DelayedEvents.Abstractions 1.0.1

DelayedEvents

DelayedEvents is a library that provides a simple way to implement delayed message. For example: you can use it to implement when order is not paid in 15 minutes, cancel the order.

Nuget packages

Name	Version	Downloads
DelayedEvents.Abstractions
DelayedEvents.RabbitMq

Installation

Add following nuget reference in business project:

PM> Install-Package DelayedEvents.Abstractions

And add following nuget reference in integration project:

PM> Install-Package DelayedEvents.RabbitMq

Make sure the plugins rabbitmq_delayed_message_exchange are enabled. https://blog.rabbitmq.com/posts/2015/04/scheduling-messages-with-rabbitmq/

How to use

First of all, you need to create a class that derived from the DelayedEvent class.

public class OrderPaymentCheckDelayedEvent : DelayedEvent
{
    public OrderPaymentCheckDelayedEvent(Guid orderId)
    {
        OrderId = orderId;
        DelayInSec = 15 * 60;   // Make 15 minutes delay   
    }

    public Guid OrderId { get; }
}

Then, you need to create a class that derived from the DelayedEventHandler class.

public class OrderPaymentCheckDelayedEventHandler : DelayedEventHandler<OrderPaymentCheckDelayedEvent>
{
    private readonly IOrderService _orderService;

    public OrderPaymentCheckDelayedEventHandler(IOrderService orderService)
    {
        _orderService = orderService;
    }

    public override async Task Handle(OrderPaymentCheckDelayedEvent e)
    {
        // We will cancel the order if it is not paid in 15 minutes
        await _orderService.CancelOrderIfNotPaidAsync(e.OrderId);
    }
}

Finally, you need to register the DelayedEventHandler in the Startup.cs file.

public void ConfigureServices(IServiceCollection services)
{
    services.AddDelayedEvents()
        .AddRabbitMq(options =>
        {
            options.HostName = "localhost";
            options.UserName = "guest";
            options.Password = "guest";
        })
        .AddDelayedEventHandler<OrderPaymentCheckDelayedEventHandler>();
}

Ok! Now you can publish the DelayedEvent class in the business project.

public class OrderService : IOrderService
{
    private readonly IDelayedEventPublisher _delayedEventPublisher;

    public OrderService(IDelayedEventPublisher delayedEventPublisher)
    {
        _delayedEventPublisher = delayedEventPublisher;
    }

    public async Task CreateOrderAsync(Order order)
    {
        // Create order

        // Publish the delayed event
        await _delayedEventPublisher.PublishAsync(new OrderPaymentCheckDelayedEvent(order.Id));
    }
}

Final

Leave a comment on GitHub if you have any questions or suggestions.

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License

This project is licensed under the MIT License