目录

• 操作Kafka
• sarama
• 下载及安装
• 注意事项
• 连接 kafka 发送消息
• 连接 kafka 消费消息
• 操作Etcd
• 安装
• put和get操作
• watch操作
• 安装报错：

操作Kafka

Kafka 是一种高吞吐量的分布式发布订阅消息系统，它可以处理消费者规模的网站中的所有动作流数据，具有高性能、持久化、多副本备份、横向扩展等特点。本文介绍了如何使用 Go 语言发送和接收 kafka 消息。

sarama

Go 语言中连接 kafka 使用第三方库:github.com/Shopify/sar…。

下载及安装

go get github.com/Shopify/sarama

注意事项

sarama v1.20 之后的版本加入了zstd压缩算法，需要用到 cgo，在 Windows 平台编译时会提示类似如下错误：

# github.com/DataDog/zstd
exec: "gcc":executable file not found in %PATH%

所以在 Windows 平台请使用 v1.19 版本的 sarama。

连接 kafka 发送消息

package main
import (
	"fmt"
	"github.com/Shopify/sarama"
)
// 基于sarama第三方库开发的kafka client
func main() {
	config := sarama.NewConfig()
	config.Producer.RequiredAcks = sarama.WaitForAll          // 发送完数据需要leader和follow都确认
	config.Producer.Partitioner = sarama.NewRandomPartitioner // 新选出一个partition
	config.Producer.Return.Successes = true                   // 成功交付的消息将在success channel返回
	// 构造一个消息
	msg := &sarama.ProducerMessage{}
	msg.Topic = "web_log"
	msg.Value = sarama.StringEncoder("this is a test log")
	// 连接kafka
	client, err := sarama.NewSyncProducer([]string{"192.168.1.7:9092"}, config)
	if err != nil {
		fmt.Println("producer closed, err:", err)
		return
	}
	defer client.Close()
	// 发送消息
	pid, offset, err := client.SendMessage(msg)
	if err != nil {
		fmt.Println("send msg failed, err:", err)
		return
	}
	fmt.Printf("pid:%v offset:%v\n", pid, offset)
}

连接 kafka 消费消息

package main
import (
	"fmt"
	"github.com/Shopify/sarama"
)
// kafka consumer
func main() {
	consumer, err := sarama.NewConsumer([]string{"127.0.0.1:9092"}, nil)
	if err != nil {
		fmt.Printf("fail to start consumer, err:%v\n", err)
		return
	}
	partitionList, err := consumer.Partitions("web_log") // 根据topic取到所有的分区
	if err != nil {
		fmt.Printf("fail to get list of partition:err%v\n", err)
		return
	}
	fmt.Println(partitionList)
	for partition := range partitionList { // 遍历所有的分区
		// 针对每个分区创建一个对应的分区消费者
		pc, err := consumer.ConsumePartition("web_log", int32(partition), sarama.OffsetNewest)
		if err != nil {
			fmt.Printf("failed to start consumer for partition %d,err:%v\n", partition, err)
			return
		}
		defer pc.AsyncClose()
		// 异步从每个分区消费信息
		go func(sarama.PartitionConsumer) {
			for msg := range pc.Messages() {
				fmt.Printf("Partition:%d Offset:%d Key:%v Value:%v", msg.Partition, msg.Offset, msg.Key, msg.Value)
			}
		}(pc)
	}
}

操作Etcd

这里使用官方的etcd/clientv3包来连接etcd并进行相关操作。

安装

go get go.etcd.io/etcd/clientv3

put和get操作

put命令用来设置键值对数据，get命令用来根据key获取值。

package main
import (
	"context"
	"fmt"
	"time"
	"go.etcd.io/etcd/clientv3"
)
func main(){
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   []string{"122.51.79.172:2379"},
		DialTimeout: 5 * time.Second,
	})
	if err != nil {
		// handle error!
		fmt.Printf("connect to etcd failed, err:%v\n", err)
		return
	}
	fmt.Println("connect to etcd success")
	defer cli.Close()
	// put
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	_, err = cli.Put(ctx, "coolops", "test")
	cancel()
	if err != nil {
		fmt.Printf("put to etcd failed, err:%v\n", err)
		return
	}
	// get
	ctx, cancel = context.WithTimeout(context.Background(), time.Second)
	resp, err := cli.Get(ctx, "coolops")
	cancel()
	if err != nil {
		fmt.Printf("get from etcd failed, err:%v\n", err)
		return
	}
	for _, ev := range resp.Kvs {
		fmt.Printf("%s:%s\n", ev.Key, ev.Value)
	}
}

watch操作

watch用来获取未来更改的通知。

package main
import (
	"context"
	"fmt"
	"time"
	"go.etcd.io/etcd/clientv3"
)
func main(){
	cli, err := clientv3.New(clientv3.Config{
		Endpoints:   []string{"122.51.79.172:2379"},
		DialTimeout: 5 * time.Second,
	})
	if err != nil {
		// handle error!
		fmt.Printf("connect to etcd failed, err:%v\n", err)
		return
	}
	fmt.Println("connect to etcd success")
	defer cli.Close()
	// watch 操作，返回的是一个通道
	rch := cli.Watch(context.Background(), "coolops") // <-chan WatchResponse
	for wresp := range rch {
		for _, ev := range wresp.Events {
			fmt.Printf("Type: %s Key:%s Value:%s\n", ev.Type, ev.Kv.Key, ev.Kv.Value)
		}
	}
}

安装报错：

go: finding github.com/coreos/pkg latest
# github.com/coreos/etcd/clientv3/balancer/resolver/endpoint
E:\DEV\Go\pkg\mod\github.com\coreos\etcd@v3.3.19+incompatible\clientv3\balancer\resolver\endpoint\endpoint.go:114:78: undefined: resolver.BuildOption
E:\DEV\Go\pkg\mod\github.com\coreos\etcd@v3.3.19+incompatible\clientv3\balancer\resolver\endpoint\endpoint.go:182:31: undefined: resolver.ResolveNowOption
# github.com/coreos/etcd/clientv3/balancer/picker
E:\DEV\Go\pkg\mod\github.com\coreos\etcd@v3.3.19+incompatible\clientv3\balancer\picker\err.go:37:44: undefined: balancer.PickOptions
E:\DEV\Go\pkg\mod\github.com\coreos\etcd@v3.3.19+incompatible\clientv3\balancer\picker\roundrobin_balanced.go:55:54: undefined: balancer.PickOptions

解决： 将go.mod里的prpc改为1.26.0版本

google.golang.org/grpc v1.26.0