EventBus – A Lightweight Event Sourcing Library for Go

EventBus is a simple and efficient event-driven system for Go applications.
It allows you to publish and subscribe to events seamlessly.

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📦 Installation

To install the library, run:

go get github.com/Raezil/GoEventBus

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🚀 Quick Start

1️⃣ Initialize a New Project

mkdir eventbus-demo
cd eventbus-demo
go mod init eventbus-demo

2️⃣ Create main.go

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"

	gbus "github.com/Raezil/GoEventBus"
	"github.com/gorilla/mux"
)

// HouseWasSold represents an event for a house sale.
type HouseWasSold struct{}

// NewDispatcher sets up event handlers.
func NewDispatcher() *gbus.Dispatcher {
	return &gbus.Dispatcher{
		HouseWasSold{}: func(data map[string]interface{}) (gbus.Result, error) {
			price, ok := data["price"].(int)
			if !ok {
				return gbus.Result{}, fmt.Errorf("invalid or missing 'price'")
			}
			message := fmt.Sprintf("House sold for %d!", price)
			log.Println(message)
			return gbus.Result{Message: message}, nil
		},
	}
}

func main() {
	dispatcher := NewDispatcher()
	eventStore := gbus.NewEventStore(dispatcher)

	router := mux.NewRouter()
	router.HandleFunc("/house-sold", func(w http.ResponseWriter, r *http.Request) {
		eventStore.Publish(gbus.NewEvent(HouseWasSold{}, map[string]interface{}{"price": 100}))
		
		if err := eventStore.Broadcast(); err != nil {
			log.Printf("Error broadcasting event: %v", err)
			http.Error(w, "Event processing failed", http.StatusInternalServerError)
			return
		}
		
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(map[string]string{"status": "House sold event published"})
	})

	log.Println("Server running on :8080")
	log.Fatal(http.ListenAndServe(":8080", router))
}

3️⃣ Run Your Application

go run main.go

Now, visiting http://localhost:8080/house-sold will trigger the event and process it.

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🐇 RabbitMQ Integration

1️⃣ Start RabbitMQ

docker run -it --rm --name rabbitmq -p 5672:5672 -p 15672:15672 rabbitmq:4.0-management

2️⃣ Implement Event Publishing in main.go

package main

import (
	"fmt"
	"log"
	. "github.com/Raezil/GoEventBus"
)

func NewDispatcher() *RabbitDispatcher {
	return &RabbitDispatcher{
		"HouseWasSold": func(data map[string]interface{}) (Result, error) {
			price, ok := data["price"].(float64)
			if !ok {
				return Result{}, fmt.Errorf("invalid or missing 'price'")
			}
			return Result{Message: fmt.Sprintf("House sold for %.2f", price)}, nil
		},
	}
}

func main() {
	dispatcher := NewDispatcher()
	rabbitStore, err := NewRabbitEventStore(dispatcher, "amqp://guest:guest@localhost:5672/", "events_queue")
	if err != nil {
		log.Fatalf("Failed to initialize RabbitEventStore: %v", err)
	}

	rabbitStore.Publish(&Event{Id: "12345", Projection: "HouseWasSold", Args: map[string]interface{}{"price": 100.0}})
	rabbitStore.Publish(&Event{Id: "123456", Projection: "HouseWasSold", Args: map[string]interface{}{"price": 200.0}})

	go rabbitStore.Broadcast()
	select {}
}

3️⃣ Run Your Application

go run main.go

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📖 References

• GoEventBus GitHub Repository
• RabbitMQ Official Documentation
• Event Sourcing Overview