/// <summary>
/// Stops the partition pump. In case it isn't running, nothing happens.
/// </summary>
///
/// <param name="reason">The reason why the processing for the associated partition is being stopped. In case it's <c>null</c>, the internal close reason set by this pump is used.</param>
///
/// <returns>A task to be resolved on when the operation has completed.</returns>
///
public async Task StopAsync(CloseReason?reason)
{
if (RunningTask != null)
{
await RunningTaskSemaphore.WaitAsync().ConfigureAwait(false);
try
{
if (RunningTask != null)
{
RunningTaskTokenSource.Cancel();
RunningTaskTokenSource = null;
try
{
// RunningTask is only expected to fail when the event processor throws while processing
// an error, but unforeseen scenarios might happen.
await RunningTask.ConfigureAwait(false);
}
catch (Exception)
{
// TODO: delegate the exception handling to an Exception Callback.
}
RunningTask = null;
// It's important to close the consumer as soon as possible. Failing to do so multiple times
// would make it impossible to create more consumers for the associated partition as there's a
// limit per client.
await InnerConsumer.CloseAsync().ConfigureAwait(false);
// In case an exception is encountered while the processing is stopping, don't catch it and let
// the event processor handle it. The pump has no way to guess when a partition was lost or when
// a shutdown request was sent to the event processor, so it expects a "reason" parameter to provide
// this information. However, in case of pump failure, the external event processor does not have
// enough information to figure out what failure reason to use, as this information is only known
// by the pump. In this case, we expect the processor-provided reason to be null, and the private
// CloseReason is used instead.
if (OwnerEventProcessor.ProcessingForPartitionStoppedAsync != null)
{
var stopContext = new PartitionProcessingStoppedContext(Context, reason ?? CloseReason);
await OwnerEventProcessor.ProcessingForPartitionStoppedAsync(stopContext).ConfigureAwait(false);
}
}
}
finally
{
RunningTaskSemaphore.Release();
}
}
}
/// <summary>
/// Starts the partition pump. In case it's already running, nothing happens.
/// </summary>
///
/// <returns>A task to be resolved on when the operation has completed.</returns>
///
public async Task StartAsync()
{
if (RunningTask == null)
{
await RunningTaskSemaphore.WaitAsync().ConfigureAwait(false);
try
{
if (RunningTask == null)
{
// We expect the token source to be null, but we are playing safe.
RunningTaskTokenSource?.Cancel();
RunningTaskTokenSource = new CancellationTokenSource();
// In case an exception is encountered while the processing is initializing, don't catch it
// and let the event processor handle it.
EventPosition startingPosition = StartingPosition;
if (OwnerEventProcessor.InitializeProcessingForPartitionAsync != null)
{
var initializationContext = new InitializePartitionProcessingContext(Context);
await OwnerEventProcessor.InitializeProcessingForPartitionAsync(initializationContext).ConfigureAwait(false);
startingPosition = startingPosition ?? initializationContext.DefaultStartingPosition;
}
InnerConsumer = new EventHubConsumerClient(ConsumerGroup, Context.PartitionId, startingPosition ?? EventPosition.Earliest, Connection);
// Before closing, the running task will set the close reason in case of failure. When something
// unexpected happens and it's not set, the default value (Unknown) is kept.
RunningTask = RunAsync(RunningTaskTokenSource.Token);
}
}
finally
{
RunningTaskSemaphore.Release();
}
}
}
/// <summary>
/// Starts the partition pump. In case it's already running, nothing happens.
/// </summary>
///
/// <returns>A task to be resolved on when the operation has completed.</returns>
///
public async Task StartAsync()
{
if (RunningTask == null)
{
await RunningTaskSemaphore.WaitAsync().ConfigureAwait(false);
try
{
if (RunningTask == null)
{
// We expect the token source to be null, but we are playing safe.
RunningTaskTokenSource?.Cancel();
RunningTaskTokenSource = new CancellationTokenSource();
InnerConsumer = new EventHubConsumerClient(ConsumerGroup, Context.PartitionId, DefaultEventPosition, Connection);
// In case an exception is encountered while partition processor is initializing, don't catch it
// and let the event processor handle it. The inner consumer hasn't connected to the service yet,
// so there's no need to close it.
if (OwnerEventProcessor.InitializeProcessingForPartitionAsync != null)
{
await OwnerEventProcessor.InitializeProcessingForPartitionAsync(Context).ConfigureAwait(false);
}
// Before closing, the running task will set the close reason in case of failure. When something
// unexpected happens and it's not set, the default value (Unknown) is kept.
RunningTask = RunAsync(RunningTaskTokenSource.Token);
}
}
finally
{
RunningTaskSemaphore.Release();
}
}
}
/// <summary>
/// The main loop of a partition pump. It receives events from the Azure Event Hubs service
/// and delegates their processing to the event processor processing handlers.
/// </summary>
///
/// <param name="cancellationToken">A <see cref="CancellationToken"/> instance to signal the request to cancel the operation.</param>
///
/// <returns>A task to be resolved on when the operation has completed.</returns>
///
private async Task RunAsync(CancellationToken cancellationToken)
{
List <EventData> receivedEvents;
Exception unrecoverableException = null;
// We'll break from the loop upon encountering a non-retriable exception. The event processor periodically
// checks its pumps' status, so it should be aware of when one of them stops working.
while (!cancellationToken.IsCancellationRequested && unrecoverableException == null)
{
try
{
receivedEvents = (await InnerConsumer.ReceiveAsync(MaximumMessageCount, Options.MaximumReceiveWaitTime, cancellationToken).ConfigureAwait(false)).ToList();
using DiagnosticScope diagnosticScope = EventDataInstrumentation.ClientDiagnostics.CreateScope(DiagnosticProperty.EventProcessorProcessingActivityName);
diagnosticScope.AddAttribute("kind", "server");
if (diagnosticScope.IsEnabled)
{
foreach (var eventData in receivedEvents)
{
if (EventDataInstrumentation.TryExtractDiagnosticId(eventData, out string diagnosticId))
{
diagnosticScope.AddLink(diagnosticId);
}
}
}
// Small workaround to make sure we call ProcessEvent with EventData = null when no events have been received.
// The code is expected to get simpler when we start using the async enumerator internally to receive events.
if (receivedEvents.Count == 0)
{
receivedEvents.Add(null);
}
diagnosticScope.Start();
foreach (var eventData in receivedEvents)
{
try
{
var processorEvent = new EventProcessorEvent(Context, eventData, OwnerEventProcessor.UpdateCheckpointAsync);
await OwnerEventProcessor.ProcessEventAsync(processorEvent).ConfigureAwait(false);
}
catch (Exception eventProcessingException)
{
diagnosticScope.Failed(eventProcessingException);
unrecoverableException = eventProcessingException;
CloseReason = CloseReason.Exception;
break;
}
}
}
catch (Exception eventHubException)
{
// Stop running only if it's not a retriable exception.
if (RetryPolicy.CalculateRetryDelay(eventHubException, 1) == null)
{
unrecoverableException = eventHubException;
CloseReason = CloseReason.Exception;
break;
}
}
}
if (unrecoverableException != null)
{
// In case an exception is thrown by ProcessExceptionAsync, don't catch it and
// let the calling method (StopAsync) handle it.
var errorContext = new ProcessorErrorContext(Context.PartitionId, unrecoverableException);
await OwnerEventProcessor.ProcessExceptionAsync(errorContext).ConfigureAwait(false);
}
}
/// <summary>
/// The main loop of a partition pump. It receives events from the Azure Event Hubs service
/// and delegates their processing to the inner partition processor.
/// </summary>
///
/// <param name="cancellationToken">A <see cref="CancellationToken"/> instance to signal the request to cancel the operation.</param>
///
/// <returns>A task to be resolved on when the operation has completed.</returns>
///
private async Task RunAsync(CancellationToken cancellationToken)
{
IEnumerable <EventData> receivedEvents;
Exception unrecoverableException = null;
// We'll break from the loop upon encountering a non-retriable exception. The event processor periodically
// checks its pumps' status, so it should be aware of when one of them stops working.
while (!cancellationToken.IsCancellationRequested)
{
try
{
receivedEvents = await InnerConsumer.ReceiveAsync(MaximumMessageCount, Options.MaximumReceiveWaitTime, cancellationToken).ConfigureAwait(false);
using DiagnosticScope diagnosticScope = EventDataInstrumentation.ClientDiagnostics.CreateScope(DiagnosticProperty.EventProcessorProcessingActivityName);
diagnosticScope.AddAttribute("kind", "server");
if (diagnosticScope.IsEnabled)
{
foreach (var eventData in receivedEvents)
{
if (EventDataInstrumentation.TryExtractDiagnosticId(eventData, out string diagnosticId))
{
diagnosticScope.AddLink(diagnosticId);
}
}
}
diagnosticScope.Start();
try
{
await OwnerEventProcessor.ProcessEventsAsync(Context, receivedEvents).ConfigureAwait(false);
}
catch (Exception partitionProcessorException)
{
diagnosticScope.Failed(partitionProcessorException);
unrecoverableException = partitionProcessorException;
CloseReason = PartitionProcessorCloseReason.PartitionProcessorException;
break;
}
}
catch (Exception eventHubException)
{
// Stop running only if it's not a retriable exception.
if (RetryPolicy.CalculateRetryDelay(eventHubException, 1) == null)
{
unrecoverableException = eventHubException;
CloseReason = PartitionProcessorCloseReason.EventHubException;
break;
}
}
}
if (unrecoverableException != null)
{
// In case an exception is encountered while partition processor is processing the error, don't
// catch it and let the calling method (StopAsync) handle it.
await OwnerEventProcessor.ProcessExceptionAsync(Context, unrecoverableException).ConfigureAwait(false);
}
}
