go-micro/internal/website/docs/broker.md

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Broker

The broker provides pub/sub messaging for Go Micro services.

Features

• Publish messages to topics
• Subscribe to topics
• Multiple broker implementations

Implementations

Supported brokers include:

• HTTP (default)
• NATS (go-micro.dev/v5/broker/nats)
• RabbitMQ (go-micro.dev/v5/broker/rabbitmq)
• Memory (go-micro.dev/v5/broker/memory)

Plugins are scoped under go-micro.dev/v5/broker/<plugin>.

Configure the broker in code or via environment variables.

Example Usage

Here's how to use the broker in your Go Micro service:

package main

import (
    "go-micro.dev/v5"
    "go-micro.dev/v5/broker"
    "log"
)

func main() {
    service := micro.NewService()
    service.Init()

    // Publish a message
    if err := broker.Publish("topic", &broker.Message{Body: []byte("hello world")}); err != nil {
        log.Fatal(err)
    }

    // Subscribe to a topic
    _, err := broker.Subscribe("topic", func(p broker.Event) error {
        log.Printf("Received message: %s", string(p.Message().Body))
        return nil
    })
    if err != nil {
        log.Fatal(err)
    }

    // Run the service
    if err := service.Run(); err != nil {
        log.Fatal(err)
    }
}

Configure a specific broker in code

NATS:

import (
    "go-micro.dev/v5"
    bnats "go-micro.dev/v5/broker/nats"
)

func main() {
    b := bnats.NewNatsBroker()
    svc := micro.NewService(micro.Broker(b))
    svc.Init()
    svc.Run()
}

RabbitMQ:

import (
    "go-micro.dev/v5"
    "go-micro.dev/v5/broker/rabbitmq"
)

func main() {
    b := rabbitmq.NewBroker()
    svc := micro.NewService(micro.Broker(b))
    svc.Init()
    svc.Run()
}

Configure via environment

Using the built-in configuration flags/env vars (no code changes):

MICRO_BROKER=nats MICRO_BROKER_ADDRESS=nats://127.0.0.1:4222 micro server

Common variables:

• MICRO_BROKER: selects the broker implementation (http, nats, rabbitmq, memory).
• MICRO_BROKER_ADDRESS: comma-separated list of broker addresses.

Notes:

• NATS addresses should be prefixed with nats://.
• RabbitMQ addresses typically use amqp://user:pass@host:5672.