当尝试 `ReadAll(response.Body)` 时，goroutine 泄漏，其中 `response` 由 http `client.Do(...)` 返回

php小编百草在解决编程问题时，发现了一个常见的goroutine泄漏情况。当我们尝试使用`ReadAll(response.Body)`时，返回的`response`对象是由`http`包的`client.Do(...)`方法返回的。然而，这种操作会导致goroutine泄漏的问题。为了避免这种情况的发生，我们需要采取一些措施来正确处理http响应。

问题内容

该问题来自一个非常常见的场景，即在 http 方法调用后从响应正文中读取所有字节。

在 https://github.com/uber-go/goleak 的帮助下，我发现了一个有趣的 goroutine 泄漏。

为了演示该问题，请使用 go test 运行以下测试代码，这会导致 found 出现意外的 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)
}

完整测试输出：

$ 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

有人知道如何解决这个问题吗？

谢谢！

解决方法

在 Go 中，http.Client 使用 Transport（http.RoundTripper 接口）。 http.Transport 是它的默认实现。默认的 http.Transfer 维护一个连接池，其中保存由于某种原因保持活动或空闲的连接。

基本上，您需要做的就是确保在调用goleak.Verify时池中没有连接*

这可以通过以下方式完成：

1. 在执行任何请求之前禁用所有 http 客户端的 keep-alive：
   client := http.Client{Transport: &http.Transport{DisableKeepAlive: true}}
2. 在调用goleak.Verify之前关闭空闲连接*：
   client.CloseIdleConnections() // 自 Go 1.12 起可用

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