hyperledger/fabric · error

error marshaling

Error message

error marshaling

What it means

In `encodeProto` (cmd/configtxlator/main.go:151), `proto.Marshal(msg)` failed while serializing the decoded message to protobuf binary. This indicates the message content violates proto serialization constraints (e.g. required content missing, invalid enum, oversized/invalid nested values). configtxlator wraps it as 'error marshaling'.

Source

Thrown at cmd/configtxlator/main.go:151

	msgType := reflect.TypeOf(mt.Zero().Interface())

	if msgType == nil {
		return errors.Errorf("message of type %s unknown", msgType)
	}
	msg := reflect.New(msgType.Elem()).Interface().(proto.Message)

	err = protolator.DeepUnmarshalJSON(input, msg)
	if err != nil {
		return errors.Wrapf(err, "error decoding input")
	}

	if msg == nil {
		return errors.New("error marshaling: proto: Marshal called with nil")
	}
	out, err := proto.Marshal(msg)
	if err != nil {
		return errors.Wrapf(err, "error marshaling")
	}

	_, err = output.Write(out)
	if err != nil {
		return errors.Wrapf(err, "error writing output")
	}

	return nil
}

func decodeProto(msgName string, input, output *os.File) error {
	mt, err := protoregistry.GlobalTypes.FindMessageByName(protoreflect.FullName(msgName))
	if err != nil {
		return errors.Wrapf(err, "error encode input")
	}

	msgType := reflect.TypeOf(mt.Zero().Interface())

View on GitHub (pinned to 2736b63f8f)

Solutions

1. Read the wrapped inner proto error to find the offending field.
2. Fix invalid field values in the input JSON (ports in range, valid policy types, well-formed signatures).
3. Re-export the JSON via `configtxlator proto_decode` from a known-good .pb and re-apply only intended edits.
4. Confirm input/output Fabric proto versions are consistent.

Example fix

// before (invalid value fails proto.Marshal)
{ "payload": { "header": { "channel_header": { "version": -1 } } } }
// after
{ "payload": { "header": { "channel_header": { "version": 0 } } } }

// Sanity-check risky numeric fields before marshaling
def check_config(cfg):
    for org in cfg.get('channel_group', {}).get('groups', {}).values():
        for o in org.get('groups', {}).values():
            ap = o.get('values', {}).get('AnchorPeers', {})
    # also validate enum fields are in range before encode
    return True

out, err := exec.Command("configtxlator", "proto_encode", ...).CombinedOutput()
if err != nil && strings.Contains(string(out), "error marshaling") {
	return fmt.Errorf("content invalid for proto.Marshal; inspect wrapped proto error: %s", out)
}

When it happens

Trigger: Running `configtxlator proto_encode` where the JSON decodes into a message whose content fails proto.Marshal — e.g. invalid field values that pass JSON parsing but fail proto validation, or deeply inconsistent config content.

Common situations: Hand-crafted config JSON with out-of-range values (ports, policy rules); corrupted JSON round-trips mixing Fabric versions; fields containing invalid bytes or malformed nested messages.

Related errors

• error encode input
• message of type %s unknown
• error marshaling: proto: Marshal called with nil
• error marshaling computed config update
• unmarshal failed

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/2aefb6ab8de58269. Report an issue: GitHub.