DotNetBrightener.Plugins.EventPubSub.MassTransit 2024.0.14.6-preview-2381603

MassTransit Integration for Event PubSub Library

© 2024 DotNet Brightener

Versions

Library	Version
EventPubSub Core
MassTransit Integration Library
Dependency Injection Library
Azure Service Bus with MassTransit Library
RabbitMq with MassTransit Library

Installation

dotnet package add DotNetBrightener.Plugins.EventPubSub
dotnet package add DotNetBrightener.Plugins.EventPubSub.DependencyInjection
dotnet package add DotNetBrightener.Plugins.EventPubSub.MassTransit
dotnet package add DotNetBrightener.Plugins.EventPubSub.MassTransit.AzureServiceBus
# or 
dotnet add package DotNetBrightener.Plugins.EventPubSub.MassTransit.RabbitMq

Usage

Configuration

Option 1: Use IConfiguration to configure the service bus

// Initialize EventPubSubService
var eventPubSubConfig = builder.Services
                               .AddEventPubSubService()
                                // scan for event messages in the given assembly
                               .AddEventMessagesFromAssemblies(Assembly.GetExecutingAssembly(), typeof(DistributedTestMessage).Assembly)
                                // scan for event handlers in the given assembly
                               .AddEventHandlersFromAssemblies(Assembly.GetExecutingAssembly());

var massTransitConfigurator = eventPubSubConfig.EnableMassTransit();

// Add Azure Service Bus
massTransitConfigurator.UseAzureServiceBus(builder.Configuration);

// Or Add RabbitMq - Note that only one or the other can be used in an application.
// massTransitConfigurator.UseRabbitMq(builder.Configuration);

// this should be called before builder.Build(), or before exiting ConfigureServices method
massTransitConfigurator.Finalize();

In your appsettings.json file, add the the following configuration:

  "ServiceBusConfiguration": {
    "ConnectionString": "<your-endpoint-to-azure-service-bus>",
    "SubscriptionName": "<application-name>",
    "IncludeNamespaceForTopicName": false
  },
  "RabbitMqConfiguration": {
    "Host": "<rabbit-mq-host>",
    "Username": "<rabbit-mq-username>",
    "Password": "<rabbit-mq-password>",
    "VirtualHost": "<rabbit-mq-virtual-host>",
    "SubscriptionName": "<application-name>",
    "IncludeNamespaceForTopicName": false
  }

Option 2: Configure from code

// Initialize EventPubSubService
var eventPubSubConfig = builder.Services
                               .AddEventPubSubService()
                                // scan for event messages in the given assembly
                               .AddEventMessagesFromAssemblies(Assembly.GetExecutingAssembly(), typeof(DistributedTestMessage).Assembly)
                                // scan for event handlers in the given assembly
                               .AddEventHandlersFromAssemblies(Assembly.GetExecutingAssembly());

var massTransitConfigurator = eventPubSubConfig.EnableMassTransit();

massTransitConfigurator.SetSubscriptionName("<application-name>");
// if you want to exclude namespace in entity name
massTransitConfigurator.ExcludeNamespaceInEntityName();

// Add Azure Service Bus
massTransitConfigurator.UseAzureServiceBus("<azure-connection-string>");

// Or Add RabbitMq - Note that only one or the other can be used
/*
massTransitConfigurator.UseRabbitMq("<rabbit-mq-host>",
                                    "<rabbit-mq-username>",
                                    "<rabbit-mq-password>",
                                    "<rabbit-mq-virtual-host>");
*/

// this should be called before builder.Build(), or before exiting ConfigureServices method
massTransitConfigurator.Finalize();

Event Message Definition

Create a class that represents the event message. The class must implement the IDistributedEventMessage interface.

namespace YourProject.NameSpace;

public class DistributedTestMessage : IDistributedEventMessage
{
    public string Name { get; set; }

    // more payload properties
}

Event Handler Definition

Create a class derived from DistributedEventEventHandler<YourEventMessage> and override HandleEvent method to handle the event message.

With this implementation, you'll be able to access the original payload of the messsage by accessing OriginPayload property.

public class TestEventHandlerDistributed(ILogger<TestEventHandlerDistributed> logger)
    : DistributedEventEventHandler<DistributedTestMessage>
{
    private readonly ILogger _logger = logger;
    
    public override Task<bool> HandleEvent(DistributedTestMessage eventMessage)
    {
        // access the `OriginPayload` 
        var origin = OriginPayload;

        _logger.LogInformation($"Received message: {eventMessage.Name}");

        return Task.FromResult<bool>(true);
    }
}

Request - Response Message Pattern

Create 2 (two) classes that represents the request message and the response message. The request message class must implement the IRequestMessage interface, while the response message class must implement the IResponseMessage<T> interface, where T is the request message type.

namespace YourProject.NameSpace;

public class RequestMessage : IRequestMessage
{
    public string Name { get; set; }

    // more payload properties
}

public class ResponseMessage : IResponseMessage<RequestMessage>
{
    public string Name { get; set; }

    // more payload properties
}

When you want to initiate a request to obtain the needed response, use IEventPublisher to initiate it as follow:

var requestMessage = new RequestMessage
{
    Name = eventMessage.Name
};

var response = await eventPublisher.GetResponse<ResponseMessage, RequestMessage>(requestMessage);

Request - Response Handler Definition

Create a class derived from RequestResponder<YourRequestMessage> and override HandleEvent method to handle the event message.

public class HandleRequestMessage(ILogger<HandleRequestMessage> logger)
    : RequestResponder<RequestMessage>
{    
    public override async Task<bool> HandleEvent(RequestMessage eventMessage)
    {
        // do something with the request message, e.g. logging it
        logger.LogInformation($"Received message: {eventMessage.Name}");

        // create a response message - this response message must implement IResponseMessage<T> interface
        var responseMessage = new ResponseMessage
        {
            Name = eventMessage.Name
        };

        // send the response message
        await SendResponse(responseMessage);

        return Task.FromResult<bool>(true);
    }
}