EventBus

About

Arcturus EventBus is a standardized eventbus implementation, used for common distributed systems.

FAQ

Usage

Basics

Arcturus provide different clients used to either produce or consume events.

Producing

When producing events, use the event publisher from the IEventBusFactory, example:

var publisher = eventBusFactory.CreatePublisher("task_queue");

var eventMessage = new MessageEvent { Message = "Hello World" };
await publisher.Publish(eventMessage, cancellationToken);

Consuming

You can consume events using either a IProcessor or a ISubscriber.

var processor = eventBusFactory.CreateProcessor();
processor.OnProcessAsync += async (eventMessage, cancellationToken) =>
{
    // handle eventMessage
    await Task.CompletedTask; // Simulate async processing
};
Task.Run(() => processor.WaitForEvents());

Events

Events are strongly typed classes implementing the IEventMessage interface. Example:

public sealed class MessageEvent : IEventMessage
{
    public required string Message { get; set; }
}

When using the event processor (implementations of IProcessor), events can be auto-wired using the IEventMessageHandler interface. Example:

public sealed class MessageEventEventHandler(
    ILogger<MessageEventEventHandler> logger)
    : IEventMessageHandler<MessageEvent>
{
    private readonly ILogger<MessageEventEventHandler> _logger = logger;
    public Task Handle(MessageEvent@event, CancellationToken cancellationToken = default)
    {
        // ... code
        return Task.CompletedTask;
    }
}

Middleware & pipeline

Middleware is software that's assembled into an app pipeline to handle requests and responses. Each component:

• Chooses whether to pass the request to the next component in the pipeline.
• Can perform work before and after the next component in the pipeline.

Request delegates are used to build the request pipeline. The request delegates handle each eventbus request.

Arcturus support implementation of middleware as a pipeline when implementing the IEventMessageHandler approach.

Using IProcessor.OnProcessAsync does not call the middleware framework.

Middleware follow this syntax:

public class SampleMiddlware
{
    public async Task InvoiceAsync(EventContext context)
    {

    }
}

You can inject services injected as singleton in the constructor of the middleware, whilst scoped and transient services must be injected within the InvokeAsync method.

Implementations

RabbitMQ

Implements Arcturus.EventBus using RabbitMQ as queue and intermediate.

dotnet add package Arcturus.EventBus.RabbitMQ

using Arcturus.EventBus.RabbitMQ;
...
// console sample
var builder = Host.CreateApplicationBuilder();
builder.Services.AddRabbitMQEventBus(o => {
    o.ApplicationId = "sampleApplication";
    o.ClientName = Guid.NewGuid().ToString()[..10];
    o.HostName = "localhost";
}); 
var host = builder.Build();

...

SQLite

Implements Arcturus.EventBus using SQLite as queue and intermediate.

dotnet add package Arcturus.EventBus.SQLite

using Arcturus.EventBus.SQLite;
...
// console sample
var builder = Host.CreateApplicationBuilder();
builder.Services.AddSqliteEventBus(o => {
    o.ConnectionString = "Data Source=:memory:;";
});
var host = builder.Build();

...

Azure ServiceBus

Implements Arcturus.EventBus using Azure ServiceBus as queue and intermediate.

dotnet add package Arcturus.EventBus.AzureServiceBus

Azure Storage Queue

Implements Arcturus.EventBus using Azure Storage as queue and intermediate.

dotnet add package Arcturus.EventBus.AzureStorageQueue

using Arcturus.EventBus.AzureStorageQueue;
...
// console sample
var builder = Host.CreateApplicationBuilder();
builder.Services.AddAzureStorageQueueEventBus(o => {
    o.ApplicationId = "sampleApplication";
    o.ConnectionString = @"DefaultEndpointsProtocol=https;...EndpointSuffix=core.windows.net";
    o.MessageProcessing.MessageIntervalMilliseconds = 1500;
});
var host = builder.Build();

...