prometheus/node_exporter · error

failed to parse device filter flags

Error message

failed to parse device filter flags: %w

What it means

On OpenBSD/amd64 (platform-specific file diskstats_openbsd_amd64.go), NewDiskstatsCollector likewise compiles the device filter regex flags via newDiskstatsDeviceFilter(logger). A regexp.Compile failure in the flags aborts construction with "failed to parse device filter flags: %w".

Solutions

1. Inspect the wrapped regexp error (%w) for the exact position of the syntax error and fix the flag value.
2. Quote the pattern on the command line: --collector.diskstats.device-exclude='^(wd|sd)\d+$'.
3. Validate with a Go RE2-compatible regex tester before deploying.
4. Remove the filter flag to confirm the collector otherwise starts, then reintroduce a corrected pattern.

Example fix

// before
--collector.diskstats.device-exclude=^(wd|sd\d+$
// after
--collector.diskstats.device-exclude='^(wd|sd)\d+$'

if _, err := regexp.Compile(deviceExcludeFlag); err != nil {
    // reject before passing to NewDiskstatsCollector
}

if _, err := NewDiskstatsCollector(logger); err != nil {
    if strings.Contains(err.Error(), "failed to parse device filter flags") {
        log.Fatalf("fix device filter regex: %v", err)
    }
    log.Fatalf("diskstats init failed: %v", err)
}

When it happens

Trigger: node_exporter startup on OpenBSD amd64 with a device include/exclude flag value that fails regexp.Compile; same for direct invocation of this NewDiskstatsCollector variant.

Common situations: Unquoted regex values altered by the shell, typos creating invalid syntax (e.g. missing closing bracket), or patterns using syntax unsupported by Go's RE2 engine.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• failed to parse device filter flags
• failed to parse device filter flags
• failed to parse device filter flags
• failed to parse device filter flags
• --collector.diskstats.ignored-devices and…

AI-assisted analysis of prometheus/node_exporter@17ddd77c59 (2026-09-07). Data as JSON: /api/errors/24717a94e88ec5ae. Report an issue: GitHub.

Appendix: source

Thrown at collector/diskstats_openbsd_amd64.go:65

	rxfer  typedDesc
	rbytes typedDesc
	wxfer  typedDesc
	wbytes typedDesc
	time   typedDesc

	deviceFilter deviceFilter
	logger       *slog.Logger
}

func init() {
	registerCollector("diskstats", defaultEnabled, NewDiskstatsCollector)
}

// NewDiskstatsCollector returns a new Collector exposing disk device stats.
func NewDiskstatsCollector(logger *slog.Logger) (Collector, error) {
	deviceFilter, err := newDiskstatsDeviceFilter(logger)
	if err != nil {
		return nil, fmt.Errorf("failed to parse device filter flags: %w", err)
	}

	return &diskstatsCollector{
		rxfer:  typedDesc{readsCompletedDesc, prometheus.CounterValue},
		rbytes: typedDesc{readBytesDesc, prometheus.CounterValue},
		wxfer:  typedDesc{writesCompletedDesc, prometheus.CounterValue},
		wbytes: typedDesc{writtenBytesDesc, prometheus.CounterValue},
		time:   typedDesc{ioTimeSecondsDesc, prometheus.CounterValue},

		deviceFilter: deviceFilter,
		logger:       logger,
	}, nil
}

func (c *diskstatsCollector) Update(ch chan<- prometheus.Metric) (err error) {
	diskstatsb, err := unix.SysctlRaw("hw.diskstats")
	if err != nil {
		return err

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