Go 并发编程工程实践：Goroutine 控制、管道设计与性能排查

// 错误示范：缺乏退出机制，导致 goroutine 永久阻塞在 channel 读取上
func QueryData(ctx context.Context) <-chan Result {
    ch := make(chan Result)
    go func() {
        res := doRpcCall()
        ch <- res // 如果 ctx 超时，外部放弃接收，这里将永久阻塞！
    }()
    return ch
}

func BatchFetch(ctx context.Context, ids []int64) ([]*Data, error) {
    // 限制最大并发数 10，防止下游直接被打爆
    g, ctx := errgroup.WithContext(ctx)
    g.SetLimit(10)

    results := make([]*Data, len(ids))
    for i, id := range ids {
        i, id := i, id // 避开闭包变量逃逸问题（Go 1.22 虽已修复，但保留好习惯没坏处）
        g.Go(func() error {
            data, err := fetchOne(ctx, id)
            if err != nil {
                return err
            }
            results[i] = data
            return nil
        })
    }

    if err := g.Wait(); err != nil {
        return nil, err
    }
    return results, nil
}

// benchmark_test.go
func BenchmarkMutex(b *testing.B) {
    var mu sync.Mutex
    var count int
    b.RunParallel(func(pb *testing.PB) {
        for pb.Next() {
            mu.Lock()
            count++
            mu.Unlock()
        }
    })
}

func BenchmarkChannel(b *testing.B) {
    ch := make(chan int, 1000)
    go func() {
        for range ch {}
    }()
    b.RunParallel(func(pb *testing.PB) {
        for pb.Next() {
            ch <- 1
        }
    })
}

goos: darwin
goarch: arm64
pkg: demo/concurrency
cpu: Apple M2
BenchmarkMutex-8          38192085        30.21 ns/op        0 B/op        0 allocs/op
BenchmarkChannel-8        11402834       104.30 ns/op        0 B/op        0 allocs/op

var bufferPool = sync.Pool{
    New: func() any {
        return new(bytes.Buffer)
    },
}

func BenchmarkWithoutPool(b *testing.B) {
    b.RunParallel(func(pb *testing.PB) {
        for pb.Next() {
            buf := new(bytes.Buffer)
            buf.Write([]byte("benchmark-test-payload-data"))
            _ = buf.String()
        }
    })
}

func BenchmarkWithPool(b *testing.B) {
    b.RunParallel(func(pb *testing.PB) {
        for pb.Next() {
            buf := bufferPool.Get().(*bytes.Buffer)
            buf.Reset()
            buf.Write([]byte("benchmark-test-payload-data"))
            _ = buf.String()
            bufferPool.Put(buf)
        }
    })
}

BenchmarkWithoutPool-8    14920429        78.50 ns/op       64 B/op        2 allocs/op
BenchmarkWithPool-8       43810935        26.40 ns/op        0 B/op        0 allocs/op