/// <summary>
/// Creates and starts a new partition pump associated with the specified partition. Partition pumps that are overwritten by the creation
/// of a new one are properly stopped.
/// </summary>
///
/// <param name="partitionId">The identifier of the Event Hub partition the partition pump will be associated with. Events will be read only from this partition.</param>
///
/// <returns>A task to be resolved on when the operation has completed.</returns>
///
private async Task AddOrOverwritePartitionPumpAsync(string partitionId)
{
// Remove and stop the existing partition pump if it exists. We are not specifying any close reason because partition
// pumps only are overwritten in case of failure. In these cases, the close reason is delegated to the pump as it may
// have more information about what caused the failure.
await RemovePartitionPumpIfItExistsAsync(partitionId).ConfigureAwait(false);
// Create and start the new partition pump and add it to the dictionary.
var partitionContext = new PartitionContext(InnerClient.EventHubName, ConsumerGroup, partitionId);
var checkpointManager = new CheckpointManager(partitionContext, Manager, Identifier);
try
{
var partitionProcessor = PartitionProcessorFactory(partitionContext, checkpointManager);
var partitionPump = new PartitionPump(InnerClient, ConsumerGroup, partitionId, partitionProcessor, Options);
await partitionPump.StartAsync().ConfigureAwait(false);
PartitionPumps[partitionId] = partitionPump;
}
catch (Exception)
{
// If partition pump creation fails, we'll try again on the next time this method is called. This should happen
// on the next load balancing loop as long as this instance still owns the partition.
// TODO: delegate the exception handling to an Exception Callback.
}
}
/// <summary>
/// The main loop of an event processor. It loops through every owned <see cref="PartitionPump" />, checking
/// its status and creating a new one if necessary.
/// </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>
///
/// <remarks>
/// The actual goal of this method is to perform load balancing between multiple <see cref="EventProcessor" />
/// instances, but this feature is currently out of the scope of the current preview.
/// </remarks>
///
private async Task RunAsync(CancellationToken cancellationToken)
{
while (!cancellationToken.IsCancellationRequested)
{
await Task.WhenAll(PartitionPumps
.Where(kvp => !kvp.Value.IsRunning)
.Select(async kvp =>
{
try
{
await kvp.Value.StopAsync();
}
catch (Exception)
{
// We're catching every possible unhandled exception that may have happened during Partition Pump execution.
// TODO: delegate the exception handling to an Exception Callback.
}
var partitionId = kvp.Key;
var partitionContext = new PartitionContext(InnerClient.EventHubName, ConsumerGroup, partitionId);
var checkpointManager = new CheckpointManager(partitionContext, Manager, Identifier);
var partitionProcessor = PartitionProcessorFactory(partitionContext, checkpointManager);
var partitionPump = new PartitionPump(InnerClient, ConsumerGroup, partitionId, partitionProcessor, Options);
PartitionPumps.TryUpdate(partitionId, partitionPump, partitionPump);
await partitionPump.StartAsync();
})).ConfigureAwait(false);
try
{
// Wait 1 second before the next verification.
await Task.Delay(1000, cancellationToken).ConfigureAwait(false);
}
catch (TaskCanceledException) { }
}
}
/// <summary>
/// Starts the event processor. 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)
{
RunningTaskTokenSource?.Cancel();
RunningTaskTokenSource = new CancellationTokenSource();
PartitionPumps.Clear();
var partitionIds = await InnerClient.GetPartitionIdsAsync().ConfigureAwait(false);
await Task.WhenAll(partitionIds
.Select(partitionId =>
{
var partitionContext = new PartitionContext(InnerClient.EventHubName, ConsumerGroup, partitionId);
var checkpointManager = new CheckpointManager(partitionContext, Manager, Identifier);
var partitionProcessor = PartitionProcessorFactory(partitionContext, checkpointManager);
var partitionPump = new PartitionPump(InnerClient, ConsumerGroup, partitionId, partitionProcessor, Options);
PartitionPumps.TryAdd(partitionId, partitionPump);
return(partitionPump.StartAsync());
})).ConfigureAwait(false);
RunningTask = RunAsync(RunningTaskTokenSource.Token);
}
}
finally
{
RunningTaskSemaphore.Release();
}
}
}
/// <summary>
/// Creates and starts a new partition pump associated with the specified partition. Partition pumps that are overwritten by the creation
/// of a new one are properly stopped.
/// </summary>
///
/// <param name="partitionId">The identifier of the Event Hub partition the partition pump will be associated with. Events will be read only from this partition.</param>
/// <param name="initialSequenceNumber">The sequence number of the event within a partition where the partition pump should begin reading events.</param>
///
/// <returns>A task to be resolved on when the operation has completed.</returns>
///
private async Task AddOrOverwritePartitionPumpAsync(string partitionId,
long?initialSequenceNumber)
{
// Remove and stop the existing partition pump if it exists. We are not specifying any close reason because partition
// pumps only are overwritten in case of failure. In these cases, the close reason is delegated to the pump as it may
// have more information about what caused the failure.
await RemovePartitionPumpIfItExistsAsync(partitionId).ConfigureAwait(false);
// Create and start the new partition pump and add it to the dictionary.
var partitionContext = new PartitionContext(InnerClient.FullyQualifiedNamespace, InnerClient.EventHubName, ConsumerGroup, partitionId, Identifier, Manager);
try
{
BasePartitionProcessor partitionProcessor = PartitionProcessorFactory(partitionContext);
EventProcessorOptions options = Options.Clone();
// Ovewrite the initial event position in case a checkpoint exists.
if (initialSequenceNumber.HasValue)
{
options.InitialEventPosition = EventPosition.FromSequenceNumber(initialSequenceNumber.Value);
}
var partitionPump = new PartitionPump(InnerClient, ConsumerGroup, partitionContext, partitionProcessor, options);
await partitionPump.StartAsync().ConfigureAwait(false);
PartitionPumps[partitionId] = partitionPump;
}
catch (Exception)
{
// If partition pump creation fails, we'll try again on the next time this method is called. This should happen
// on the next load balancing loop as long as this instance still owns the partition.
// TODO: delegate the exception handling to an Exception Callback.
}
}