Bustr

Bustr

Bustr is an event bus middleware abstraction and simplification on top of MassTransit so you can easily inject the pub-sub pattern into your applications in an uniform way and provides a scalable and flexible solution for handling location information in a distributed system, allowing other services or applications to easily and reliably retrieve location information as needed.

It focuses on topics in case you want to use it with Azure Service Bus and fan-out if you use RabbitMQ and it creates both and their respective subscriptions with only a few lines of code as showcased below.

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Usage

Publishing/sending messages

Just inject and use IEventBus interface to publish messages (which will go to the mapped topic) or send a message to any queue or topic like the example below:

public class PersonCreateHandler
{
    private readonly IEventBus _eventBus;

    public PersonCreateHandler(IEventBus eventBus)
    {
        _eventBus = eventBus;
    }

    public async Task CreatePersonAsync(Person person)
    {
        // business logic and person creation ...
        
        var PersonEvent = new PersonEvent
        {
            PersonId = person.Id,
            Created = true
        };

        // Publish event to the registered topic for PersonEvent
        await _eventBus.PublishAsync<PersonEvent>(PersonEvent);

        // Or Send a message of any type to a topic
        await _eventBus.SendAsync<Person>(person, "some-topic", true);
        // Or send it serialized
        var topicMessage = JsonSerializer.Serialize(person);
        await _eventBus.SendAsync(topicMessage, "some-topic", true);
        
        // Or Send a message of any type to a queue
        await _eventBus.SendAsync<Person>(person, "some-queue", false);
        // Or send it serialized
        var message = JsonSerializer.Serialize(person);
        await _eventBus.SendAsync(message, "some-queue", false);
    }
}

Subscribing/consuming messages

public class PersonEventConsumer : IEventBusConsumer<PersonEvent>
{
    public async Task Consume(ConsumeContext<PersonEvent> context)
    {
        var eventData = context.Message;
        
        // Do something with the message
    }
}

Configuration

Scenario 1: Producer microservice

This is the most basic, yet common, scenario in which the application sends an event (PersonEvent class) to a topic (person-event topic) and has no subscription to any event from external applications.

services.AddBustr(options =>
{
    options.Configure(BusType.RabbitMq, connectionString)
        .RetryImmediately(3)
        .MapTopic("person-event", typeof(PersonEvent));
});

Scenario 2: Producer microservice with async events to itself

This configuration will create 3 topics and 3 subscription (optional) to themselves which is useful for cases were you want the application to do post-action processing like clearing the cache, sending more messages, send email notifications, etc.

It creates 3 topics under the same directory (location as in location/city-event) and define which classes are going to consume the subscriptions.

    services.AddBustr(options =>
    {
        options.Configure(BusType.AzureServiceBus, connectionString)
        .SetRetryIntervals(TimeSpan.FromMinutes(2), TimeSpan.FromMinutes(5), TimeSpan.FromMinutes(10))
        .UseDeadLetterQueue(true)
            .MapTopic("location/city-event", typeof(CityEvent), typeof(CityEventConsumer), "self.city.location.service")
            .MapTopic("location/state-event", typeof(StateEvent), typeof(StateEventConsumer), "self.state.location.service")
            .MapTopic("location/country-event", typeof(CountryEvent), typeof(CountryEventConsumer), "self.country.location.service");
    });

Scenario 3: Publishing events and consuming events from external applications

This configuration will create 2 topics and 1 subscription to itself, then it will create another just to send events and finally it will subscribe to 2 events coming from external applications.

services.AddBustr(options =>
{
    options.Configure(BusType.RabbitMq, connectionString)
        .RetryImmediately(3)
        .MapTopic("person/payment-event", typeof(CityEvent), typeof(CityEventConsumer), "self.person.service")
        .MapTopic("person/person-event", typeof(PersonEvent))
        .AddSubscription("some-external-topic", typeof(CountryEvent), "census-person-service")
        .AddSubscription("some-other-topic", typeof(DiscountEvent), "discount-person-service");
});

Contributing

It is simple, as all things should be:

1. Clone it
2. Improve it
3. Make pull request

Credits

• Initial development by Slukad
• MassTransit awesome library by phatboyg