Better behavior would be to sleep and retry the connection instead of this:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x4ee6c6]

goroutine 1 [running]:
io/ioutil.devNull.ReadFrom(0x0, 0x0, 0x0, 0x7ea2c0, 0x800b73601, 0x800c1aa38)
/usr/local/go/src/io/ioutil/ioutil.go:147 +0x66
io.copyBuffer(0x8bcaa0, 0xb86f08, 0x0, 0x0, 0x0, 0x0, 0x0, 0x7c0a60, 0x201, 0xc0003aae40)
/usr/local/go/src/io/io.go:388 +0x303
io.Copy(0x8bcaa0, 0xb86f08, 0x0, 0x0, 0x0, 0x8bc060, 0xc00042a6e0)
/usr/local/go/src/io/io.go:364 +0x5a
github.com/optix2000/go-nsdctl.NewClient(0x84f3c5, 0x3, 0x7fffffffedc5, 0xe, 0x7fffffffed6e, 0x21, 0x7fffffffed95, 0x22, 0x7fffffffed47, 0x22, ...)
/wrkdirs/usr/ports/net-mgmt/nsd_exporter/work/src/github.com/optix2000/go-nsdctl/nsdctl.go:267 +0x58d
main.NewNSDCollector(0x84f3c5, 0x3, 0x7fffffffedc5, 0xe, 0x7fffffffed6e, 0x21, 0x7fffffffed95, 0x22, 0x7fffffffed47, 0x22, ...)
/wrkdirs/usr/ports/net-mgmt/nsd_exporter/work/src/github.com/optix2000/nsd_exporter/nsd_exporter.go:150 +0xc1
main.main()
/wrkdirs/usr/ports/net-mgmt/nsd_exporter/work/src/github.com/optix2000/nsd_exporter/nsd_exporter.go:201 +0x30f

Hi,

We found the following strange behavior due to high amount of incoming /metrics queries....

``fatal error: concurrent map read and map write
goroutine 855 [running]:
runtime.throw(0x857b0c, 0x21)
/usr/local/go/src/runtime/panic.go:1117 +0x72 fp=0xc0003c1c48 sp=0xc0003c1c18 pc=0x4389f2
runtime.mapaccess2_faststr(0x7e4200, 0xc00020e9f0, 0xc00024e6d8, 0xf, 0x0, 0x1)
/usr/local/go/src/runtime/map_faststr.go:116 +0x4a5 fp=0xc0003c1cb8 sp=0xc0003c1c48 pc=0x415ca5
main.(*NSDCollector).updateMetric(0xc000210110, 0xc00024e6d8, 0x11, 0xc00024e6d8, 0x11)
/drone/src/nsd_exporter.go:117 +0xdc fp=0xc0003c1de0 sp=0xc0003c1cb8 pc=0x79a61c
main.(*NSDCollector).Collect(0xc000210110, 0xc000074f00)
/drone/src/nsd_exporter.go:81 +0x61e fp=0xc0003c1f20 sp=0xc0003c1de0 pc=0x79a29e
github.com/prometheus/client_golang/prometheus.(*Registry).Gather.func1()
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:443 +0x12b fp=0xc0003c1fe0 sp=0xc0003c1f20 pc=0x759c2b
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:1371 +0x1 fp=0xc0003c1fe8 sp=0xc0003c1fe0 pc=0x46e161
created by github.com/prometheus/client_golang/prometheus.(*Registry).Gather
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:535 +0xe4d

goroutine 1 [IO wait]:
internal/poll.runtime_pollWait(0x7f04dd6aaaf0, 0x72, 0x0)
/usr/local/go/src/runtime/netpoll.go:222 +0x55
internal/poll.(*pollDesc).wait(0xc00025c298, 0x72, 0x0, 0x0, 0x84c859)
/usr/local/go/src/internal/poll/fd_poll_runtime.go:87 +0x45
internal/poll.(*pollDesc).waitRead(...)
/usr/local/go/src/internal/poll/fd_poll_runtime.go:92
internal/poll.(*FD).Accept(0xc00025c280, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0)
/usr/local/go/src/internal/poll/fd_unix.go:401 +0x212
net.(*netFD).accept(0xc00025c280, 0x8c4f7df3af0f2851, 0x0, 0x0)
/usr/local/go/src/net/fd_unix.go:172 +0x45
net.(*TCPListener).accept(0xc0002ae870, 0x64804546, 0xc0003bfd20, 0x4d31c6)
/usr/local/go/src/net/tcpsock_posix.go:139 +0x32
net.(*TCPListener).Accept(0xc0002ae870, 0xc0003bfd70, 0x18, 0xc000000180, 0x71ffdb)
/usr/local/go/src/net/tcpsock.go:261 +0x65
net/http.(*Server).Serve(0xc00024c380, 0x8cae60, 0xc0002ae870, 0x0, 0x0)
/usr/local/go/src/net/http/server.go:2981 +0x285
net/http.(*Server).ListenAndServe(0xc00024c380, 0xc00024c380, 0x8)
/usr/local/go/src/net/http/server.go:2910 +0xba
net/http.ListenAndServe(...)
/usr/local/go/src/net/http/server.go:3164
main.main()
/drone/src/nsd_exporter.go:253 +0x313

goroutine 66 [select]:
github.com/prometheus/client_golang/prometheus.(*Registry).Gather(0xc0000ca500, 0x0, 0x0, 0x0, 0x0, 0x0)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:510 +0xb65
github.com/prometheus/client_golang/prometheus/promhttp.HandlerFor.func1(0x7f04dc4fdef8, 0xc0001442d0, 0xc000512500)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/promhttp/http.go:126 +0x99
net/http.HandlerFunc.ServeHTTP(0xc0002a9f10, 0x7f04dc4fdef8, 0xc0001442d0, 0xc000512500)
/usr/local/go/src/net/http/server.go:2069 +0x44
github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerInFlight.func1(0x7f04dc4fdef8, 0xc0001442d0, 0xc000512500)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/promhttp/instrument_server.go:40 +0xab
net/http.HandlerFunc.ServeHTTP(0xc00020ff20, 0x7f04dc4fdef8, 0xc0001442d0, 0xc000512500)
/usr/local/go/src/net/http/server.go:2069 +0x44
github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerCounter.func1(0x8cb040, 0xc00030e1c0, 0xc000512500)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/promhttp/instrument_server.go:100 +0xdf
net/http.HandlerFunc.ServeHTTP(0xc0002b8030, 0x8cb040, 0xc00030e1c0, 0xc000512500)
/usr/local/go/src/net/http/server.go:2069 +0x44
net/http.(*ServeMux).ServeHTTP(0xafa5e0, 0x8cb040, 0xc00030e1c0, 0xc000512500)
/usr/local/go/src/net/http/server.go:2448 +0x1ad
net/http.serverHandler.ServeHTTP(0xc00024c380, 0x8cb040, 0xc00030e1c0, 0xc000512500)
/usr/local/go/src/net/http/server.go:2887 +0xa3
net/http.(*conn).serve(0xc0002461e0, 0x8cbe58, 0xc00002e100)
/usr/local/go/src/net/http/server.go:1952 +0x8cd
created by net/http.(*Server).Serve
/usr/local/go/src/net/http/server.go:3013 +0x39b

goroutine 775 [runnable]:
strconv.readFloat(0xc0003911ed, 0x1, 0x0, 0x0, 0x680500, 0xc000178158, 0xc00032625b)
/usr/local/go/src/strconv/atof.go:175 +0x5cb
strconv.atof64(0xc0003911ed, 0x1, 0x415b7d, 0xc00021be40, 0xc0003911e0, 0xc)
/usr/local/go/src/strconv/atof.go:620 +0x85
strconv.parseFloatPrefix(0xc0003911ed, 0x1, 0x40, 0xc0003911e0, 0xc0002aa538, 0x2, 0xc0002aa4e0)
/usr/local/go/src/strconv/atof.go:703 +0x95
strconv.ParseFloat(0xc0003911ed, 0x1, 0x40, 0xc, 0xc0002aa590, 0x1)
/usr/local/go/src/strconv/atof.go:691 +0x45
main.(*NSDCollector).Collect(0xc000210110, 0xc00020c480)
/drone/src/nsd_exporter.go:92 +0x3c8
github.com/prometheus/client_golang/prometheus.(*Registry).Gather.func1()
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:443 +0x12b
created by github.com/prometheus/client_golang/prometheus.(*Registry).Gather
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:535 +0xe4d

goroutine 795 [select]:
github.com/prometheus/client_golang/prometheus.(*Registry).Gather(0xc0000ca500, 0x0, 0x0, 0x0, 0x0, 0x0)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:510 +0xb65
github.com/prometheus/client_golang/prometheus/promhttp.HandlerFor.func1(0x7f04dc4fdef8, 0xc000642190, 0xc000512200)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/promhttp/http.go:126 +0x99
net/http.HandlerFunc.ServeHTTP(0xc0002a9f10, 0x7f04dc4fdef8, 0xc000642190, 0xc000512200)
/usr/local/go/src/net/http/server.go:2069 +0x44
github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerInFlight.func1(0x7f04dc4fdef8, 0xc000642190, 0xc000512200)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/promhttp/instrument_server.go:40 +0xab
net/http.HandlerFunc.ServeHTTP(0xc00020ff20, 0x7f04dc4fdef8, 0xc000642190, 0xc000512200)
/usr/local/go/src/net/http/server.go:2069 +0x44
github.com/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerCounter.func1(0x8cb040, 0xc000168540, 0xc000512200)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/promhttp/instrument_server.go:100 +0xdf
net/http.HandlerFunc.ServeHTTP(0xc0002b8030, 0x8cb040, 0xc000168540, 0xc000512200)
/usr/local/go/src/net/http/server.go:2069 +0x44
net/http.(*ServeMux).ServeHTTP(0xafa5e0, 0x8cb040, 0xc000168540, 0xc000512200)
/usr/local/go/src/net/http/server.go:2448 +0x1ad
net/http.serverHandler.ServeHTTP(0xc00024c380, 0x8cb040, 0xc000168540, 0xc000512200)
/usr/local/go/src/net/http/server.go:2887 +0xa3
net/http.(*conn).serve(0xc000246280, 0x8cbe58, 0xc0004a81c0)
/usr/local/go/src/net/http/server.go:1952 +0x8cd
created by net/http.(*Server).Serve
/usr/local/go/src/net/http/server.go:3013 +0x39b

goroutine 821 [IO wait]:
internal/poll.runtime_pollWait(0x7f04dd6aa3b0, 0x72, 0xffffffffffffffff)
/usr/local/go/src/runtime/netpoll.go:222 +0x55
internal/poll.(*pollDesc).wait(0xc0000fe618, 0x72, 0x0, 0x1, 0xffffffffffffffff)
/usr/local/go/src/internal/poll/fd_poll_runtime.go:87 +0x45
internal/poll.(*pollDesc).waitRead(...)
/usr/local/go/src/internal/poll/fd_poll_runtime.go:92
internal/poll.(*FD).Read(0xc0000fe600, 0xc00028a461, 0x1, 0x1, 0x0, 0x0, 0x0)
/usr/local/go/src/internal/poll/fd_unix.go:166 +0x1d5
net.(*netFD).Read(0xc0000fe600, 0xc00028a461, 0x1, 0x1, 0xc0000be180, 0x0, 0x0)
/usr/local/go/src/net/fd_posix.go:55 +0x4f
net.(*conn).Read(0xc00061a258, 0xc00028a461, 0x1, 0x1, 0x0, 0x0, 0x0)
/usr/local/go/src/net/net.go:183 +0x91
net/http.(*connReader).backgroundRead(0xc00028a450)
/usr/local/go/src/net/http/server.go:692 +0x58
created by net/http.(*connReader).startBackgroundRead
/usr/local/go/src/net/http/server.go:688 +0xd5

goroutine 823 [semacquire]:
sync.runtime_Semacquire(0xc0003901e8)
/usr/local/go/src/runtime/sema.go:56 +0x45
sync.(*WaitGroup).Wait(0xc0003901e0)
/usr/local/go/src/sync/waitgroup.go:130 +0x65
github.com/prometheus/client_golang/prometheus.(*Registry).Gather.func2(0xc0003901e0, 0xc00020c480, 0xc00020c4e0)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:460 +0x2b
created by github.com/prometheus/client_golang/prometheus.(*Registry).Gather
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:459 +0x60d

goroutine 801 [semacquire]:
sync.runtime_Semacquire(0xc0000ba048)
/usr/local/go/src/runtime/sema.go:56 +0x45
sync.(*WaitGroup).Wait(0xc0000ba040)
/usr/local/go/src/sync/waitgroup.go:130 +0x65
github.com/prometheus/client_golang/prometheus.(*Registry).Gather.func2(0xc0000ba040, 0xc000074f00, 0xc000075080)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:460 +0x2b
created by github.com/prometheus/client_golang/prometheus.(*Registry).Gather
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:459 +0x60d

goroutine 799 [IO wait]:
internal/poll.runtime_pollWait(0x7f04dd6aaa08, 0x72, 0xffffffffffffffff)
/usr/local/go/src/runtime/netpoll.go:222 +0x55
internal/poll.(*pollDesc).wait(0xc000186198, 0x72, 0x0, 0x1, 0xffffffffffffffff)
/usr/local/go/src/internal/poll/fd_poll_runtime.go:87 +0x45
internal/poll.(*pollDesc).waitRead(...)
/usr/local/go/src/internal/poll/fd_poll_runtime.go:92
internal/poll.(*FD).Read(0xc000186180, 0xc00014b1e1, 0x1, 0x1, 0x0, 0x0, 0x0)
/usr/local/go/src/internal/poll/fd_unix.go:166 +0x1d5
net.(*netFD).Read(0xc000186180, 0xc00014b1e1, 0x1, 0x1, 0xc0002e0730, 0x466aa0, 0xc00023cd80)
/usr/local/go/src/net/fd_posix.go:55 +0x4f
net.(*conn).Read(0xc0000bc2c8, 0xc00014b1e1, 0x1, 0x1, 0x0, 0x0, 0x0)
/usr/local/go/src/net/net.go:183 +0x91
net/http.(*connReader).backgroundRead(0xc00014b1d0)
/usr/local/go/src/net/http/server.go:692 +0x58
created by net/http.(*connReader).startBackgroundRead
/usr/local/go/src/net/http/server.go:688 +0xd5``

Seeing this after building on Alpine 3.12 with Go 1.13 from aports;

# ./nsd_exporter -config-file /usr/local/etc/nsd/nsd.conf
2020/07/14 15:30:30 open /usr/local/etc/nsd/nsd: no such file or directory
# ./nsd_exporter -key /usr/local/etc/nsd/nsd_control.key -cert /usr/local/etc/nsd/nsd_control.pem -ca /usr/local/etc/nsd/nsd_server.pem
2020/07/14 15:28:33 -cert, -key, and -ca must all be defined.

golang/go#1435 is finally fixed so we can drop privileges.

Hello!

Trying to run nsd_exporter getting the following error message:

# ./nsd_exporter 
2020/06/10 12:20:16 dial tcp: lookup tcp/⋸: Servname not supported for ai_socktype

what does this error message means?

I enabled %s.stats in my nsd configuration to get metrics per zone, but one of my zones contains a - which is a forbidden character in prometheus. Is there a way to configure nsd_exporter to parse these "forbidden" characters, and the issue is solved by renaming metrics in prometheus scrape configs.
thanks for the answer in advance

cli error message:

panic: descriptor Desc{fqName: "nsd_xn--d1alf_stats_num_udp", help: "number of queries on xn--d1alf over UDP ip4.", constLabels: {}, variableLabels: []} is invalid: "nsd_xn--d1alf_stats_num_udp" is not a valid metric name

goroutine 1 [running]:
github.com/prometheus/client_golang/prometheus.(*Registry).MustRegister(0xc000088550, 0xc0001ddc10, 0x1, 0x1)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:400 +0xb7
github.com/prometheus/client_golang/prometheus.MustRegister(...)
/go/pkg/mod/github.com/prometheus/[email protected]/prometheus/registry.go:177
main.main()
/drone/src/nsd_exporter.go:250 +0x226

Hello, could you please help to understand what does it mean and how can i fix it?
There are a lot of errors in a log file and nsd_exporter returns http/500.

http.log
nsd-control-stats.txt

Mar 13 00:24:26 nl nsd_exporter[29420]: 2024/03/13 00:24:26 New metric gadskypapa.com.num.queries found. Refreshing.                                                   
Mar 13 00:24:26 nl nsd_exporter[29420]: 2024/03/13 00:24:26 Metric %!(EXTRA string=gadskypapa.com.num.queries, string= not found in config.)                           
Mar 13 00:24:26 nl nsd_exporter[29420]: 2024/03/13 00:24:26 Metric gadskypapa.com.num.queriesnot configured. Skipping                                                  
...

/usr/local/bin/nsd_exporter -cert /usr/local/etc/nsd/nsd_control.pem -ca /usr/local/etc/nsd/nsd_server.pem -key /usr/local/etc/nsd/nsd_control.key -nsd-address 127.0.0.1:8952 -listen-address 127.0.0.1:9132

nsd -v

NSD version 4.8.0
Written by NLnet Labs.

Configure line: --localstatedir=/var --with-configdir=/usr/local/etc/nsd --with-libevent=/usr/local --with-pidfile=/var/run/nsd/nsd.pid --with-ssl=/usr --with-user=nsd
--enable-bind8-stats --disable-checking --disable-dnstap --enable-ipv6 --enable-largefile --enable-minimal-responses --disable-mmap --enable-nsec3 --disable-packed --
enable-radix-tree --enable-ratelimit --enable-zone-stats --prefix=/usr/local --mandir=/usr/local/man --infodir=/usr/local/share/info/ --build=amd64-portbld-freebsd14.0
Event loop: libevent 2.1.12-stable (uses kqueue)
Linked with OpenSSL 3.0.12 24 Oct 2023

Copyright (C) 2001-2020 NLnet Labs. This is free software.
There is NO warranty; not even for MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE.

Will need a change in optix2000/go-nsdctl