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Events

An EventBus is a communication mechanism or pattern used in software development to enable the exchange of messages, events, or notifications between different parts of a software system or between loosely coupled components. It simplifies the decoupling of components and promotes a more scalable and maintainable architecture.

Local Eventbus​

github: https://github.com/goxiaoy/go-eventbus

The Repository uses local eventbus to publish entities change events

Distributed Event​

Producer​

type Producer interface {
	io.Closer
	Send(ctx context.Context, msg Event) error
	BatchSend(ctx context.Context, msg []Event) error
}
warning

Not all the underlying distributed event buses support atomic batch sending.

Consumer​

type HandlerOf[T any] interface {
	Process(context.Context, T) error
}
type ConsumerHandler HandlerOf[Event]

type Consumer interface {
	io.Closer
	// Process start process event with handler
	Process(ctx context.Context, handler ConsumerHandler) error
}

Consistency​

Unit of Work Producer​

Combining with Aggregate Root allows for delayed event sending until the unit of work is committed.

event.ConsumerFactoryServer implements kratos transport.Server You can apply middleware pattern to ConsumerFactoryServer

	srv := event.NewConsumerFactoryServer(e, container)
    // panic recovery,tracing,logging,unit of work
	srv.Use(event.ConsumerRecover(event.WithLogger(logger)), trace.Receive(), event.Logging(logger), event.ConsumerUow(uowMgr))

Two-phase message Exposed Endpoint​

You can embed eventserver.EventProviderSet to your di container to expose grpc endpoints for cases like Cache Consistency

eventserver "github.com/go-saas/kit/event/server"

service EventService{
  rpc HandleEvent(HandleEventRequest)returns(google.protobuf.Empty){
  }
  rpc PublishEvent(PublishEventRequest)returns(google.protobuf.Empty){
  }
}

Provider​

Kafka​

Pulsar​