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net: Misleading error "no such host" when running out of file descriptiors #56192

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polarina opened this issue Oct 13, 2022 · 7 comments
Closed

net: Misleading error "no such host" when running out of file descriptiors #56192

polarina opened this issue Oct 13, 2022 · 7 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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@polarina
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What version of Go are you using (go version)?

$ go version
go version go1.19.2 linux/amd64

Does this issue reproduce with the latest release?

Yes.

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

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/mce-gabrielp/.cache/go-build"
GOENV="/home/mce-gabrielp/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/mce-gabrielp/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/mce-gabrielp/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.19.2"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
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 -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build969251111=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Given the following program:

package main

import "net/http"

func main() {
	for {
		_, err := http.DefaultClient.Get("https://google.com")
		if err != nil {
			panic(err)
		}
	}
}

Then build and execute as follows:

$ go build main.go 
$ bash -c 'ulimit -n 6 && ./main'

We initially encountered this bug in a production program (where, due to our bug, a request got repeated in a loop without closing the response body) with far more gracious ulimit. This is not a fringe case limited to setting the ulimit haphazardly low.

What did you expect to see?

panic: Get "https://google.com": dial tcp: lookup google.com: too many open files

What did you see instead?

panic: Get "https://google.com": dial tcp: lookup google.com: no such host
@joedian joedian added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Oct 14, 2022
@mateusz834
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mateusz834 commented Oct 16, 2022 •
edited

It only happens with the cgo resolver, while using the go resolver it returns the correct error: lookup google.com on [::1]:53: dial udp [::1]:53: socket: too many open files

@mateusz834 mateusz834 mentioned this issue Oct 16, 2022
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@gopherbot
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Change https://go.dev/cl/443255 mentions this issue: net: cgo resolver return correctly the too many open files error

@nightlyone
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@mateusz834 could you please mention which libc and version of it you are using?

https://dev.to/0xbf/how-to-get-glibc-version-c-lang-26he describes how to do that for glibc.

@mateusz834
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@nightlyone (GNU libc) 2.36

@mateusz834
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As discussed in CL 443255 this is caused by a glibc bug. I filled a bug report here: https://sourceware.org/bugzilla/show_bug.cgi?id=29717

@mateusz834
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For now it can be workarounded by forcing the go resolver, or using different libc (musl).

@seankhliao seankhliao added this to the Backlog milestone Nov 19, 2022
@bcmills
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bcmills commented Jan 31, 2023

Duplicate of #18588

@bcmills bcmills marked this as a duplicate of #18588 Jan 31, 2023
@bcmills bcmills closed this as not planned Won't fix, can't repro, duplicate, stale Jan 31, 2023
@bcmills bcmills mentioned this issue Jan 31, 2023
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@golang golang locked and limited conversation to collaborators Jan 31, 2024
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net: cgo resolver return correctly the too many open files error mateusz834/go
7 participants
@polarina @nightlyone @bcmills @gopherbot @seankhliao @joedian @mateusz834