCommandResult> ExecuteAsync(CancellationToken cancellationToken)
{
lock (_stopWaitingTaskSourceLock)
{
if (_stopWaitingTaskSource != null)
{
_stopWaitingTaskSource.TrySetResult(null);
}
_stopWaitingTaskSource = new TaskCompletionSource <object>();
}
IEnumerable <IStorageQueueMessage> batch;
try
{
batch = await _queue.GetMessagesAsync(_queueProcessor.BatchSize,
_visibilityTimeout,
options : null,
operationContext : null,
cancellationToken : cancellationToken);
}
catch (StorageException exception)
{
if (exception.IsNotFoundQueueNotFound() ||
exception.IsConflictQueueBeingDeletedOrDisabled() ||
exception.IsServerSideError())
{
// Back off when no message is available, or when
// transient errors occur
return(CreateBackoffResult());
}
else
{
throw;
}
}
if (batch == null)
{
return(CreateBackoffResult());
}
bool foundMessage = false;
foreach (var message in batch)
{
if (message == null)
{
continue;
}
foundMessage = true;
// Note: Capturing the cancellationToken passed here on a task that continues to run is a slight abuse
// of the cancellation token contract. However, the timer implementation would not dispose of the
// cancellation token source until it has stopped and perhaps also disposed, and we wait for all
// outstanding tasks to complete before stopping the timer.
Task task = ProcessMessageAsync(message, _visibilityTimeout, cancellationToken);
// Having both WaitForNewBatchThreshold and this method mutate _processing is safe because the timer
// contract is serial: it only calls ExecuteAsync once the wait expires (and the wait won't expire until
// WaitForNewBatchThreshold has finished mutating _processing).
_processing.Add(task);
}
// Back off when no message was found.
if (!foundMessage)
{
return(CreateBackoffResult());
}
_foundMessageSinceLastDelay = true;
return(CreateSucceededResult());
}