grpc/grpc-go · warning

invalid header/message length config: %q, %v

Error message

invalid header/message length config: %q, %v

What it means

Returned by fillMethodLoggerWithConfigString when parseHeaderMessageLengthConfig fails on the suffix of a method or service entry (env_config.go:102-104). The suffix (e.g., '{h:256;m:512}') extracted from the entry must match one of the three recognized patterns: {h}, {h:N}, {m}, {m:N}, {h;m}, or {h:N;m:N}. The %q is the suffix string; %v is the parse error. This differs from error 276 in that it applies to method/service entries, not the global '*' rule, and uses a different error prefix ('invalid header/message length config').

Source

Thrown at internal/binarylog/env_config.go:104

	// "*{h:256;m:256}"
	if config[0] == '*' {
		hdr, msg, err := parseHeaderMessageLengthConfig(config[1:])
		if err != nil {
			return fmt.Errorf("invalid config: %q, %v", config, err)
		}
		if err := l.setDefaultMethodLogger(&MethodLoggerConfig{Header: hdr, Message: msg}); err != nil {
			return fmt.Errorf("invalid config: %v", err)
		}
		return nil
	}

	s, m, suffix, err := parseMethodConfigAndSuffix(config)
	if err != nil {
		return fmt.Errorf("invalid config: %q, %v", config, err)
	}
	hdr, msg, err := parseHeaderMessageLengthConfig(suffix)
	if err != nil {
		return fmt.Errorf("invalid header/message length config: %q, %v", suffix, err)
	}
	if m == "*" {
		if err := l.setServiceMethodLogger(s, &MethodLoggerConfig{Header: hdr, Message: msg}); err != nil {
			return fmt.Errorf("invalid config: %v", err)
		}
	} else {
		if err := l.setMethodMethodLogger(s+"/"+m, &MethodLoggerConfig{Header: hdr, Message: msg}); err != nil {
			return fmt.Errorf("invalid config: %v", err)
		}
	}
	return nil
}

const (
	// TODO: this const is only used by env_config now. But could be useful for
	// other config. Move to binarylog.go if necessary.
	maxUInt = ^uint64(0)

View on GitHub (pinned to 0c51461d27)

Solutions

1. Use valid suffix formats: '{h:256}', '{m:512}', '{h:256;m:512}', '{h}', '{m}', or omit the suffix for full logging
2. Ensure only 'h' (header) and 'm' (message) keys are used
3. Ensure numeric values are decimal integers parseable by strconv.ParseUint

Example fix

# before (malformed length suffix on method entry)
export GRPC_BINARY_LOG_FILTER="Foo/Bar{h:abc}"

# after (valid numeric header length)
export GRPC_BINARY_LOG_FILTER="Foo/Bar{h:256}"

// Validate header/message length suffix on method/service entries
var lengthSuffixRe = regexp.MustCompile(`^\{(?:(?:h(?::\d+)?)?(?:;m(?::\d+)?)?|m(?::\d+)?)\}$`)

func validateLengthSuffix(entry string) error {
    braceStart := strings.Index(entry, "{")
    if braceStart < 0 {
        return nil // no suffix, valid
    }
    suffix := entry[braceStart:]
    if !lengthSuffixRe.MatchString(suffix) {
        return fmt.Errorf("invalid length suffix %q; use {h:N}, {m:N}, {h:N;m:N}, {h}, or {m}", suffix)
    }
    return nil
}

When it happens

Trigger: A method or service entry in GRPC_BINARY_LOG_FILTER with a malformed length suffix, e.g., 'Foo/Bar{invalid}', 'Foo/Bar{h:abc}' (non-numeric), 'Foo/Bar{x:256}' (unknown key), or 'Foo/Bar{}'. The suffix must match headerConfigRegexp, messageConfigRegexp, or headerMessageConfigRegexp.

Common situations: Typos in the header/message length specification. Using unsupported keys (only 'h' and 'm' are valid). Non-numeric values where ParseUint expects decimal integers.

Related errors

• conflicting global rules found
• conflicting service rules for service %v found
• conflicting blacklist rules for method %v found
• conflicting method rules for method %v found
• invalid config: %q, %v

AI-assisted analysis of grpc/grpc-go@0c51461d27 (2026-08-11). Data as JSON: /api/errors/868b77412146179a. Report an issue: GitHub.