henrygd/beszel · error

failed to marshal request: %w

Error message

failed to marshal request: %w

What it means

sendMessage CBOR-marshals the request payload before writing it to the WebSocket. This error is returned when cbor.Marshal fails on the request data, so nothing is sent over the wire.

Source

Thrown at internal/hub/ws/request_manager.go:96

		rm.cancelRequest(reqID)
		return nil, fmt.Errorf("failed to send request: %w", err)
	}

	// Start cleanup watcher for timeout/cancellation
	go rm.cleanupRequest(req)

	return req, nil
}

// sendMessage encodes and sends a message over WebSocket
func (rm *RequestManager) sendMessage(data any) error {
	if rm.conn == nil {
		return gws.ErrConnClosed
	}

	bytes, err := cbor.Marshal(data)
	if err != nil {
		return fmt.Errorf("failed to marshal request: %w", err)
	}

	return rm.conn.WriteMessage(gws.OpcodeBinary, bytes)
}

// handleResponse processes a single response message
func (rm *RequestManager) handleResponse(message *gws.Message) {
	var response common.AgentResponse
	if err := cbor.Unmarshal(message.Data.Bytes(), &response); err != nil {
		// Legacy response without ID - route to first pending request of any type
		rm.routeLegacyResponse(message)
		return
	}

	if response.Id == nil {
		rm.routeLegacyResponse(message)
		return
	}

View on GitHub (pinned to b38fb7dafa)

Solutions

1. Log the wrapped cause (%w) to identify the offending value
2. Ensure the request payload contains only CBOR-serializable types (primitives, slices, maps, structs with exported fields)
3. Send nil or a plain struct/map as the request data

Example fix

// before
req := map[string]any{"cb": make(chan int)} // not CBOR-serializable
rm.SendRequest(ctx, action, req)
// after
req := map[string]any{"action": "status"}
rm.SendRequest(ctx, action, req)

if err := cbor.Marshal(data); err != nil {
    return fmt.Errorf("request payload not CBOR-serializable: %w", err)
}

if _, err := rm.SendRequest(ctx, action, data); err != nil {
    if strings.Contains(err.Error(), "failed to marshal request") { /* fix payload types */ }
    return err
}

When it happens

Trigger: Passing a request payload containing types cbor.Marshal cannot encode (e.g. channels, funcs, cyclic structures, or unexported fields expected to serialize) to SendRequest.

Common situations: Sending custom structs with unsupported field types or channels; attaching context values or non-serializable objects to the request; a custom CBOR encoder mode rejecting a type.

Related errors

• failed to encode request: %w
• HUB_URL environment variable not set
• invalid signature - check KEY value
• service name is required
• no websocket connection

AI-assisted analysis of henrygd/beszel@b38fb7dafa (2026-08-31). Data as JSON: /api/errors/442c90df002adccf. Report an issue: GitHub.