Go Micro PubSub Tutorial

PubSub is a very important theme in Microservices. In fact, if there is no PubSub in your microservices, then what's the point of your Microservices? Right?

Benefits of PubSub Messaging from AWS:

"In modern cloud architecture, applications are decoupled into smaller, independent building blocks that are easier to develop, deploy and maintain. Publish/Subscribe (Pub/Sub) messaging provides instant event notifications for these distributed applications.

The Publish Subscribe model enables event-driven architectures and asynchronous parallel processing, while improving performance, reliability and scalability."

Preparation

Please make sure you check out Asim's examples from time to time. Though it seems to be too simple, too little, it can actually help you out when you encounter a confusing bug that is keeping you from moving forward. In this case, check out examples/broker.

Getting Broker

To get broker, do the following:

Inside srv service

yourBroker := yourSRVService.Options().Broker

Inside web service (I spent a lot of time trying to figure out how to get broker out of web service.)

yourBroker := yourWEBService.Options().Service.Options().Broker

Now don't forget to Init and Connect yourBroker:

if err := b.Init(); err != nil {
	log.Fatalf("Broker Init error: %v", err)
}
if err := b.Connect(); err != nil {
	log.Fatalf("Broker Connect error: %v", err)
}

Subscribing to A Topic

if _, err := yourBroker.Subscribe(yourTopic, yourHandler); err != nil {
	log.Fatalf("broker.Subscribe topic %v error: %v", yourTopic, err)
}

Publishing A Message under A Topic

Don't forget to import broker to compose messages.

import "github.com/micro/go-micro/broker"

msg := &broker.Message{
	Body: body,
}

if err := b.Publish(yourTopic, msg); err != nil {
	log.Logf("error publishing: %v", err)
}

Checking whether The Message Queue You Choose Are Being Used

log.Logf("broker.String(): %v", b.String())

If you are not using "any", broker.String() will be http.

If you are using NATS, broker.String() will be nats.