First steps

OpenSleigh is intended to be flexible and developer-friendly. It makes use of Dependency Injection for its own initialization and the setup of the dependencies.

The first step, once you have installed the Core library, is to add OpenSleigh to the Services collection:

Host.CreateDefaultBuilder(args)
    .ConfigureServices((hostContext, services) => {
                services.AddOpenSleigh(cfg =>{ ... });
    });

Configure Transport and Persistence

OpenSleigh needs to be configured to point to a specific Transport bus and a Persistence mechanism for the Saga States:

Host.CreateDefaultBuilder(args)
    .ConfigureServices((hostContext, services) => {
        services.AddOpenSleigh(cfg =>{ 
            var rabbitSection = hostContext.Configuration.GetSection("Rabbit");
            var rabbitCfg = new RabbitConfiguration(rabbitSection["HostName"], 
                rabbitSection["UserName"],
                rabbitSection["Password"]);

            gfg.UseRabbitMQTransport(rabbitCfg);

            var mongoSection = hostContext.Configuration.GetSection("Mongo");
            var mongoCfg = new MongoConfiguration(mongoSection["ConnectionString"],
                mongoSection["DbName"],
                MongoSagaStateRepositoryOptions.Default);

            cfg.UseMongoPersistence(mongoCfg);
        });
    });

In this example, the system is configured to use RabbitMQ as message bus and MongoDB to persist the data.

IMPORTANT: for detailed instructions on each Transport and Persistence mechanism, please refer to the library's documentation.

Adding a Saga

A Saga is a simple class inheriting from the base Saga class:

public record MyAwesomeSagaState { }

public class MyAwesomeSaga : Saga
{
    private readonly ILogger<MyAwesomeSaga> _logger;       

    public ParentSaga(ILogger<MyAwesomeSaga> logger)
    {
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }
}

Dependency injection can be used to provide services to a Saga.

Now, all you have to do is register and configure the Saga:

services.AddOpenSleigh(cfg =>{
    cfg.AddSaga<MyAwesomeSaga>();
});

Sagas can also hold some state. In this case, we need to define its shape by creating a class or a record and setting it on the Saga:

public record MySagaState
{
    public int Foo = 42;
    public string Bar = "71";
};

public class SagaWithState : Saga<MySagaState> {

}

Now you can register it this way:

services.AddOpenSleigh(cfg =>{
    cfg.AddSaga<SagaWithState, MySagaState>();
});

The State can be accessed later on via this.Context.State and is also persisted automatically after a message is processed. For more details, check the Handling Messages page.

IMPORTANT: each Saga should have its own State class. Don't reuse State classes!