ntpq input plugin: panicked: runtime error: index out of range [0] with length 0

[flohoff]

Relevant telegraf.conf

[[inputs.ntpq]]
        # Disable nameserice lookup
        options = "-n"

Logs from Telegraf

Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: 2024-10-28T17:11:50Z E! FATAL: [inputs.ntpq] panicked: runtime error: index out of range [0] with length 0, Stack:
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: goroutine 69 [running]:
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: github.com/influxdata/telegraf/agent.panicRecover(0xc0025a03f0)
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/agent/agent.go:1203 +0x70
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: panic({0x8b0a9c0?, 0xc0029ebf20?})
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /usr/local/go/src/runtime/panic.go:785 +0x132
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: github.com/influxdata/telegraf/plugins/inputs/ntpq.processLine({0x0?, 0x0?})
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/plugins/inputs/ntpq/ntpq.go:288 +0xfa
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: github.com/influxdata/telegraf/plugins/inputs/ntpq.(*NTPQ).gatherServer(0x40eebf?, {0xa109f40, 0xc002595920}, {0x0, 0x0})
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/plugins/inputs/ntpq/ntpq.go:162 +0x29a
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: github.com/influxdata/telegraf/plugins/inputs/ntpq.(*NTPQ).Gather(0xc002451400, {0xa109f40, 0xc002595920})
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/plugins/inputs/ntpq/ntpq.go:139 +0x3d
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: github.com/influxdata/telegraf/models.(*RunningInput).Gather(0xc0025a03f0, {0xa109f40, 0xc002595920})
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/models/running_input.go:232 +0x262
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: github.com/influxdata/telegraf/agent.(*Agent).gatherOnce.func1()
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/agent/agent.go:584 +0x58
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: created by github.com/influxdata/telegraf/agent.(*Agent).gatherOnce in goroutine 57
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/agent/agent.go:582 +0xf7
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: goroutine 1 [semacquire]:
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: sync.runtime_Semacquire(0xc002451590?)
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /usr/local/go/src/runtime/sema.go:71 +0x25
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: sync.(*WaitGroup).Wait(0xc00245c500?)
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /usr/local/go/src/sync/waitgroup.go:118 +0x48
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: github.com/influxdata/telegraf/agent.(*Agent).Run(0xc00245c500, {0xa0c54f0, 0xc002451540})
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/agent/agent.go:197 +0xa2a
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: main.(*Telegraf).runAgent(0xc00243e160, {0xa0c54f0, 0xc002451540}, 0x6?)
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/cmd/telegraf/telegraf.go:466 +0x1725
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: main.(*Telegraf).reloadLoop(0xc00243e160)
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/cmd/telegraf/telegraf.go:202 +0x26b
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: main.(*Telegraf).Run(0xc00243e160)
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/cmd/telegraf/telegraf_posix.go:19 +0xbc
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: main.runApp.func1(0xc002408fc0)
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]:         /go/src/github.com/influxdata/telegraf/cmd/tele
Oct 28 18:11:50 telegraf-ntpd-host telegraf[313911]: 2024-10-28T17:11:50Z E! PLEASE REPORT THIS PANIC ON GITHUB with stack trace, configuration, and OS information: https://github.com/influxdata/telegraf/issues/new/choose

System info

Debian/Bookworm, telegraf (from deb) 1.32.1-1

Docker

No response

Steps to reproduce

Running the ntpq input plugin without "-n" works - disabling nameservice lookup and adding "-n" lets telegraf fail with a backtrace.

Expected behavior

No backtrace

Actual behavior

Backtrace in ntpq plugin

Additional info

root@telegraf-ntpd-host:~# ntpq -n -c pe
     remote                                   refid      st t when poll reach   delay   offset   jitter
=======================================================================================================
 0.europe.pool.ntp.org                   .POOL.          16 p    -  256    0   0.0000   0.0000   0.0001
 1.europe.pool.ntp.org                   .POOL.          16 p    -  256    0   0.0000   0.0000   0.0001
 2.europe.pool.ntp.org                   .POOL.          16 p    -  256    0   0.0000   0.0000   0.0001
 3.europe.pool.ntp.org                   .POOL.          16 p    -  256    0   0.0000   0.0000   0.0001
+172.31.2.111                            192.53.103.104   2 u  659 1024  377   0.1348  -4.5526   3.2355
+94.198.159.11                           .TMNL.           1 u  691 1024  377  17.4125  -2.2900   3.6388
*193.134.29.11                           .PTPs.           1 u 1018 1024  377  16.0927  -2.1828   1.4075
+178.239.19.57                           10.1.105.4       2 u  662 1024  377  19.2814  -2.3140   1.6363
+195.201.20.16                           100.10.69.89     2 u  607 1024  377  11.8093  -2.3424  19.6606
+213.157.100.71                          131.130.251.107  2 u  763 1024  377  22.3144  -1.9906   1.4815
+45.87.76.3                              244.220.219.218  2 u  863 1024  377  16.5980  -2.5092   1.9171

[srebhan]

@flohoff I will add a fix to avoid the panic, but the reason you are running into this is that you are effectively running ntpq -n with your settings and this will open an ntpq shell as no command is specified... So set

[[inputs.ntpq]]
        # Disable nameserice lookup
        options = "-p -n"

[srebhan]

@flohoff please test the binary in PR #16110, available as soon as CI finished the tests, and let me know if this fixes the issue!