feat: Support configuring rule.Reason as a Sprintf format string by jessehu · Pull Request #1068 · kubernetes/node-problem-detector

jessehu · 2025-06-11T05:33:35Z

So we can define one templated Reason to generate many Reasons, e.g. generating Reasons for Nvidia GPU Xid errors in dmesg log.

Close #1067

k8s-ci-robot · 2025-06-11T05:33:44Z

Hi @jessehu. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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k8s-ci-robot · 2025-06-11T05:33:44Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: jessehu
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hakman · 2025-06-18T18:56:42Z

/ok-to-test

jessehu · 2025-06-19T01:14:04Z

/retest

jessehu · 2025-06-19T01:40:14Z

Thanks @hakman for review! Looks like pull-npd-e2e-test failed twice. Not sure if it's related to this PR ?

hakman · 2025-06-21T04:02:57Z

Thanks @hakman for review! Looks like pull-npd-e2e-test failed twice. Not sure if it's related to this PR ?

Unrelated to the PR, please ignore.

jessehu · 2025-06-22T02:32:33Z

/retest

jessehu · 2025-06-22T02:51:35Z

Thanks @hakman. 1 test passed now but 2 tests still failed. Please take a look again.

jessehu · 2025-06-22T02:53:47Z

/retest

jessehu · 2025-07-21T23:46:00Z

/retest

So we can define one templated Reason to generate many Reasons, e.g. generating Reasons for Nvidia GPU Xid errors in dmesg log.

…eason

jessehu · 2025-08-20T09:44:52Z

hi @hakman would you mind review this PR again please? The pull-npd-e2e-test passed now.

k8s-triage-robot · 2025-11-18T10:44:14Z

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/lifecycle stale

k8s-triage-robot · 2025-12-18T11:06:05Z

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/lifecycle rotten

hakman · 2025-12-18T11:11:57Z

/remove-lifecycle rotten

daveoy · 2026-02-18T15:03:49Z

i also experimented with writing a feature like this, but abandoned it due to the cleanup ramifications. if you set a bunch of similar conditions on nodes they hang around until the node is deleted, will inflate prometheus metrics cardinality etc.

i wrote a feature to delete deprecated conditions (conditions that have been removed from config) on startup that wasn't reviewed / approved here that could help with this fact #1022 -- this is in use in my org with great success

interested to hear what others think about this situation

k8s-triage-robot · 2026-05-19T15:16:54Z

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/lifecycle stale

k8s-triage-robot · 2026-06-18T15:25:32Z

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/lifecycle rotten

DigitalVeer · 2026-07-09T22:43:50Z

+
+	reason := rule.Reason
+	// Support configuring rule.Reason as a Sprintf format string and formatting it with the matched capturing groups in rule.Pattern.
+	if strings.Contains(reason, "%") {


This turns every % into a template.

"Disk90%" becomes --> "Disk90%!(NOVERB)" and can cause us to fail to match.

@DigitalVeer An invalid template string like "Disk90%" will cause NPD process to panic when launching, so the user can find it out easily rather than not matching silently.

Thanks, Jesse. I tried to reproduce the panic with a new filelog monitor:

{ "plugin": "filelog", "pluginConfig": { "timestamp": "^(\\S+)", "message": "^\\S+ (.*)$", "timestampFormat": "2006-01-02T15:04:05Z07:00" }, "logPath": "/repro/pr_1068_literal_percent.log", "lookback": "24h", "bufferSize": 1, "source": "literal-percent-e2e", "metricsReporting": true, "conditions": [], "rules": [ { "type": "temporary", "reason": "Disk90%", "pattern": "disk usage reached 90%" } ] }

I wrote this line to the log file:

2026-07-15T09:58:59Z disk usage reached 90%

NPD started normally. After filelog read and matched the line, NPD logged:

Got wrong string "Disk90%!(NOVERB)" for reason "Disk90%" with pattern "disk usage reached 90%"

The process remained alive, but NPD generated no status or event. I could not reproduce either a launch or runtime panic. The match is dropped at runtime instead.

If the goal is to surface bad reason strings easily one option is validating them in ValidateRules which would let us catch them at startup.

@DigitalVeer I see. "pattern": "disk usage reached 90%" is a valid regex pattern，so NPD doesn't panic in ValidateRules, but "reason": "Disk90%" is not a valid Sprintf templated string. I have added validation for reason in ValidateRules().

Dry-run fmt.Sprintf against the pattern's capturing group count so misconfigured Reason templates (wrong verb count or unsupported verbs for string args) fail at config load time instead of being silently dropped at runtime.

kubernetes-prow · 2026-07-16T07:03:00Z

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kubernetes-prow · 2026-07-16T07:04:44Z

@jessehu: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-npd-test	`aea47a2`	link	true	`/test pull-npd-test`
pull-npd-e2e-test	`aea47a2`	link	true	`/test pull-npd-e2e-test`

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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k8s-ci-robot requested review from hakman and mmiranda96 June 11, 2025 05:33

k8s-ci-robot added the size/L Denotes a PR that changes 100-499 lines, ignoring generated files. label Jun 11, 2025

jessehu force-pushed the templating-reason branch from 24e9230 to 411a1ba Compare June 12, 2025 07:42

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k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Jun 18, 2025

googs1025 reviewed Jun 22, 2025

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Comment thread pkg/systemlogmonitor/log_monitor.go Outdated

k8s-ci-robot added size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. and removed size/L Denotes a PR that changes 100-499 lines, ignoring generated files. labels Aug 20, 2025

jessehu added 2 commits August 20, 2025 17:32

feat: Support configuring rule.Reason as a Sprintf format string

0fd1dff

So we can define one templated Reason to generate many Reasons, e.g. generating Reasons for Nvidia GPU Xid errors in dmesg log.

fix: Allow capturing groups in rule.Pattern with non-templated rule.R…

50016aa

…eason

jessehu force-pushed the templating-reason branch from ea452dd to 50016aa Compare August 20, 2025 09:33

k8s-ci-robot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. and removed size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. labels Aug 20, 2025

k8s-ci-robot added the lifecycle/stale Denotes an issue or PR has remained open with no activity and has become stale. label Nov 18, 2025

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k8s-ci-robot added lifecycle/rotten Denotes an issue or PR that has aged beyond stale and will be auto-closed. and removed lifecycle/stale Denotes an issue or PR has remained open with no activity and has become stale. labels Jun 18, 2026

DigitalVeer reviewed Jul 9, 2026

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