/// <summary>
/// Handles a response for the distributed task.
/// </summary>
/// <param name="context"></param>
/// <param name="message"></param>
/// <returns></returns>
public async Task Handle(QueueContext context, SampleDistributedTaskResponse message)
{
_log.Info($"Distributed Task Complete: {message.A} {message.Operation} {message.B} = {message.Result}");
// update our saga data, keeping track of how much work is remaining.
Data.PendingTasks--;
_log.Info($"{Data.PendingTasks} Tasks Remaining.");
if (Data.PendingTasks == 0)
{
// all tasks are complete, so we can inform the application
// that this saga has finished.
_log.Info($"Completing SagaId {message.AppId}");
await _queueWriter.WriteMessage(context.SourceQueue,
new SampleSagaComplete { AppId = message.AppId });
SagaComplete = true;
}
else
{
// there is more work to do, so dispatch another distributed task.
_log.Info($"Distributing more work for SagaId {message.AppId}");
await _queueWriter.WriteMessage(context.SourceQueue,
new SampleDistributedTaskRequest
{
AppId = message.AppId,
B = (Data.PendingTasks - 1) * 3,
A = (Data.PendingTasks - 1) * 4,
Operation = "+"
});
}
// demonstrate interaction with our application database.
await _dataAccess.Audit($"Pending Tasks {Data.PendingTasks}");
}
public async Task Handle(QueueContext context, SampleDistributedTaskRequest message)
{
// This handler does math on two values.
// Not a realistic example, in that you wouldn't go through all the trouble of sending
// a message to add numbers. The point is to demontrate assigning a task to be completed
// by code which may be running in a different process or even on a different machine.
_log.Info("Processing Distributed Task.");
if (message.Operation != "+")
{
throw new ApplicationException($"I only know how to add!. I don't know how to {message.Operation}.");
}
// compute the response.
var response = new SampleDistributedTaskResponse
{
AppId = message.AppId,
A = message.A,
B = message.B,
Operation = message.Operation,
Result = message.A + message.B
};
// send a response message
await _queueWriter.WriteMessage(context.SourceQueue, response);
// demonstrate interacting with our application data.
var auditMessge = $"Distrbuted Task Result {response.A} { response.Operation} {response.B} = {response.Result}";
_log.Info(auditMessge);
await _dataAccess.Audit(auditMessge);
}
public async Task Run()
{
const string QueueName = "SampleQueue";
// Sends a few Saga Start messages to kick off the processing of messages in the example program.
for (var i = 0; i < 10; i++)
{
_dataAccess.BeginTransaction();
for (var j = 0; j < 10; j++)
{
await _queueWriter.WriteMessage(QueueName, new SampleSagaStart { AppId = Guid.NewGuid() });
}
_dataAccess.CommitTransaction();
}
}
/// <summary>
/// Writes a message to a queue
/// </summary>
public static Task WriteMessage <T>(this IQueueWriter writer, string queueName, T message, DateTime?NotBefore = null)
{
return(writer.WriteMessage(queueName, typeof(T), message, NotBefore));
}