/// <summary>
/// Executes pipeline behavior:
///
/// Create a new transaction if there is not already an active transaction within the database context,
/// then await the pipeline result through the <c>RequestHandlerDelegate</c> 'next'.
/// When the remainder of the pipeline has finished, publish whatever integration events that may have
/// spawned during the transaction through the event bus.
/// </summary>
public async Task <TResponse> Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate <TResponse> next)
{
var response = default(TResponse);
try
{
// Do not start a new transaction if an active one already exists
if (_context.HasActiveTransaction)
{
_logger.LogDebug("Has active transaction. Calling command handler.");
response = await next();
_logger.LogDebug("Response: {0}", response);
return(response);
}
// Execution strategy includes retry on failure
var strategy = _context.Database.CreateExecutionStrategy();
await strategy.ExecuteAsync(async() =>
{
Guid transactionId;
// Start a new transaction to ensure invariance in the domain
using (var transaction = await _context.BeginTransactionAsync())
{
_logger.LogDebug("New transaction begun. Calling command handler.");
response = await next();
_logger.LogDebug("Response: {0}", response);
// Commit transaction to database, if this fails a rollback of all changes recorded during the transaction will be rolled back
await _context.CommitTransactionAsync(transaction);
transactionId = transaction.TransactionId;
}
_logger.LogDebug("TransactionId: {0}", transactionId);
// Publish integration events to event bus if everything succeeded
await _integrationEventService.PublishEventsThroughEventBusAsync(transactionId);
});
return(response);
}
catch (Exception ex)
{
_logger.LogError(ex, "Something terrible happened in the MediatR Pipeline!");
throw;
}
}
