WaitGroup

WaitGroup在go语言中，用于线程同步，单从字面意思理解，wait等待的意思，group组、团队的意思，WaitGroup就是指等待一组，等待一个系列执行完成后才会继续向下执行。

package main

import (
    "fmt"
    "sync"
    "time"
)

func main() {
    wg := sync.WaitGroup{}

    for i := 0; i < 10; i++ {
        wg.Add(1)
        go calc(&wg, i)
    }

    wg.Wait()
    fmt.Println("all goroutine finish")
}
func calc(w *sync.WaitGroup, i int) {

    fmt.Println("calc:", i)
    time.Sleep(time.Second)
    w.Done()
}

输出如下：

PS E:golanggo_prosrcsafly> go run waitGroup.go
calc: 0
calc: 1
calc: 4
calc: 2
calc: 3
calc: 9
calc: 6
calc: 7
calc: 5
calc: 8
all goroutine finish
PS E:golanggo_prosrcsafly>

kafka消费者

以下博客是通过生产者创建、发送消息至kafka
博客链接

现在我们站在消费者的角度，来进行收取消息

package main

import (
    "fmt"
    "strings"
    "sync"

    "github.com/Shopify/sarama"
)

var (
    wg sync.WaitGroup
)

func main() {
    //创建消费者
    consumer, err := sarama.NewConsumer(strings.Split("192.168.11.48:9092", ","), nil)
    if err != nil {
        fmt.Println("Failed to start consumer: %s", err)
        return
    }
    //设置分区
    partitionList, err := consumer.Partitions("nginx_log")
    if err != nil {
        fmt.Println("Failed to get the list of partitions: ", err)
        return
    }
    fmt.Println(partitionList)
    //循环分区
    for partition := range partitionList {
        pc, err := consumer.ConsumePartition("nginx_log", int32(partition), sarama.OffsetNewest)
        if err != nil {
            fmt.Printf("Failed to start consumer for partition %d: %sn", partition, err)
            return
        }
        defer pc.AsyncClose()
        go func(pc sarama.PartitionConsumer) {
            wg.Add(1)
            for msg := range pc.Messages() {
                fmt.Printf("Partition:%d, Offset:%d, Key:%s, Value:%s", msg.Partition, msg.Offset, string(msg.Key), string(msg.Value))
                fmt.Println()
            }
            wg.Done()
        }(pc)
    }
    //time.Sleep(time.Hour)
    wg.Wait()
    consumer.Close()
}

接下来我们测试上面的消费者示例代码，在进行测试前我们需要如下的准备工作
1、启动zookeeper
2、启动kafka
3、创立生产者topic

PS E:developkafkakafka_2.12-1.0.0> .binwindowskafka-console-consumer.bat --topic nginx_log --zookeeper 127.0.0.1 2
181

4、执行生产者发送消息至kafka代码
5、执行消费者代码程序

第4步的代码如下：

package main

import (
    "fmt"
    "github.com/Shopify/sarama"
)

func main() {
    config := sarama.NewConfig()
    config.Producer.RequiredAcks = sarama.WaitForAll
    config.Producer.Partitioner = sarama.NewRandomPartitioner
    config.Producer.Return.Successes = true

    msg := &sarama.ProducerMessage{}
    msg.Topic = "nginx_log"
    msg.Value = sarama.StringEncoder("this is a good test, my message is good")

    client, err := sarama.NewSyncProducer([]string{"192.168.11.28:9092"}, config)
    if err != nil {
        fmt.Println("producer close, err:", err)
        return
    }

    defer client.Close()

    pid, offset, err := client.SendMessage(msg)
    if err != nil {
        fmt.Println("send message failed,", err)
        return
    }

    fmt.Printf("pid:%v offset:%vn", pid, offset)
}

然后最后看效果图如下：