x/net/http2: connection reused with DisableKeepAlives

[benburkert]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.9 darwin/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="darwin"
GOOS="darwin"
GOPATH="/Users/benburkert"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.9/libexec"
GOTOOLDIR="/usr/local/Cellar/go/1.9/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/qs/qkt9twmx4qg379d6f8kxl1vm0000gn/T/go-build568362356=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
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?

Send multiple requests to the same h2 server with keep alives disabled.

https://play.golang.org/p/sxjh2Yq-hg

What did you expect to see?

no output because connections are not used across requests.

What did you see instead?

connection reused: "[::1]:61658"
connection reused: "[::1]:61658"
connection reused: "[::1]:61658"
connection reused: "[::1]:61658"
connection reused: "[::1]:61661"
connection reused: "[::1]:61665"
connection reused: "[::1]:61668"
connection reused: "[::1]:61668"
connection reused: "[::1]:61668"
connection reused: "[::1]:61668"
connection reused: "[::1]:61671"

[ianlancetaylor]

CC @tombergan

[tombergan]

Might be related to #22413

[tombergan]

https://golang.org/cl/33153 was wrong. When keep alives are disabled, we don't start graceful shutdown (i.e., send GOAWAY) until the first request completes. We should actually start graceful shutdown when the first request is received.

[tombergan]

Actually, this is WAI according to https://golang.org/cl/33153:
https://go-review.googlesource.com/c/net/+/33153/1/http2/server.go#1281

I don't think this gets all the cases. What if the client sends a second request before the first completes?

I think that's fine. It's supposed to be close-ish in behavior. I figure that the user's intention was probably to minimize open connections, closing them as soon as possible. So if their goal is to minimize conns, it's better to support reusing one conn for multiple requests.

@benburkert, what are you trying to achieve by disabling keep alives on HTTP/2? This feature happened in #17717 where Brad was trying to give meaning to SetKeepAlivesEnabled for HTTP/2. In all honesty it's kind of weird for the HTTP/2 library to support this option, since "keep alives" are an HTTP/1 notion that doesn't translate to HTTP/2.

[tombergan]

Removing the 1.10 milestone since there is no bug that I can see. I will leave this open in state WaitingForInfo in case @benburkert wants to respond to the above question.

[gopherbot]

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)