net: DialContext returns "dial tcp <addr>: context deadline exceeded" error

[benburkert]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.9.3 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="/go"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build672889649=/tmp/go-build -gno-record-gcc-switches"
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?

A reverse proxy triggered a bunch of dial timeouts while connecting to a backend over a short period of time.

What did you expect to see?

A bunch of "dial tcp <addr>: i/o timeout" error messages.

What did you see instead?

A reverse proxy logged a quick burst of "dial tcp <addr>: context deadline exceeded" errors. The errors originated from the DialContext method a *net.Dialer with a Timeout value set.

[benburkert]

My guess is that the context.DeadlineExceeded message is in the error string because mapErr isn't being called here. But I haven't been able to reproduce the error message locally.

[ianlancetaylor]

Closing as dup of #22724.

[gopherbot]

Change https://golang.org/cl/103518 mentions this issue: net: map context errors from aborted dial to internal net package errors