Go 典型并发任务

学习-极客时间-Go语言从入门到实战 笔记

单例模式

代码片段举例：

package once

import (
    "fmt"
    "sync"
    "testing"
    "unsafe"
)

type Movie struct {
}

var once sync.Once
var SingleInstance *Movie

func GetInstance() *Movie {
    once.Do(func() {
        fmt.Println("create instance")
        SingleInstance = new(Movie)
    })
    return SingleInstance
}

func TestSingleInstance(t *testing.T) {
    var wg sync.WaitGroup
    for i := 0; i < 5; i++ {
        wg.Add(1)
        go func() {
            sing := GetInstance()
            fmt.Println(unsafe.Pointer(sing))
            wg.Done()
        }()
    }
    wg.Wait()
}

仅需任意任务完成

代码片段举例：

package only

import (
    "fmt"
    "runtime"
    "testing"
    "time"
)

func runTask(id int) string {
    time.Sleep(10 * time.Millisecond)
    return fmt.Sprintf("The result is from %d", id)
}

func FirstResponse() string {
    numOfRunner := 10
    ch := make(chan string, numOfRunner)
    //没有指定channel容量，会导致阻塞，channel等待接收者，协程泄漏
    //ch := make(chan string)
    for i := 0; i < numOfRunner; i++ {
        go func(i int) {
            ch <- runTask(i)
        }(i)
    }
    return <-ch
}

func TestOnly(t *testing.T) {
    t.Log("Before: ", runtime.NumGoroutine())
    fmt.Println(FirstResponse())
    time.Sleep(time.Second * 1)
    t.Log("After: ", runtime.NumGoroutine())
}

所有任务完成

代码片段举例：

package all

import (
    "fmt"
    "runtime"
    "testing"
    "time"
)

func runTask(id int) string {
    time.Sleep(10 * time.Millisecond)
    return fmt.Sprintf("The result is from %d", id)
}

func FirstResponse() string {
    numOfRunner := 10
    ch := make(chan string, numOfRunner)
    //没有指定channel容量，会导致阻塞，channel等待接收者，协程泄漏
    //ch := make(chan string)
    for i := 0; i < numOfRunner; i++ {
        go func(i int) {
            ch <- runTask(i)
        }(i)
    }
    res := ""
    for j := 0; j < numOfRunner; j++ {
        res += <-ch + "\n"
    }
    return res
}

func TestOnly(t *testing.T) {
    t.Log("Before: ", runtime.NumGoroutine())
    fmt.Println(FirstResponse())
    time.Sleep(time.Second * 1)
    t.Log("After: ", runtime.NumGoroutine())
}