cloudflare/cloudflared · error · ErrInsuficientFields

expected file descriptor information to have %d fields got %

Error message

expected file descriptor information to have %d fields got %d: %w

What it means

ParseSysctlFileDescriptorInformation parses whitespace-separated sysctl output (e.g. `kern.openfiles` style limits) and expects exactly 3 whitespace-separated fields, with the current open-file count at index 0 and the max at index 2. This error is thrown when strconv.ParseUint fails on field 0, meaning the 'current files' value is not a plain base-10 unsigned integer. It wraps the strconv error so the offending text is included in the message.

Source

Thrown at diagnostic/system_collector_utils.go:234

		maxFilesField              = 2
		fileDescriptorLimitsFields = 3
	)

	fields := strings.Fields(output)

	if len(fields) != fileDescriptorLimitsFields {
		return nil,
			fmt.Errorf(
				"expected file descriptor information to have %d fields got %d: %w",
				fileDescriptorLimitsFields,
				len(fields),
				ErrInsuficientFields,
			)
	}

	fileDescriptorCurrent, err := strconv.ParseUint(fields[openFilesField], 10, 64)
	if err != nil {
		return nil, fmt.Errorf(
			"error parsing files current field '%s': %w",
			fields[openFilesField],
			err,
		)
	}

	fileDescriptorMaximum, err := strconv.ParseUint(fields[maxFilesField], 10, 64)
	if err != nil {
		return nil, fmt.Errorf("error parsing files max field '%s': %w", fields[maxFilesField], err)
	}

	return &FileDescriptorInformation{fileDescriptorMaximum, fileDescriptorCurrent}, nil
}

func ParseFileDescriptorInformationFromKV(
	output string,
	fileDescriptorMaximumKey string,
	fileDescriptorCurrentKey string,

View on GitHub (pinned to 2253eeeb25)

Solutions

1. Check the raw sysctl output and pass only the line containing the numeric fields, stripping any key/label prefixes
2. Verify the queried sysctl key returns the 3-field numeric format expected (open-files current, intermediate, max)
3. If output contains labels, use ParseFileDescriptorInformationFromKV instead, which matches keys explicitly
4. Sanitize values (remove commas, units, whitespace) before parsing

Example fix

// before
info, err := ParseSysctlFileDescriptorInformation(out) // out = "kern.openfiles: 12"
// after
line := "12 0 256" // extract numeric fields only
info, err := ParseSysctlFileDescriptorInformation(line)

fields := strings.Fields(out)
if len(fields) != 3 {
    return fmt.Errorf("unexpected sysctl fd output %q", out)
}
if _, err := strconv.ParseUint(fields[0], 10, 64); err != nil {
    return fmt.Errorf("non-numeric open-files field %q: %w", fields[0], err)
}

func isNumericFields(out string, n int) bool {
    fields := strings.Fields(out)
    if len(fields) != n { return false }
    for _, f := range fields {
        if _, err := strconv.ParseUint(f, 10, 64); err != nil { return false }
    }
    return true
}

info, err := ParseSysctlFileDescriptorInformation(out)
if err != nil {
    var parseErr *strconv.NumError
    if errors.Is(err, ErrInsuficientFields) || errors.As(err, &parseErr) {
        // log raw output and skip FD metrics rather than failing collection
        return nil, nil
    }
    return nil, err
}

When it happens

Trigger: Calling ParseSysctlFileDescriptorInformation with output whose first whitespace-delimited token is not a decimal number: empty input, a labeled line like "current 10 max 100" (words shift the indices), localized output, or a value with units/commas such as "1,024".

Common situations: sysctl command output format differs across OS versions or locales; the caller captured stderr instead of stdout; a different sysctl key was queried so the output contains a header or label; macOS vs Linux field ordering differences.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• error parsing files max field '%s': %w
• error parsing files current field '%s': %w
• parsing file descriptor information: %w, key=%s
• error parsing OriginCert: %v
• parsing memory information: %w, key=%s

AI-assisted analysis of cloudflare/cloudflared@2253eeeb25 (2026-09-06). Data as JSON: /api/errors/b5fa183851570c7b. Report an issue: GitHub.