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()
}@H_403_59@ 
输出如下：
 
PS E:\golang\go_pro\src\safly> 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:\golang\go_pro\src\safly>@H_403_59@ 
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: %s\n",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()
}@H_403_59@ 
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:\develop\kafka\kafka_2.12-1.0.0> .\bin\windows\kafka-console-consumer.bat --topic Nginx_log --zookeeper 127.0.0.1 2
181@H_403_59@ 
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:%v\n",pid,offset)
}@H_403_59@ 
然后最后看效果图如下： 
 
 原文链接：https://www.f2er.com/go/187629.html