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bassam opened this issue Oct 24, 2017 · 5 comments
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cmd/compile: "can't find import" error due to race during concurrent build #22423

bassam opened this issue Oct 24, 2017 · 5 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.

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@bassam
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bassam commented Oct 24, 2017

Please answer these questions before submitting your issue. Thanks!

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

go version go1.9.1 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="/home/rook/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"
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?

on a machine with 16 cores (like a c4.4xlarge instance in EC2) I run the rook build system as follows:

git clone https://github.com/rook/rook
make distclean
build/run make -j16 build.all V=1 | tee build.log

What did you expect to see?

I expect the build to succeed every time.

What did you see instead?

Instead, I see intermittent errors that look like a race in the go build process. For example:

# github.com/rook/rook/vendor/k8s.io/api/autoscaling/v1
vendor/k8s.io/api/autoscaling/v1/types.go:20:2: can't find import: "github.com/rook/rook/vendor/k8s.io/api/core/v1"
mkdir -p /home/rook/go/pkg/linux_arm64_static/github.com/rook/rook/vendor/k8s.io/api/core/
cp $WORK/github.com/rook/rook/vendor/k8s.io/api/core/v1.a /home/rook/go/pkg/linux_arm64_static/github.com/rook/rook/vendor/k8s.io/api/core/v1.a

Note that the cp command happened after the can't find import error.
@bassam bassam mentioned this issue Oct 24, 2017
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@ALTree ALTree changed the title "can't find import" error due to race during concurrent build cmd/compile: "can't find import" error due to race during concurrent build Oct 24, 2017
@ALTree ALTree added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Oct 24, 2017
@bassam
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bassam commented Oct 24, 2017

Note that our build system runs concurrent go build from the makefile. Not sure if this is causing .a packages to be removed form the file system and resulting in errors like the can't import

@ALTree
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ALTree commented Oct 24, 2017 •
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Easy to test if there is an issue in your makefile: force sequential compilation in the Go compiler. Does the error go away?

@bassam
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bassam commented Oct 24, 2017

@ALTree with export GO19CONCURRENTCOMPILATION=0 and after 5 builds I've not seen the build error. Note however that we are running concurrent go build commands for the same platform and they might be attempting to build similar import packages. Is this a supported scenario?

Looking at the copyFile function I see that it attempts to remove the file before copying. I can't imagine this being safe to do when concurrent builds of go build are running and import the same packages.

I'm going to change our makefile to only run concurrently across build platforms, and sequentially within a build platform. I'll report back here.

@ianlancetaylor
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Running concurrent go build commands in the same GOPATH is clearly unsafe. Don't do that.

@bassam
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bassam commented Oct 24, 2017

@ianlancetaylor yes I see why now. Fixed our makefile to avoid that. Thanks!

@bassam bassam closed this as completed Oct 24, 2017
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@bassam @ianlancetaylor @ALTree @gopherbot