prometheus/node_exporter · error

failed to parse device filter flags

Error message

failed to parse device filter flags: %w

What it means

On Linux, after opening proc/sysfs successfully, NewDiskstatsCollector compiles the device include/exclude flag regexes via newDiskstatsDeviceFilter(logger). An invalid regular expression in those flags aborts construction with "failed to parse device filter flags: %w".

Solutions

1. Use the wrapped regexp error (%w) to pinpoint the syntax problem and fix the flag value.
2. Quote the pattern: --collector.diskstats.device-exclude='^(ram|loop|fd)\d+$'.
3. Validate the regex against a Go regexp tester or a quick Go snippet before deploying.
4. Start without the filter flag to confirm the collector initializes, then re-add a corrected pattern.

Example fix

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

if _, err := regexp.Compile(deviceExcludeFlag); err != nil {
    return fmt.Errorf("invalid diskstats device filter %q: %w", deviceExcludeFlag, err)
}

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

When it happens

Trigger: node_exporter startup on Linux with --collector.diskstats.device-exclude (or include) whose value fails regexp.Compile; same for any direct call of NewDiskstatsCollector with such flags.

Common situations: Unquoted regex values altered by the shell (globs like disk* expanded, brackets eaten), unbalanced groups/brackets in hand-written patterns, or patterns copied between tools with different regex syntax.

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
• failed to open sysfs

AI-assisted analysis of prometheus/node_exporter@17ddd77c59 (2026-09-07). Data as JSON: /api/errors/d032f9a151537ca5. Report an issue: GitHub.

Appendix: source

Thrown at collector/diskstats_linux.go:97

	getUdevDeviceProperties func(uint32, uint32) (udevInfo, error)
}

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

// NewDiskstatsCollector returns a new Collector exposing disk device stats.
// Docs from https://www.kernel.org/doc/Documentation/iostats.txt
func NewDiskstatsCollector(logger *slog.Logger) (Collector, error) {
	var diskLabelNames = []string{"device"}
	fs, err := blockdevice.NewFS(*procPath, *sysPath)
	if err != nil {
		return nil, fmt.Errorf("failed to open sysfs: %w", err)
	}

	deviceFilter, err := newDiskstatsDeviceFilter(logger)
	if err != nil {
		return nil, fmt.Errorf("failed to parse device filter flags: %w", err)
	}

	collector := diskstatsCollector{
		deviceFilter: deviceFilter,
		fs:           fs,
		infoDesc: typedDesc{
			desc: prometheus.NewDesc(prometheus.BuildFQName(namespace, diskSubsystem, "info"),
				"Info of /sys/block/<block_device>.",
				[]string{"device", "major", "minor", "path", "wwn", "model", "serial", "revision", "rotational"},
				nil,
			), valueType: prometheus.GaugeValue,
		},
		descs: []typedDesc{
			{
				desc: readsCompletedDesc, valueType: prometheus.CounterValue,
			},
			{
				desc: prometheus.NewDesc(

View on GitHub (pinned to 17ddd77c59)