cloudflare/cloudflared · error

error parsing files max field '%s': %w

Error message

error parsing files max field '%s': %w

What it means

ParseSysctlFileDescriptorInformation parses whitespace-separated sysctl file-descriptor limits and expects the maximum at whitespace field index 2. This error is returned when strconv.ParseUint fails on that field, i.e. the third token is not a base-10 unsigned integer. The wrapped strconv error and the offending string are included in the message.

Source

Thrown at diagnostic/system_collector_utils.go:243

				"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,
) (*FileDescriptorInformation, error) {
	mapper := func(field string) (uint64, error) {
		return strconv.ParseUint(field, 10, 64)
	}

	pairs := findColonSeparatedPairs(output, []string{fileDescriptorMaximumKey, fileDescriptorCurrentKey}, mapper)

	fileDescriptorMaximum, exists := pairs[fileDescriptorMaximumKey]
	if !exists {

View on GitHub (pinned to 2253eeeb25)

Solutions

1. Inspect the raw output and ensure the third whitespace-separated token is a plain decimal integer
2. Strip units, commas, or labels from the value before calling the parser
3. Prefer ParseFileDescriptorInformationFromKV when output is key/value formatted rather than positional
4. Confirm the sysctl command/version produces the expected 3-field numeric layout

Example fix

// before
raw := "10 0 1,024" // thousands separator
info, err := ParseSysctlFileDescriptorInformation(raw)
// after
raw = strings.ReplaceAll(raw, ",", "")
info, err := ParseSysctlFileDescriptorInformation(raw)

fields := strings.Fields(out)
if len(fields) < 3 {
    return fmt.Errorf("sysctl fd output too short: %q", out)
}
if _, err := strconv.ParseUint(fields[2], 10, 64); err != nil {
    return fmt.Errorf("non-numeric max-files field %q", fields[2])
}

func hasValidUintField(out string, idx int) bool {
    fields := strings.Fields(out)
    if idx >= len(fields) { return false }
    _, err := strconv.ParseUint(fields[idx], 10, 64)
    return err == nil
}

info, err := ParseSysctlFileDescriptorInformation(out)
if err != nil {
    var numErr *strconv.NumError
    if errors.As(err, &numErr) {
        // fall back to key/value parser or degrade gracefully
        return nil, nil
    }
    return nil, err
}

When it happens

Trigger: Calling ParseSysctlFileDescriptorInformation where fields[2] is non-numeric or empty: truncated output, output with fewer tokens that happened to still be 3 but labeled (e.g. "10 open max"), values with units like "256K", or a comma-separated number "1,024".

Common situations: OS-version differences in sysctl output; locale-formatted numbers with thousands separators; capturing the wrong command output; cgroup/container environments reporting abbreviated limits.

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

• expected file descriptor information to have %d fields got %
• 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/df716c71649a5c32. Report an issue: GitHub.