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net/http: misleading description of Transport.DisableKeepAlives field #26128

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juhwany opened this issue Jun 29, 2018 · 3 comments

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commented Jun 29, 2018

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.9 linux/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/hanmail/gospace"
GORACE=""
GOROOT="/data1/hanadmin/go"
GOTOOLDIR="/data1/hanadmin/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build037036632=/tmp/go-build"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

What did you do?

http.Transport struct has DisableKeepAlives field and its description says it's related to TCP connection re-use like TCP Keep-alive.

type Transport struct {
...
	// DisableKeepAlives, if true, prevents re-use of TCP connections
	// between different HTTP requests.
	DisableKeepAlives bool
}

But it's actually related to HTTP Keep-alive not TCP Keep-alive. I've found that if it is set to true, then HTTP request header will have "Connection:Close".

net/http/transport.go around 1997 line.

...
	if pc.t.DisableKeepAlives {
		req.extraHeaders().Set("Connection", "close")
	}
...

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

What did you expect to see?

The description about DisableKeepAlive field should be modified. It could make misunderstanding.

What did you see instead?

@juhwany juhwany changed the title Wrong description related to KeepAlive in http.Transport Wrong description related to KeepAlive in net/http/Transport struct Jun 29, 2018

@ianlancetaylor ianlancetaylor changed the title Wrong description related to KeepAlive in net/http/Transport struct net/http: misleading description of Transport.DisableKeepAlives field Jun 29, 2018

@ianlancetaylor ianlancetaylor added this to the Go1.11 milestone Jun 29, 2018

@ianlancetaylor

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commented Jun 29, 2018

@bradfitz

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commented Jun 29, 2018

There are two types of keep-alives: HTTP keep-alives and TCP keep-alives. HTTP almost always runs on top of TCP, so it's not inaccurate to use "TCP" in the description of HTTP keep-alives. The docs you cite never said "TCP keep-alives". It says:

prevents re-use of TCP connections

I really don't think there's any problem here, but I'll add a sentence.

@gopherbot

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commented Jun 29, 2018

Change https://golang.org/cl/121616 mentions this issue: net/http: update docs on Transport.DisableKeepAlives

@gopherbot gopherbot closed this in cbce223 Jun 29, 2018

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