// Processes two types of events
// 1) Event hub events
// 2) Maximum wait events. These are generated when we have not received an event hub
// event for a certain time period and this event is used to flush events in the current window.
protected virtual async Task ProcessEventHandler(ProcessEventArgs eventArgs)
{
if (eventArgs.CancellationToken.IsCancellationRequested)
{
// The event arguments contain a cancellation token that the EventProcessorClient uses to signal the handler that processing should cease as soon as possible.
// This is most commonly seen when the EventProcessorClient is stopping or has encountered an unrecoverable problem.
Logger.LogTrace($"ProcessEventArgs contain a cancellation request {eventArgs.Partition.PartitionId}");
return;
}
IEventMessage evt;
if (eventArgs.HasEvent)
{
evt = EventMessageFactory.CreateEvent(eventArgs);
}
else
{
evt = new MaximumWaitEvent(eventArgs.Partition.PartitionId, DateTime.UtcNow);
}
await EventConsumerService.ConsumeEvent(evt);
}
public async Task RunAsync(EventProcessorClient processor, CancellationToken ct)
{
EnsureArg.IsNotNull(processor);
// Processes two types of events
// 1) Event hub events
// 2) Maximum wait events. These are generated when we have not received an event hub
// event for a certain time period and this event is used to flush events in the current window.
async Task ProcessEventHandler(ProcessEventArgs eventArgs)
{
IEventMessage evt;
if (eventArgs.HasEvent)
{
evt = EventMessageFactory.CreateEvent(eventArgs);
}
else
{
evt = new MaximumWaitEvent(eventArgs.Partition.PartitionId, DateTime.UtcNow);
}
await _eventConsumerService.ConsumeEvent(evt);
}
// todo: consider retry
Task ProcessErrorHandler(ProcessErrorEventArgs eventArgs)
{
_logger.LogError(eventArgs.Exception);
return(Task.CompletedTask);
}
async Task ProcessInitializingHandler(PartitionInitializingEventArgs initArgs)
{
var partitionId = initArgs.PartitionId;
_logger.LogTrace($"Initializing partition {partitionId}");
try
{
var checkpoint = await _checkpointClient.GetCheckpointForPartitionAsync(partitionId);
initArgs.DefaultStartingPosition = EventPosition.FromEnqueuedTime(checkpoint.LastProcessed);
_logger.LogTrace($"Starting to read partition {partitionId} from checkpoint {checkpoint.LastProcessed}");
_logger.LogMetric(EventMetrics.EventHubPartitionInitialized(), 1);
}
#pragma warning disable CA1031
catch (Exception ex)
#pragma warning restore CA1031
{
_logger.LogTrace($"Failed to initialize partition {partitionId} from checkpoint");
_logger.LogError(ex);
}
}
processor.ProcessEventAsync += ProcessEventHandler;
processor.ProcessErrorAsync += ProcessErrorHandler;
processor.PartitionInitializingAsync += ProcessInitializingHandler;
try
{
Console.WriteLine($"Starting event hub processor at {DateTime.UtcNow}");
await processor.StartProcessingAsync();
while (!ct.IsCancellationRequested)
{
}
await processor.StopProcessingAsync();
}
finally
{
processor.ProcessEventAsync -= ProcessEventHandler;
processor.ProcessErrorAsync -= ProcessErrorHandler;
processor.PartitionInitializingAsync -= ProcessInitializingHandler;
}
}