select、定时器

怼烎@ 2022-01-10 11:27 176阅读 0赞

应用场景举例：  
一个任务管道满了，再往里面塞就塞不进去了，浏览器刷不出来了。用户即便关了浏览器可能依然在阻塞......

package main
    
    import "fmt"
    import "time"
    
    func main() {
       var ch chan int
       ch = make(chan int, 10)
       ch2 := make(chan int, 10)
       go func() {
          var i int
          for {
             ch <- i
             time.Sleep(time.Second)
             ch2 <- i * i
             time.Sleep(time.Second)
             i++
          }
       }()
       for {
          select { //这个case如果不能从ch中获取数据，则会立即走下一个
          case v := <-ch:
             fmt.Println(v) //这个case如果不能从ch2中获取数据，则会立即走下一个
          case v := <-ch2:
             fmt.Println(v) //然而这样写可能有内存泄漏！
          case <-time.After(time.Second):
             fmt.Println("get data timeout")
             time.Sleep(time.Second)
          default:
             fmt.Println("===================")
             time.Sleep(time.Second)
          }
       }
    }

> **上面的写法可能会有内存泄漏！**

package main
    
    import (
       "fmt"
       "runtime"
       "time"
    )
    
    func main() {
       num := runtime.NumCPU()
       runtime.GOMAXPROCS(num - 1)
       for i := 0; i < 16; i++ {
          go func() {
             for { 
                //每秒执行一次
                t := time.NewTicker(time.Second)
                select {
                case <-t.C:
                   fmt.Println("timeout")
                } //一定要关闭
                t.Stop()
             }
          }()
       }
    
       time.Sleep(time.Second * 100)
    }

go官方文档的建议：  
![goroutine/channel（select、定时器）][goroutine_channel_select]

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转载于:https://blog.51cto.com/5660061/2372096

[goroutine_channel_select]: https://s1.51cto.com/images/blog/201902/05/8507581063952d5ebe988fb47d560610.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=
[image.png]: https://s1.51cto.com/images/20190331/1554047589320269.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=
[image.png 1]: https://s1.51cto.com/images/20190331/1554047667319707.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=
[image.png 2]: https://s1.51cto.com/images/20190331/1554047683683274.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=
[image.png 3]: https://s1.51cto.com/images/20190331/1554047713994280.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=
[image.png 4]: https://s1.51cto.com/images/20190331/1554047726411826.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=
[image.png 5]: https://s1.51cto.com/images/20190401/1554098556556660.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=
[image.png 6]: https://s1.51cto.com/images/20190401/1554098616245236.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=
[image.png 7]: https://s1.51cto.com/images/20190401/1554098639358512.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=
[image.png 8]: https://s1.51cto.com/images/20190401/1554098659221493.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=