Sagas add state to your messagaging and allows you to handle long running processes within the same code. A Saga is a long lived transaction that is started by one or more specific messages and is finished by one or more messages. The messages can be either events or commands.


Setup KnightBus for Sagas by registering it in the host:

var knightBusHost = new KnightBusHost()
//Enable the StorageBus Transport
.UseTransport(new StorageTransport(storageConnection)
.Configure(configuration => configuration
    //Register our message processors without IoC using the standard provider
    .UseMessageProcessorProvider(new StandardMessageProcessorProvider()
        .RegisterProcessor(new SampleSagaMessageProcessor(client))
    //Enable Saga support using the table storage Saga store
    .EnableSagas(new StorageTableSagaStore(storageConnection))

await knightBusHost.StartAsync();

Sample Implementation

class SampleSagaMessageProcessor: Saga<MySagaData>,
        IProcessCommand<SampleSagaMessage, SomeProcessingSetting>,
        IProcessCommand<SampleSagaStartMessage, SomeProcessingSetting>,
        private readonly IStorageBus _storageBus;

        public SampleSagaMessageProcessor(IStorageBus storageBus)
            _storageBus = storageBus;
            //Map the messages to the Saga
            MessageMapper.MapStartMessage<SampleSagaStartMessage>(m=> m.Id);
            MessageMapper.MapMessage<SampleSagaMessage>(m=> m.Id);
        public override string PartitionKey => "sample-saga";
        public async Task ProcessAsync(SampleSagaStartMessage message, CancellationToken cancellationToken)
            await _storageBus.SendAsync(new SampleSagaMessage());

        public async Task ProcessAsync(SampleSagaMessage message, CancellationToken cancellationToken)
            Console.WriteLine("Counter is {0}", Data.Counter);
            if (Data.Counter == 5)
                Console.WriteLine("Finishing Saga");
                await CompleteAsync();

            await UpdateAsync();
            await _storageBus.SendAsync(new SampleSagaMessage());

        public Task ProcessDuplicateAsync(SampleSagaMessage message, CancellationToken cancellationToken)
            // Saga duplicate found

            return Task.CompletedTask;

    // This is exposed as `Data` property to classes that implements Saga<MySagaData>
    class MySagaData
        public int Counter { get; set; }

    class SomeProcessingSetting : IProcessingSettings
        public int MaxConcurrentCalls => 1;
        public int PrefetchCount => 1;
        public TimeSpan MessageLockTimeout => TimeSpan.FromMinutes(5);
        public int DeadLetterDeliveryLimit => 2;