/// <inheritdoc />
public ITaskImplementation LocateAndCreate(TaskDescription taskDescription)
{
if (_registeredTaskTypes.TryGetValue(taskDescription.TaskType, out var taskImplementationType))
{
return((ITaskImplementation)JsonConvert.DeserializeObject(taskDescription.TaskPayload, taskImplementationType));
}
return(null);
}
public static TaskDescription ToTaskDescription(ITaskImplementation taskImplementation)
{
if (taskImplementation == null)
{
throw new ArgumentNullException(nameof(taskImplementation));
}
var description = new TaskDescription(Guid.NewGuid(), taskImplementation.GetType().FullName, JsonConvert.SerializeObject(taskImplementation));
return(description);
}
/// <inheritdoc />
protected override async Task RunAsync(CancellationToken cancellationToken)
{
var queue = await TimeoutRetryHelper.Execute(
(token, state) => StateManager.GetOrAddAsync <IReliableQueue <MessageWrapper> >(_queueName),
cancellationToken : cancellationToken)
.ConfigureAwait(false);
while (true)
{
try
{
cancellationToken.ThrowIfCancellationRequested();
//peek task description
var taskDescriptionMessage = await TimeoutRetryHelper
.ExecuteInTransaction(StateManager,
(tran, token, state) => queue.TryPeekAsync(tran, TimeSpan.FromSeconds(4), token), cancellationToken : cancellationToken)
.ConfigureAwait(false);
if (!taskDescriptionMessage.HasValue)
{
continue;
}
//deserialize task description, create task implementation
var description = this.Deserialize <TaskDescription>(taskDescriptionMessage.Value);
var implementation = TaskDescription.ToTaskImplementation(_typeLocator, description);
if (implementation == null)
{
ServiceEventSourceMessageCallback?
.Invoke($"Received TaskDescription message with type {description.TaskType} and id {description.TaskId} that could not be transformed into a TaskImplementation type.");
continue;
}
//run task
ServiceEventSourceMessageCallback?
.Invoke($"Processing TaskDescription message with type {description.TaskType} and id {description.TaskId}, using implementation {implementation.GetType().Name}.");
await implementation.ExecuteAsync().ConfigureAwait(false);
var taskDescriptionMessageDequeued = await TimeoutRetryHelper
.ExecuteInTransaction(StateManager,
(tran, token, state) => queue.TryDequeueAsync(tran, TimeSpan.FromSeconds(4), token), cancellationToken : cancellationToken)
.ConfigureAwait(false);
//dequeue task, compare it with the peeked task
if (taskDescriptionMessageDequeued.HasValue &&
taskDescriptionMessageDequeued.Value.Payload.GetHashCode()
== taskDescriptionMessage.Value.Payload.GetHashCode())
{
ServiceEventSourceMessageCallback?
.Invoke($"Processed TaskDescription message with type {description.TaskType} and id {description.TaskId}, using implementation {implementation.GetType().Name}.");
}
else
{
ServiceEventSourceMessageCallback?
.Invoke($"Unexpected error. The peeked message is not the dequeued message.");
}
}
catch (TaskCanceledException)
{//swallow and move on..
}
catch (OperationCanceledException)
{//swallow and move on..
}
catch (ObjectDisposedException)
{//swallow and move on..
}
catch (Exception ex)
{
ServiceEventSourceMessageCallback?.Invoke($"Exception caught while processing messages:'{ex.Message}'");
//swallow and move on..
}
finally
{
await Task.Delay(Period, cancellationToken).ConfigureAwait(false);
}
}
}
public static ITaskImplementation ToTaskImplementation(ITypeLocator typeLocator, TaskDescription taskDescription)
{
return(typeLocator.LocateAndCreate(taskDescription));
}