Code Samples: Careful Object Pooling and Reuse

00_correct_but_wasteful.go

package main

import (
	"bytes"
	"fmt"
	"runtime"
)

func main() {
	ch := make(chan *bytes.Buffer)
	go write(ch)
	read(ch)
}
func write(out chan *bytes.Buffer) {
	defer close(out)
	for range 10 {
		out <- bytes.NewBufferString(randomKey())
	}
}
func read(in chan *bytes.Buffer) {
	for b := range in {
		content := b.Bytes()
		runtime.Gosched() // simulate some minimal processing
		s := string(content)
		if _, ok := valid[s]; !ok {
			fmt.Println("invalid key:", s)
		}
	}
}
func randomKey() string {
	for key := range valid {
		return key
	}
	panic("no values")
}

var valid = map[string]struct{}{
	"A":   {},
	"BB":  {},
	"CCC": {},
}

01_efficient_but_incorrect.go

package main

import (
	"bytes"
	"fmt"
	"runtime"
	"sync"
)

func main() {
	pool := &sync.Pool{
		New: func() any { return bytes.NewBuffer(nil) },
	}
	ch := make(chan *bytes.Buffer)
	go write(pool, ch)
	read(pool, ch)
}
func write(pool *sync.Pool, out chan *bytes.Buffer) {
	defer close(out)
	for range 10 {
		b := pool.Get().(*bytes.Buffer)
		b.Reset()
		b.WriteString(randomKey())
		out <- b
	}
}
func read(pool *sync.Pool, in chan *bytes.Buffer) {
	for b := range in {
		content := b.Bytes()
		pool.Put(b)
		runtime.Gosched() // simulate some minimal processing
		s := string(content)
		if _, ok := valid[s]; !ok {
			fmt.Println("invalid key:", s)
		}
	}
}
func randomKey() string {
	for key := range valid {
		return key
	}
	panic("no values")
}

var valid = map[string]struct{}{
	"A":   {},
	"BB":  {},
	"CCC": {},
}

02_correct_and_efficient.go

package main

import (
	"bytes"
	"fmt"
	"io"
	"runtime"
	"sync"
)

func main() {
	pool := &sync.Pool{
		New: func() any { return bytes.NewBuffer(nil) },
	}
	ch := make(chan *bytes.Buffer)
	go write(pool, ch)
	read(pool, ch)
}
func write(pool *sync.Pool, out chan *bytes.Buffer) {
	defer close(out)
	for range 10 {
		b := pool.Get().(*bytes.Buffer)
		b.Reset()
		b.WriteString(randomKey())
		out <- b
	}
}
func read(pool *sync.Pool, in chan *bytes.Buffer) {
	buffer := bytes.NewBuffer(nil)
	for b := range in {
		buffer.Reset()
		_, _ = io.Copy(buffer, b)
		pool.Put(b)
		content := buffer.Bytes()
		runtime.Gosched() // simulate some minimal processing
		s := string(content)
		if _, ok := valid[s]; !ok {
			fmt.Println("invalid key:", s)
		}
	}
}
func randomKey() string {
	for key := range valid {
		return key
	}
	panic("no values")
}

var valid = map[string]struct{}{
	"A":   {},
	"BB":  {},
	"CCC": {},
}