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Printf "database/sql" got panic under high qps pressure. #27507

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Exlsunshine opened this issue Sep 5, 2018 · 3 comments
Closed

Printf "database/sql" got panic under high qps pressure. #27507

Exlsunshine opened this issue Sep 5, 2018 · 3 comments
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FrozenDueToAge WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided.

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@Exlsunshine
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Exlsunshine commented Sep 5, 2018 •
edited

Please answer these questions before submitting your issue. Thanks!
The following package is not thread safe: "database/sql"

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

go version go1.7 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="/data/home/markgyang/project/video-content-platform/spcdp_cp"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build491876654=/tmp/go-build"
CXX="g++"
CGO_ENABLED="1"

What did you do?

I imported this package "database/sql", and got a object: db *sql.DB
Then I initialized it and printed it: fmt.Printf("%v", db)

What did you expect to see?

Print db structure as usual.

What did you see instead?

It printed the db structure as normal, but as long as I increased the frequency of calling fmt.Printf("%v", db), I got golang concurrent map read and map write error, then the program panic during runtime.
@davecheney
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This looks like memory corruption. Have you tried running your program under the race detector? See https://blog.golang.org/race-detector .

@davecheney davecheney added the WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided. label Sep 5, 2018
@kardianos
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The sql.DB contains several maps which should only be read or written to under locks.

Calling fmt.Printf("%v", &sql.DB{}) will attempt to read these map structures. This will cause a race condition the runtime can (and did) detect for you.

  1. Don't do this.
  2. What are you trying to do by printing out the sql.DB? Are you trying to get stats? Stats has been expanded greatly in Go1.11.

@Exlsunshine
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The sql.DB contains several maps which should only be read or written to under locks.

Calling fmt.Printf("%v", &sql.DB{}) will attempt to read these map structures. This will cause a race condition the runtime can (and did) detect for you.

  1. Don't do this.
  2. What are you trying to do by printing out the sql.DB? Are you trying to get stats? Stats has been expanded greatly in Go1.11.

Thanks for the reply.
I want to print out the db because I want to identify which database I am currently working on.

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@davecheney @kardianos @Exlsunshine @gopherbot