记录一个初学者bug。
在并发场景下，使用slice时，需要时刻谨记，slice是共用底层数组的。
intSlice = intSlice[0:0]
这里实际上并没有清空slice，只是重置了位置指针，从而造成数据覆盖，后面继续使用intSlice时会覆盖之前的数据。
错误示例代码：
package main
import (
"fmt"
"sync"
"time"
"unsafe"
)
// 并发度参数
var consumerCount = 2
var producerLogicDuration = 100000 * time.Nanosecond // 减小该参数可增加获取到重复数字的概率
var consumerLogicDuration = 100000 * time.Nanosecond
// 业务参数
var wgStatic sync.WaitGroup
var dupMap sync.Map
var intSlice []int
var sliceChan chan []int
func main() {
sliceChan = make(chan []int, 10)
for i := 0; i < consumerCount; i++ {
wgStatic.Add(1)
go consume(sliceChan, i)
}
wgStatic.Add(1)
go produce()
wgStatic.Wait()
}
func produce() {
defer wgStatic.Done()
i := 0
index := 0
for {
intSlice = append(intSlice, i)
if index > 1 {
sliceChan <- intSlice
intSlice = intSlice[0:0] // wrong
//intSlice = nil // correct
index = 0
} else {
index++
}
if i > 1000 {
break
}
i++
// mock to do some logic
time.Sleep(producerLogicDuration)
}
close(sliceChan)
}
func consume(sliceChan chan []int, goroutineID int) {
defer wgStatic.Done()
for s := range sliceChan {
fmt.Printf("rid = %v, s = %v, &array = %v, &s = %p\n", goroutineID, s, unsafe.Pointer(&s[0]), &s)
for _, num := range s {
actual, loaded := dupMap.LoadOrStore(num, goroutineID)
if loaded {
errMsg := fmt.Sprintf("key is loaded by goroutine already, key = %v, actual_goroutineID = %v," +
" current_goroutineID = %v\n", num, actual, goroutineID)
panic(errMsg)
}
}
// mock to do some logic
time.Sleep(consumerLogicDuration)
}
}