golang基础-WaitGroup、kafka消费者

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 mainimport (    "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:\golang\go_pro\src\safly> go run waitGroup.gocalc: 0calc: 1calc: 4calc: 2calc: 3calc: 9calc: 6calc: 7calc: 5calc: 8all goroutine finishPS E:\golang\go_pro\src\safly>

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 mainimport (    "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()}

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 2181

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 mainimport (    "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)}

然后最后看效果图如下：