當嘗試 `ReadAll(response.Body)` 時，goroutine 洩漏，其中 `response` 由 http `client.Do(...)` 傳回

php小編百草在解決程式設計問題時，發現了一個常見的goroutine洩漏情況。當我們嘗試使用`ReadAll(response.Body)`時，傳回的`response`物件是由`http`包的`client.Do(...)`方法傳回的。然而，這種操作會導致goroutine洩漏的問題。為了避免這種情況的發生，我們需要採取一些措施來正確處理http回應。

問題內容

該問題來自一個非常常見的場景，即在 http 方法呼叫後從回應正文中讀取所有位元組。

在 https://github.com/uber-go/goleak 的幫助下，我發現了一個有趣的 goroutine 洩漏。

為了示範該問題，請使用 go test 執行以下測試程式碼，這會導致 found 出現意外的 goroutine：

package main

import (
    "io"
    "net/http"
    "testing"

    "go.uber.org/goleak"
    "gotest.tools/v3/assert"
)

func testleak(t *testing.t) {
    defer goleak.verifynone(t)

    request, err := http.newrequest(http.methodget, "https://google.com", nil)
    assert.nilerror(t, err)

    client := http.client{}

    response, err := client.do(request)
    assert.nilerror(t, err)

    defer response.body.close()

    _, err = io.readall(response.body)

    assert.nilerror(t, err)
}

完整測試輸出：

$ go test
--- FAIL: TestLeak (1.26s)
    main_test.go:28: found unexpected goroutines:
        [Goroutine 14 in state IO wait, with internal/poll.runtime_pollWait on top of the stack:
        goroutine 14 [IO wait]:
        internal/poll.runtime_pollWait(0x7f945c1e0398, 0x72)
                /home/wxh/.local/go/src/runtime/netpoll.go:305 +0x89
        internal/poll.(*pollDesc).wait(0xc000154280?, 0xc0000ca000?, 0x0)
                /home/wxh/.local/go/src/internal/poll/fd_poll_runtime.go:84 +0x32
        internal/poll.(*pollDesc).waitRead(...)
                /home/wxh/.local/go/src/internal/poll/fd_poll_runtime.go:89
        internal/poll.(*FD).Read(0xc000154280, {0xc0000ca000, 0x2000, 0x2000})
                /home/wxh/.local/go/src/internal/poll/fd_unix.go:167 +0x25a
        net.(*netFD).Read(0xc000154280, {0xc0000ca000?, 0xc00017edd8?, 0xc0004d5808?})
                /home/wxh/.local/go/src/net/fd_posix.go:55 +0x29
        net.(*conn).Read(0xc00009c000, {0xc0000ca000?, 0xc0000c68f0?, 0x2c?})
                /home/wxh/.local/go/src/net/net.go:183 +0x45
        crypto/tls.(*atLeastReader).Read(0xc0002d4138, {0xc0000ca000?, 0x0?, 0x29f6540f238f2947?})
                /home/wxh/.local/go/src/crypto/tls/conn.go:787 +0x3d
        bytes.(*Buffer).ReadFrom(0xc0000a0278, {0x7c3860, 0xc0002d4138})
                /home/wxh/.local/go/src/bytes/buffer.go:202 +0x98
        crypto/tls.(*Conn).readFromUntil(0xc0000a0000, {0x7c3b80?, 0xc00009c000}, 0xc0000a41c0?)
                /home/wxh/.local/go/src/crypto/tls/conn.go:809 +0xe5
        crypto/tls.(*Conn).readRecordOrCCS(0xc0000a0000, 0x0)
                /home/wxh/.local/go/src/crypto/tls/conn.go:616 +0x116
        crypto/tls.(*Conn).readRecord(...)
                /home/wxh/.local/go/src/crypto/tls/conn.go:582
        crypto/tls.(*Conn).Read(0xc0000a0000, {0xc0001cf000, 0x1000, 0x11?})
                /home/wxh/.local/go/src/crypto/tls/conn.go:1287 +0x16f
        bufio.(*Reader).Read(0xc0001af1a0, {0xc0001aad60, 0x9, 0xc0004d5d18?})
                /home/wxh/.local/go/src/bufio/bufio.go:237 +0x1bb
        io.ReadAtLeast({0x7c3760, 0xc0001af1a0}, {0xc0001aad60, 0x9, 0x9}, 0x9)
                /home/wxh/.local/go/src/io/io.go:332 +0x9a
        io.ReadFull(...)
                /home/wxh/.local/go/src/io/io.go:351
        net/http.http2readFrameHeader({0xc0001aad60?, 0x9?, 0xc0004d5df0?}, {0x7c3760?, 0xc0001af1a0?})
                /home/wxh/.local/go/src/net/http/h2_bundle.go:1565 +0x6e
        net/http.(*http2Framer).ReadFrame(0xc0001aad20)
                /home/wxh/.local/go/src/net/http/h2_bundle.go:1829 +0x95
        net/http.(*http2clientConnReadLoop).run(0xc0004d5f98)
                /home/wxh/.local/go/src/net/http/h2_bundle.go:8875 +0x130
        net/http.(*http2ClientConn).readLoop(0xc00009e180)
                /home/wxh/.local/go/src/net/http/h2_bundle.go:8771 +0x6f
        created by net/http.(*http2Transport).newClientConn
                /home/wxh/.local/go/src/net/http/h2_bundle.go:7478 +0xaaa
        
         Goroutine 37 in state IO wait, with internal/poll.runtime_pollWait on top of the stack:
        goroutine 37 [IO wait]:
        internal/poll.runtime_pollWait(0x7f945c1e02a8, 0x72)
                /home/wxh/.local/go/src/runtime/netpoll.go:305 +0x89
        internal/poll.(*pollDesc).wait(0xc0003ca000?, 0xc000202000?, 0x0)
                /home/wxh/.local/go/src/internal/poll/fd_poll_runtime.go:84 +0x32
        internal/poll.(*pollDesc).waitRead(...)
                /home/wxh/.local/go/src/internal/poll/fd_poll_runtime.go:89
        internal/poll.(*FD).Read(0xc0003ca000, {0xc000202000, 0x1300, 0x1300})
                /home/wxh/.local/go/src/internal/poll/fd_unix.go:167 +0x25a
        net.(*netFD).Read(0xc0003ca000, {0xc000202000?, 0xc0004e6798?, 0xc0004c0808?})
                /home/wxh/.local/go/src/net/fd_posix.go:55 +0x29
        net.(*conn).Read(0xc000014028, {0xc000202000?, 0xc000136630?, 0x2c?})
                /home/wxh/.local/go/src/net/net.go:183 +0x45
        crypto/tls.(*atLeastReader).Read(0xc000276288, {0xc000202000?, 0x0?, 0x150fbb8ccb566149?})
                /home/wxh/.local/go/src/crypto/tls/conn.go:787 +0x3d
        bytes.(*Buffer).ReadFrom(0xc0000a0978, {0x7c3860, 0xc000276288})
                /home/wxh/.local/go/src/bytes/buffer.go:202 +0x98
        crypto/tls.(*Conn).readFromUntil(0xc0000a0700, {0x7c3b80?, 0xc000014028}, 0xc0004cc2c0?)
                /home/wxh/.local/go/src/crypto/tls/conn.go:809 +0xe5
        crypto/tls.(*Conn).readRecordOrCCS(0xc0000a0700, 0x0)
                /home/wxh/.local/go/src/crypto/tls/conn.go:616 +0x116
        crypto/tls.(*Conn).readRecord(...)
                /home/wxh/.local/go/src/crypto/tls/conn.go:582
        crypto/tls.(*Conn).Read(0xc0000a0700, {0xc00023c000, 0x1000, 0x11?})
                /home/wxh/.local/go/src/crypto/tls/conn.go:1287 +0x16f
        bufio.(*Reader).Read(0xc00022a2a0, {0xc00020e2e0, 0x9, 0xc0004c0d18?})
                /home/wxh/.local/go/src/bufio/bufio.go:237 +0x1bb
        io.ReadAtLeast({0x7c3760, 0xc00022a2a0}, {0xc00020e2e0, 0x9, 0x9}, 0x9)
                /home/wxh/.local/go/src/io/io.go:332 +0x9a
        io.ReadFull(...)
                /home/wxh/.local/go/src/io/io.go:351
        net/http.http2readFrameHeader({0xc00020e2e0?, 0x9?, 0xc0004c0df0?}, {0x7c3760?, 0xc00022a2a0?})
                /home/wxh/.local/go/src/net/http/h2_bundle.go:1565 +0x6e
        net/http.(*http2Framer).ReadFrame(0xc00020e2a0)
                /home/wxh/.local/go/src/net/http/h2_bundle.go:1829 +0x95
        net/http.(*http2clientConnReadLoop).run(0xc0004c0f98)
                /home/wxh/.local/go/src/net/http/h2_bundle.go:8875 +0x130
        net/http.(*http2ClientConn).readLoop(0xc00019e300)
                /home/wxh/.local/go/src/net/http/h2_bundle.go:8771 +0x6f
        created by net/http.(*http2Transport).newClientConn
                /home/wxh/.local/go/src/net/http/h2_bundle.go:7478 +0xaaa
        ]
FAIL
exit status 1

有人知道如何解決這個問題嗎？

謝謝！

解決方法

在 Go 中，http.Client 使用 Transport（http.RoundTripper 介面）。 http.Transport 是它的預設實作。預設的 http.Transfer 維護一個連線池，其中保存由於某種原因保持活動或空閒的連線。

基本上，您需要做的就是確保在呼叫goleak.Verify時池中沒有連線*

這可以透過以下方式完成：

1. 在執行任何請求之前停用所有 http 用戶端的 keep-alive：
   client := http.Client{Transport: &http.Transport{DisableKeepAlive: true}}
2. #在呼叫goleak.Verify之前關閉空閒連線*：
   client.CloseIdleConnections() // 自 Go 1.12 起可用

以上是當嘗試 `ReadAll(response.Body)` 時，goroutine 洩漏，其中 `response` 由 http `client.Do(...)` 傳回的詳細內容。更多資訊請關注PHP中文網其他相關文章！