tokio-events

A modern, type-safe async event bus for Rust applications built on Tokio.

Quick Example

// Create an event bus
let bus = EventBus::builder()
    .with_metrics()
    .build();

// Subscribe to events
bus.subscribe(|event: UserRegistered| async {
    println!("New user: {}", event.email);
}).await?;

// Publish events
bus.publish(UserRegistered {
    id: 123,
    email: "user@example.com".into(),
}).await?;

Core Components

1. EventBus – The Main API

• Single instance shared across your application
• Provides publish() and subscribe() methods
• Manages component lifecycle

2. Registry – Type Mapping

• Maps event types to their subscribers
• Uses TypeId for type-safe routing
• Thread-safe using DashMap

3. Dispatcher – Event Queue

• MPSC channel for queuing events
• Worker thread processes events
• Configurable queue size and backpressure

4. Subscription Manager – Handler Execution

• Stores active handlers
• Spawns async tasks for parallel execution
• Manages subscription lifecycle

publish(UserRegistered) 
    ↓
Create EventEnvelope (type erasure)
    ↓
Send to channel (Arc wrap)
    ↓
Worker receives
    ↓
Lookup by TypeId → Find handlers
    ↓
Spawn tasks (parallel)
    ↓
Each handler:
  - Downcast to UserRegistered
  - Execute user function
  - Update metrics
    ↓
Cleanup (Arc refcount → 0)