Outboxer

Available at Nuget

This lib intends to provide a simple and broker agnostic Outbox Pattern implementation.

The only requirement to use Outboxer is to use Entity Framework as we use its built-in Unit-Of-Work to assure everything is saved at the same time and guarantee consistency.

To use Outboxer follow these steps

• Make sure your DbContext inherits OutboxerContext<T>. If the name of your context is StudentsContext, your class should look like this.

public class StudentsContext : OutboxerContext<StudentsContext>
{
    public StudentsContext(DbContextOptions<StudentsContext> options,
        ITransactionalMessageContainer transactionalMessageContainer) : base(options, transactionalMessageContainer)
    {
    }

    // Your code
}

• Run dotnet ef migrations add/dotnet ef database update to create the outbox table

• Register Outboxer using services.AddOutboxer<StudentsContext>(); at your Startup.cs or Program.cs(.net core 6+)

• To be broker agnostic means that you'll have to implement your own broker communication mechanism. Make sure your class implements the IBrokerPublisher interface. All your sending logic should be inside Publish method.

• Register your custom broker communication class on DI container using services.AddScoped<IBrokerPublisher, MyBrokerImplementation>(). You can use AddSingleton as well.

• To publish a message inject the interface IPublisher and use the Publish method like this await _publisher.Publish(new Entry("studentsQueue", messageContent));. The content will just be added to outbox and enqueued on your broker if the database commit runs fine.

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Important warnings

If the BackgroundWorker that sends the messages gets restarted it will re-enqueue ALL the messages with ENQUEUED status at the outbox table. This normaly just occurs when the app gets restarted, yet it is a good idea to implement idempotency at your consumers.

Currently there is no Dead-Letter implementation. If a message reaches the maximum amount of retries it will rest in the table with FAILED status. DLQ Handling to be implemented in next version.

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Messages Status

• 1 - Pending
• 2 - Enqueued
• 3 - Delivered
• 4 - Failed

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Changelog

v1.1.0 - Fixing bug that was preventing the persistence of Destination and Retries on the outbox table. - REQUIRES MIGRATION