caddyserver/caddy · warning

unsupported type

Error message

unsupported type

What it means

After a successful DNS publication, Caddy records publication history into each config's metadata (cfg.meta.Publications maps of publisher -> name -> time) and json.Marshal of that metadata failed. Like the rotation-path marshal error, this is a near-impossible defensive path for well-formed data.

Source

Thrown at modules/caddyhttp/logging.go:192

type StringArray []string

// UnmarshalJSON satisfies json.Unmarshaler.
func (sa *StringArray) UnmarshalJSON(b []byte) error {
	var jsonObj any
	err := json.Unmarshal(b, &jsonObj)
	if err != nil {
		return err
	}
	switch obj := jsonObj.(type) {
	case string:
		*sa = StringArray([]string{obj})
		return nil
	case []any:
		s := make([]string, 0, len(obj))
		for _, v := range obj {
			value, ok := v.(string)
			if !ok {
				return errors.New("unsupported type")
			}
			s = append(s, value)
		}
		*sa = StringArray(s)
		return nil
	}
	return errors.New("unsupported type")
}

// errLogValues inspects err and returns the status code
// to use, the error log message, and any extra fields.
// If err is a HandlerError, the returned values will
// have richer information.
func errLogValues(err error) (status int, msg string, fields func() []zapcore.Field) {
	var handlerErr HandlerError
	if errors.As(err, &handlerErr) {
		status = handlerErr.StatusCode
		if handlerErr.Err == nil {

View on GitHub (pinned to 50e54ee279)

Solutions

1. Capture the wrapped error and Caddy version; report upstream as a bug.
2. Restart the instance to rebuild metadata from storage.
3. Reset the ech/configs folder if it recurs and blocks publication bookkeeping.

Catch and log with full context (publisher key, config IDs); publication already succeeded, so bookkeeping failure is non-fatal — retry occurs on the next publication cycle.

When it happens

Trigger: json.Marshal(cfg.meta) errors because a value in the publication history is not JSON-serializable — only plausible via memory corruption or a bug writing unmarshalable dynamic values.

Common situations: Essentially never in practice; treat an occurrence as a Caddy bug or memory fault and gather diagnostics.

Related errors

• missing 'req' argument
• private key does not match issuer public key
• --config is required
• --input is required
• --output is required

AI-assisted analysis of caddyserver/caddy@50e54ee279 (2026-08-15). Data as JSON: /api/errors/4cbaca8f319ebee9. Report an issue: GitHub.