theluckiestsoul / chronicle

Implementation of saga pattern for .NET Core

Chronicle is simple process manager/saga pattern implementation for .NET Core that helps you manage long-living and disitrbuted transactions.

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Installation

Chornicle is available on NuGet

Package manager

Install-Package Chronicle_ -Version 1.8.0

.NET CLI

dotnet add package Chronicle_ --version 1.8.0

Getting started

In order to create and process saga you need to go through few steps:

1. Create a class that dervies either from Saga or Saga<TData>.
2. Inside saga implement particular steps that needs to be done or compensated in case of error. The initial step must be implemented as ISagaStartAction<TMessage> while the rest ISagaAction<TMessage>. It's worth mentioning that up can implement as many start actions as you want. In this case first incomming message is going to initialize saga.
3. Register all your sagas in Startup.cs by calling services.AddChronicle().
4. Inject ISagaCoordinator and inoke ProcessAsync() methods passing a message. Cooridnator will take care of everything by looking for all implemented sagas that can handle given message.

Bellow is the very simple example of saga that completes once both messages (Message1 and Message2) are received:

public class Message1
{
    public string Text { get; set; }
}

public class Message2
{
    public string Text { get; set; }
}

public class SagaData
{
    public bool IsMessage1Received { get; set; }
    public bool IsMessage2Received { get; set; }
}

public class SampleSaga : Saga<SagaData>, ISagaStartAction<Message1>, ISagaAction<Message2>
{
    public Task HandleAsync(Message1 message, ISagaContext context)
    {
        Data.IsMessage1Received = true;
        Console.WriteLine($"Received message1 with message: {message.Text}");
        CompleteSaga();
        return Task.CompletedTask;
    }
    
    public Task HandleAsync(Message2 message, ISagaContext context)
    {
        Data.IsMessage2Received = true;
        Console.WriteLine($"Received message2 with message: {message.Text}");
        CompleteSaga();
        return Task.CompletedTask;
    }

    public Task CompensateAsync(Message1 message, ISagaContext context)
        => Task.CompletedTask;

    public Task CompensateAsync(Message2 message, ISagaContext context)
        => Task.CompletedTask;

    private void CompleteSaga()
    {
        if(Data.IsMessage1Received && Data.IsMessage2Received)
        {
            Complete();
            Console.WriteLine("SAGA COMPLETED");
        }
    }
}

Both messages are processed by mentioned coordinator:

var coordinator = app.ApplicationServices.GetService<ISagaCoordinator>();

var context = SagaContext
    .Create()
    .WithCorrelationId(Guid.NewGuid())
    .Build();

coordinator.ProcessAsync(new Message1 { Text = "Hello" }, context);
coordinator.ProcessAsync(new Message2 { Text = "World" }, context);

The result looks as follows:

Documentation

If you're looking for documentation, you can find it here.

Icon

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