golang微服务框架go-micro使用 (五) Message Broker

前一篇文章，我们讨论了在micro中如何发布/订阅消息。它的优点是简单，缺点是缺乏灵活性。如果你想使用底层去发送与接收消息，需要使用接口：github.com/micro/go-micro/v2/broker.Broker
这个接口是micro异步消息处理的核心，事实上，发布/订阅也依赖它

下面，使用一个例子来使用Broker

package main

import (
	"fmt"
	"github.com/micro/go-micro/v2"
	"github.com/micro/go-micro/v2/broker"
	"log"
	"time"
)

var topic string = "com.foo.topic"

func pub(brk broker.Broker) {
	i := 0
	for range time.Tick(time.Second) {
		msg := &broker.Message{
			Header: map[string]string{"id" : fmt.Sprintf("%d", i)},
			Body:   []byte(fmt.Sprintf("%d:%s", i, time.Now().String())),
		}
		if err := brk.Publish(topic,msg); err != nil {
			log.Printf("[pub] failed: %v\n", err)
		} else  {
			log.Printf("[pub] pubbed message:%s\n", string(msg.Body))
		}
		i++
	}
}

func sub(brk broker.Broker)  {
	_, err := brk.Subscribe(topic, func(event broker.Event) error {
		fmt.Println("[sub] received message:", string(event.Message().Body), ", header:", event.Message().Header)
		return nil
	}, broker.Queue(topic))
	if err != nil {
		fmt.Println(err)
	}
}

func main()  {
	service := micro.NewService(
		micro.Name("com.foo.broker.example"),
		)
	service.Init(micro.AfterStart(func() error {
		brk := service.Options().Broker
		if err := brk.Connect(); err != nil {
			log.Fatalf("Broker connect error:%v", err)
		}
		go sub(brk)
		go pub(brk)
		return nil
	}))
	service.Run()
}

结果：

2020-05-25 10:23:47.846793 I | [pub] pubbed message:0:2020-05-25 10:23:47.845600764 +0800 CST m=+1.747833554
[sub] received message: 0:2020-05-25 10:23:47.845600764 +0800 CST m=+1.747833554 , header: map[Micro-Topic:com.foo.topic id:0]
2020-05-25 10:23:48.845661 I | [pub] pubbed message:1:2020-05-25 10:23:48.845603507 +0800 CST m=+2.747836227
[sub] received message: 1:2020-05-25 10:23:48.845603507 +0800 CST m=+2.747836227 , header: map[Micro-Topic:com.foo.topic id:1]
2020-05-25 10:23:49.845608 I | [pub] pubbed message:2:2020-05-25 10:23:49.845576914 +0800 CST m=+3.747809559
[sub] received message: 2:2020-05-25 10:23:49.845576914 +0800 CST m=+3.747809559 , header: map[Micro-Topic:com.foo.topic id:2]
2020-05-25 10:23:50.845687 I | [pub] pubbed message:3:2020-05-25 10:23:50.845612017 +0800 CST m=+4.747844777
[sub] received message: 3:2020-05-25 10:23:50.845612017 +0800 CST m=+4.747844777 , header: map[Micro-Topic:com.foo.topic id:3]
2020-05-25 10:23:51.845613 I | [pub] pubbed message:4:2020-05-25 10:23:51.845573602 +0800 CST m=+5.747806265
[sub] received message: 4:2020-05-25 10:23:51.845573602 +0800 CST m=+5.747806265 , header: map[Micro-Topic:com.foo.topic id:4]

Broker

// Broker is an interface used for asynchronous messaging.
type Broker interface {
	Init(...Option) error
	Options() Options
	Address() string
	Connect() error
	Disconnect() error
	Publish(topic string, m *Message, opts ...PublishOption) error
	Subscribe(topic string, h Handler, opts ...SubscribeOption) (Subscriber, error)
	String() string
}

func Publish(topic string, msg *Message, opts ...PublishOption) error {
	return DefaultBroker.Publish(topic, msg, opts...)
}

func Subscribe(topic string, handler Handler, opts ...SubscribeOption) (Subscriber, error) {
	return DefaultBroker.Subscribe(topic, handler, opts...)
}

拿broker.Subscribe方法来说，第三个参数为SubscribeOption，它的含义与server.SubscribeOption 相同（前一篇文章）. 有三种设置broker.DisableAutoAck, broker.Queue, broker.SubscribeContext， 它们与server.SubscribeOption 相同。不同的是其他broker 插件也可以提供额外的broker.SubscribeOption来实现插件具体的方法
例如：
在go.mod中加入

github.com/micro/go-plugins v1.5.1

...
import "github.com/micro/go-plugins/broker/rabbitmq"
...
_, err := broker.Subscribe(topic, func(p broker.Event) error {
   ...
   p.Ack()
   return nil
}, broker.Queue(topic), broker.DisableAutoAck(), rabbitmq.DurableQueue()，)

注意：，如果使用了DisableAutoAck， 我们可以在方法中执行p.Ack()来进行确认

使用kafka作为消息队列

首先，go.mod：

module micro-hello-pub

go 1.13

require (
	github.com/golang/protobuf v1.4.0
	github.com/micro/go-micro/v2 v2.7.0
	github.com/micro/go-plugins/broker/kafka/v2 v2.5.0
)

main.go

package main

import (
	"fmt"
	"github.com/micro/go-micro/v2"
	"github.com/micro/go-micro/v2/broker"
	_ "github.com/micro/go-plugins/broker/kafka/v2"
	"log"
	"time"
)

var (
	topic  string = "com.foo.topic"
	send_i        = 0
	recv_i        = 0
)

func pub(brk broker.Broker) {
	for range time.Tick(time.Second) {
		msg := &broker.Message{
			Header: map[string]string{"id" : fmt.Sprintf("%d", send_i)},
			Body:   []byte(fmt.Sprintf("%d:%s", send_i, time.Now().String())),
		}
		if err := brk.Publish(topic,msg); err != nil {
			log.Printf("[pub] failed: %v\n", err)
		} else  {
			log.Printf("[pub] pubbed message:%s\n", string(msg.Body))
		}
		send_i++
	}
}

func sub(brk broker.Broker)  {
	_, err := brk.Subscribe(topic, func(event broker.Event) error {
		recv_i++
		fmt.Println("[sub] received message:", string(event.Message().Body), ", header:", event.Message().Header)
		return nil
	}, broker.Queue(topic))
	if err != nil {
		fmt.Println(err)
	}
}

func main()  {
	service := micro.NewService(
		micro.Name("com.foo.broker.example"),
		)
	service.Init(micro.AfterStart(func() error {
		brk := service.Options().Broker
		if err := brk.Connect(); err != nil {
			log.Fatalf("Broker connect error:%v", err)
		}
		go sub(brk)
		go pub(brk)
		return nil
	}),
	micro.BeforeStop(func() error {
		log.Printf("send:%d,recv:%d\n", send_i, recv_i)
		return nil
	}))

	service.Run()
}

启动时，在environment中加入：

MICRO_BROKER=kafka;MICRO_BROKER_ADDRESS=1127.0.0.1:9192,127.0.0.1:9292,127.0.0.1:9392

结果：

luslin@local:~/go/workspace/tools/micro-hello-pub$ MICRO_REGISTRY=etcd MICRO_BROKER=kafka MICRO_BROKER_ADDRESS=127.0.0.1:9192,127.0.0.1:9292,127.0.0.1:9392 ./micro_hello_pub 
2020-05-25 14:25:04  file=auth.go:31 level=info Auth [noop] Authenticated as com.foo.broker.example-72df0e38-5791-467d-af6f-1019fcb17662 in the go.micro namespace
2020-05-25 14:25:04  file=service.go:205 level=info Starting [service] com.foo.broker.example
2020-05-25 14:25:04  file=grpc.go:845 level=info Server [grpc] Listening on [::]:45751
2020-05-25 14:25:04  file=grpc.go:676 level=info Registry [etcd] Registering node: com.foo.broker.example-72df0e38-5791-467d-af6f-1019fcb17662
[sub] received message: 0:2020-05-25 14:25:05.978230301 +0800 CST m=+1.882055700 , header: map[id:0]
2020-05-25 14:25:05.985487 I | [pub] pubbed message:0:2020-05-25 14:25:05.978230301 +0800 CST m=+1.882055700
[sub] received message: 3:2020-05-25 14:22:33.897258745 +0800 CST m=+4.857683803 , header: map[id:3]
2020-05-25 14:25:06.987850 I | [pub] pubbed message:1:2020-05-25 14:25:06.978188043 +0800 CST m=+2.882013423
[sub] received message: 1:2020-05-25 14:25:06.978188043 +0800 CST m=+2.882013423 , header: map[id:1]
^C2020-05-25 14:25:07.468866 I | send:2,recv:3
2020-05-25 14:25:07  file=grpc.go:772 level=info Deregistering node: com.foo.broker.example-72df0e38-5791-467d-af6f-1019fcb17662
2020-05-25 14:25:07  file=grpc.go:940 level=info Broker [kafka] Disconnected from 127.0.0.1:9192