cloudflare/cloudflared · error · ErrKeyNotFound

parsing file descriptor information: %w, key=%s

Error message

parsing file descriptor information: %w, key=%s

What it means

ParseFileDescriptorInformationFromKV scans colon-separated key/value output for the given file-descriptor maximum key. This error is returned when the requested key is absent from the parsed pairs, wrapped with ErrKeyNotFound. It indicates the output text does not contain a recognizable `<key>: <number>` entry for the maximum file-descriptor limit.

Source

Thrown at diagnostic/system_collector_utils.go:262

	}

	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 {
		return nil, fmt.Errorf(
			"parsing file descriptor information: %w, key=%s",
			ErrKeyNotFound,
			fileDescriptorMaximumKey,
		)
	}

	fileDescriptorCurrent, exists := pairs[fileDescriptorCurrentKey]
	if !exists {
		return nil, fmt.Errorf(
			"parsing file descriptor information: %w, key=%s",
			ErrKeyNotFound,
			fileDescriptorCurrentKey,
		)
	}

	return &FileDescriptorInformation{fileDescriptorMaximum, fileDescriptorCurrent}, nil
}

View on GitHub (pinned to 2253eeeb25)

Solutions

1. Print the raw output and confirm the exact key spelling, including case and spacing, matches what is passed as fileDescriptorMaximumKey
2. Use the key constant/string the OS actually emits (e.g. "maxfiles" vs "open files")
3. Handle empty output from the upstream command before parsing (check command exit status)
4. If values may be non-numeric, provide a lenient mapper or sanitize the values first

Example fix

// before
info, err := ParseFileDescriptorInformationFromKV(out, "MaxFiles", "OpenFiles")
// after
info, err := ParseFileDescriptorInformationFromKV(out, "maxfiles", "openfiles") // exact key emitted by the OS

if !strings.Contains(out, maxKey+":") {
    return fmt.Errorf("output %q missing key %q", out, maxKey)
}

info, err := ParseFileDescriptorInformationFromKV(out, maxKey, curKey)
if err != nil {
    if errors.Is(err, ErrKeyNotFound) {
        // degrade: skip FD diagnostic or try alternate key set
        return nil, nil
    }
    return nil, err
}

When it happens

Trigger: Calling ParseFileDescriptorInformationFromKV with an output string missing the max key: wrong key string (case/spacing mismatch), the command output changed format across OS versions, empty output, or output where values failed ParseUint and were dropped from the pairs map.

Common situations: macOS `ulimit -Hn`/launchctl output vs Linux `ulimit -n` wording differences; container runtimes omitting limits; querying the wrong sysctl key; trailing whitespace or tabs after the key name.

Related errors

• parsing memory information: %w, key=%s
• error parsing files current field '%s': %w
• expected file descriptor information to have %d fields got %
• error parsing files max field '%s': %w
• error parsing OriginCert: %v

AI-assisted analysis of cloudflare/cloudflared@2253eeeb25 (2026-09-06). Data as JSON: /api/errors/1e44e89e41e67c37. Report an issue: GitHub.