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database/sql: incorrect count for DBStats.MaxLifetimeClosed for connections not closed in background goroutine #38058

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colinking opened this issue Mar 25, 2020 · 3 comments
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database/sql: incorrect count for DBStats.MaxLifetimeClosed for connections not closed in background goroutine #38058

colinking opened this issue Mar 25, 2020 · 3 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Unplanned

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

$ go version
go version go1.13.8 darwin/amd64

Does this issue reproduce with the latest release?

Based on the latest master, yeah.

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

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/colinking/Library/Caches/go-build"
GOENV="/Users/colinking/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GONOPROXY="github.com/segment*"
GONOSUMDB="github.com/segment*"
GOOS="darwin"
GOPATH="/Users/colinking/dev"
GOPRIVATE="github.com/segment*"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.13.8/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.13.8/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/colinking/dev/src/github.com/segmentio/cell-ctlstore/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/p6/62gms5fd2sd51_yf9qzbrs9c0000gn/T/go-build662696632=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

We were tracking the number of closed connections over the lifetime of a process with MaxLifetimeClosed from DBStats after setting a max connection lifetime with SetConnMaxLifetime.

What did you expect to see?

We expected MaxLifetimeClosed to be incremented once for every connection that was closed due to SetConnMaxLifetime.

What did you see instead?

Only connections closed via the background goroutine (connectionCleaner) were counted. Connections that are closed in conn (here and here) because it determines they are expired (and currently free) were not counted.

If this is the expected behavior, then I'm happy to open a PR with a fix.
@colinking colinking changed the title [database/sql] MaxLifetimeConnections [database/sql] Incorrect count for DBStats.MaxLifetimeClosed Mar 25, 2020
@odeke-em odeke-em changed the title [database/sql] Incorrect count for DBStats.MaxLifetimeClosed database/sql: incorrect count for DBStats.MaxLifetimeClosed for connections not closed in background goroutine Mar 25, 2020
@andybons andybons added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Mar 25, 2020
@andybons andybons added this to the Unplanned milestone Mar 25, 2020
@andybons
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@bradfitz @kardianos @kevinburke

@kardianos
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Yes, I believe you are correct. Those are closed due to max lifetime, but are not recorded in Stats.

Please keep this CL in mind if you send a patch.

@kardianos kardianos added NeedsFix The path to resolution is known, but the work has not been done. and removed NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Mar 25, 2020
colinking added a commit to colinking/go that referenced this issue Apr 5, 2020
@colinking
database/sql: connections expired in foreground should count towards …
ab87799 
…DBStats.MaxLifetimeClosed

Fixes: golang#38058
@colinking colinking mentioned this issue Apr 5, 2020
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@gopherbot
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Change https://golang.org/cl/227278 mentions this issue: database/sql: count connections expired in foreground with MaxLifetimeClosed

@bcmills bcmills mentioned this issue Apr 22, 2020
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@golang golang locked and limited conversation to collaborators Apr 22, 2021
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database/sql: count connections expired in foreground with MaxLifetimeClosed colinking/go
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