sync.Pool

Learn object reuse with Pool.

sync.Pool

sync.Pool recycles temporary objects to reduce GC pressure. You get an object with Get() and return it with Put(). If the pool is empty New creates one.

Pool is ideal for short-lived reusable objects (e.g. buffers, byte slices). But Pool may be cleared during GC; there is no persistence guarantee. So it is not for state.

Pool and reuse

Pool recycles buffers or temporary slices. var pool = sync.Pool{New: func() interface{} { return &bytes.Buffer{} }} creates a fresh buffer. pool.Get().(*bytes.Buffer) takes, pool.Put(buf) returns.

An object from the pool may not be empty; reset it before use (e.g. buf.Reset()). This prevents stale data from causing issues.

Exercise Print with Pool

Inside main, add a sync.Pool declaration and print pool done with fmt.Println.

Show example solution

package main

import (
    "fmt"
    "sync"
)

func main() {
    var pool sync.Pool
    pool.New = func() interface{} { return "x" }
    v := pool.Get()
    fmt.Println("pool tamam")
    _ = v
}

Test yourself

What does sync.Pool reduce?
- Network latency
- Memory leaks
- CPU usage
- GC pressure
Show answer

GC pressure — Memory leaks are not directly about Pool.

Pool usage

var pool = sync.Pool{
    New: func() interface{} { return &Buffer{} },
}
buf := pool.____().(*Buffer)
// use buf
pool.Put(buf)

Show answer

var pool = sync.Pool{
    New: func() interface{} { return &Buffer{} },
}
buf := pool.Get().(*Buffer)
// use buf
pool.Put(buf)

Match Pool concepts

Get

Al
Put

Koy
New

Create
sync.Pool

Tip

Next lesson: Summary - sync package

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