Bytes.Buffer in Go language causes memory leak: How does the client correctly close the response body to avoid memory usage?

Go language bytes.Buffer memory leak analysis and solution

In Go, bytes.Buffer is used for string splicing. If it is handled improperly, it may lead to memory leakage. This article analyzes a case that explains how bytes.Buffer (indirectly, through its internal bytes.makeSlice ) causes high memory footprint and how to solve it.

Case description:

The server uses the Fiber framework, and /test route creates bytes.Buffer when processing requests, writing a large amount of data (1 million "123" strings). The client sends 500 requests concurrently. Using go tool pprof analysis, it was found that bytes.makeSlice consumed a lot of memory and was not released.

Server-side code snippet (simplified):

 package main

import (
    "bytes"
    "github.com/gofiber/fiber/v2"
)

func main() {
    app := fiber.New()
    app.Get("/test", func(c *fiber.Ctx) error {
        buffer := bytes.NewBufferString("")
        for i := 0; i <p> <strong>Client code snippets (simplified):</strong></p><pre class="brush:php;toolbar:false"> package main

import (
    "fmt"
    "net/http"
    "sync"
)

func main() {
    var wg sync.WaitGroup
    for i := 0; i <p> <strong>The root of the problem:</strong></p><p> The client code is missing <code>resp.Body.Close()</code> . <code>resp.Body</code> is <code>io.ReadCloser</code> , which contains data received from the server. Without calling <code>Close()</code> , the underlying connection and buffer will not be released, resulting in memory leaks. <code>bytes.makeSlice</code> high memory footprint is because the server-generated <code>bytes.Buffer</code> data is received by the client but is not properly closed. Even if the server code has no memory management errors, the client does not close the response body.</p><p> <strong>Solution:</strong></p><p> Add <code>resp.Body.Close()</code> in the client code:</p><pre class="brush:php;toolbar:false"> resp, err := http.Get("http://localhost:9001/test")
if err != nil {
    fmt.Println("Error:", err)
    Return
}
defer resp.Body.Close() // Add this line // ... Process resp.Body ...

Use defer resp.Body.Close() to ensure that the function is executed and close resp.Body is freed to avoid memory leakage. This is the key to solving the memory usage problem of bytes.makeSlice . The problem is not bytes.Buffer itself, but the resource is not released correctly.

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