AsyncEventBus 1.0.4

About

This library contains two EventBus implementations: AsyncEventBus, which is thread-safe and designed for asynchronous and multi-threaded operations; and SyncEventBus, which is thread-safe and synchronous. The core concept is subscribing to any event represented by a class/struct with optional input parameters and a constructor to initialize them (recommended). When an event is published, its subscribed handlers receive an instance of the class (i.e., the event) with the necessary parameters.

Features:

• ✅Asynchronous
• ✅Multi-threading
• ✅Thread-safe
• ✅Retry policy
• ✅Execution reporting
• ✅Configurable

Using

Event

An event is a class/struct that inherits from IEvent. You can define parameters for the handler within the class (properties are recommended), as well as a constructor to initialize them.

public class TestEvent : IEvent
{
    public int Value { get; init; }
    
    public TestEvent(int value)
    {
        Value = value;
    }
}

Init and Dispose

AsyncEventBus _asyncEventBus = EventBusFactory.CreateAsync();
SyncEventBus _syncEventBus = EventBusFactory.CreateSync();
// Do Something
_asyncEventBus.DisposeAsync();
_syncEventBus.Dispose();

• Init: via factory.
• Dispose: EventBus has a built-in Dispose method that fully cleans up the EventBus instance. Calling any EventBus method after disposal will throw an ObjectDisposedException. For AsyncEventBus, the Dispose method is asynchronous: DisposeAsync.

Subscribe

There’s no need to declare events explicitly in the EventBus; an event is automatically added to the bus on the first Subscribe call for that event. Subscription is done by specifying the event type and a handler whose parameter is the event class/struct. You can also use the subscribeOnce: bool parameter. After the first publication of the event, all its subscribers with subscribeOnce = true will be unsubscribed automatically.

private async Task Handler(TestEvent @event)
{
    var value = @event.Value;
}
_eventBus.Subscribe<TestEvent>(Handler);
// OR
_eventBus.Subscribe<TestEvent>(Handler, true);

Unsubscribe

Unsubscription is done via the return value of the Subscribe method: IDisposable. Its Dispose method unsubscribes the handler from the event.

IDisposable token = _eventBus.Subscribe<TestEvent>(Handler);
token.Dispose();

Publish

For AsyncEventBus, use PublishAsync, which sends the event invocation to a Channel queue. For SyncEventBus, call Publish, which immediately starts invoking all handlers.

await asyncEventBus.PublishAsync(new TestEvent(10));
syncEventBus.Publish(new TestEvent(10));

Clear

The bus provides two cleanup methods (apart from full cleanup via Dispose): Clear and ClearAll.

• Clear: removes a specific event and all its handlers.
• ClearAll: clears all events and all handlers.

_eventBus.Clear<TestEvent>();  
_eventBus.ClearAll();

Config

You can specify custom parameters for certain EventBus settings.

More About Reports

EventBus provides the GetEventReport method, which returns the latest report for a given event type (if specified) or all reports. Return type is EventPublishReport.

Properties of EventPublishReport:

• EventType: Type – the event type
• HandlersCount: int – number of subscribed handlers
• ErrorHandlers: int – number of handlers that threw an error during execution
• Exceptions: List<Exception> – thrown exceptions

var config = AsyncEventBusConfig.Default with
{
    ShutdownTimeout = TimeSpan.FromSeconds(30),
    MaxRetryCount = 3,
    EnableReporting = true
};
var eventBus = EventBusFactory.CreateAsync(config);

Sync vs Async: When to Use Which

SyncEventBus:

• Event processing is fast and synchronous
• Guarantees handler invocation order
• Guarantees handler completion order
• ⚠️ Subsequent code runs only after ALL handlers finish

AsyncEventBus:

• High performance and non-blocking processing
• Events are processed in the background
• Guarantees handler invocation order
• Handlers run concurrently, the fastest finishes first
• ⚠️ Does NOT guarantee handler completion order